C7 Organisms Flashcards
(141 cards)
1
Q
multicellular
A
organisms with multiple cells
- have levels of organisation (cells, tissues, organs, organ systems)
- cells are specialised to perform specific funtions that sustain life + maintain homeostasis
2
Q
unicellular
A
organisms that are only one cell
- includes bacteria and protozoa
- must perform all necessary functions within one cell
- are very adapted to suit their environment (relies on and is vulnerable to it)
3
Q
levels of organisation
A
- cell: basic unit of life
- tissue: a group of specialised cells that work to serve a specific function
- organ: structure made up of different tissues that have a specific function
- system: a collection of organs that perform a function in the body
- organism: entire being
4
Q
Outline the advantages of multicellularity.
A
increased efficiency
- ‘division of labour’ - the functions of an organism are distributed amongst specialised cells, which perform a specific function = efficient
longer life spans
- death of some cells does not kill the organism
- more cells = less stress and vulnerability
- the immune systems protects the body and fights infection
dead cells can have function
- surface cells on organisms are mostly dead
- they provide support, protection and tools to body (horns, hooves, nails, xylem in plants)
evolution and intelligence
- greater genetic diversity within species - sexual reproduction, bringing more adaptations and resistance to change
- the organisms can develop a higher level of learning
size
- organisms can grow large
- larger brain = increased intelligence
- increased mobility
- reduce chance of being prey
smaller cell size
- tend to have smaller cells compared to unicellular organisms
- due to SA:V ratio, this provides them with greater efficiency (energy, nutrients etc)
5
Q
Outline the disadvantages of being multicellular.
A
energy use and waste
- more energy is required to supply to all cells
- increased energy consumption = more waste
- waste may be difficult to eliminate and cause toxicity
- organisms spend more time eating/searching for food for energy
maturity and reproduction
- a more complex structure means organisms take longer to reach maturity
- offspring development takes longer due to the complex genetic makeup
infection
- the more complex/significant the cells of an organism are, the more likely to be attacked by pathogens
- the organism is ideal to be used for food, habitat, energy
systems
- if one organ system fails, they potentially all can = failure of entire body
6
Q
ingestion
A
food is taken in through the mouth
7
Q
digestion
A
food molecules are broken down (mouth, stomach, small intestine)
8
Q
absorption
A
the products of digestion are absorbed across the gut wall (into the bloodstream)
9
Q
egestion
A
unwanted material is eliminated (defecation)
10
Q
alimentary canal
A
- human gut
- includes ALL the organs that the food passes through (esophagus, stomach, intestines etc)
- 9m long
11
Q
accessory organs
A
organs not part of the alimentary canal but play a key role in digestion (gall bladder, pancreas, liver, salivary glands)
12
Q
mechanical digestion
A
the breakdown of food via mechanical processes
- chewing, churning, contractions
13
Q
chemical digestion
A
the breakdown of food via chemical processes
- stomach acids, bile, enzymes
14
Q
mouth
A
- mechanical digestion
- tongue: moves food around in mouth
- teeth: breaks down food
- work to turn food into a bolus
15
Q
bolus
A
mushed up ball of food created by mouth (tongue + teeth)
16
Q
salivary glands
A
- chemical digestion
- produce saliva
- has enzymes that break down food (amylase)
17
Q
epiglottis
A
flap at top of larynx to prevent food entering the lungs
18
Q
oesophagus
A
- mechanical digestion
- food pushed down into the stomach via muscular contractions (contract/relax), forces bolus down (peristalis)
19
Q
peristalis
A
the contractions that force a bolus down the oesophagus
20
Q
stomach
A
- muscular bag with a valve at each end (cardiac sphincter: top, pyloric sphincter: bottom)
Mechanical
- churning turns bolus into chyme (slurry)
Chemical
- secretes pepsin for protein digestion
- secretes HCl (kills bacteria: immune system, provides optimum pH for pepsin)
21
Q
HCl
A
- hydrochloric acid is produced by the stomach
- chemical defense in the immune system as it kills bacteria
- provides an optimum (acidic -pH2) for pepsin
22
Q
chyme
A
mushed up food slurry produced by the stomach
23
Q
gastric glands
A
- glands in stomach lining
- have mucus-secreting cells
- mucus protects from the acidity of the stomach HCl
24
Q
cardiac sphincter
A
valve at the top of the stomach
- cardiac = closer to heart
- allows entry of food
25
pyloric sphincter
valve at bottom of stomach
- allows exit of food
26
accessory organ
organs that are not part of the actual digestive tract, but play an important role in digestion
27
liver
- accessory organ
- secretes bile (basic/alkali)
- this neutralises the acidic chyme from the stomach (HCl) before it enters the small intestine
28
bile
fluid secreted by the liver
- basic/alkali
- neutralises the acidic chyme before it moves into the small intestine
29
emulsification
a process in which bile breaks down lipids into smaller droplets
- allows a larger surface area for lipids so that enzymes can break them down
30
gall bladder
- accessory organ
- stores bile and releases it when needed
31
pancreas
- accessory organ
- produces and releases digestive enzymes into the intestines (lipase, phospholipase, esterase)
32
small intestine
functions to absorb nutrients from chyme
- secretes enzymes from intestinal wall
- receives enzymes from pancreas
- food molecules are absorbed through intestinal wall
33
Describe how the small intestine's **structure** aids its **function**.
