Exams Flashcards

Question

The parathyroid gland

Answer 1

One of four (usually) small glands about the size of a small pea embedded in the rear surface of the thyroid gland; secretes PTH which control calcium and Phosphate levels in blood.

Answer 2

An endocrine gland located in the chest just above the heart and behind the sternum; secretes a group of hormones called thymosins. these hormones influence the maturation of disease-fighting cells called T lymphocytes.

Answer 3

− 2, one above each kidney | − Each has an inner adrenal medulla and an outer adrenal cortex

Answer 4

The inner portion of an adrenal gland; secretes the hormones adrenaline and noradrenaline − Adrenaline (epinephrine) prepares the body for the fight or flight responses; also acts as a neurotransmitter by transferring nervous impulses across the junction (synapse) between adjacent nerve cells − Noradrenaline (norepinephrine) has effects similar to adrenaline; in particular it increases the rate and force of the heart beat

Answer 5

More than 20 different hormones are produced in the adrenal cortex and they are known collectively as corticosteroids. the 2 main ones are: − Aldosterone, which acts on the kidney to reduce the amount of sodium and increase the amount of potassium in the urine − Cortisol, which, with related hormones promotes normal metabolism, helping the body to withstand stress, and also helps with repair of damaged tissues

Answer 6

A gland that lies just below the stomach; both an endocrine and exocrine gland; that secretes digestive enzymes from the exocrine glands, and the hormones insulin and glucagon from a cluster of special cells called Islets of Langerhans, which are part of the endocrine part of the pancreas. − Insulin, reduces the amount of glucose in the blood, the blood sugar level. Promotes the uptake of glucose from the blood by cells. The level of secretion is determined by the amount of sugar in the blood and controlled through a negative feedback system − Glucagon, increases the blood sugar level

Answer 7

− Androgens, are the male sex hormones produced by the testes. Responsible for the development and maintenance of the male sex characteristics − Oestrogen and progesterone ate the female sex hormones produced by the ovaries. Stimulate the development and maintenance of the female sexual characteristics

Answer 8

There are other tissues, many of which are not called endocrine glands, that secrete hormones. − Stomach and small intestines, both secrete hormones that coordinate the exocrine glands of the digestive system − Kidneys, secrete hormones including erythropoietin (EPO), stimulates production of red blood cells by the bone marrow − Heart, secretes hormone that helps reduce blood pressure − Placenta, secretes many hormones during pregnancy that help to maintain the pregnancy and stimulate the mother's mammary glands

Answer 9

The body system involved with control and coordination of the body

Answer 10

The part of the nervous system that consists of the brain and spinal cord

Answer 11

The part of the nervous system that connects the CNS with the receptors, muscles and glands

Answer 12

− Neuron, a nerve cell; the basic structural and functional unit of NS − Vary in shape and size, but all consist of a cell body and 2 extensions form the cell; the dendrites and the axon − Most neurons are Interneurons, they have many branches that are able to send or receive messages to or from adjacent neurons − The cell body is part of the neuron that contains the nucleus − Dendrites, an extension of the body of a nerve cell; carries nerve impulses into the cell body − Axon, an extension of the body of a nerve cell, carries nerve impulses away from the cell body − Axon length varies, short in brain and up to a metre long from spinal cord to foot − Most axons covered with a layer of fatty material call the myelin sheath − Nerve fibres (axon) with myelin sheath call myelinated fibres and those without are called unmyelinated fibres − White matter consists of nerve cell bodies and unmyelinated fibres − Grey matter consists of nerve cell bodies and myelinated fibres − Outside the brain and spinal cord the myelin sheath is formed by special cells called Schwann cells, which wrap around the axon − At intervals along the axon are gaps in the myelin sheath, called nodes of Ranvier − Sheaths 3 main functions; acts as an insulator, protects axon form damage and speed up the movement of nerve impulses along the axon − Neurilemma, a sheath surrounding a nerve fibre; helps in the repair of injured fibres

Answer 13

carry messages form receptors in the sense organs (or skin) to CNS

Answer 14

carry messages from CNS to muscles and glands (effectors)

Answer 15

are located in CNS and link sensory and motor neurons

Answer 16

one axon and multiple dendrites

Answer 17

one axon and one dendrite. Occur in the eye, ear and nose

Answer 18

just one axon. Most sensory neurons

Answer 19

The junction between the branches of adjacent neurons. − At synapse neurons don't actually join, small gap − Messages have to be carried across the synapse − Neuromuscular junction, where an axon meets a skeletal muscle cell

Answer 20

The electrochemical charge that travels along the membrane of a nerve cell; the message carried by a nerve. Transmitted very quick, makes it possible for the body to respond rapidly to any change. − The speed at which an impulse travels depends on whether the nerve fibre is myelinated or unmyelinated − Unmyelinated, the impulse travels steadily (max speed 7km/h) − Myelinated, the myelin sheath is not continuous. Gaps called nodes of Ravier. Impulse jumps from node to node − This jumping is known as saltatory conduction, allows faster travel

Answer 21

− CNS and PNS − PNS consists nerve fibres, carry info to and from the CNS and groups of cell bodies called ganglia (lie outside the brain and spinal cord) − 12 pairs of nervous arise from the brain, these are the cranial nerves − Most cranial nerves are mixed nerves, carry impulses to and away from brain − Fibres that carry impulses into the CNS are called sensory fibres − Motor fibres, carry impulses away from CNS − 31 pairs of spinal nerves arise from spinal cord − They all mixed nerves and joined to spinal cord by 2 roots − Ventral root contains axons of motor neurons (grey matter) − Dorsal root, axons of sensory neurons (cell bodies in small swelling on the dorsal root, dorsal root ganglion)

Answer 22

− Carry impulses into the CNS − Carried by sensory nerve cells from receptors in the skin and around the muscles and joints − Nerve cells called somatic sensory neurons − Visceral sensory neurons take impulses from internal organs to CNS

Answer 23

Has fibres that carry impulses away from the CNS. It is subdivided into: − Somatic Division - takes impulses from CNS to the skeletal muscles − Autonomic Division - Carries impulses from CNS to heart muscle, involuntary muscle and glands (further divided into sympathetic and parasympathetic division)

Answer 24

− Part of PNS − Responsible for control of body's internal environment e.g. heart rate, blood pressure, body temp, digestion, release of energy, pupil diameter, air flow to the lungs, defecation and urination − Usually operates without conscious control and regulated by groups of nerve cells in the medulla oblongata, hypothalamus and cerebral cortex − 2 motor neurons involved in the autonomic pathway carry impulses from the CNS to the effector − Most organs under autonomic control receive 2 sets of nerve fibres (sympathetic and parasympathetic fibres) − Acetylcholine or noradrenaline carries the message to the effector − Parasympathetic division generally produces responses that maintain the body during relatively quiet conditions − Sympathetic division tends to produce responses that prepare the body for strenuous physical activity (fight or flight responses) − Message form autonomic nerves to the muscle and glands under their control is carried by a neurotransmitter at the nerve endings − Parasympathetic nerve endings release acetylcholine − Sympathetic nerve endings release noradrenaline

Answer 25

Fear, anger, stress, danger and competition provoke fight or flight responses. Activation of the sympathetic division results in the following responses: − Increase blood pressure − Blood vessels dilate (heart, liver and skeletal muscles) − Blood vessels constrict (kidney, stomach, intestines and skin) − Breathing increases − Blood glucose levels rise − Increase sweat

Answer 26

Bothe the endocrine system and NS do not duplicate each other's roles; rather, they complement and reinforce each other. The difference between the actions of nerves and hormones are as follows: − Ns more rapid response (impulses travel rapidly along nerve fibres and hormone transported in the bloodstream) − Nerve impulses immediate response, but hormones are slow-acting − Nervous messages are an electrochemical charge and hormones are chemicals − Nerve impulses specific target (effector), but hormones go everywhere and may affect a number of organs Important similarities between the 2 systems: − Hormones secreted by neurons into the extracellular fluid (OT and adrenaline) − Function as both hormone and neurotransmitter (noradrenaline, ADH and dopamine) − Some hormones and neurotransmitters have same effect on the same target cells

Answer 27

− Bone − Membranes called meninges − A fluid called cerebrospinal fluid (CSF) Outermost layer is bone (cranium) − Spinal cord runs through vertebral canal (opening in the vertebrae) − 3 layers of connective tissue cover surface of brain and spinal cord, called meninges − Outer meninge layer, tough and fibrous − Middle meningeal layer is loose mesh of fibres − Inner layer is far more delicate, contains many blood vessels and sticks closely to the surface of the brain and spinal cord − CSF occupies space between middle and inner layers of meninges − CSF is clear, watery fluid containing a few cells and some glucose, protein, urea and salts − Acts as a shock absorber − Also supports brain − Circulates and takes nutrients to cells of the brain and spinal cord and carries away their waste − CSF; protection, support and transport

Answer 28

− Biggest part of brain − Outer surface of grey matter (2-4mm thick) known as cerebral cortex − Below cortex is white matter − Deep inside is additional grey matter, basal ganglia − Cerebral cortex, folded patterns, increases SA − Cortex contains 70% all neurons in CNS − Folds create convolutions (or gyri), separated by shallow down folds called sulci or deep down folds called fissures − Longitudinal fissure (deepest) almost separates the cerebrum into 2 halves, left and right cerebral hemispheres − Corpus Callosum, a large bundle of nerve fibres that connects the 2 hemispheres, can't be seen on the outside of the brain − Certain fissures and sulci are fairly constant used to separate into 4 lobes - frontal, temporal, occipital and parietal lobes − Insula, deep inside the brain regarded as 5th lobe − Within CNS bundles of nerve fibres are called tracts (outside CNS called nerves) − 3 types - connect various areas of cortex within the same hemisphere, carry impulses between left and right hemispheres and connects cortex to other parts of the brain or spinal cord

Answer 29

Cerebral cortex is involved in meta; activities such as; thinking, reasoning, learning, memory, intelligence and sense of responsibility. Also concerned with perception of the senses and the initiation and control of voluntary muscle contraction. There are 3 types of functional area in cortex: − Sensory areas, which impulses form receptors (receives and processes nerve impulses form the senses) − Motor areas, which control muscular movement (send impulses to muscles, especially for voluntary movement) − Association areas, which are concerned with intellectual and emotional processes (interpret info form the sense and make it useful)

Answer 30

A wide band of nerve fibres that lies underneath the cerebrum at the base of the longitudinal fissure. Nerve fibres in the corpus callosum cross from one cerebral hemisphere to the other and allow the 2 sides of the cerebrum to communicate with each other

Answer 31

− Lies under the rear part of the cerebrum − 2nd largest part of the brain − Folded into a series of parallel ridges (surface) − Outer, grey matter − Inside, white matter − Control over posture, balance and the fine coordination of voluntary muscle movement − Receives sensory information from inner ear (for posture and balance) and from stretch receptors in the skeletal muscles − All functions take place below the conscious level − Without cerebellum could still move but would be spasmodic, jerky and uncontrolled

Answer 32

Lies in the middle of the brain and cannot be seen from the outside. Although small, the hypothalamus controls many body activities, mainly concerned with homeostasis (maintaining a constant environment for cells). Functions of the hypothalamus include regulation of: − The autonomic NS e.g. heart rate, blood pressure, the secretion of digestive juices, movements of the alimentary canal and the diameter of the pupil of the eye − Body temp − Patterns of walking and sleeping − Contraction of urinary bladder − Emotional responses e.g. fear, anger, aggression, pleasure and contentment − Secretion of hormones

Answer 33

Continuation of the spinal cord. It is about 3cm long and extends from just above the point where the spinal cord enters the skull. The Medulla Oblongata contains: − Cardiac centre, which regulates the rate and force of heartbeat − Respiratory centre, which controls rate and depth of breathing − Vasomotor centre, which regulates the diameter of blood vessels There are others that regulate the reflexes of swallowing, sneezing, coughing and vomiting. All centre's are influenced and controlled by higher centre's in the brain, particularly the hypothalamus.

