Biology (Unit 2) R#2 Flashcards
(232 cards)
1
Q
3h Transport
A
2
Q
What is the function of the xylem?
A
It transports water and mineral ions from roots to leaves and provides structural support.
3
Q
What is the function of the phloem?
A
It transports sucrose and amino acids from leaves to the rest of the plant (translocation).
4
Q
How does water enter root hair cells?
A
By osmosis, from high water potential in the soil to lower water potential in the root.
5
Q
How are mineral ions absorbed by root hair cells?
A
By active transport, using energy.
6
Q
What are the adaptive features of root hair cells? (3 points)
A
- Large surface area for faster absorption.
- Thin walls for a short diffusion distance.
- Large number of mitochondria to produce energy for active transport.
7
Q
What is transpiration?
A
The evaporation of water from the spongy mesophyll cells and its diffusion out through the stomata.
8
Q
Why is transpiration important?
A
- Cools down the plant.
- Creates a transpiration pull (suction) that helps transport water and minerals from root to leaf.
9
Q
How does temperature affect transpiration?
A
Higher temperatures increase kinetic energy of particles, leading to faster evaporation and increased transpiration.
10
Q
How does light intensity affect transpiration?
A
Higher light intensity keeps stomata open longer, allowing more water to escape, increasing transpiration.
11
Q
How does wind affect transpiration?
A
Wind removes water particles near the stomata, maintaining a steep concentration gradient and increasing transpiration.
12
Q
How does humidity affect transpiration?
A
High humidity reduces the concentration gradient, leading to lower transpiration rates.
13
Q
Why do large animals need a transport system?
A
They have a small surface area to volume ratio and large distances between organs, making diffusion too slow for oxygen and glucose to reach all cells efficiently.
14
Q
What are the three main types of blood vessels?
A
Arteries, veins, and capillaries.
15
Q
What are the structural adaptations of veins?
A
- Thin walls to be squeezed by skeletal muscles.
- Wide lumen to decrease resistance.
- Valves to prevent backflow of blood.
16
Q
Describe the pathway of blood circulation in the body.
A
Vena cava → Right atrium → Right ventricle → Pulmonary artery → Lungs → Pulmonary vein (oxygenated blood) → Left atrium → Left ventricle → Aorta → Body organs → Veins (deoxygenated blood) → Vena cava.
17
Q
What are the two types of heart valves and their locations?
A
Atrioventricular valves (in heart chambers):
* Tricuspid valve: Between the right atrium and ventricle.
* Bicuspid valve: Between the left atrium and ventricle.
Semi-lunar valves: At the start of arteries.
18
Q
How does exercise affect heart rate?
A
During exercise, heart rate increases to pump more blood carrying oxygen and glucose to muscles for increased aerobic respiration, providing energy for muscle contraction.
19
Q
How do you measure heart rate?
A
Press your middle and index fingers on an artery (e.g., wrist or neck), count beats for one second, multiply by 2, and take an average of multiple readings.
20
Q
What happens in coronary heart disease?
A
Cholesterol builds up in coronary artery walls, reducing elasticity, leading to less oxygen reaching the heart muscle, decreasing aerobic respiration and increasing anaerobic respiration, lactic acid buildup, and potential heart attack.
21
Q
What does plasma transport?
A
- Nutrient molecules from intestines to body cells.
- Hormones from glands to target organs.
- CO₂ from cells to lungs.
- Waste (urea) from liver to kidney.
22
Q
What is the function and adaptations of red blood cells?
A
Function:
* Transport oxygen.
Adaptations:
* Biconcave shape for larger surface area and faster diffusion.
* No nucleus to maximize space for hemoglobin.
23
Q
What are the two types of white blood cells and their functions?
A
Phagocytes:
* Engulf and digest pathogens using enzymes (phagocytosis) and absorb their products.
Lymphocytes:
* Produce antibodies that bind to specific antigens.
* Label pathogens for phagocytosis.
* Form memory cells that recognize pathogens upon re-exposure and produce antibodies faster (second immune response).
24
Q
What are the advantages of blood clotting?
A
- Prevents excessive bleeding.
- Prevents entry of pathogens.
25
What is the mechanism of blood clotting?
* Platelets stick to the edges of the cut blood vessel.
* Platelets release enzymes that convert **soluble fibrinogen** into **insoluble fibrin**, forming a mesh that traps blood cells.
26
How does insulin regulate blood glucose levels?
Insulin stimulates the liver to convert excess glucose into glycogen for storage.
27
Which blood vessel supplies the kidney with oxygenated blood>
Renal artery.
28
Which blood vessel carries filtered blood away from the kidney?
Renal vein.
29
Why don’t plasma proteins and blood cells pass into the filtrate?