HIGH SA
- small intestine is long (6m)
- inner surface is highly folded (villi + microvilli)
= massive surface area: efficient absorption of nutrients
THIN WALL
- villi wall is only 1 cell thick
- allows efficient absorption of nutrients via diffusion
GOOD BLOOD SUPPLY
- each villus supplied with blood vessels which receive: glucose/AAs/vitamins/minerals - absorbed into blood capillaries, lipds - absorbed into lacteal (lymphatic capillary)
OTHER
- many channel/pump proteins for rapid absorption
- many mitochondria provide sufficient ATP for active transport
- blood capillaries are close to the epithelial (intestine lining) for efficient absorption via diffusion
34
villi + microvilli
present in small intestine
- villi: finger-like projections off intestinal cells
- microvilli: hair-like projections off villi
- increase SA
35
large intestine
final part of intestine (the thicker part that wraps around), functions to:
- reabsorb water + mineral ions (sodium, chlorine)
- forms + temporarily stores faeces
- maintains a pop. of good bacteria
- ferments indigestible materials
- food then travels through the colon, then exits via anus
36
incisors
- describe the differences between **carnivores**, **herbivores** and **omnivores**
8 front teeth
- cutting/ripping off food
CARN: sharp, pointed, to cut off meat
HERB: small, chisel shaped, to cut through plants
OMNI: wide, chisel shaped, cut up variety of food
37
canines
- describe the differences between **carnivores**, **herbivores** and **omnivores**
teeth next to incisors
- sharper, pointed
- similar to incisors: ripping/tearing food
CARN: large, sharp, pointed, gripping + killing prey
HERB: none
OMNI: sharp, pointed, biting + tearing
38
molars/premolars
- describe the differences between **carnivores**, **herbivores** and **omnivores**
12 teeth at back of mouth
CARN: carnassials (specialised molars), tearing meat
HERB: broad, flat, rough, increase SA to grind plants
OMNI: broad, flat, grind variety of food
39
carnassials
carnivores (a defining feature)
- specialised molars
- sharp, serrated, narrow
- move like scissors, slot together
- cut/slice meat
40
diastema
herbivores (a defining feature)
- the gap/spacing between incisors and molars
- provides room for food to move around
- provides different angles for chewing
- temporary plant storage in cheeks
41
Describe the need for digestion within the body.
- the body needs to break down food to nutrients the (useable form) that can be absorbed
- digestion makes use of the micromolecules of food, to make macromolecules
- plants do not need it (phs)
42
Summarise the types of digestion within the body.
MECHANICAL
Chewing: mouth
- teeth (grinding)
- tongue (pushing)
Churning: stomach
- muscles squeeze + mix food
- turns to chyme
- enters small intestine
- nutrients absorbed
CHEMICAL
Stomach acids
- acidic environment denatures proteins
- breaks down molecules
Bile
- released by liver, stored in gallbladder
- emulsifies lipids
Enzymes
- decrease activation energy to aid in catalysing/breaking down molecules
- most secreted by the pancreas
- have an ideal pH
43
Explain the role of enzymes in digestion.
work to break down large food molecules
- speed up digestion by lowering the activation energy required for reactions
- work at body temperature (37°)
- majority are secreted from the pancreas (some from liver, salivary gland, stomach, small intestine)
44
amylase (role in digestion)
1.
Made in: salivary glands
Works in: mouth
Role: breaks starches into disaccharides
2
Made in: pancreas
Works in: small intestine
Role: continues starch breakdown
45
proteases e.g. pepsin (role in digestion)
Made in: stomach
Works in: stomach
Role: breaks proteins into peptides
46
bile (role in digestion)
Made in: liver (stored gall bladder)
Works in: small intestine
Role: breaks fats into fatty acids
47
trypsin (role in digestion)
Made in: pancreas
Works in: small intestine
Role: continues protein breakdown
48
lipase (role in digestion)
Made in: pancreas
Works in: small intestine
Role: breaks fats into fatty acids
49
maltose, sucrose, lactase (role in digestion)
Made in: small intestine
Works in: small intestine
Role: breaks remaining disaccharides into monosaccharides (glucose)
50
peptidase (role in digestion)
Made in: small intestine
Works in: small intestine
Role: breaks dipeptides into AAs
51
Describe the role of enzymes in **carb** digestion.