Answer 34

− A roughly cylindrical structure that extends from the foramen magnum (the large opening at the base of the skull to the second lumbar vertebrae) − About 44cm long − Cord is enclosed in the vertebral canal (inside ring of bone, 3 meningeal layers) − Outermost layer not connected to bone − Space containing fat, connective tissue and blood vessels − Serve as padding around spinal cord, allows the cord to be bent when the spine is bent − Grey and white matter (grey centre) − Grey matter roughly shape letter H − Central canal, a hollow that runs through the centre of the spinal cord; filled with cerebrospinal fluid − Ascending tracts are sensory axons that carry impulses upwards, towards the brain − Descending tracts contain motor axons that conduct impulses downwards, away from brain

Answer 35

− Structure that is able to detect change in body's internal or external environment (stimulus) − Receptor cells of particular type grouped together in a sense organ

Answer 36

− Able to respond to heat and cool | − Located in the skin or the hypothalamus

Answer 37

− Receptors sensitive to osmotic pressure of body fluids − Located hypothalamus − Osmotic pressure determine by the concentration of substances in the water of the blood plasma

Answer 38

− Sensitive to particular chemicals | e.g. present in nose and mouth

Answer 39

− Receptor sensitive to touch − Mainly found in skin − receptors close to surface of skin are sensitive to very light touches e.g. lips, fingertips and eyelids − Receptors located deeper in the skin are sensitive to pressure and vibrations

Answer 40

− Stimulated by damage to tissues e.g. from a cut or a heavy bump, poor blood flow to a tissue, or by excessive stimulation from stimuli such as heat or chemicals − Occur in most organs, not brain − Pain is uncomfortable but essential − Warns us of damage to tissues occurring − Pain receptor adapt little or not at all