They are too large to pass through the filtration membrane.
30
What substances are reabsorbed into the blood?
Glucose and amino acids.
31
What happens to plasma concentration when a person overheats?
Sweating causes plasma to become more concentrated.
32
Which organ detects changes in plasma concentration?
The hypothalamus.
33
Give an example of codominance in human blood groups.
IA = Group A, IB = Group B, IO = Group O.
34
Why do multicellular organisms require a transport system, and what features must it have?
In large organisms, not all cells contact the external environment, so diffusion alone is too slow and inefficient to supply oxygen, nutrients and remove wastes. A transport system must:
1. Move substances to and from cells quickly (bulk flow).
2. Be able to carry a variety of dissolved materials (soluble nutrients, gases, hormones, waste).
3. Operate continuously.
4. Have vessels or channels to direct flow.
35
What are the two types of vascular tissues in plants?
Xylem and Phloem.
36
What is a mass potometer used for?
To measure the mass decrease of water due to transpiration over time.
37
What is a bubble potometer used for?
To measure the distance an air bubble moves in a capillary tube over time, indicating the rate of water uptake.
38
What is the purpose of the reservoir in a bubble potometer?
It resets the bubble’s position for repeated measurements.
39
What are the structural adaptations of arteries?
1. Thick walls to withstand high pressure.
2. Elastic fibers to stretch and recoil.
3. Narrow lumen to maintain high pressure.
40
What are the structural adaptations of capillaries?
1. Thin walls for a short diffusion distance.
2. Pores between cells for rapid gas exchange.
41
What is the function of the septum?
It prevents the mixing of oxygenated and deoxygenated blood.
42
What happens if there is a hole in the septum?
Oxygenated and deoxygenated blood mix, decreasing oxygen levels, leading to less aerobic respiration and less energy production.
43
Why does the left ventricle have thicker walls than the right ventricle?
* The left ventricle pumps blood at high pressure to the whole body
* The right ventricle pumps at lower pressure to the lungs to prevent damage.
44
What are the risk factors for CHD?
* Smoking
* Stress
* Obesity
* Lack of exercise
* High consumption of animal fats in diet
45
How does vaccination work?
1. Injecting dead or weakened pathogens.
2. Lymphocytes identify the pathogen, produce antibodies, and create memory cells for faster future responses.
46
What is the function of the central nervous system (CNS)?
The CNS (brain and spinal cord) coordinates body responses by processing information from receptors and sending signals to effectors.
47
What is the correct pathway of a nerve impulse?
Stimulus → Receptor → Sensory Neurone → CNS → Motor Neurone → Effector → Response
48
What are receptors?
Cells that receive stimulus and convert it into electric impulses. Light, sound, heat and touch receptors
49
What are effectors?
Tissues that bring up a response. Ex: muscles, glands
50
How do hormones travel in the body?
Hormones are secreted by glands and travel through the bloodstream to target organs.
51
How does hormonal coordination differ from nervous coordination?
* Feature |Nervous |Hormonal
* Signal Type|Electrical|Chemical
* Speed |Fast |Slow
* Transport |Neurone|Blood
* Duration |Short |Long-lasting
52
What is the function of the cornea?
It refracts (bends) light to help focus it on the retina.
53
What is the function of the retina?
It contains light receptors (rods & cones) that convert light into electrical impulses.
54
What happens to the pupil in bright light?
The pupil constricts (gets smaller) because circular muscles contract and radial muscles relax.
55
What happens to the pupil in dim light?
The pupil dilates (gets larger) because circular muscles relax and radial muscles contract.
56
How does the body respond to overheating?
* Sweating: Sweat evaporates, cooling the body.
* Vasodilation: Blood vessels widen, increasing heat loss.
57
How does the body respond to overcooling?
* Vasoconstriction: Blood vessels narrow to retain heat.
* Shivering: Muscle contractions generate heat.
* Hairs stand up: Traps air for insulation.
58
What is tropism?
Tropism is a plant’s growth response to a stimulus, such as light or gravity.
59
How do plant stems respond to light?
Plant stems bend towards the light, showing **positive phototropism.**
60
How do plant roots respond to gravity?
Roots grow downwards, showing **positive geotropism.**
61
What occurs during fertilization in plants? (long)
* Fertilization is the fusion of male and female nuclei to form a zygote.
* It begins when pollen lands on the stigma, then the pollen grows a tube down the style, reaches the ovary, and enters the ovule through the micropyle.
* Once the ovule is fertilized, it becomes a seed and the ovary becomes a fruit.
62
What is the function of the fallopian tubes (oviducts)?
They are the site of fertilization.
63
What is the function of the vagina?
It is involved in copulation and sperm deposition.
64
What are secondary sexual characteristics in females?