- amylase, in mouth (from salivary glands) breaks starches into disaccharides
- amylase, in small intestine (from pancreas) breaks starches into disaccharides
- maltose, sucrose, lactase, in small intestine (from small intestine) breaks disaccharides into monosaccharides (glucose)
- in humans: cellulose passes through undigested (no cellulase enzyme present)
52
Explain why there needs to be two regions that produce amylase.
- produced in salivary glands to break down carbs
- once the food enters the stomach, HCl (very acidic, low pH) causes the enzyme to denature
- therefore amylase must be produced again by pancreas + released into small intestine, in order to continue carb breakdown
53
Describe the role of enzymes in **lipid** digestion.
- bile, in intestines (from liver/gall bladder) emulsifies fat, breaks down to smaller droplets
- lipase, in intestines (from pancreas) in small intestine breaks down fat to fatty acid chains and glycerol
54
Describe the role of enzymes in **protein** digestion.
- proteases (e.g. pepsin), in stomach (from stomach) break proteins into polypeptide chains
- trypsin, in small intestine (from pancreas) in neutral pH 7 environment, breaks PP chains to dipeptides
- peptidase, in small intestine (from small intestine) breaks dipeptides into AAs
55
Describe the general trend of digestive systems within vertebrates.
the more complex the diet, the more complex the digestive system (more breaking down required)
56
Describe the role of enzymes in **nucleic acid** digestion.
- nucleases in intestines (from pancreas) digest nucleic acids into nucleotides
57
State the 3 'points of comparison/difference' between the types of digestive systems in vertebrates.
1. stomach(s)
2. system length/size
3. caecum (size/present/absent)
58
Describe the elements of **monogastric** digestive system.
- single chambered stomach
- enzymes, bile and gastric juices break down food
- carnivores + scavengers, most omnivores, some herbivores
59
Describe the structure of a carnivore's digestive system and how it relates to it's function.
- monogastric
short, simple digestive tract
- digestion of meat (protein) is easy and fast
- scavengers: tract even shorter to avoid a bacterial infection from meat
no or very small caecum
- in carnivores it is used for the breakdown of mineral salts/water
- not used for plant matter breakdown, therefore they don't need to have many bacteria/a large caecum
60
Provide some examples of animals that have a monogastric digestive system.
Carnivores, humans, horses, rabbits and pigs
61
Describe the elements of a **ruminant** digestive system.
- foregut fermenters
- 4 chambered stomach: very large, 70% of tract volume
- cows, sheep, goats, kangaroos
Rumen
- first, large, stomach chamber
- contains bacteria to break down plant cellulose
Massive stomach size + length
- a high SA increases time that bacteria can break down dense, cellulose-rich food
62
Describe the elements of a **avian** digestive system.
- 2-chambered stomach
- no teeth but a beak
specialised bird organs
- crop: an organ for food storage
- gizzard: an organ for breakdown of seeds, grains etc
63
Birds have which type of digestive system, which special organs to aid digestion, with how many stomachs?
avian system, with two stomachs
- crop, for storing food
- gizzard, for breakdown of grainy foods
64
foregut fermenter
- ruminant herbivores
- digestion mainly occurs in the first part of the digestive tract
65
Carnivores, humans, horses, rabbits and pigs all have which type of digestive system with how many stomachs?
monogastric system, with one stomach
66
Cows, sheep, goats and kangaroos have which type of digestive system, with how many stomachs?
ruminant system, with 4 stomachs
67
Describe the elements of a **non-ruminant herbivore** digestive system.
- hindgut fermenters
- monogastric (1 stomach)
Caecum
- VERY large, at start of large intestine
- contains many bacteria to ferment dense, cellulose-rich food
Large digestive tract
- increases SA, increasing time that bacteria can break down and absorb plant cellulose
68
hindgut fermenters
- non-ruminant herbivores
- digestion mainly occurs in the last part of the digestive tract
69
Describe the elements of a **pseudo-ruminant** digestive system.
- 3 chambered stomach
- large caecum
70
Rabbits, koalas and horses have which type of digestive system, with how many stomachs?
non-ruminant herbivore system (hindgut fermenters), with monogastric (1 chamber) stomach
71
Why is gas exchange in organisms important?
- cellular respiration
- input of O2 in to cells, and output of CO2 out of cells
- this constant demand for cellular respiration requires gas exchange
72
gas exchange
the movement of gases from a high to low concentration (diffusion)
73
Outline the factors affecting gas exchange and their relationship.