Answer 41

``` Is a rapid, automatic response to a change in the external or internal environment. All reflexes have four important properties: − Stimulus is required − Reflex is involuntary − Reflex response is rapid − Reflex response is stereotyped ``` − Most are coordinated by the spinal cord − Spinal reflex, carried out by the spinal cord without involvement of the brain − Reflex arc, the pathway travelled by nerve impulse form receptor to effector − Spinal reflex, a spinal reflex arc pathway travelled by nerve impulses from receptor to effector − Spinal reflex, involuntary (doesn't involve brain)

Answer 42

− A receptor, either the ending of a sensory neuron or a specialised cell associated with the end of a sensory neuron − A sensory neuron, carries impulses form the receptor to CNS − There is at least one synapse − A motor neuron, carried the nerve impulse to an effector − An effector, receives the nerve impulse and carries out appropriate response

Answer 43

1. Pain receptors in the skin detect the stimulus and produce a nerve impulse 2. Sensory neuron conducts the nerve impulse from the receptor to the spinal cord 3. Information is processed in the CNS. 1 or more interneuron's pass the message to the appropriate motor neuron 4. Motor neuron carries a nerve impulse to the effector 5. he effector, in this case the biceps muscle contracts, removing the hand form the painful stimulus − Response occurs in fraction of a second − Impulses would travel up the spinal cord to the brain − After response, person becomes consciously aware − Many reflexes protect body from injury − Other reflexes secretion

Answer 44

− More complex motor patterns during a baby's development e.g. suckling, chewing or following movements with the eyes − Determined genetically − Acquired reflexes, a response to a stimulus that has been learned through practice e.g. muscular adjustments whilst riding a bike, catching ball and jamming on brakes in car

Answer 45

− The process of keeping the environment inside the body fairly constant e.g. body temp, pH, oxygen and glucose levels and waste removal − Equilibrium, input and output of materials and energy are balanced − All systems of body contribute to homeostasis − NS and endocrine system are the main sensory and controlling body systems, in the case of homeostasis

Answer 46

− Core body temp − pH concentration of dissolved substances in the body fluids − Concentration glucose, oxygen and carbon dioxide in blood − Blood pressure − Concentration of metabolic wastes

Answer 47

− Limits of factors such as temp and fluid balance beyond which the body malfunctions − The upper and lower limits to a range of factors − Within these limits the body functions normally − Rise above, fall below the normal range means that the individuals tolerance limits have been exceeded and dysfunctions will occur

Answer 48

− Circular situation which the body responds to a change (stimulus), with response altering original stimulus − Negative feedback system, a situation in which feedback brings about a change opposite to, or reduces the effect of, the original stimulus

Answer 49

− Stimulus, the change in environment that causes the system to operate − Receptor, detects change − Modulator, control centre responsible for processing info received from receptor and sending info to effector − Effector, carries out a response counteracting the effect of the stimulus − Feedback, achieved because original stimulus been changed by the response

Answer 50

− Feedback that reduces the effect of , or eliminates, the original stimulus e.g. feeling cold. Response, you put on a jumper and no longer feel cold. Response has reduced or eliminated the original stimulus of feeling cold − Dynamic equilibrium, a state reached when the rates of forward and reverse changes are equal; a stable balanced or unchanging system results e.g. concentration of blood glucose and body temp fluctuate around a normal level − Set point, the level at which a variable is to be maintained e.g. body temp of 37°C

Answer 51

− Feedback that reinforces the original stimulus e.g. occurs during childbirth and blood clotting and high fever (dangerous) − Positive feedback has no role in homeostasis

Answer 52

The regulation of body temp; the balance of heat gain and heat loss in order to maintain a constant internal body temp independent of the environmental temp. − Cells are very heat-sensitive − Optimum 37°C − Heat produced from metabolic activity helps to maintain this high level − Increased body temp can cause nerve malfunction, change in the structure of proteins and death − Lowest body temp usually occurring in the morning and highest in the evening

Answer 53

− Most energy is released in the form of heat − The rate at which energy is released by the breakdown of food is called metabolic rate − During exercise metabolic rate is increased and large quantities of heat are released

Answer 54

− Thermoreceptors − Those in skin and in some mucous membranes are called peripheral thermoreceptors − Others are located in the hypothalamus are called central thermoreceptors − Peripheral receptors provide the hypothalamus with info about the external environment − Hypothalamus is the body's main temp-regulating centre

Answer 55

− Cold Receptors; a receptor stimulated by low temp | − Heat Receptors; a receptor stimulated by high temp

Answer 56

− Changes in skin can speed up or slow down the rate at which heat is lost from the body − Blood vessels carry hear to the skin from the core of the body − Heat can then be lost from the skin by conduction, convection, radiation and evaporation − Diameter of blood vessels to the skin controlled by autonomic nerves, can act to increase to decrease the flow of blood near the surface therefore increase or decrease the rate of heat loss − These adjustments keep core body temp constant − Body heat must be lost and skin blood vessels already at max dilation, sweating occurs − Sweating is an active secretion of fluid by sweat glands − Evaporation of swear form skin is a cooling process − Cooling of skin results in the cooling of the blood flowing through the skin

Answer 57

The body can respond by physiological changes and behavioral changes: − Vasoconstriction; a decrease in the diameter of blood vessels, increasing the flow of blood. The skin becomes cooler as there is less warm blood flowing through, helps maintain body temp in cold conditions − Stimulation of the adrenal medulla by sympathetic nerves. Results in the release of adrenaline and noradrenaline in the blood therefore increase in cellular metabolism which leads to increase in heat production. Helps maintain their rapid heat loss − Shivering can increase body heat production − Increase in production of thyroxine . Causes increase in metabolic rate resulting in body temp. Slower to have an effect − Behavioural response; put on a jumper

Answer 58

The following responses ensure that body temp does not rise: − Vasodilatation; an increase in the diameter of blood vessels, increasing the flow of blood. The skin becomes reddish in colour, surface temp rises and there is greater heat loss through radiation and convection − Sweating is needed for temps above approx. 28°C, to increase heat loss − Decrease in metabolic rate, means less heat is produced − Behavioural response; air conditioner or fan

Answer 59

Hypothalamus monitors the temp of blood and receives impulses from peripheral thermoreceptor

Answer 60

− Core body temp over 42°C dangerous, death usually above 45°C − Temp and relative humidity high, difficult to lose heat to radiation and evaporation − Heat stroke is the failure of a person's temp-regulating mechanisms when exposed to excessive heat − Heat exhaustion is the collapse of a person after exposure to heat, during which their body's heat-regulating mechanisms continue to function normally − Extreme cold can also cause death, core temp drops below 33°C, metabolic rate is so low heat production can't replace heat loss, body temp continues to fall, called hypothermia

Answer 61

− Body approx. 60% water (45% - 75%) − Males, average 65% − Females, average 55% − Water is contained in various body fluids − Fluid inside cells called the intracellular fluid or cytosol − Fluid outside cells is the extracellular fluid − Extracellular fluid included the blood plasma and the fluid between the cells, called intercellular fluid (interstitial fluid and tissue fluid) − Plasma separated form the intercellular fluid by thin walls of the capillaries, there is relatively free exchange of material between the 2

Answer 62

− Fluid gain must equal fluid loss − Most body fluid obtained from water − Small amount formed as a product of cellular resp − Fluids are lost from the body via the kidneys, through the skin, from the surface of the lungs and from alimentary canal − Typically, 2.5L lost each day

Answer 63

Removal of wastes of metabolism from the body. Many wastes are toxic, harmful if allowed to accumulate in the body fluids. Several organs in the body take part in excretion: − Lungs excrete CO2 − Sweat glands in the skin secrete water containing by-products of metabolism such as salts, urea and lactic acid − Alimentary canal passes out bile pigments that entered the small intestine with the bile. These pigments are the breakdown products of haemoglobin in RBC, they leave body with faeces − Kidneys are the principal excretory organs. they are responsible for maintaining a constant concentration of materials in the body fluids

Answer 64

− Approx. 60% of water lost form body each day is excreted by the kidneys as urine − only water loss from the kidneys can be regulated to achieve a constant concentration of dissolved substances in the body fluids − Not just excretory organs, they play a major role in regulating the composition of body fluids − Ureter; the tube that leaves each kidney and drains into the urinary bladder − Urethra; the tube that empties the bladder to the outside − Each kidney contains about 1.2 million nephrons − Nephron; the functional unit of the kidney, carries out the kidney's role in excretion and water regulation

Answer 65

1. If a decreased amount of water is in the blood, such as would result from increased loss of water through sweat, the water concentration of the blood plasma would decrease. This means the osmotic pressure of the blood is raised. 2. Osmoreceptors in the hypothalamus detect the increases osmotic pressure of the blood. 3. The hypothalamus stimulates the posterior lob to release ADH into the bloodstream. 4. ADH is carried all over the body by the blood but it affects target organs. 5. More water is then reabsorbed into the blood plasma form the tubules and ducts. 6. The reabsorption of water increases the water concentration in the plasma and so the osmotic pressure of the blood is decreased. 7. The response is decreased osmotic pressure of the blood. This has eliminated or reduced the originals stimulus that was increasing osmotic pressure of the plasma. negative feedback has occurred. − Aldosterone is another hormone that plays a part in the regulation of water output − Secreted by adrenal gland − Increased aldosterone secretion has the indirect effect of increasing blood pressure

Answer 66

The events that take place to bring about intake of water and restoration of the water balance: 1. As water is lost from the various body fluids, there is reduction in plasma volume and an increase in osmotic concentration of the extracellular fluid 2. Osmosis receptors in a thirst center in the hypothalamus detect the rising osmotic concentration of the blood. Other stimuli such as a dry mouth are also involved. 3. Stimulations of the thirst center makes the person feel thirsty. 4. The conscious feeling of thirst stimulates the person to drink. 5. The fluid consumed is absorbed into the plasma from the alimentary canal. 6. As the blood circulates through the body, it enables the intercellular fluid and intracellular fluid to return to the proper osmotic concentrations. 7. Drinking, the thirst center is no longer stimulated and the desire to take in water ceases. This is another negative feedback loop.

Answer 67

- Dehydration; excessive loss of water accompanying salts from the body, results when the body loses more fluid than it takes in. - Symptoms include; serve thirst, low blood pressure, dizziness and headaches - Water intoxication; a potential life threatening conduction caused by drinking too much water when the amount of salt (and other electrolytes) in the body is low; commonly caused by long bouts of intensive exercise during which electrolytes are not replenished and large amounts of water are consumed. - First sign is usually lightheadedness - Headaches, vomiting and collapsing may follow.

Answer 68

− Forms of glucose − Glucose is source of energy − Energy is released from glucose through cellular respiration C6H12O6 + O2 → CO2 + H2O + energy − Carbohydrates broken down into glucose during digestion − Absorbed through walls of small intestine − After meal, blood glucose concentration increase rapidly − Homeostatic mechanisms begin to decrease blood glucose concentration and maintain normal level − Excess must be stored, for future activity − Glycogen; made of long chains of glucose, stored in liver and muscle cells − Pancreas and adrenal glands secrete hormones to affect the level of glucose in blood − Glycogen stored, can turn to glucose and be added to blood

Answer 69

− Able to convert glucose into glycogen or vice versa to release into blood

Answer 70

− Glucose may be removed from blood by liver to provide energy for liver functioning − May be removed by liver/ or muscle and converted into glycogen for storage − May continue to circulate in blood, for cells to absorb for energy − Excess glucose (normal blood sugar and tissue glycogen) converted to fat − Glycogenesis; the process whereby glucose molecules are chemically combined in log chains to form glycogen molecules − Glycogenesis is stimulated by the pancreatic hormone insulin − Glycogen has to be converted back to glucose to be usable − Glycogenolysis; the process of converting glycogen back to glucose − Frequently occurs between meal and is stimulated by another by another pancreatic hormone, glucagon − Glycogen is short term energy supply − After that is used the body uses the energy reserves in stored fat

Answer 71

− Within pancreas are clusters of hormone - secreting cells called the Islet of Langerhans − Contains alpha cells, secrete glucagon and the beta cells, secrete insulin − Insulin cause decrease in blood sugar levels − It accelerate transport of glucose from the blood into the cells and also accelerates the conversion of glucose into glycogen − Glucogen from the alpha cells cause increase in blood sugar levels − Glycogenolysis is the conversion of glycogen to glucose, in the liver − Glucose is then released into the blood and blood sugar rises − Glucagon stimulates liver to produce new sugar molecules from fats and amino acid, process called Gluconeogenesis

Answer 72

− Outer part called the Cortex – stimulated by ATCH by anterior lobe − Inner part called Medulla − Secretion of glucocorticoids by the adrenal cortex - cortisol − Adrenaline and noradrenaline secreted by adrenal medulla − Cortisol regulates carbohydrates metabolism (making sure enough energy is provided to cells − Stimulate conversion of glycogen to glucose − increase rate that amino acids are removed form cells and transported to liver − Some amino acids are converted to glucose, if glycogen and fat levels are low (gluconeogenesis) − Adrenaline and noradrenaline stimulates breakdown of glycogen in liver and release of glucose into blood

Answer 73

Formation of glycogen from other carbs, especially glucose

Answer 74

Breakdown of glycogen to glucose

Answer 75

Conversion of fats or proteins into glucose

Answer 76

− Oxygen for respiration, CO2 waste product | − Lungs exchange gases

Answer 77

− Intercostal muscle and diaphragm: skeletal muscle these require nerve impulses to create contraction. − Diaphragm stimulated by the phrenic nerve and intercostal muscle stimulated by intercostal nerve − Origin of nerve in spinal cord (nerve) − If injury results in paralysis of muscle, this results in death − Control by respiratory center muscles in medulla oblongata − There are 2 regions; one that controls the expiration and one that controls the inspiration − To coordinate breathing, messages need to pass back and forth between the neurons of these 2 regions − Oxygen and carbon dioxide are carried in blood and concentrations affect breathing rate

Answer 78

− If concentration of oxygen falls below normal and other factors remain then the breathing rate increases − Concentration has to fall to very low levels before it has a major effect − Chemoreceptors that are very sensitive to changes in the oxygen concentration in the blood plasma are known as aortic and carotid bodies − A large decrease in oxygen concentration stimulates the chemoreceptor's and nerve impulses are transmitted, so breathing rate increases

Answer 79

− Major factor in regulation of breathing rate | − Any small increase in the concentration of carbon dioxide is enough to cause an increase in rate of breathing

Answer 80

− As the hydrogen ion concentration of the blood increase, pH decrease, causing an increase in the breathing rate − Decrease in pH stimulates chemorecpetors in the aortic and carotid bodies, which then transmit impulses to the respiratory centre, resulting in an increase in the breathing rate

Answer 81

− Humans are able to voluntary control their rate and depth of breathing , factors very important in speech − We can stop breathing for a limited time − Rapid , deep breathing can provide more oxygen than required and remove more carbon dioxide than necessary, this is called hyperventilation

Answer 82

− During exercise the contracting muscle cells require large amounts of oxygen and produce large amounts of carbon dioxide − In responding to this increased demand for gas exchange, the respiratory system increases both the rate of breathing and the depth of breathing

Answer 83

− Output of blood from the heart is therefore crucial to maintaining homeostasis of gases and body fluids − The heart rate is the number of times the heart beats per minutes, while the stroke volume is the volume of blood from the heart with each contraction − Cardiac output is a combination of the 2 and is the amount of blood leaving the heart every minute Cardiac output (mL/min) = heart rate (beats/min) X stroke volume (mL) − Blood pressure is the force with which the blood presses on the walls of the blood vessels

Answer 84

− The cardiac output - as cardiac output increases so does blood pressure − The diameter of blood vessels - constriction of blood vessels increase pressure and dilation decreases blood pressure

Answer 85

− The bundles of specialised cells controlling the hearts activity are called the sinoatrial node (SA node) and the atriocentricular node (AV node) − SA node is responsible for the rhythmical contractions

Answer 86

1. The SA node sends out nerve impulses that spread through the atria 2. The stimulus reaches the AV node. At about this time, contraction of the muscle of the atrium begins 3. Stimulation of the Av node causes it to send out its own impulses. These travel down the fibres in the septum between the ventricles 4. The impulses then spread through the muscles of the ventricles. Atrial contraction is now complete and ventricular contraction begins

Answer 87

− Person has abnormally high blood glucose level, a condition called hyperglycaemia − They do not produce enough insulin or their cells have an abnormal resistance to the effects of insulin − Insulin; main role is to stimulate cells to take in glucose from the blood, it also stimulates the conversion of glucose into glycogen

Answer 88

− Secretes thyroxine (T4) and tri-iodothyronine (T3) − Thyroxine affects nearly every tissue in the body by stimulating carbohydrate, protein and fat metabolism − Secretion of thyroxine is controlled by TSH, which the ant pit secretes but its release is controlled by the hypothalamus − Imbalance in thyroxine can be due to an imbalance in TSH

Answer 89

− Too much thyroxine, when thyroid gland produces too much − Cause; graves' disease − Symptoms; rapid heartbeat, weight loss, increased appetite, fatigue, sweating and anxiety − Can be treated by drugs that block the thyroid glands use of iodine or by surgery to remove all or part of the thyroid gland − Can also have a drink containing radioactive iodine

Answer 90

− Too little thyroxine, much more common − Symptoms; slow heart rate, weight gain, fatigue, intolerance to cold and swelling of the face − Causes; lack of iodine in diet it prevent the thyroid from producing enough hormones, another cause is an attack on the immune system (Hashimotos disease) or surgery of the thyroid

Answer 91

any condition in which normal functioning is impaired

Answer 92

− Emphysema; a lung disease in which the walls of the alveoli (air sacs) break down, resulting in abnormally large air spaces. this reduces the SA available for gas exchange, so the patient has difficulty taking in enough oxygen. the most common cause is smoking − Fever; is an elevation in body temp. It is not a disease but a symptom of infectious or other diseases. In the case of infectious disease, the higher body temp seem to help the immune system to overcome the infection , but it may affect many of the reactions occurring in the body, and thus disrupts homeostasis − Hypertension; or high blood pressure, occurs when homeostatic responses are unable to keep the blood pressure at the normal level. Factors that can contribute to hypertension include genetic factors, excessive salt intake, overweight or obesity, lack of exercise, high alcohol consumption and kidney disease

Answer 93

− A disease-causing organism; often referred to as a pathogenic organism − The most common pathogens that affect the human body are bacteria and viruses. Also fungi and animal parasites can be involved

Answer 94

− Majority harmless to humans − Many bacteria are essential to life, through their role in decomposition of organic material and the cycling of the elements − Huge numbers live on our skin, in our alimentary canal and other parts of the body − Bacteria all consists of a single cell (only seen with a microscope) − Cell shape used to classify bacteria

Answer 95

An infectious agent, too small to be seen with a light microscope, consisting of a protein sheath surrounding a core a nucleic acid; viruses are totally dependent on living cells for reproduction/ − All viruses were found to contain genetic material in the form of a molecule of either DNA or RNA (but never both) − The molecule of DNA or RNA is surrounded by a coat of protein − When viruses infect a living cell, its DNA or RNA induces the cell to manufacture more virus particles − New virus particles are then able to leave the host cell to infect others − Some viruses multiply in bacterial cells, causing death to bacterium, viruses known as bacteriophages

Answer 96

Communicable disease may be spread by the transmission of pathogenic organism from one person to another. This transfer can occur in a number of way

Answer 97

involves the spread of the pathogen by actual physical contact e.g. direct or indirect

Answer 98

when blood or other body fluids from an infected person comes into contact with the mucous membranes (such as mouth, nose, throat and genitals) or the bloodstream of an uninfected person (such as a needle or broken skin) then pathogens may enter to body of that person e.g. human immunodeficiency virus, hepatitis B and C are spread in this way

Answer 99

may occur when tiny droplets of moisture, harbouring pathogenic organisms are emitted when breathing, talking, sneezing or coughing e.g. measles, mumps, colds and influenza

Answer 100

food or drink contaminated with pathogens | e.g. Dysentery, typhoid fever and salmonella

Answer 101

when moisture is exhaled droplets evaporates

Answer 102

transfer of pathogens by other animals such as insects, ticks or mites e.g. malaria and dengue fever are spread by mosquitoes

Answer 103

− Many pathogens are prevented from entering the body or, if they do enter, they are dealt with before they cause symptoms of disease − Non-specific defences; work against all pathogens (1stline of defence) − Specific defences; are directed at a particular pathogen

Answer 104

``` skin mucous membrane hairs cilia acids lysozyme cerumen (ear wax) flushing action ```

Answer 105

effective barrier covering outside of body. Oily secretion called sebum is produced by oil glands in the skin, it contains substances that kill some pathogenic bacteria. sweat secreted onto the skin contains salts and fatty acids that prevent the growth of many micro-organisms

Answer 106

line body cavities that open to the exterior. Secreted mucous inhibits the entry of micro-organisms to organs