* Breast enlargement
* Axial and pubic hair
* Widening of the pelvis
* Beginning of menstruation
65
What are the functions of FSH?
* Stimulates maturation of ova
* Stimulates development of the follicle
* Stimulates secretion of oestrogen
66
What are the functions of oestrogen?
* Repairs the uterine lining
* Stops FSH secretion
67
What hormone is secreted on day 13 of the cycle?
LH (Luteinizing Hormone).
68
What are the functions of LH?
* Causes ovulation (release of an ovum from the follicle)
* Stimulates secretion of progesterone
69
What is the function of progesterone?
It maintains the thickness of the uterine lining.
70
What are the functions of the placenta?
* Gas exchange (oxygen to foetus, CO₂ to mother)
* Nutrient transfer (glucose, amino acids)
* Excretion
71
What is the function of the umbilical cord?
* Umbilical artery: transports CO₂ and wastes away from foetus
* Umbilical vein: transports O₂ and nutrients to the foetus
72
What are the functions of the amniotic sac?
* Acts as a shock absorber
* Regulates temperature
* Allows foetal movement
73
What is the function of the testis?
* Formation of sperm
* Secretion of testosterone
74
What is the function of seminal vesicles and the prostate gland?
Formation of seminal fluid.
75
What is the function of the urethra in males?
Transport of both urine and semen.
76
What are secondary sexual characteristics in males?
* Facial, axial, and pubic hair
* Deepening of voice (Coarse deep voice)
* Widening of shoulders
77
What are the adaptive features of sperm?
* Nucleus: Contains haploid DNA (23 chromosomes)
* Acrosome: Secretes enzymes to digest the egg membrane
* Neck: Contains mitochondria to provide energy for movement
* Flagellum: Helps in swimming
78
What is excretion?
The removal of metabolic wastes, toxic substances, and substances in excess.
79
Give two examples of metabolic waste.
Urea and carbon dioxide (CO₂).
80
Name a toxic substance excreted by the body.
Alcohol.
81
Name two substances excreted in excess.
Salts and water.
82
What are the three main excretory organs?
Lungs, skin, and kidneys.
83
What is the main function of the urinary system?
To filter blood, remove waste, and regulate water balance.
84
By what process are glucose and amino acids reabsorbed?
Active transport using energy.
85
What is osmoregulation?
The process by which the body controls plasma concentration.
86
What hormone is released to regulate water balance?
ADH (Antidiuretic Hormone).
87
Define a gene.
A segment of DNA occupying a specific location on a chromosome that codes for a protein.
88
In rats, black fur (B) is dominant to grey fur (b). What does the genotype BB represent?
Homozygous dominant (black fur).
89
In rats, black fur (B) is dominant to grey fur (b). What does the genotype Bb represent?
Heterozygous dominant (black fur).
90
Define a gene.
A length of DNA on a chromosome that codes for a specific protein (a sequence of bases of DNA that codes for a sequence of amino acids).
91
Define phenotype.
An observable feature of an organism.
92
Define genotype.
The allele combination an organism has (e.g., AA, Aa, or aa).
93
Define codominance.
* A case where two alleles are neither dominant nor recessive to each other, and both are expressed in the phenotype.
* The offspring shows a different phenotype than either parent.
94
What is polygenic inheritance?
A phenotype controlled by more than one gene, **resulting in continuous variation.**
95
What are the effects of biotic and abiotic factors on the distribution of organisms?
**Abiotic factors:**
* Temperature
* Light intensity
* Wind speed
* Soil pH
**Biotic factors:**
* Competition over resources
* Availability of nutrition
* Predation (predators in ecosystem for species)
* Diseases
96
State and explain the 3 types of ecological pyramids
**Pyramid of numbers:** shows the population of each trophic level
**Pyramid of biomass:** shows the biomass (mass) of each trophic level
**Pyramid of energy:** shows the energy transferred from one trophic level to the next
1. Only 10% is transferred between each trophic level
2. Energy is lost in the form of heat, and in the 8 life processes
97
What are the consequences of global warming?
1. Habitat destruction
2. Climate changes
3. Migration of animals
4. Extinction of animals
98
What three factors limit the rate of photosynthesis in crops grown in controlled environments?
* Temperature: Higher temperatures increase the reaction rate as particles gain kinetic energy, speeding up enzyme-catalyzed reactions.
* Light intensity: Increased light boosts the rate of photosynthesis.
* Carbon dioxide concentration: More CO₂ speeds up photosynthesis.
99
Why are fertilizers used in agriculture and what are some common examples (4 points)?
**Purpose:** To increase crop yield by providing essential nutrients.
**Examples:**
* Nitrates: For amino acid and protein synthesis.