SURFACE AREA
- larger SA = higher rate of GE (proportional)
- with a larger SA, there is more area for particles to diffuse through = faster movement
TEMP
- higher temp = higher rate of GE (proportional)
- with a higher temp there is more KE = faster particle movement
CONC GRADIENT
- larger conc gradient = higher rate of GE (proportional)
- diffusion occurs down a conc gradient (high to low), therefore the greater the diff between concs = higher rate of GE
DIFFUSION DISTANCE
- larger diffusion distance = lower rate of GE (inverse)
- larger distance means slower movement of particles to diffuse through cells
74
Outline the common features of gas exchange surfaces in different organisms.
- high SA
- diffusion distance is thin (approx 1 cell thick)
- highly vascularised (lots of blood vessels to carry O2)
- moist (gases must dissolve into H2O to diffuse across the membrane)
75
Outline the three elements that the structure/type of an vertebrate’s gas exchange surface depends on.
- metabolic demand (less demand = smaller/ less complex system)
- size of organism (smaller/less complex = smaller system)
- external enviro (live in water/air - will need a specific system)
76
State the 4 types of gas exchange surface in vertebrates, providing examples.
- across membrane/skin/outer surface (protists, amphibians, aquatic species)
- tracheae (insects, arthropods)
- gills (fish, sharks, rays)
- lungs/alveoli (birds, reptiles, mammals - humans)
77
Describe the gas exchange structure of through a skin/membrane.
no specialised structures for gas exchange, gases are exchanged across the skin/outer/membrane surface
78
Describe the gas exchange structure of tracheae.
- openings/holes in skin
- tracheae tubes lead inwards, extending into the circulatory system
- they distribute gases throughout the body (a network of tubes)
79
Describe the gas exchange structure of gills (structure to function)
HIGH SA
- thin feather like projections, with further projections (lamellae)
- need to spread out to work, this occurs when in water
= greater area for diffusion to occur
GOOD BLOOD SUPPLY
- there are dense capillary beds on the lamellae
- allow efficient exchange of substances between water and blood
COUNTERCURRENT FLOW
- blood flows in the opposite direction to the water
- this maintains a favourable conc gradient (there is more O2 in the water and it moves in, more CO2 in the blood moves out)
= constant diffusion
80
Describe the gas exchange structure of lungs/alveoli.
- air is taken in via breathing and goes to alveoli in the lungs
- these tiny air sacs exchange O2 and CO2 with the bloodstream
81
Describe the advantages and disadvantages of gas exchange using air.
PROS
- air has a higher concentration of oxygen than water
- O2 and CO2 diffuse faster = resp systems exposed to air are not required to have as much ventilation
- air is lighter = easier ventilation
= more efficient to sustain GE
CONS
- there is high water loss in order to keep the resp system moist
82
Describe the structure of the lungs (how gas exchange occurs).
- air enters via nose/mouth: moistens and warms air, nose filters
passes through:
TRACHEA
- cilia capture dust and pathogens
- C rings hold structure of the trachea and prevent crushing
BRONCHUS
- the two divisions from the trachea
BRONCHIOLES
- further divisions
ALVEOLI
- site of GE
- tiny air sacs at ends of bronchioles
= these structures increase surface area of the lungs for efficient gas exchange
83
Describe the structure of an alveoli and how it relates to its function.
O2 IN: (air goes to lungs, to alveoli, and is diffused to the blood)
CO2 OUT: (is a product of CR, goes from cells to alveoli, is breathed out)
STRUCTURE
- good blood supply (dense capillary bed, allows efficient exchange of gases between blood
- very thin, 1 cell thick (short diffusion distance for gases, which maintains a constant conc gradient)
- high SA:V (millions of microscopic alveoli, allowing larger surface for GE to occur)
84
Outline how the concentrations of gases change from when air is taken in to when it is taken out.
air breathed out has:
- more CO2
- less O2
- equal N
- more water vapour and is warmer (moist from the lungs)
85
Outline the needs of a plant for survival (4) and how these enter, exit and move around the organism.
H2O
- absorbed (with minerals) from roots
- transported to leaves for Phs
- lost through evapotranspiration
SUGAR
- produced via Phs
- transported and used around the plant and it’s roots
O2
- absorbed from soil via roots
- used for CR
- released as Phs waste via leaves (stomata)
CO2
- absorbed via leaves (stomata)
- used for Phs
- released via roots
86
vascular tissues/bundles
specialised for transporting substances to all areas of a plant. They contain:
- Xylem (transport water and nutrients)
- Phloem (transport sugars)
87
Describe the structure of xylem and how it relates to its function.
FUNCTION: transpiration - transport of water (+ nutrients), upwards to sites of Phs (leaves/shoots)
water movement: UNI-DIRECTIONAL (one way)
- H2O movement from roots-leaves
- water evaporates, creating an evaporative pull, pulling H2O molecules up, creating a transpiration stream (regulated by guard cells and stomata)
STRUCTURE
- xylem cells are dead, made from lignin (cellulose)
- have a strong structure
- they are hollow with no plate/sieve between cells
- narrow + small to maintain adhesion/cohesion forces
88
State the factors affecting transpiration (4) and their relationship.