Answer 107

found in nose cavity and ears. In nose, hairs and a layer of mucous trap up to 90% of particles inhaled

Answer 108

tiny hair-like projections from cells that are capable of a beating motion. Nose cavity, trachea and other air passages contain cilia. It moves mucous that contains trapped particles and micro-organisms towards throat where they are swallowed or coughed up

Answer 109

stomach juices, kills many of the bacteria taken in with food or those contained in mucous swallowed. The vagina also has acid secretions and sweat is also slightly acidic

Answer 110

is an enzyme that kills bacteria. The eyes are protected by the flushing action of tears, containing this enzyme. Also found in saliva, sweat, secretions of nose and tissue fluid

Answer 111

protects outer ear against infection by some bacteria, it is slightly acidic and contain lysozyme

Answer 112

of body fluids helps to keep some areas relatively free of pathogens e.g. urethra, tears, sweat and saliva are involved in flushing and cleansing

Answer 113

A reflex is an automatic, involuntary response to stimulus. Protective reflexes help to protect the body from injury, such as blink reflex, or from infection, such as vomiting. Four reflexes help to protect against infection:

Answer 114

stimulus is irritation in the walls of nasal cavity

Answer 115

stimulus is irritation in the lower respiratory tract (the bronchi and bronchioles)

Answer 116

psychological stimuli, excessive stretching of the stomach and bacterial toxins can all induce vomiting

Answer 117

irritation of the small and large intestines by bacteria, viruses or protozoan can cause diarrhoea

Answer 118

phagocytes leucocytes macrophages

Answer 119

cells that are able to engulf micro-organisms and cell debris

Answer 120

are WBC. Several types that all play a part in phagocytosis. Able to leave blood capillaries and migrate through the tissue to places of infection or injury. Some secrete substances that destroy bacteria before engulfing them, others engulf live bacteria

Answer 121

are large phagocytic cells that develop from some leucocytes. Some wandering through the tissues destroying pathogens, others in a fixed place. They either engulf and digest the micro-organisms or release substances that destroy them

Answer 122

The response to damage to a tissue; involves swelling, heat, pain and redness in the affected area.

Answer 123

Reduce the spread of any pathogens, to destroy them and to prevent the entry of any additional pathogens − Remove damaged tissue and cell debris − Begin repair of the damaged tissue

Answer 124

1. Mast cells; are special cells that are present in most tissues. They release histamine, heparin and other substances into the tissue fluid, Stimulate by releasing chemicals 2. Histamine; increases blood flow through the area and causes walls of the blood capillaries to become more permeable so that fluid is filtered from the blood 3. Heparin; prevents clotting, so the release of heparin from the mast cells prevents clotting in the immediate area of the injury. Clot slows the spread of the pathogen into healthy tissues 4. The chemicals released by the mast cells attract phagocytes. Phagocytosis occurs 5. The abnormal conditions in the tissue stimulate pain receptors, and so the person feels pain in the inflamed area 6. The phagocytes, filled with bacteria, debris and dead cells, begin to die. The phagocytes and tissue fluid form a yellow liquid called pus 7. New cells are produced by mitosis and repair of damaged tissue takes place

Answer 125

− During the course of an infection, such as the common cold or influenza, individuals frequently experience an elevation of body temp, often called a fever − Change in body temp is due to a resetting of the body's thermostat (controlled by hypothalamus) to a higher level − When a person has a fever, the body temp is regulated in response to heat or cold, but always at a higher set level − Rapid onset, person feels cold, as a result vasoconstriction on the skin and shivering occurs , increases heat production − Fever breaks (called crisis), person feels hot and appears flushed, as skin vasodilatation and profuse sweating take place − High body temp believed to inhibit the growth of some bacteria and viruses − Heat speeds rate of chemical reactions, may help body cells to repair themselves quicker − Death; 44.5 - 45.5°C − Resetting of the body's thermostat is thought to be due to substances called pryogens, released by WBC during inflammatory response and they act directly on hypothalamus

Answer 126

A system of vessels that drain excess fluid from the tissues; consists of : − a network of lymph capillaries joined to larger lymph vessels − Lymph nodes, which are located along the length of some lymph vessels

Answer 127

is to collect some of the fluid that escapes from the blood capillaries and return it to the circulatory system. Also an important part of the body's internal defence against pathogenic organisms. − Lymph entering the lymph nodes contains cell debris, foreign particles and micro-organisms that have penetrated hat body's external defences, may be pathogenic − Lymph nodes occur at intervals along the lymphatic vessels − Each contains masses of lymphoid tissue, cells criss-crossed by a network of fibres − Larger particles (bacteria) are trapped in the fibres as lymph flows through the spaces in the nodes − Macrophages destroy these particles, via phagocytosis, where destroyed by enzymes, most killed this way within 10 - 30 minutes − When infections occur, formation of lymphocytes increases and lymph nodes become swollen and sore − Most lymphocytes are important in specific response to a particular pathogen

Answer 128

Lymphocyte is a type of WBC found in the lymph nodes and associated with the immune system. − Cells that are involved in both non-specific and specific defence − About 20-30% of WBC are lymphocytes − Most produced in bone marrow and also in lymphoid tissue − Roam throughout the body

Answer 129

Macrophages are a phagocytic cell derived from a monocyte (a type of WBC). They are involved in specific defence by alerting the immune system to the presence of foreign material

Answer 130

− Directed towards a particular pathogen − Part of our immune system − Immune system is composed of different types of cells that occur in most of the organs of the body − They protect against foreign organisms, a range of alien chemicals. As well as cancerous and other abnormal cells

Answer 131

− Homeostatic mechanism − Deals with invasion of micro-organisms or foreign substances − Humoral response or antibody-mediated immunity; production of special proteins called antibodies, which attack invading agents − Cell-mediated response; formation of special lymphocytes that destroy invading agents − Immune response involves lymphoid tissue − Lymphoid tissue; tissue containing many lymphocytes and macrophages, found mostly in lymph nodes but also in the bone marrow, tonsils, spleen and thymus − Lymphoid tissue composed of B-cells and T-cells (lymphocytes) − B-cells; provide antibody-mediated immunity − T-cells; provide cell-mediated immunity − B-cells are matured in bone marrow − T-cells are matured in thymus − Both are produced in bone marrow

Answer 132

− A substance capable of causing a specific immune response − Large molecules − May be proteins, carbohydrates, lipids or nucleic acid − Could be whole micro-organisms or part of bacterium − Toxins produced by bacteria are also antigens − Self antigens; any large molecule produced in a person's own body, doesn't cause an immune response − Foreign compounds that do trigger an immune response are non-self antigens − Immune system only attacks non-self antigens

Answer 133

− A specialised protein that is produced in response to a non-self antigen − Antibodies belong to a group of proteins known as immunoglobulins − The antibody produced is response to an antigen can combine with that antigen to form an antigen-antibody complex − Antigen molecules have specific active sites and at these sites the antibody can overcome with the antigen

Answer 134

− Production and release of antibodies into the blood and lymph − Provides resistance to viruses, bacteria and bacterial toxins before they enter the body's cells − Lymphoid tissue contains B-cells − Respond to specific antigen − When an antigen activates B-cells, they enlarge and divide into a group of cells called a clone − Most of the clone become plasma cells − Plasma cells create antibodies and circulate into the blood, lymph and extracellular fluid and attack foreign material − B-cells that didn't form plasma cells remain as memory cells − They spread to all body tissues to allow response to occur rapidly − First exposure to antigen immune reaction called primary response − Response is fairly slow − Second exposure to the same antigen, the response is much faster because of the activity of the memory cells this is called secondary response

Answer 135

− Combine with foreign enzymes or bacterial toxins, or inactivate them by inhibiting reaction with other cells or compounds − Bind to the surface of viruses and prevent the viruses from entering cells − Coat bacteria so that the bacteria are more easily consumed by phagocytes − Cause particles such as bacteria, viruses or foreign blood cells to clump together - a process known as agglutination − Dissolve organisms − React with soluble substances to make the insoluble and this more easily consumed by phagocytes

Answer 136

− Provides resistance to the intracellular phase of bacterial and viral infections − Also important in providing resistance to fungi and parasites, and involved in the rejection to transplants of foreign tissue and fighting cancer cells − The T-lymphocytes are responsible for cellular immunity

Answer 137

migrate to the site of infection and deal with the invading antigen. They attach to the invading cells and secrete a substance that will destroy the antigen, and then go in search of more antigens

Answer 138

play an important role in both humoral and cellular immunity. They secrete a number of substance that: o Cause lymphocytes at the infection site to become sensitised, this intensifying the response o Attract macrophages to the place of infection so that the macrophages can destroy to antigens by phagocytosis o Intensify the phagocytic activity of macrophages

Answer 139

act when the immune activity becomes excessive or the infection has been dealt with successfully. They release substances that inhibit T and B cells activity, slowing down the immune response

Answer 140

− Immunity is resistance to infection by invading micro-organisms − The ability to respond rapidly may be natural or artificial − Natural immunity occurs without any human intervention − Artificial immunity results from giving people an antibody or antigen − Natural and artificial immunity can be passive or active − Passive immunity; immunity produced by the introduction of antibodies form another person − Active immunity; immunity produced by the body manufacturing antibodies against a foreign antigen

Answer 141

− Immunisation means programming the immune system so that the body can respond rapidly to injecting micro-organisms − Can occur naturally or artificially − Diphtheria, chickenpox, measles and mumps, people immune to these diseases for the rest of their lives − Vaccination is the artificial introduction of antigens of pathogenic organisms so that the ability to produce the appropriate antibodies is acquired without the person having to suffer the disease − A vaccine is the antigen preparation used in artificial immunisation

Answer 142

− Most common delivery via a syringe − Nasal spray − Sweet syrup − Patches

Answer 143

− Allergic reaction − Impossible to completely isolate one viruses from others in animal tissue − Use of preservatives, some people believe they affect the nervous system and other health issues