* Potassium: To strengthen plants and boost disease resistance.
* Phosphorus: Important for ATP production and enzyme synthesis.
* Magnesium: Needed for chlorophyll production.
100
What ecological problem can result from the overuse of fertilizers?
Overuse can lead to **eutrophication**, which disrupts aquatic ecosystems.
101
What are the main types of pests that can reduce crop yield (3 types)?
* Insects and animals that eat crops.
* Weeds that compete for nutrients, water, and space.
* Fungi that infect and cause diseases in crops.
102
What are the two main approaches to controlling pests in agriculture?
* Chemical Control: Using pesticides such as insecticides, herbicides, and fungicides.
* Biological Control: Introducing natural predators or competitive species to control pests.
103
What are the disadvantages of using chemical pesticides (4 points)?
1. They are non-selective, affecting both harmful and beneficial organisms.
2. Require repeated application.
3. Pests may develop resistance over time.
4. They accumulate in food chains (bioaccumulation)
104
What advantages does biological control offer over chemical pesticides (4 points)?
1. It is specific to the pest species.
2. Effects are long-lasting without needing reapplication.
3. No resistance develops in pests.
4. There is no bioaccumulation or pollution.
105
What are the disadvantages of biological control methods (3 points)?
1. They do not completely eliminate the pest species.
2. They may disturb the existing food chain.
3. They take longer to show effectiveness.
106
Define transgenic, restriction enzymes, and ligase enzymes.
* Transgenic: The transfer of genetic material from one species to another.
* Restriction enzymes: Enzymes that cut DNA at specific sites.
* Ligase enzymes: Enzymes that join pieces of DNA together.
107
What benefits do genetically modified crops offer (3 points)?
* Increased crop yield.
* Enhanced resistance to pests and herbicides.
* Ability to produce additional vitamins (e.g., golden rice rich in vitamin A).
108
What is pharming and how is it achieved using cloned transgenic animals (definition, steps, and example)?
**Pharming:** The process of producing useful human proteins by using transgenic animals.
**Steps:**
1. Create a transgenic animal with a gene that causes it to produce a desired compound (e.g., in its milk).
2. Clone the animal to form a herd or flock, ensuring all individuals produce the same compound.
**Examples:** Production of antibodies for cancer therapy or blood clotting factor IX for haemophilia.
109
What are the benefits of using cloned transgenic animals in biotechnology (3 points)?
1. They produce genetically identical offspring.
2. Large numbers of clones can be generated quickly.
3. They can be used to produce organs for transplant and other therapeutic compounds.
110
What is pollination and what are its two main types?
Pollination is the transfer of pollen from anther to stigma.
Self-pollination: same flower or plant.
Cross-pollination: between different plants; increases genetic variation. Agents include insects, wind, water, animals.
111
3i Excretion
112
What do the lungs excrete?
Carbon dioxide (CO₂).
113
What does the skin excrete?
Sweat (water and salts).
114
What does the kidney excrete?
Urine (water, salts, and urea).
115
What tube carries urine from the kidneys to the bladder?
Ureter.
116
What organ stores urine before excretion?
Bladder.
117
Through which structure does urine exit the body?
Urethra.
118
Where are nephrons located in the kidney?
In the cortex of the kidney.
119
What is the function of nephrons?
They filter blood and form urine.
120
Where does ultrafiltration occur?
In the glomerulus inside the Bowman’s capsule.
121
Why does ultrafiltration occur?
Due to high blood pressure in the glomerulus.
122
What substances are in the filtrate after ultrafiltration?
Water, urea, salts, glucose, and amino acids.
123
Where does selective reabsorption take place?
In the proximal convoluted tubule.
124
Which gland releases ADH?
The pituitary gland.
125
How does ADH affect the kidney?
It increases the permeability of the collecting duct, allowing more water to be reabsorbed.
126
What happens to urine when ADH levels are high?
The volume of urine decreases, and its concentration increases.
127
What is the role of ADH in maintaining body water balance?
Antidiuretic hormone (ADH), released by the posterior pituitary, increases the permeability of kidney collecting duct walls to water. When blood osmolality rises (dehydration), ADH levels ↑, more water is reabsorbed into the blood, urine becomes more concentrated, and blood water potential is restored. When over-hydrated, ADH secretion ↓, leading to dilute urine.
128
What are the main constituents of normal urine and their functions?
Urine is typically ~95 % water plus:
- Urea: from amino acid deamination (toxic).
- Electrolytes (e.g. Na⁺, K⁺, Cl⁻): help maintain ion balance.
- Creatinine: from muscle metabolism.
- Small amounts of hormones/drugs: filtered then not reabsorbed.
129
3j Co-ordination and response
130
What is the role of a sensory neurone?