TEMP: proportional (increase in temp = increase in transpiration)
LIGHT INTENSITY: proportional (increase in light = increase in transpiration)
AIR FLOW: proportional (increase in air flow = increase in transpiration)
HUMIDITY: inverse (increase in humidity = decrease in transpiration)
- this is due to the conc gradient of water inside vs outside the leaf
89
Describe the structure of phloem and how it relates to its function.
FUNCTION: translocation, transport of sugars to all parts of a plant
movement: SOURCE-SINK (not one way)
- sugars move from source (where it is made) to sink (where sugar is needed)
- driven by ATP
STRUCTURE
- sieve plates: end walls of cell have pores, allow for flow of sugars between cells and maintain correct pressure to assist with transport from high-low pressure of the sugar
- companion cells: provide the energy needed for sieve cells
- filled with cytoplasm, a small + large vacuole: for transport of sugars, no other organelles
- through sieve cells, the concentration gradient is mantained for facilitated diffusion
- in leaves, the sucrose mixes with water to form sap, which is driven by osmosis
90
Describe how sugar moves through a plant
from source to sink
- source: leaves, where it is made via Phs
- sink: storage (roots), or used (for growth)
91
Describe the structure of a leaf in relation to it's function in gas exchange.
FUNCTION
- perform Phs to produce glucose needed for CR (needs O2)
STRUCTURE: stomata
Function: open/close for gas exchange (CO2 in, O2 out)
Structure:
- guard cells respond based on water availability
- if water abundant: vacuoles fill, cell will swell (turgid), stomata will open
- if water limited: vacuoles empty, cell will shrivel (flaccid), stomata will close
- guard cells are sensitive to light: will close at night when no light to drive Phs
- they are only present on the underneath of leaves: reducing water loss as is more shaded
92
Describe the two types of water absorption that occur via the roots.
ACTIVE (symplastic pathway)
- water moves between cytoplasm/vacuoles of adjacent cells
PASSIVE (apoplastic pathway)
- water moves from cell wall to cell wall of adjacent cells, does not enter the cytoplasm
93
Why do we need a transport system?
- O2, H2O, glucose, and nutrients are needed for metabolic processes
- diffusion is too slow for multicellular organisms to transport these to all cells in their body
- a transport system is fast, increases SA, and carries to all cells
- the complexity of the system depends on the complexity and SA of the organism (smaller size = less energy demand)
94
Outline the 7 major functions of blood as a medium.
MAIN FUNCTION: blood provides transport and is a link between cells and body systems
- transports O2 and nutrients to all cells
- transport CO2 and waste products out of cells and the body
- transports hormones (chemical messengers) to cells
- maintains the pH of bodily fluids (many reactions occuring in the body must be stabilised)
- distributes heat and maintains body temp (contraction/expansion of vessels)
- maintains water balance and ion conc in body fluids
- protects against disease/pathogens (white blood cells)
95
Describe the structural components of of blood.
- just over half is comprised of plasma (liquid part)
- rest is formed elements (suspended in plasma): erthrocytes (red blood cells), leurocytes (white blood cells), thrombocytes (platelets)
96
Describe the function of plasma within the blood.
- a yellowy fluid, blood components are suspended within it
- responsible for the transport of: CO2, glucose, AAs, vitamins, minerals, hormones, waste materials
97
Describe the structure of a red blood cell and how it relates to its function.
- erthrocytes
- bi concave disc: increases SA for O2, thicker edges store more haemoglobin
- no nucleus: more room for haemoglobin
- flexible: to squeeze through small capillaries without breaking
98
Describe how O2 is transported within the body.
- not very soluable in water: majority of it is carried within haemoglobin, not water
- haemoglobin and oxygen bond to form oxyhaemglobin: this bond is weak and easily reversible, allowing O2 to release when needed
99
Describe how CO2 is transported within the body.
- small amount dissolved in plasma and carried as a solution
- some combined with the globin part of haemoglobin
- majority is carried in plasma as bicarbonate ions
100
Describe how nutrients and waste are transported within the body.
NUTRIENTS
- inorganic: carried as ions (e.g. Na, Cl)
- organic: dissolved into plasma
WASTES
- metabolic wastes (produced by cells, harmful if accumulated: urea, uric acid, CO2)
- dissolved into plasma
101
Outline the overall structure of the heart.
- a double pump
- 4 chambers, each pump has 1 atria (top chamber) and 1 ventricle (bottom chamber)
102
Describe the structure of the **atria** and how it relates to its function.