Answer 144

``` − How it was manufactured − How it was tested e.g. on animals, some have to be tested on human cells, where do they come from? − Risks associated − Has to be voluntary ```

Answer 145

− Are drugs that are used to fight infections and micro-organisms, particularly bacteria − Before antibiotics a person could die from an infected cut or scratch – today minor problem − First antibiotic was penicillin; works by preventing synthesis of walls of bacteria cells, inhibiting production of bacteria − Effectiveness of penicillin reduced – bacteria developed resistance − Actinomycetes; bacteria that produce branching filaments rather like threads of moulds, they interfere with protein synthesis in that cells of the target bacteria − Most antibiotics are developed from actinomycetes − Cephalosporin; derived from fungus, interferes with synthesis of cell wall, less likely to result in allergic reaction − Antibiotics only effective for certain types of bacteria and cannot treat viral infections − 2 types of antibiotics; Bactericidal antibiotics and bacteriostatic − Bactericidal; kill bacteria by changing structure of cell wall or membrane or disrupting action of essential enzymes − Bacteriostatic; stop bacteria from reproducing usually by disrupting protein synthesis − Broad-spectrum; effect a wide range of bacteria − Narrow-spectrum; effective against specific types − Multiple drug resistance; resistance to antibiotics used to be resolved by changing to a different antibiotic, today bacteria is resistant to most or all types

Answer 146

− Specifically for treating viral infections − Viruses enter a host cell and its DNA or RNA induces the cells to produce new virus particles which can leave the cell and infect new host cells, they duplicate and hard to find drugs that will treat this − Any drug that interferes with virus replication likely to be toxic to host cells

Answer 147

a group of individuals that share many characteristic and are able to interbreed under natural conditions to produce fertile offspring

Answer 148

are alternative forms of gene − The pairs of alleles that each person inherits from their parents control and determine the characteristics of the individual

Answer 149

− Population; a group of organisms of the same species living together in a particular place at a particular time − Gene pool; the sum of all the alleles in a given population − Allele frequencies: studying a population, geneticists are interested in how often each allele of a gene occurs in the gene pool for that population − Population’s that differ in the characteristics they possess are likely to have different frequencies of the various alleles of a gene in their respective gene pools E.g. Scandinavians commonly have blue eyes whereas black Africans have brown eyes ∴ frequency of the allele for blue eyes would be much higher in the Scandinavian gene pool than in the African gene pool − Over time, frequency of particular alleles may change in a gene pool − A mutation that alter the expression of a gene − Changes in environment − Changes to the frequency of alleles in a gene pool allow population’s to be compared at different times or different locations

Answer 150

A change in a gene or chromosome leading to new characteristics in an organism. − Not all mutations are harmful, many are − Mutant; an organism with a characteristic resulting from a mutation − Gene mutations; changes in a single gene so that the traits normally produced by that gene are changed or destroyed − Chromosomal mutations: all or part of a chromosome is affected − Gene mutations occur during the replication of the DNA molecule before cell division − DNA is a complex molecule and any subtle alteration change in the usual characteristics of the species

Answer 151

An environmental agent that increase the rate of mutation (mutagenic agent). E.g. mustard gas, sulphur dioxide and some antibiotics, also ionising radiation

Answer 152

− Mutations can occur in the body cells or in the reproductive cells − Somatic mutation; a change occurring in a gene in a body cell (not in a gamete) − Each time mutant cell body divides, mutation is passed on to daughter cells − Once individual dies, mutation is lost − Somatic mutations are involved in many cancerous growths − Germinal or germline mutations; a change in the hereditary material in the egged and sperm that becomes incorporated into the DNA of every cell in the body of the offspring − Diseases such as phenylketonuria (PKU) can arise through a mutation during the formation of gametes and can be passed on to an offspring

Answer 153

− Point mutation; a change in just one base, could alter o protein, have no affect at all, or prevent the protein from being produced − DNA of a particular gene is altered, the protein for which it codes may be missing or abnormal, one missing can have an enormous effect on the entire body E.g. Albinism, marked by an absence of pigment from the hair, skin and eyes. E.g. Duchenne, a form of muscular dystrophy E.g. Cystic fibrosis, another genetically determined disease caused by a mutation, occurs on chromosome number 7

Answer 154

− Most gene mutations produce a recessive allele because they prevent the gene from producing a protein that will be able to function in the body − If the person reproduced with a partner who had the same recessive mutation, the recessive condition could appear in their offspring E.g. Cystic fibrosis − Some recessive mutations are lethal if they are not masked by a dominant normal allele − Lethal recessive; recessive alleles that. Inherited in the homozygous condition, result in the death of the embryo, foetus or child E.g. Tay-Sachs disease (TSD) is a disorder of lipid metabolism that is inherited in an autosomal recessive pattern, it is lethal recessive − Lethal recessive could cause changes in the composition of gene pool − People who inherit 2 such alleles would die before their alleles could be passed on to the next generation ∴ the proportion of lethal alleles in the gene pool would gradually be reduced

Answer 155

Chromosomal mutations involve all or part of a chromosome and ∴ affect not just one but a number of genes. Types of chromosomal mutations are: − Deletion; part of a chromosome is lost − Duplication; a section of a chromosome occurs twice. May happed if part of a chromatid breaks off and joins onto the wrong chromatid − Inversion; breaks occur in a chromosome and the broken piece joins back in, but the wrong way around (may disrupt the pairing of homologous during meiosis) − Translocation; part of a chromosome breaks off and is re-joined to the wrong chromosome − Non-disjunction; during meiosis. A chromosome pair does not spate and so 1 daughter cell has an extra chromosome and 1 daughter cell has 1 less than the normal number. (sometimes referred to as aneuploidy; a change in the chromosome number)

Answer 156

− Chromosomal mutation that occurs relatively frequently (older mothers) − Child has 3 of chromosome 21 instead of 2 − Result of non-disjunction; failure of 1 or more chromatids to separate in the secong division of meiosis − Partial trisomy; part of an extra copy of chromosome 21 is attached to 1 of the other chromosomes

Answer 157

− A genetic disorder resulting from an extra copy of chromosome 13 − Causes mental retardation, small head, an extra finger on each hand and malformations of the ears and eyes − Occurs in 1 out of every 500 live births − 80% die within a month

Answer 158

− Trisomy can also occur with the sex chromosomes − Males; non-disjunction may occur during either 1st or 2nd meiotic divisions, individuals gain and extra X or Y chromosome − Trisomy XXY are normal as boys but develop Klinefelter’s syndrome as adults − Small testes; don't produce sperm − Large breasts − Sparse hair − Monosomy; where an individual has only one copy of a chromosome instead of 2 − Partial monosomy; where part of a pair of chromosomes is missing

Answer 159

− A rare genetic disorder caused by a missing part of chromosome 5 − Infant cry sounds like meowing cat due to problems with larynx and NS

Answer 160

− A genetic disorder resulting from inheritance of 1 X chromosome and no other sex chromosome − Females, short in stature − Lack of secondary sexual characteristics and infertile

Answer 161

the use of biological processes to produce useful products

Answer 162

− Genome; the complete set of genetic material in a cell; an organisms complete set of DNA − Complete set of nucleotides make up approx. 21,000 genes − Approx. 400 genetic disorders are known

Answer 163

− Deoxyribonucleic acid, found in cells of all organisms (nucleus, mitochondria and cytosol) − All DNA consists of 2 strands of alternating sugars (deoxyribose) and phosphates with pairs of nitrogen bases forming cross-links between the sugar molecules in the 2 strands − Double helix − 4 nitrogen bases; adenine (A), thymine (T), cytosine (C), guanine (G) − A - T and G - C

Answer 164

− Nucleotide; the basic structural unit of a nucleic acid, consisting of a simple sugar (5 - carbon), a phosphate group and a nitrogen base − DNA sequencing; the determination of the precise order of nucleotides in a sample of DNA − Each new nucleotide is bonded to the hydroxyl group (OH) of the previous nucleotide − Sanger' s method: − Synthetic nucleotides that lack OH group are added to the growing strand − Synthetic nucleotides stops the elongation of the sequence because ther is no OH group for the next nucleotide to attach to − This technique then allows the strands to be compared − Comparing DNA sequences, changed alleles can be identified − Point mutations; small insertions or deletions, identifies by DNA sequencing − Diseases such as sickle-cell anaemia, cystic fibrosis and some forms of cancer can be determined by DNA sequencing − Used for maternity and paternity tests

Answer 165

− Electrophoresis; a process in which charged molecules in solution are made to migrate and separate by passing an electric current through the solution − DNA which is negatively charged moves through the gel toward positive electrode − Smaller DNA pieces move faster than larger ones, resulting in a pattern of bands (similar to barcodes) − DNA profile/fingerprint; a technique that uses the banding patterns of DNA fragments as a means of identification, a DNA fingerprint is unique to a particular individual − Useful in identifying hereditary diseases E.g. Cystic fibrosis, Huntington’s disease − Can be used to determine the risk of having an affected child

Answer 166

A technique used in molecular biology for producing multiple copies of DNA from a sample; used in DNA fingerprinting and identifying diseases. − Segments of DNA are artificially multiplied through a series of repeated cycles of duplication using an enzyme called DNA polymerase − Primer; a strand of DNA or RNA that serves as a starting point for DNA replication − Initiate duplication, primer is required, primer is complementary to the targeted sequence of DNA − Each time the molecules of DNA are replicated, doubles the resulting amount of molecules − Compounding amplification of the original molecule has resulted in process being called a chain reaction − PCR is used to significantly shorten the time it takes to detect hereditary diseases in a particular genome − Gene of interest can be amplified by PCR, the sequenced to detect mutation in question, such as sickle-cell anaemia, phenylketonuria (PKU) or cystic fibrosis − PCR can also detect viral diseases − Forensic science, PCR has been most valuable

Answer 167

The procedures used to produce recombinant DNA; involve introducing DNA into a cell from a different type or organisms or DNA that has been modified in some way. − Used to take genes from 1 organism and place them into the chromosomes of another − Huge potential for replacing faulty genes with healthy ones − Benefits patients with cystic fibrosis, rheumatoid arthritis and certain cancers − It is another way of identifying mutations − Transgenic organisms; on organism that has had DNA from another species introduced into it artificially − Can be passed on from one generation to the next − Bacteriophages; a virus that infects bacteria − Certain enzymes in bacteria are able to restrict the duplication of infecting viruses by cutting up the viral DNA − DNA is cut at recognition site; a specific sequence of nucleotides at which an enzyme cuts a strand of DNA − Enzyme that cuts DNA is called restriction enzyme − Some of the restriction enzymes produce a straight cut at the sequence, while others produce a staggered cut − Straight cut; a cut produced when a restriction enzyme makes a clean break across the 2 strands of DNA so that the ends terminate in a base pair; called blunt ends − Staggered cut; a cut produced when a restriction enzyme creates fragments of DNA with unpaired nucleotides that overhang at the break in the strands; called sticky ends − Sticky ends very useful in recombinant DNA technology, a single-stranded overhand from one fragment can be paired with any other fragment of DNA that has a corresponding sequence, including one from another organism − DNA ligase; an enzyme capable of combining 2 small components of single-stranded DNA into a single structure − Ligation; the process of joining short strands of DNA during replication − Only in the presence of ligase that single-stranded breaks in phage DNA could be repaired − Ligase is able to form a bond between a particular end of the last nucleotide on one DNA fragment with a complementary end of the last nucleotide on an adjacent fragment

Answer 168

1. Isolate the gene of interest by cutting it out using a restriction enzyme 2. Gene is inserted into a vector; bacterial plasma, viral phage or other such agents used to transfer genetic material from one cell to another. The gene is cloned. 3. Isolate a plasmid from a bacterial cell and cut it out with the same type of restriction enzyme 4. Splice the human DNA into the plasmid using DNA ligase enzymes to join the sticky ends. Joint between human and bacterial DNA made by ligase enzymes 5. Treat the bacterium so it takes up the recombinant plasmid once this is successful, the bacterium will multiply so that either the human gene or the product of the gene can be used

Answer 169

− People with type 1 diabetes have elevated blood sugar levels due to impaired insulin production by the pancreas − Insulin regulates the use and storage of glucose − 1921, patients treated with insulin derived from the pancreas of pigs and cattle − 1982, insulin produced by genetically engineered bacteria was approved − Recombinant DNA techniques now produces the insulin and as a result there are no side effects like some people suffered from the insulin from cattle and pigs

Answer 170

− This technology has resulted in the production of growth hormone for dairy cattle − Administration of the hormone has increased milk production, drinking milk does not pose a risk to human health

Answer 171

− Haemophilia A; an inherited disorder in which a blood-clotting protein known as factor VIII is missing or in poor supply − People with condition are unable to form blood clots ∴ at risk of life-threatening bleeding from injuries − Treatment, injections of factor VIII concentrates, made from human plasma − 2 viral diseases that caused the deaths of many haemophilia’s all over the world were Human Immunodeficiency Virus (HIV) and hepatitis C

Answer 172

− Development of recombinant DNA vaccines does have disadvantages − Very expensive − `if a conventional vaccine is known to be safe, there is little incentive to develop a new one using genetic engineering

Answer 173

− A hereditary disease is caused by defective genetic information being transmitted from parents to their children − Genes contain coded instructions that direct the development of all our inherited characteristics − A particular gene may suddenly change from its original structure and produce a totally different characteristic; a mutation − Mutations involve a change in genetic material, can be passed on to future generations

Answer 174

The treatment of disease by replacing, manipulating or supplementing non-functional genes in cell and tissues.

Answer 175

A disorder controlled by a recessive allele carried on an autosome that is incurable but can be detected during foetal development; mucus – secreting glands, particularly in the lungs and pancreas, resulting in, among other things, chest infections. − Logical choice for treatment using gene therapy − Single-gene disorder, and the most servely affected organ, the lung, is relatively easy to access to provide treatment

Answer 176

− Single-gene disorder − Believed that gene therapy could be used to slow down or prevent its development − Mutation of chromosome 4, called IT15 − Symptoms appear before age of 40 − Nerve cells in the brain being damaged, causing physical, mental and emotional changes − Affected person also suffer from progressive dementia, the loss of ability to think clearly

Answer 177

− Cell replacement therapy; the replacement of damaged cells with healthy ones − Cell replacement therapy of the NS has generated the most interest, due to widespread occurrence of neurodegenerative disorders such as Parkinson’s and Alzheimer’s diseases − Stem cells are increasingly being used for tissue engineering − Tissue engineering; the rebuilding of damaged tissue by the use of biology, medicine and engineering − Eliminates the need for tissue or organ transplants, or artificial implants − Tissue engineering requires an abundant supply of disease – free cells of specific types − These cells then need to be induced to grow on a scaffold of natural or synthetic material to produce a 3D tissue − Scaffolds serve as a template for tissue growth − Frequently need to be biodegradable so they can be absorbed by the surrounding tissues without having to be removed surgically − While new cells are manufacturing their own natural matrix structure around themselves, the scaffold is providing a support structure that will eventually breakdown, leaving newly formed tissue − Once scaffold has been devised, suitable stem cells need to be cultured − Cells are seeded onto scaffold, enables further cell growth − Cell-covered scaffold is then implanted into the patient at the site where new tissue is required − New cells continue to grow and divide, material making up the scaffold begins to degrade or in some cases, be absorbed

Answer 178

− Random assortment of chromosomes during meiosis results in gametes that have a huge number of possible combinations of the chromosomes that originally came from the male parent and the female parent − Crossing over of chromatids during meiosis may result in pieces of chromatid being broken off and attaching to a different chromatid. This results in a changed sequence, or recombination of the alleles along the resulting chromosome − Non-disjunction is where one or more members of a chromosome pair fall to separate during meiosis. This results in gametes that have more or less than the correct number of chromosomes. If such gametes are involved in fertilisation, the resulting embryo will have the incorrect number of chromosomes − Random fertilisation means that, b/c each person will produce a huge number of different sperm or eggs with respect to the alleles each contains, and b/c any sperm can fertilise any egg, there is an infinite number of possible combination of alleles in the offspring − Mutations are permanent changes in the DNA of a chromosome and may result in totally new characteristics in an individual. If the mutation occurs in a gamete, it can be passed on from generation to generation − With respect to evolution, or gradual change of a species’ characteristics, mutations are the most important source of variation in individuals − Mutations introduce new and different alleles into the gene pool − If the new allele helps the individual to survive, the alleles composition of the gene pool may change