It transmits electrical impulses from receptors to the CNS.
131
What is a synapse?
* A synapse is a small gap between two neurones.
* Impulses cross synapses by neurotransmitters.
132
What is a reflex arc?
A rapid, automatic response to stimuli that bypasses the brain for quicker reaction to protect the body from danger.
133
What is the function of a relay neurone?
It connects sensory and motor neurones within the CNS to relay impulses.
134
What is the function of adrenaline?
* It prepares the body for "fight or flight"
* Increases heart rate, breathing rate, and blood glucose levels.
* Dialates pupils for better vision
135
What do rods and cones detect?
* Rods: Black & white vision (dim light).
* Cones: Color vision (bright light).
136
What happens to the lens when focusing on a distant object?
* Ciliary muscles relax.
* Suspensory ligaments tighten.
* Lens becomes thinner (less convex).
137
What happens to the lens when focusing on a near object?
* Ciliary muscles contract.
* Suspensory ligaments loosen.
* Lens becomes thicker (more convex).
138
What is homeostasis?
The regulation of internal conditions to maintain a stable environment.
139
What is phototropism?
Phototropism is a plant’s growth response to light.
140
What is the advantage of positive phototropism?
It allows more light absorption, leading to increased photosynthesis and growth.
141
Which plant hormone is responsible for phototropism?
Auxins control phototropism by regulating cell elongation.
142
Where are auxins produced?
Auxins are produced at the tip of the stem.
143
What happens to auxins in response to strong directional light?
Auxins diffuse away from the light and accumulate on the shaded side of the stem.
144
How do auxins cause bending towards the light?
Auxins stimulate cell elongation on the shaded side, making the stem bend towards the light
145
What is geotropism?
Geotropism is a plant’s growth response to gravity.
146
Why is positive geotropism in roots beneficial?
* Anchors the plant securely in the soil.
* Helps roots absorb water and mineral ions.
147
What are the main characteristics of sexual reproduction in plants? (6)
Sexual reproduction in plants:
* Involves 2 parents
* Produces non‑identical offspring
* Variation occurs
* Gametes are present
* Fertilization occurs
* Is a slow process.
148
What are the main characteristics of asexual reproduction in plants? (6)
Asexual reproduction in plants:
* Involves 1 parent
* Produces identical offspring
* No variation
* No gametes are present,
* No fertilization occurs
* Is a rapid process
149
What advantages does sexual reproduction offer in plants? (2)
* Sexual reproduction increases variation, which enhances adaptation to changes in the environment
* Increases resistance to diseases.
150
What advantages does asexual reproduction offer in plants? (2)
* Asexual reproduction is a rapid process
* Since offspring are identical, favourable features are passed on
151
What is the function of the anther in sexual reproduction of plants?
The anther produces pollen, which contains the male gamete.
152
What is the function of the stigma in sexual reproduction of plants?
The stigma receives pollen during pollination.
153
What is the role of the ovary in sexual reproduction of plants?
The ovary contains **ovules**, which house the female gamete.
154
What is pollination in the context of plant sexual reproduction?
Pollination is the transfer of pollen from the anther to the stigma.
155
What are examples of asexual reproduction in plants using natural methods?
Natural examples include strawberry runners and potato tubers.
156
What is an artificial example of asexual reproduction in plants?
An artificial example is taking cuttings (note the correct spelling).
157
Define producer, consumer, decomposer, herbivore, carnivore, and trophic level
* **Producer:** an organism that makes its own nutrients usually using energy from the sun (photosynthesis)
* **Consumer:** an organism that gets its energy by feeding
* **Decomposer:** an organism that gets its energy from decomposing dead or waste organic material
* **Herbivore:** an animal that gets its energy by eating plants
* **Carnivore:** an animal that gets its energy by eating animals
* **Trophic level:** the position of an organism in a food chain, food web, or a pyramid of biomass/numbers
158
What benefits do polythene tunnels provide in outdoor crop production (3 points)?
* Protect crops from harsh weather (rain, wind, high temperatures).
* Prevent the entry of pests.
* Slightly increase the internal temperature.
159
Describe the role of yeast in the production of bread. (4 points)
1. Yeast performs **anaerobic respiration**, producing ethanol and carbon dioxide.
2. Enzymes from yeast break down starch into glucose for energy.
3. The produced CO₂ is trapped in dough, causing it to rise.
4. During baking, ethanol evaporates and yeast dies due to high temperatures.
160
How does lactobacillus contribute to yoghurt production (4 points)?
1. Equipment is sterilized, and milk is pasteurized to eliminate competing bacteria.
2. After cooling, lactobacillus is added to ferment lactose into lactic acid.
3. The increase in acidity causes the milk to clot and form yoghurt.
4. Cooling the yoghurt stops the fermentation process.
161
How are genetically modified bacteria used to produce human proteins like insulin (4 points)?