Function: collect blood, from body or lung
Structure:
- thin walled/smaller, as only required for blood collection/draining into the ventricle
103
Describe the function of the **ventricle** and how it relates to its function.
Function: pump blood at higher pressure to lungs and body
Structure: thick walls (more muscular), larger, to pump blood to whole body with force
104
Why are the walls of the left ventricle more muscular than the right ventricle?
- the left ventricle must pump blood to the entire body, which takes a lot of force
- the right ventricle must only pump blood to the lungs, which is not as far and requires less force
105
What important feature must be noted when looking at a diagram of a heart?
The left side of the heart will be on the right side of the diagram (because it is the patient's left side), and vice versa
106
Describe the cardiac cycle (2 phases)
- 1 cycle is one complete heartbeat (one contraction and one relaxation)
2 phases
SYSTOLE: pumping (heart contracts)
DIASTOLE: filling (heart relaxes
- each movement out of an atrium/ventricle is a contraction
- 1-way valves ensure blood doesn't flow the wrong way
107
Describe the flow of the blood, starting with deoxygenated blood.
deoxygenated blood - right atrium - right ventricle - lungs (O2 replenished) - oxygenated blood - left atrium - left ventricle - body (O2 used) - deoxygenated blood
108
vessels
tubes for blood transport around the body, including:
- arteries
- veins
- capillaries
109
Describe the structure of **arteries** and how it relates to their function.
FUNCTION
- transport high O2 blood away from the heart to body tissues/organs
- HIGH pressure
STRUCTURE
- narrow lumen (relative to wall thickness): maintains blood flow at high pressure
- thick arterial walls: outer layer contains flexible strong fibres that prevent tearing, another layer of muscle/elastic fibres, contracts/releases to maintain flow and pressure
110
Describe the structure of **veins** and how it relates to their function.
FUNCTION
- transports/collects low O2 blood from body tissues and back to heart/lungs
- LOW pressure
STRUCTURE
- wide lumen (relative to wall thickness): maximises blood flow at low pressure
- thin arterial walls: contain less muscle/elastic fibres, not needed
- one-way valves: prevent backflow of blood/pooling at lower points such as feet
- flow in veins is driven by skeletal muscle contractions (contractions compress vein, valve opens, blood moves up)
111
Describe the structure of **capillaries** and how it relates to their function.
FUNCTION
- exchange (CO2, O2, nutrients, waste etc) between blood and body cells
STRUCTURE
- very thin: 1 cell thick, low pressure
- small/narrow lumen: only fit 1 red blood cell across
this means that:
- small diffusion distance between blood and capillary, allowing efficient exchange
- SA is increased, allowing longer exposure for cells to exchange substances
- basement membrane and a permeable outer layer: allow exchange of substances in/out
112
Summarise how blood flows through the body in a cycle, starting at the heart.
- oxygenated, high pressure blood exits heart via aorta from left ventricle
- arteries
- arterioles
- capillaries: materials are exchanged between blood and cells, O2 is used (blood becomes deoxygenated)
- venuoles
- veins
- deoxygenated, low pressure blood enters heart via vena cava
- right atrium
- right ventricle: pumped to lungs (becomes oxygenated)
- left atrium
- left ventricle
- exits again via aorta
113
excretion
the removal of metabolic wastes from the body
- excretes CO2, ammonia, ions/salts, etc
114
State the organs/components involved in excretion and what they excrete.
- Lungs (breathing): CO2, water
- Skin (sweat): H2O, ions/salts
- Liver: converts ammonia to urea
URINARY SYSTEM
- Kidneys: nephrons (filtering + osmoregulation)
- Ureter: connection to-
- Bladder: storage
- Urethra: removal
115
urea
- where is it produced
- how is it transported
- produced in: liver
- transported in: blood
116
What is the origin of nitrogenous waste products in animals?
protein
- excess breaks down into AAs, is converted to ammonia
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Why do we have to convert ammonia to urea?
- liver converts ammonia to urea using H2O
- we cannot store proteins like we can with fats/carbs
- excess AAs are broken down and converted to ammonia
- it is very toxic, converted to urea which is less toxic, is then excreted from body
118
Why do plants not need an excretory system?
- plants do not have an excessive excretory system
- vacuoles: store and expel wastes (e.g. contractile vacuole)
- storage of waste in other places: bark, leaves, fruit, which can be shed/dropped
119
Briefly outline the function of nephrons:
- where are they located?