Answer 179

The process by which a species becomes better adapted to its environment; those individuals with favourable characteristics on subsequent generations. − Natural selection is a major cause of changes to allele frequencies in a gene pool

Answer 180

The occurrence of characteristics on a population as a result of chance rather than natural selection; occurs in small populations; also called Sewall Wright Effect. − Natural selection is not random − Alleles are not passed on randomly to the next generation − The alleles passed on tend to be the ones that enhance survival and reproduction of the individual and ∴ of the species − 2 populations could be closely related, but due to genetic drift in one or both populations, their gene pools could be quite different

Answer 181

A type of genetic drift that occurs when a new population is formed by a small number of individuals; the small size of the sample can cause marked deviations in allele frequencies from the original population. − This effect occurs when a small group moves away from its homeland to a totally new area and establishes a community, which later expands − This new community, ∴ generally shows features that are not typical of the original homeland population

Answer 182

− Changes in allele frequencies in a gene pool can also be due to migration − Migration described as gene flow from one population to another − Gene flow; the transfer of alleles from one population to another through migration − Immigrants to a certain country bring alleles that are not already in the population, the frequencies for the alleles of that gene will be altered − Spread of diseases e.g. chickenpox, smallpox, influenza and measles

Answer 183

− No 2 environments are exactly the same, the environmental pressures on 1 population will be different from the pressures on the other − Over time the allele frequencies of each gene pool will change, depending on which characteristics are favoured for survival − Isolation results in the development of separate gene pools − Geographical barriers; a feature of the landscape that prevent populations form interbreeding; included oceans, mountain ranges, large lake systems, deserts and expansive ice sheets − Sociocultural barriers; barriers to interbreeding that are due to social and cultural factors − Economic status, educational background and social position are barriers to interbreeding

Answer 184

− Result in changes to allele frequencies in a gene pool − An allele causing an inherited , fatal disease would be expected to be gradually eliminated from a population b/c people with the allele would die and not pass it on to the next generation

Answer 185

− Tay-Sachs disease (TSD) is a hereditary disorder of lipid metabolism that occurs most frequently in individuals od Jewish descent from Eastern Europe − Caused be a missing enzyme that results in the accumulation of a fatty substance in the NS − Death usually occurs by the age of 4-5 − Frequency worldwide is very low; approx., 1 in every 500,000 births − Scientists have speculated on what could be responsible for such high frequency of the allele in this population − Genetic drift; Jewish populations tend to be small and isolated, factors that increase the chances of genetic drift − Resistance to TB; individuals with 2 normal alleles would be more susceptible to TB, and would possibly die, while individuals with 2 Tay-Sachs would dies early in life. Heterozygotes, would have a survival advantage and more likely to reproduce and pass their alleles on to the next generation − It has been suggested that the mutation may have entered the Cajun population when a Jewish family assimilated into Cajun society; another example of how migration can change the frequency of alleles in a population

Answer 186

− Mainly occurs in black Africans or in people of black African ancestry − Occurs when a person inherits the allele from both parents − Sickle-shaped cells do not carry as much oxygen as normal RBD and they stick together and block small blood vessels − Individuals with only one allele; suffer from Sickle-Cell trait, provides a degree of immunity to malaria

Answer 187

− Until 1800’s it was widely believed that god had individually created each species; special creation − Evolution; is a gradual change in the characteristics of a species − The theory of evolution through natural selection was put forward independently by Charles Darwin and Alfred Russel Wallace in 1858 − Darwin was a keen amateur naturalist and as a young man he joined a surveying expedition a as it’s biologist − Observations led Darwin to question the commonly held belief that living species had always been exactly the same as they than appeared − Carolus Linnaeus (1707-78) established the basis of our present system of classification and the binomial systems − Binomial system; the system of naming organisms using the generic (genus) and specific (species) names to describe a species

Answer 188

1. Variation: all members of a species vary. These variations were passed on from 1 generation to another 2. Birth rate: all living organisms reproduce at a rate greater than that at which resources increase. This would normally result in overcrowding 3. Nature’s balance: although the birth rate or organisms was very high, each species’ numbers tended to remain at a relatively constant rate

Answer 189

1. There is variation of characteristics within a species 2. More offspring of a species are produced than can possibly survive to maturity 3. B/c of excessive birth rate and limited resources, there is a struggle for existence – competition for survival 4. Individuals with characteristics best suited to the environment have more chance of survival and reproducing – survival of the fittest 5. Favourable characteristics (those with survival value) are passed on to the next generation 6. In the gene pool, the proportion of alleles that produce favourable characteristics gradually increases

Answer 190

− Individuals with long bodies and short limbs have a smaller SA in relation to body volume than those with short bodies and long limbs − Such individuals lose less heat in very cold environments and ∴ have a survival advantage − They pass on alleles and survival advantage to their offspring − Fewer short bodied and long limbed would survive and less alleles passed on to their offspring − Overtime, the frequency alleles controlling body stature in population would have changed − Evolution or genetic change has taken place

Answer 191

− Reproductive isolation may lead to the development of separate gene pools − No 2 environments are exactly the same − Different alleles favoured in one environment more than others − Allele frequencies of each gene pool will change, depending on which characteristics are favoured for survival − Speciation; the process of new species developing

Answer 192

A population exists on an islands | − A range of variations exist within the population, which shares a common gene pool

Answer 193

The species is divided into 2 populations − A barrier has formed, dividing the population into 2. No interbreeding occurs between the 2 populations. Each population has a spate gene pool.

Answer 194

2 subspecies begin to form − Different selection pressures act on each of the 2 populations over a number of generations. This brings about a change in the gene frequencies of each gene pool. Such changes lead to evolution of separates subspecies.

Answer 195

Two species now exist − Over a long period of time the changes in the gene frequencies may be great enough to prevent the production of fertile offspring by interbreeding between the 2 populations from ever occurring again. When this happens, 2 species exist.

Answer 196

− All species or organisms have DNA, the sequence of bases in the DNA varies − New genes are gained by mutation; others are lost by natural selection, genetic drift or some other process − Despite common ancestor , the code in the DNA is different for different species − When speciation occurs, the new species would have very similar DNA − Humans have 23 pairs of chromosomes while chimpanzees have 24 pairs. Scientists believe that this can be explained by 2 small chromosomes found in chimpanzees having fused to form one of the human chromosomes at some time in the past − Chromosomes also contain some non-coding sequences of bases in the DNA. Referred to as ‘junk DNA’ as they have no apparent function and appear to serve no purpose − Good examples of stretches of apparently non-functional DNA are endogenous retroviruses (ERV’s) − ERV; a retrovirus that has become part of an organisms genome and exists in every cell of the body − Retroviruses store their genetic info as RNA − Upon entering a cell, retrovirus copies its RNA genome into DNA (reverse) transcription) − DNA then inserted into one of the host cell’s chromosomes − Retrovirus only becomes endogenous if it inserts into a cell whose chromosome will be inherited by the next generation (ovum or sperm cell) − Offspring of the infected individual will then have a copy − ERV’s make up 8% of the human genome

Answer 197

− Mitochondria; structures in the cytoplasm of a cell in which the aerobic stage of respiration occurs − Mitochondrial DNA; DNA found in the mitochondria of the cells rather than in the nucleus (mtDNA) − mtDNA is in the form of small circular molecules − mtDNA has 37 genes; 24 code for making tRNA and 13 for making enzymes necessary for the reactions of cellular resp. − Some rare diseases may be caused by mutations in mtDNA − Most cells contain 500-1000 copies of mtDNA − In humans the mtDNA genome consists of about 16,500 base pairs

Answer 198

− After a sperm has penetrated the egg at fertilisation, the mitochondria in the sperm are rapidly destroyed − Our mtDNA only comes from the egg − Nuclear DNA from both parents − mtDNA higher rate of mutation

Answer 199

− Protein consists of long chain a.a − By comparing the type and sequence of a.a in similar proteins from different species, the degree of similarity can be established − Ubiquitous proteins; one of a group of proteins that appears to be in all species from bacteria to humans; the small protein called ubiquitin was so-named b/c it is present in all types of cells − Cytochrome C; an iron-containing protein that can alternate btw a reduced form of an oxidised form; important the electron transport system in cellular resp. (example of ubiquitous protein)

Answer 200

The use of computers to describe the molecular components of living things. − Annotation; identification of genes in a DNA sequence − This process needs to be computerised as most genomes are far too large to annotate by hand

Answer 201

Comparison of genome sequences of different species

Answer 202

Involves comparing the structural features of related animals to ascertain the degree of similarity btw them. − Embryology – comparing the very early stages of the development of organism − Homologous organs – organs that are similar in structure but are used in different ways − Vestigial organs – organs that may once have been important but have lost pr changed their function

Answer 203

− Forelimb bones are described as homologous organs b/c they possess a similar structure

Answer 204

− Structures o reduced size that appear to have no function − Humans may have as many as 90 − Nictitating membrane; a transparent fold of skin (third eyelid) that protects the eyes of birds and reptiles; in humans it occurs as a vestigial organ in the corner of the eye − Wisdom teeth, pyramidalis muscles (lies above the pubic bone), coccyx (tail bone), appendix and nipples (males)

Answer 205

− Isolated land areas and island groups have frequently evolved their own distinctive plant and animal populations − Darwin (in South America) encountered what has become one of the classic pieces of evidence of evolution − Finches on the mainland and Galapagos Island, they were different − Their beaks have changes on the island due to diet − Eventually they evolved into 13 different species

Answer 206

− Fossil; evidence of, or remains of, an organism that lived long ago − Doesn’t have to be part of an organism − Any preserved trace left by an organism e.g. footprints, burrows, faeces or impressions of all or part of an animal or plant as well as bones, shells or teeth

Answer 207

− Normally, dead organisms are decayed by micro-organisms and no trace of their existence is left − Parts of organisms may be fossilised when buried by drifting sand, mud deposited by rivers, volcanic ash − If buried rapidly, decomposition may be slowed or prevented − Soil nature important − If wet acid soil, minerals in bone dissolved – no fossilisation occurs − Soil which contains no O2 (e.g. peat) compete preservation of soft tissues and bones may occur − Alkaline soil best, minerals in bones not dissolved and new minerals (often lime or iron oxide) are deposited in pores of n-bone replacing organic matter that makes up 35% weight of bone − Bone becomes petrified (turn to rock) − Details and structure preserved − Fossils of human ancestors are often found at edges of ancient lakes and river systems, in caves or in volcanically active areas

Answer 208

− Chance at the surface, uncovered by erosion − Usually result of slow and pain-staking excavation of likely sites − Surface discoveries are indications of places where excavations may prove fruitful − Area to be investigated first surveyed are marked out in sections − Small hand tools used to remove soil gently, prevent damage to material − Soil removed usually sieved for small fragments − Fossils of human ancestors, artefacts often found − Artefacts; an object made or modified by humans e.g. stone tools, beads, carvings, charcoal from cooking fires and cave paintings − Photos taken at every stage − Each item carefully labelled and catalogued − In lab, fossil bones carefully scraped clean, broken parts pieced together, measurements made and plaster casts or latex moulds mat be made

Answer 209

− Dating; determining the age of excavated artefacts or fossils − Knowledge of age, crucial in finding sequence of changes resulted in present-day humans − Various methods, some provide: − Absolute dates – that is, the specimen in years − Relative dates – which tell us whether one sample is older or younger than another − The age or date of a fossil or artefact is usually given in years before the present time

Answer 210

− Potassium-argon dating: a method of calculating the age of a fossil or artefact using the known rate of decay of radioactive K, forming argon − Limited use fullness – not all rock types suitable for this method of dating and it can only date rocks older than 100,000 to 200,000 years − Radiocarbon dating; the calculation of the age of a fossil or artefact using the known rate of decay of radioactive carbon, forming nitrogen − By measuring the amount of radiation liberated by a sample, the ratio of carbon-14 to carbon-12 can be estimated, and from this the age of the sample can be calculated − Normal method of radiocarbon dating requires at least 3g of organic material so that the rate of radioactive decay of carbon-14 in the sample can be measured − Accelerator mass spectrometry (AMS) radioactive dating; a technique used to give radiocarbon dates for very small samples of material, as small as 100 micrograms − Involves breaking sample up into its constituent atoms − Can be used to date cave paintings − Cannot be used to date back more than about 60,000 years − Material to be dated must contain organic compounds – must contain carbon − Corrections for the fluctuations in the carbon-14 content of the atmosphere − Dendrochronology; a method of determining the age of wood by counting the annual growth rings in the timber − Each ring represents a year’s growth and rings differ in width according to how favourable the growing season was − Certain rings produced in years of exceptional weather conditions can be used as marker rings − Conditions necessary for the use of the method do not occur often and timber is rarely preserve for more than a few thousand years

Answer 211

− Not possible for actual age, can determine whether it is older or younger than another sample

Answer 212

The study of the sequence of rock layers as a means of relative dating. There are 2 ways in which stratigraphy can be useful in dating fossil material: − Superposition; which assumes that in layers of sedimentary rock the layers at the top are younger than those beneath them − Distortions of Earth’s crust occur and a sequence of rock layers may be turned upside down − Fossils or artefacts may be buried by animals or humans, in this case specimen may be younger than some of the layers above it − Correlation of rock strata; which involves matching layers of rock from different areas − Matching of strata can be done by examining the rock itself and also by studying the fossil it contains − Index fossils; fossils or organisms that were on Earth for only a short period of time and are therefore useful in the relative dating of rock strata

Answer 213

A method of determining the relative age of a fossil or artefact by measuring the amount of fluoride absorbed from the soil. − Based on the fact that when a bone is left in soil, fluoride ions, which are present in the water in the soil, replace some of the ions in the bone itself − The older the fossil the more fluoride it contains − Absolute ages not possible, concentration of fluoride in ground water varies from place to place

Answer 214

A diagram showing evolutionary relationships btw related organism; also called a dendrogram. − The ancestral organism forms the base of the tree and those organisms that have arisen from it are placed on the ends of ‘branches − Relationships btw various organisms shown by the distance btw them on the tree − Often used to simplify more complex relationships − Useful for representing relationships as well as organising knowledge of genetic diversity and structural classifications

Answer 215

Earths geological history has been divided up into geological time scale. The time scale consists of eras, which are subdivided into periods and further subdivided into epochs

Answer 216

− A quick burial of the material − The presence of hard body parts − An absence of decay organisms − A long period of stability – the organism needs to be left undisturbed − Gaps in fossil record also due to a small population of fossils have been discovered − Some buried too deep or in inaccessible places, some destroyed by human activity (i.e. agriculture and industry)

Answer 217

a member of an order of mammals that includes the lemurs, lorises, tarsiers, monkeys, apes and humans

Answer 218

was one of the first to consider that similarities in structure could form the basis of a systematic classification of all the known animals and plants

Answer 219

the system of naming organisms using the generic (genus) and specific (species) names to describe a species

Answer 220