1. The human insulin gene is cut with a restriction enzyme.
2. A bacterial plasmid is also cut using the same enzyme.
3. Ligase enzyme joins the human insulin gene with the plasmid, forming recombinant DNA.
4. The plasmid acts as a vector to transfer the insulin gene into bacteria, which then reproduce in a fermenter to produce insulin.
162
Compare sexual and asexual reproduction in terms of method and genetic variation.
Sexual: fusion of haploid gametes → genetically variable offspring; requires two parents; energy cost high.
Asexual: mitotic division from one parent (e.g. binary fission, runners, budding) → clones; rapid population increase; no variation (unless mutation).
163
Describe the structure and function of the male human reproductive organs.
Testes: produce sperm & testosterone.
Epididymis: sperm maturation.
Vas deferens: sperm transport.
Seminal vesicles & prostate: add seminal fluid.
Urethra & penis: deliver semen into female tract.
164
Describe the structure and function of the female human reproductive organs.
Ovaries: produce eggs (ova) & hormones (oestrogen, progesterone).
Fallopian tubes: site of fertilisation, carry egg to uterus.
Uterus: implantation and fetal development.
Cervix: opens into vagina.
Vagina: receptacle for sperm, birth canal.
165
4a Reproduction
166
What are the distinguishing features of insect-pollinated flowers? (5)
Insect-pollinated flowers have:
* large bright petals
* A sticky stigma
* The anther and stigma are inside the flower
* They have nectar
* Pollen is large and sticky
167
What are the distinguishing features of wind-pollinated flowers? (5)
Wind-pollinated flowers have:
* Small dull petals
* Feathery stigma
* The anther and stigma hang outside the flower
* They have no nectar
* Pollen is smooth and small
168
What role does water play in the germination of a seed?
Water activates enzymes and acts as a medium for chemical reactions necessary for germination.
169
Why is an optimum temperature important for seed germination?
An optimum temperature is necessary for optimum enzyme activity during germination.
170
How does oxygen contribute to seed germination?
Oxygen is required for aerobic respiration, which releases energy for the growing seed.
171
What is the function of the ovaries?
They form ova by meiosis and secrete oestrogen.
172
What is the function of the uterus?
It is the site of implantation.
173
What happens to the cervix during childbirth?
It dilates.
174
What hormone is released at the beginning of the menstrual cycle?
FSH (Follicle Stimulating Hormone).
175
Describe the process and significance of fertilisation.
Fertilisation is the fusion of a male gamete (sperm/pollen) with a female gamete (egg/ovule) to form a diploid zygote. It restores the full chromosome number and combines parental alleles, creating genetic diversity essential for adaptation.
176
Label the main parts of a flowering plant and state their functions.
Sepal: protects bud.
Petals: attract pollinators.
Stamen (anther + filament): produces pollen (male gametes).
Carpel/Pistil (stigma, style, ovary): receives pollen; style conducts pollen tube; ovary contains ovules (female gametes).
177
Outline the steps of fertilisation in flowering plants.
1. Pollen grain hydrates and germinates on stigma, forming a pollen tube.
2. Tube grows down the style to the ovary.
3. Two male nuclei travel: one fuses with the egg (forming zygote), the other with two polar nuclei (forming endosperm)—double fertilisation.
178
How does a fertilised ovule develop into a seed?
Zygote → embryo (radicle, plumule, seed leaves).
Endosperm → food store.
Ovule integuments → seed coat. The whole ovary wall may become a fruit.
179
Why is seed dispersal important, and what methods do plants use?
Dispersal reduces competition and spreads species. Mechanisms:
- Wind (e.g. dandelion, sycamore).
- Animal ingestion (fleshy fruits).
- Attachment (burrs).
- Explosive (peas pods).
180
What roles do FSH and LH play in the menstrual cycle?
FSH (follicle-stimulating hormone): stimulates follicle growth and oestrogen secretion.
LH (luteinising hormone): triggers ovulation and formation of the corpus luteum.
181
What is the role of oestrogen in the menstrual cycle?
Secreted by growing follicles, oestrogen:
- Thickens endometrium.
- Inhibits further FSH (negative feedback).
- At high concentration, triggers LH surge (positive feedback).
182
How does progesterone regulate the menstrual cycle?
Produced by the corpus luteum, progesterone:
- Maintains endometrium for implantation.
- Inhibits FSH and LH to prevent further ovulation.
If pregnancy doesn’t occur, corpus luteum degenerates, progesterone falls, endometrium sheds (period).
183
Summarise the hormonal changes over a 28-day menstrual cycle.