- what are they for? (2)
- kidneys filter blood via nephrons
FUNCTION
- Selective reabsorption (nephron to blood): needed substances are reabsorbed into the blood
- Secretion (blood to nephron): waste substances are kept in the nephron to be excreted in urine
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NEPHRONS
Describe the main function and process involved in the components of a nephron:
- bowman's capsule
- proximal tubule
- loop of henle
- distal tubule
- collecting duct
BOWMAN'S CAPSULE: Filtration
- filtering of blood components at high pressure
- filters: glucose, AAs, urea, ions etc into the nephron
- does not filter: lipids, blood cells, proteins
- once filtered, substance is called filtrate
PROXIMAL TUBULE: Selective Reabsorption
- some substances that the body needs are reabsorbed
- 80% of reabsorption occurs here
- all AAs + glucose
- most H2O, ions, bicarb
- Secretion: of some harmful substances into blood (alcohol, drugs, toxins)
LOOP OF HENLE: Osmoregulation
- loop hangs into medulla (in kidneys)
Descending (down) limb:
- medulla is very salty: free water moves into it, is reabsorbed
- has a low permeability to ions
Ascending (up) limb:
- ions are reabsorbed
- low permeability to water
DISTAL TUBULE: Selective Reabsorption
- final reabsorption of substances (H2O, bicarb, ions)
- can be controlled by hormones (ADH for H2O) as needed
- filtrate changes to urine, is more concentrated
- Secretion: of some harmful substances into blood (alcohol, drugs, toxins)
COLLECTING DUCT: Osmoregulation
- is permeable to H2O, but is regulated by ADH (a hormone)
Body is dehydrated:
- hypothalamus detects this
- triggers release of ADH hormone
- permeability to H2O increases
- more H2O is absorbed out of nephron
- urine is more concentrated, has a lesser volume
Body is hydrated:
- less ADH release
- becomes less permeable to H2O
- less H2O absorbed out of nephron
- urine is more diluted, has a greater volume
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Explain why drinking alcohol results in severe dehydration.
- alcohol blocks the release of ADH hormone
- body will not reabsorb H2O
- urine will be diluted, despite body being dehydrated
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OSMOREGULATION
- why control of water/ions is important
- how they are controlled
- ADH hormone
WHY
- Ions: essential, but wrong amounts = cell damage
- Water: too much = lysis, too little = cells become flaccid
CONTROLLED
- mainly controlled by kidneys (nephrons)
- some ions/water by sweat, some water by breathing
ADH
- antidiuretic hormone
- acts on nephron in the kidneys to either reabsorb more water if dehydrated, or release water if hydrated
123
Describe how ammonia is excreted by different types of organisms (3):
- name of substance
- what happens
- energy requirement
- provide example of an organism
EXPULSION
- ammonia expelled directly into water which flushes it away
- low energy
- e.g. aquatic animals, fish
UREA
- ammonia converted to urea via the liver, expelled from bodyin urine (made in kidney nephrons)
- medium energy
- mammals, most amphibians
URIC ACID
- ammonia excreted in a white paste, requiring little water, for conservation
- high energy
- birds, some reptiles
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ammonia
a toxic metabolic waste produced by the breakdown of excess AAs, must be eliminated from the body
125
homeostasis
- maintenance of the body's internal enviro, despite changes in the external/internal enviro
- a state of BALANCE amongst the body's systems, necessary for survival
126
Why is homeostasis important?
- must maintain body's conditions (temp, pH) so that organism can function
- outside the ideal range = organism/cell death
127
Explain how homeostasis is a negative feedback loop.
NEGATIVE FEEDBACK
- a change is reversed/reduced to bring the body back to stability again
- a constant balancing of internal enviro to maintain stable levels
128
stimulus-response pathway
- the negative feedback loop through which homeostasis is controlled
- each homeostatic process is controlled by a specific stimulus-response pathway
Sequence:
NORMAL LEVELS > stimulus > receptor> sensory neuron > Nervous System > motor neuron > effector > response > NORMAL LEVELS
129
State the 3 main stimulus-response pathways for homeostasis.
1. Blood glucose conc
2. Osmoregulation (water balance)
3. Thermoregulation (body temp)
130
Outline what a positive feedback loop is (+ examples).
- a change is amplified/continued within the body
- childbirth, lactation, blood clotting
131
Outline the main 2 body systems involved in homeostasis, and their components.