``` In trying to develop an understanding of how human characteristics evolved, a number of sources of evidence can be used: − Comparative anatomy of the primates − Comparative biochemistry − Behavior of living primates − Fossils of primates ``` − All living things are classified into groups that form a hierarchy − 1st grouped into kingdoms, plants and animals − Each kingdom is the divided into groups known as phyla (singular phylum) − Phylum divided into classes − Classes divided into orders − As we go down the hierarchy, the organisms in each group have more and more characteristics in common

Answer 221

− Study of protein sequences and DNA has changes the way scientists view the relationships between various groups of primates − Were based solely on morphology (body form and structure) − Humans are classified in the same family as the great apes; chimpanzees, bonobos, gorillas and orangutans

Answer 222

− There is no one characteristics that can be used to separate the primates from all other mammals − Most of these features are a evolved in an arboreal − Arboreal; living in trees; for example as monkeys do − 2 of these, grasping fingers and toes and overlapping vision, when taken together are distinctive to the primates

Answer 223

− Pentadactyl; describes a limb with 5 fingers or toes − Highly mobile, can be related to the arboreal way of life − Prehensile; grasping, refers to the digits of a hand or a foot that can grasp an object − Essential for climbing by wrapping the digits around the branches of trees − Most highly developed digits – thumb and big toe. They are independent − Opposability; the ability to use the thumb to touch the tips of each of the other digits on the hand − Almost all species of primate show some opposability of the big toe − Humans don’t − Opposability was lost when the human foot became weight-bearing rather than a grasping appendage − Primates have nails instead of claws on their fingers and toes now − Claws limit grasping − Some of the evolutionary less advanced primate still possesses claws e.g. lemurs have a claw on their 2nd toe. Known as ‘toilet claw’, for scratching − Ends of the digits have sense receptors – digits can grip and manipulate objects − Friction ridge; one of the many small ridges on the skin of the hands and feet of some primates, fingerprints − Precision grip; the grasping of an object btw thumb tip and fingertip, as in holding a pencil when writing − Precision grip requires the presence of a truly opposable thumb – seen in old world monkeys, particularly ground-living baboons, mandrills and macaques

Answer 224

− Change in number and structure − Dental formula; a formula that gives the number of each type of tooth in ¼ of the jaw − Primitive mammals had a dental formula of 3:1:4:3 – 3 incisors, 1 canine, 4 premolars and 3 molars on each side of the jaw – total 44 teeth − Natural selection caused decrease − Most primates with large canines have a gap, or diastema, btw upper 2nd incisor and upper canine to accommodate large lower canine − Diastema; a gap in a row of teeth; usually refers to a gap next to the canine teeth in primates with canine teeth that are much longer than the other teeth − Large upper canine – 1st lower premolar crown slanted back and sharp edge. Upper canine fits tightly and sharpened by grinding that occurs − Lower molars – 5 cusps forming Y-5 pattern (evolved predominately fruit diet) − Upper molars – 4 cusp pattern

Answer 225

− With an arboreal life, primates gradually evolved an increasing emphasis on vision accompanied by a decreasing reliance on the sense of smell, o olfaction − Olfaction; sense of smell − Accompanied by an overall change in the shape of skull − General tendency for region around nose and snout - become smaller and flatter − Region that houses brain has become larger − Forward-facing eyes (due to flattening of face) allows for stereoscopic vision − Stereoscopic vision; a state where each eye sees slightly different view of an object, so that depth can be seen; also called 3-dimensional vision − Most mammals have eye sockets that face sideways − As the eyes become more forward facing, total field of view decreases but degree of overlap of the field of the 2 eyes increases. Greater the degree of overlap, the better the stereoscopic vision − Primates compensated (forward-facing eyes – narrow field of vision) by evolving a highly mobile head and neck − Most primates have both rods and cones in the retina of their eyes − Rod; a receptor in the retina that is sensitive to dim light − Cone; receptor in retina that is sensitive to bright light and colour − Nocturnal primates only have rods − Nerves connecting rods and cones to the brain have improved – more acute in each eye and the coordination btw the 2 eyes is far better than in other mammals (also enhanced stereoscopic vision) − Forward-facing, bony eye socket developed for protection − Increasing importance for vision – region of brain for interpretation of visual info increase but for olfaction decrease

Answer 226

− Increased in size − Concerned with so-called higher function – vision, memory, reasoning and manipulative ability - necessary to cope successfully to environmental changes − Most significant features of primate evolution − The brains of apes and humans have a strong pattern of convolutions − These convolutions, or folds, enable the SA of the brain, hence the cerebral cortex greatly increases − Convolutions resulted in a 50% increase in SA of the human brain compared to brain with none − Allowed them to move about and locate food and develop special skills − Increase in size of cerebral cortex allowed greater variety of behavioural responses to meet a wide array of environmental problems

Answer 227

− Most species not restricted to a limited reproductive season and show a rhythmical sexual cycle − Most only have one offspring − Primates are placental mammals – offspring develop inside mothers body, nourishment from bloodstream via placenta − Placenta; organ that supplies nutrients to, and removes waste from, the foetus; also produces a number of hormones including oestrogen and progesterone − Apes and humans, have more efficient placenta that allows a closer contact btw the blood supplies of the mother and developing offspring − Gestation relatively long in primates − Once offspring are born, period of parental care can be even more protracted − Lengthening of the period of growth and development, associated delay in maturation − Sexual maturity is attained much later in apes and humans − Late arrival of sexual maturity and maturation tend sto reduce the number of offspring a female can have during her lifetime