Days 1–5: Low FSH/LH/oestrogen/progesterone → menstruation.
Days 6–14: FSH↑ → follicle grows → oestrogen↑ → endometrium rebuilds → LH surge → ovulation.
Days 15–28: Corpus luteum → progesterone↑ & oestrogen moderate → endometrium maintained; if no fertilisation, hormones fall → menstruation.
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4b Inheritance
185
Describe the overall structure of DNA.
DNA consists of two strands coiled together to form a double helix.
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What are the three components of a DNA monomer?
A DNA monomer (nucleotide) consists of:
* A sugar (deoxyribose)
* A phosphate group
* A nitrogenous base.
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What are the four nitrogenous bases found in DNA?
* Adenine (A)
* Thymine (T)
* Cytosine (C)
* Guanine (G)
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How do the nitrogenous bases hold the two DNA strands together?
Through base pairing:
* Adenine (A) pairs with Thymine (T)
* Cytosine (C) pairs with Guanine (G)
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How many strands does RNA have?
One strand.
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What type of sugar is found in RNA?
Ribose.
191
What are the four nitrogenous bases found in RNA?
* Adenine (A)
* **Uracil (U)**
* Cytosine (C)
* Guanine (G).
192
Define an allele.
Different forms of the same gene.
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Define a chromosome.
A strand of DNA carrying genes.
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Define a dominant allele.
The form of a gene that is expressed in the phenotype of a heterozygous genotype.
195
Define a recessive allele.
The form of a gene expressed in the phenotype only in the absence of a dominant allele.
196
Briefly describe transcription.
DNA unzips and unwinds, and the sequence of bases of DNA is copied into mRNA.
197
Briefly describe translation.
* mRNA leaves the nucleus and attaches to a ribosome in the cytoplasm.
* tRNA with an anticodon brings a specific amino acid, and amino acids bind together to form a protein molecule.
198
Define mutation.
A change in the sequence of bases in DNA, resulting in a change in the sequence of amino acids in a protein molecule, causing a change in the shape and function of the protein.
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How does mutation lead to variation within a species?
Mutation introduces new alleles, which can result in different traits.
200
How does natural selection occur?
Individuals with favorable alleles survive and reproduce at a higher rate, increasing the number of individuals with those alleles in the population.
201
Give an example of natural selection.
The development of antibiotic resistance in bacteria.
202
Describe the key features of mitosis.
Produces 2 daughter cells, which are diploid and identical to the parent cell.
| Example: growth/repair.
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Describe the key features of meiosis.
Produces 4 daughter cells, which are haploid and not identical to the parent cell.
| Example: production of gametes.
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5a The organism in the environment
205
Define population, community, habitat, environment, ecosystem, and biodiversity
1. **Population:** the number of living organisms of the same species living in the same place and time
2. **Community:** different populations in a habitat
3. **Habitat:** a place where living organisms live
4. **Environment:** biotic and abiotic factors
5. **Ecosystem:** interaction between organisms and their environment
6. **Biodiversity:** the measure of the rage of species in an ecosystem
206
How is population size in a habitat (estimate) investigated?
* Select a quadrat of a suitable size (Ex: 1m²)
* The quadrat is placed randomly using random generator
* Count number of organisms in the quadrat
* Repeat and take average
* Calculate total estimated number of organisms in habitat
* a. This is done by multiplying the average by the total area
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Which diagrams represent energy flow in an ecosystem?
* Food chain: a diagram showing the flow of energy from one organism to the next beginning with a producer
1. Ex: Plant → Primary consumer → Secondary consumer
* Food web: a network of interconnected food chains
208
What are the types of pesticides and their primary effects on pest populations (3 advantages)?
* Insecticides: Kill insect pests.
* Herbicides: Kill plant pests (weeds).
* Fungicides: Kill fungal pests
**Advantages:**
1. They can kill the entire pest population
2. Are inexpensive and easily accessible
3. Have immediate effect
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5b Feeding relationships
210
5c Cycles within ecosystems
211
What processes occur in the carbon cycle?
* **Combustion:** fossil fuels and plants can be burnt for fuel releasing carbon dioxide into the atmosphere
* **Decomposition:** bacteria/fungi convert complex molecules (waste/dead organic) into carbon dioxide
* **Photosynthesis:** takes in carbon dioxide, so less carbon dioxide in atmosphere
* **Respiration:** releases carbon dioxide to the atmosphere
* **Feeding:** animals eat plants/other organisms
* **Incomplete decomposition and fossilisation:** leads to formation of fossil fules
212
What processes occur in the nitrogen cycle, and what organisms preform them?