NERVOUS
Central: brain, spinal cord
Peripheral: neurons (sensory/motor), sense organs
ENDOCRINE
- hormones
- glands
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STIMULUS-RESPONSE PATHWAYS:
1. blood glucose concentration
- outline the pathway
Stimulus
- too much/too little glucose in blood
Receptor
- chemoreceptors in pancreas detect the change in levels
Control
- Too much glucose: Beta cells in pancreas secrete insulin (hormone) into the blood
- Too little glucose: Alpha cells in pancreas secrete glucagon (hormone) into blood
Effector
- liver and skeletal muscles receive message
- Too much glucose: glucose taken out of blood, converted to glycogen for storage
- Too little glucose: glycogen broken down, glucose released into blood
Response
- levels are returned back to stability, pancreas cells stop release of hormone
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STIMULUS-RESPONSE PATHWAYS:
2. Osmoregulation
- outline the pathway
Stimulus
- too much/too little water in blood (over/dehydrated
Receptor
- osmoregulators in the hypothalamus detect change in H2O blood volume
Control
- hypothalamus signals pituitary gland (controls ADH release) to:
- Too much H2O: slow/stop release of ADH
- Too little H2O: increase release of ADH
Effector
- Too much H2O: kidneys stop receiving signals to keep aquaporins of collecting ducts in nephrons open, less H2O absorbed
- Too little H2O: kidneys keep receiving signal to keep aquaporins open, more H2O absorbed
Response
- urine is greater/lesser in quantity, and more dilute/concentrated
- blood h2O volume reaches stability
134
STIMULUS-RESPONSE PATHWAYS:
3. Thermoregulation
- outline the pathway
Stimulus
- body temp decrease/increase
Receptor
- thermoreceptors (in skin + hypothalamus) detect change
Control
- hypothalamus activates mechanisms to cool/warm body
Effector
- To warm body: shivering, body hair stands up, vasoconstriction (blood vessels constrict to reduce blood flow to extremities)
- To cool body: pituitary gland signalled to trigger sweat glands to produce sweat, body hair flattens, vasodilation (blood vessels widen to increase blood flow to extremities)
Response
- body temp returns to normal/stable 37°, mechanisms stop
135
Describe how **fennec foxes** are adapted for efficient osmoregulation and thermoregulation.
- live in deserts: lack of water, hot days and cold nights. Must be adapted to cope
THERMOREGULATION
- small size: higher SA:V ratio allows faster rate of heat release
- large ears: release heat quickly through many blood vessels in ears
- fur: thick, keeps fox warm at night, light coloured, reflects the sun during hot daytime
- panting: very fast panting allows fox to release heat at a faster rate
OSMOREGULATION
- enlarged medulla in kidneys: more exposure to salty solution, more water is reabsorbed into blood, urine becomes more concentrated
- long Loop of Henle: allows more water to be reabsorbed back into blood
136
Describe how **polar bears** are adapted for efficient thermoregulation.
- live in artic: very cold. Must be adapted to cope
THERMOREGULATION
- undercoat: short hairs trap and dry air close to skin
- top layer of guard hairs: waterproof, preventing water coming in contact with skin, hollow, trap air for insulation = keep bear warm
- thick fat layer: insulation
- large and rounded: small SA:V ratio, decreases rate of heat loss as smaller area for heat to disperse
- countercurrent heat exchange: heat is transferred from warm arterial blood to cold venous blood, prevents heat loss
137
Describe how **mangroves** are adapted for efficient osmoregulation.
- live in tropic environments, in bays and estuaries: high salinity, waterlogged soil, humid. Must be adapted to cope
OSMOREGULATION
Salt-controlling processes prevent water loss via osmosis:
- removal of salt: in leaves or roots via ultrafiltration
- high water conc in leaves: salt is drawn into the leaves, balancing salt conc
- dropping of leaves: aged leaves drop from tree, removing salt from the organism
- SOME mangroves, hydrophobic barrier: located in roots, prevents majority of salt entering plant
138
Describe how **eucalypts** are adapted for efficient thermoregulation and osmoregulation.
- live in Australian climate: dry, sunny. Cannot survive in cold. Must be adapted to cope
OSMOREGULATION
- shedding: of mature leaves and twigs to reduce water loss through transpiration
- twisting of stems/leaves: hang vertically, preventing exposure to sun and therefore evaporation
THERMOREGULATION
- evaporation from leaves: cools down tree
- frost-proof sap: prevents damage to tree by frost
139
Describe how **desert animals** are adapted for efficient homeostasis.
- Large SA:V to maximise heat loss (may be smaller, have thinner features, skinner etc)
- Blood vessels close to surface to remove excess heat, especially near ears
- Urine highly concentrated
- Convert fat to water from food (not much H2O available for drinking)
- Loop of Henle is extra long to reabsorb H2O
140
Describe how **polar animals** are adapted for efficient homeostasis.
* Thick layer of insulation (e.g. blubber, penguins have
waterproof feathers)
- Small SA: V to reduce heat loss (rounded/compact
shape)
- Countercurrent heat exchange (moves heat to veins
before it is lost to environment)
141
Describe how **desert plants** are adapted for efficient homeostasis.
- Sunken stomata
- Thick waxy cuticle (prevents H2O loss)
- Hairs on leaves prevent water loss from wind
- Rolled in leaves minimises SA available for H20 loss
- rounded, compact shape
- cacti spines: hold stomata instead of leaves reduce H2O loss through transpiration, provide shade for plant