Answer 228

− Humans have some basic characteristics as the apes and together are classified in the family, Hominidae − Humans have developed adaptions to help survive and reproduce in their particular environment − Humans are classified as homonons; they belong to the tribe Hominins − Tribe; a level of biological classification that occurs btw subfamily and genus; usually contains several genera e.g. the tribe Hominini includes modern humans and their extinct ancestors − Homininis are relatively hairless and their structure of their upper and lower limbs allows for a fully bipedal way of walking − Bipedal locomotion; walking upright on 2 legs − Homininis also have greater development of brain, changes in size and shape of the teeth, development of speech and sexual characteristics

Answer 229

− Australopithecines – hominins classified in the genus Australopithecus − Australopithecus; a genus of fossil ape-like primates found in rock layers dating to 3.6 million years ago − Homo; the genus of hominin to which humans belong to − Homo erectus; a species of genus homo that lived btw 300,000 and 1.8 million years ago − Homo neanderthalensis; a regional population of hominins that existed in Europe during the last of the ice ages; recent evidence suggests that the Neanderthals may date back as far as 230,000 years ago − Homo sapiens; modern humans

Answer 230

− Skeleton and muscles evolved (millions of yrs.) − Adaption; a particular structure, physiological process or form of behaviour that makes an organism better able to survive and reproduce in a particular environment − Erect posture helped our human ancestors to survive

Answer 231

− Brain joins the spinal cord there is a hole in the skull − Centrally under skull (humans) − Towards back of skull (quadrupeds) − Gradually moved forward until skull is able to balance in top of the vertebral column − Ape requires large neck muscles, humans not

Answer 232

− Humans have a double curvature, giving the spine an s-shape that contributes to upright stance − Lumbar region (small of back) are wedge-shaped from front to back – forming forward-jutting curve − Improves body balance in upright position − Enables head balance on top of neck − Cervical curve in neck brings vertebral column directly under centre of gravity of skull

Answer 233

− Human jaw has gradually been reduced | − Important balance skull on top of spine, weight in front of foramen magnum approx. equal to weight behind

Answer 234

− Bowl shape, supports the abdominal organs when standing erect − Females, supports developing foetus − Broad hips provide space for large buttock muscles, move legs and keep upper body erect − Humans broader and shorter from top – bottom, than in apes

Answer 235

− Hip joint being directly under the trunk and head − Allows weight of body transfer from pelvis – legs − Head of femur is larger and fits into the acetabulum (hip socket) − Pelvis is broad, hip sockets are wide apart but femurs tend to converge towards knees − Femurs form an angle to the vertical termed carrying angle – ensures weight distribution remains axis of body when walking − Allows greater stability, striding gait instead of swaying side-side

Answer 236

− Knee joint – 2 part hinge joint with 1 hinge on either side of ligaments in the middle of the joint − Outer hinge stronger and larger – weight transmitted to it − Centre of gravity falls through a line just in front of knees − Force tries to bend knee backward – resisted by ligaments − Natural resistance produces joint requires no energy to support the body in standing position

Answer 237

− From knee joint – most weight transmitted through tibia to ankle − Human foot is 1 of the most distinctive adaptions for bipedal locomotion – result lost prehensility − Bones of foot btw toes and ankle (metatarsal ) – shaped to form 2 arches − Longitudinal arch – running from front to back − Transverse arch – running from side to side − Transverse arch unique to humans − 2 arches have enabled humans to perfect bipedal locomotion − Humans walk bipedally using the striding gait – walking in such a way that the hip and knee fully extended

Answer 238

− Long legs increase the length of the stride when walking − Point at which all the weight of the body appears to be concentrated – centre of gravity − The lower centre of gravity humans contributes to stability when moving bipedally or when standing erect

Answer 239

− Hominins walk bipedally on 2 legs with body upright − Homo neanderthalensis (Neanderthal man), homo erectus and Australopithecus are extinct Hominins – fossil bones show us these people could have walked upright on 2 legs − Muscle tone essential for maintaining upright stance − Muscle tone; partial contractions of skeletal muscle − Even walking on their hind legs, the apes have their knees bent and their bodies bent forward at the hips − When walking, the trunk rotates about the pelvis − Forward swinging of the arms compensates for this natural rotation of the body – right arm naturally swings forward as the left leg is extended − Swinging of the arms tends to keep the shoulder at right angles to the direction of travel − Reduces amount of energy expended

Answer 240

− Cerebrum (frontal lobe) has greatest enlargement in SA – humans make up 47% but in apes 33% − Humans, more of the skull is used in housing the brain than in apes − Result, brow tends to be vertical and lacks the prominent brow ridges − Together with a shortening of the snout, humans have a flat face, but have far more prominent nose than any other primate − Brains of early hominins have not been fossilised but b/c brain fills the whole of the cranium, brain size can be determined by measuring volume inside cranium − Shape of brain determined from endocasts − Endocasts; impression of the inside of the brain case, made o rock or some other solid material − Endocasts also show gradual increase in number of convolutions and size of frontal lobe − As brain expanded, face tended to become flatter and noticeable forehead began to develop

Answer 241

− Humans canine teeth do not project beyond the level of the other teeth and interlock − They look more like incisors and take up less room in jaw − Dental arcade evolved into different shape − Dental arcade; the shape of the pattern made by the teeth as they are set in the jaw − Early hominins (Australopithecus afarensis) – lower jaw and face, more like ape, teeth large and distinctive gap btw canine and incisors, with rows of teeth parallel rather larger − Humans that lived about 100,000 yrs. Ago had teeth that were about 10% larger − Modern humans gradually losing wisdom teeth (3rd molar) − Apes and early hominins had prognathism and a distinct brow ridge − Prognathism; having a protruding jaw − Brow ridge; the bony ridge located above the eye socket

Answer 242

− Using geological and chemical info, and info about the types of fossilized plants and animals found − Between 5 and 6 million yrs. Ago environment was changing − Temps began to fall and forest areas diminished in size – patches of forest separated by increasingly open grassland − In these conditions many arboreal animals not able to survive − Forests thinned and trees got further apart (more open space) – natural selection favoured apes (better at bipedal walking) − These apes evolved into early hominins

Answer 243

− An increase range of vision for detecting prey and predators at a greater distance − Increase size, deterring predators − Hands free for carrying food and, perhaps, for tool use − Higher reach when picking fruit from trees − Improved cooling of the body (sun strikes smaller fraction of it, helping to avoid overheating and upper body above ground – wind) − As African forests replaced by grasslands, food supplies became limited (2.5 million yrs. Ago – australopithecines were evolving from the earliest of the hominins)

Answer 244

− 1st fossil found in Southern Africa in early 1920’s − Raymond Dart − Face not as protruding as ape − Teeth (especially 1st molars) – more like humans − Skull more rounded − Not even the beginnings of a brow ridge

Answer 245

− Teeth typically those of a hominin – canines short and non-projecting (resembling incisors) − Incisors and canines make a row of cutting teeth – no gap btw them and the following premolars − Facial profile of australopithecines has low forehead and more projecting upper and lower jaw − Australopithecines body weight probably a 1/3 of gorilla − Brain size lies btw chimpanzees and modern human − Endocasts indicates brains of australopithecines more human-like than ape-like − Foramen magnum more forward − Skull more rounded

Answer 246

Two main variants of australopithecine have been discovered so far: − Gracile; slender in form, used to refer to the body build of some human ancestors − Robust; a term used to describe the heavy build of some human ancestors

Answer 247

a species of the genus Homo that lived about 1.9 million yrs. ago; believed to have lived alongside robust Australopithecines. − Many authorities considered it to be nothing more than an advanced Australopithecine or an East African variant of Australopithecus africanus − H.habilis – larger brain and smaller teeth than Australopithecines, taller than the gracile forms and stood more erect − Existence confirmed in 1972, fossil skull found with features midway btw Australopithecines and modern humans − ‘skull 1470’ − Originally dated 2.5 to 3 million yrs. Old − Recent techniques indicate 1.9 million yrs. Old − Estimated brain volume of 775 cm3 − Early homo walked upright and had hands that were more robust than modern humans − They had more powerful grasp than ours – similar to chimpanzees − Hand suited to climbing trees − Daylight – bipedally walking on the ground while food-gathering in trees − Nightfall – retire to trees for safety − Brain significantly larger than that of the gracile or the robust form of Australopithecines − Brain uses a lot of energy – only grows larger in species that are routinely consuming high-energy food − Brain size to increase – shift to meat eating would be necessary

Answer 248

− ‘Pecking man’ − Brains average size of 1075cm3 − Curve of the dental arcade shorter and more compact − Jaw was shorter and more compact (suggests chin was beginning to form) − Teeth modern – similar to modern humans − Discovered footprints in 21.5 million yrs. old sedimentary layers – provide the oldest evidence to date of an essentially modern human – like foot anatomy (big toe parallel to other toes) − These footprints believed to be made by Homo ergaster − Footprints strong evidence that hominins have been walking upright for over 1.5 million yrs. − Smaller teeth (particularly molars) – progressive change in diet to softer foods (meat)

Answer 249

− 1933, skull found with no lower jaw and severe damage behind left eye − Sizeable hole in base − Estimate brain size averages 1150cm3 − Brain case had contours similar to modern humans − Forehead more prominent than homo erectus − Brow large and heavy − Back of skull more rounded − Number of back teeth preserved in upper jaw − Estimated age 250,000 – 350,000 yrs. old − Fossil transition btw H.erectus and Sapiens

Answer 250

− 1st recognized fossils of Neanderthal people were found in 1856 − Fossils found in the 1990’s suggest Neanderthals were only a side-branch along the pathway to modern humans − Concluded that the Neanderthals were a distinct biological species, Homo Neanderthals − Had big faces, low but large skulls and heavy brow ridges − Brain slightly larger than average for humans today and its shape was different − Back of skull – ‘bun’ shape − Lower jaw lacked a definite chin and cheeks swept back to give a streamlined appearance − Robust nature of the Neanderthal skull echoes the physical appearance of H.erectus − Much larger brain of Neanderthals considered a modern feature − Extreme forward thrust to face – prognathism – accentuated by the way the nasal bone projects forward − Neanderthals nose projected more and wider than modern humans − Larger, wider nose – adaption for life in seasonally cold and dry environment − Short in stature − Limbs short and heavily jointed with powerful muscles, they would have appeared more heavily built than modern humans − Barrel-shaped chest and thick neck muscles – added to rugged appearance − Large skull – brain on average slightly large than modern humans (1485cm3 – 1350cm3 ) − Extra brain capacity required to control extra muscles

Answer 251

− Cro-Magnon people; the first automatically modern people found in Europe − Aurignacian tools; the tool culture of stone, bone and antler associated with early Cro-Magnon people − Skulls tended to be shorter from front to back, higher in the region of the top of the skull and rounded at back − Less prominent brow ridges, reduction in projection of face and smaller jaw − Brain- average size 1350cm3 − Face – relatively broad and short with orbits well separated − Orbits; the bony cavity of the skull that holds the eyeballs; the eye socket − Teethe tended to be smaller and chin well developed

Answer 252

- oldowan (single faced pebble tools) - Acheulian (two sided bifaces hand axes) - Mousterian (hand-axes, blades and points) - Aurignacian ( - Solutrean (pressure flaked blade tools) - Magdalenian (bone and antler tools)

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