* **Nitrification:** nitrifying bacteria oxidise the ammonia to nitrites, then to nitrates
* **Denitrification:** denitrifying bacteria: convert nitrates in the soil to nitrogen
* **Nitrogen Fixation:** nitrogen fixing bacteria convert nitrogen to ammonia
* **Decomposers:** produce ammonia from nitrogen in proteins in dead organisms
* **Lightning:** nitrogen fixation by nitrogen in air (Harber process)
213
5d Human influences on the environment
214
What human influences affect the environment regarding pollution?
**Pollution by sulfur dioxide:**
* Sulfur dioxide reacts with water vapour to form acid rain
* Acid rain increases the acidity of lakes and soil, this leads to death of fish and plants
* Acid rain leads to erosion of buildings
* Inhalation of sulfur dioxide causes asthma and lung damage
**Pollution by carbon monoxide:**
* Reacts with haemoglobin in the blood to form carboxyhaemoglobin which decreases the concentration of oxygen in the blood
215
What are the greenhouse gases and how does the greenhouse gas effect work?
**Greenhouse gases:**
* **Water vapour:** naturally exists
* **Carbon dioxide:** burning fuels / In car exhausts
* **Nitrous oxides:** fertilizers / Cattle waste / At high temperatures in car engines
* **Methane:** released from cattle (livestock) / In rice paddy fields)
* **CFCs:** when fridges are disposed of (they are used in fridges) / Aerosol sprays
**Greenhouse gas effect:**
Greenhouse gases form a layer of impenetrable gasses that trap the Sun’s radiation in the Earth’s atmosphere causing global warming
216
What are the causes of eutrophication and sewage pollution?
* Overuse of fertilizers
* Sewage disposal in water
217
What is the process of eutrophication?
* Leaching of mineral ions into rivers and lakes
* Overgrowing of algae (algal bloom) blocks sunlight
* Underwater plants don’t photosynthesise and die
* Increase in number of decomposers consuming O₂ in water causing death of fish
218
What is the relation between sewage pollution and eutrophication?
* Sewage contains microorganisms which will consume O₂ causing death of fish
* Sewage contains nutrients that will cause algal bloom
219
What are the effects of deforestation?
* Leaching
* Soil erosion as the roots of trees hold soil together
* Less transpiration, so less water vapour in air, so less rain
* Imbalance of CO₂ and O₂ in the atmosphere
* Destruction of habitats and extinction of animals
220
6a Food production
221
How are temperature, light intensity, and CO₂ concentration controlled in glasshouses?
* Temperature: Artificial heaters are used to reach optimum levels.
* Light intensity: Artificial lighting supplements natural light.
* Carbon dioxide: CO₂ levels are increased by burning paraffin wax.
222
What additional environmental factor should be controlled in glasshouses besides temperature, light, and CO₂?
Humidity control is crucial. Maintaining optimal humidity helps manage transpiration rates and prevents fungal diseases
223
What is an industrial fermenter and what conditions are controlled within it (6 points)?
**Industrial fermenter:** A container used to culture large quantities of microorganisms (bacteria and fungi).
**Controls include:**
1. Aseptic precautions: Sterilization by steam.
2. Agitation: Stirring for even distribution of nutrients, heat, and organisms.
3. Temperature: Monitored by probes and regulated via a water jacket.
4. pH: Controlled with probes and buffer solutions.
5. Oxygenation: Ensuring sufficient O₂ for aerobic respiration.
6. Nutrition: Supply of essential nutrients and ammonia
224
What measures are taken to ensure high yields in fish farming (7 points)?
1. Water quality: Use of filters and regular oxygen pumping.
2. Predation control:
**Intraspecific:** Separating small and large fish.
**Interspecific:** Using nets to prevent predation by other species.
3. Disease management: Adding antibodies.
4. Feeding: Providing food in small, regular amounts.
5. Waste management: Regular cleaning of tanks, nets, and fences.
6. Selective breeding: Using fish with desired traits for reproduction.
225
What are the environmental concerns associated with fish farming?
Fish farming can lead to water pollution and may spread diseases to wild populations if not managed properly.
226
6b Selective breeding
227
What is selective breeding and how is it carried out (in animals & plants)?
**Definition:** Choosing individuals with desired traits to breed, then selecting offspring with those traits over many generations.
**Application:**
* **In plants:** Select and cross plants with favorable characteristics while preventing undesired ones from reproducing.
* **In animals:** Choose and breed animals with desired traits, then select the best offspring for further breeding.
228
6c Genetic modification
229
What is genetic engineering and what is its main objective?
**Definition:** Modifying an organism’s genome by introducing a gene from another species to give a desired characteristic.
**Goal:** To enhance traits such as crop yield, pest resistance, and nutritional value.
230
6d Cloning
231
What is micropropagation and how is it performed (5 points)?
**It is plant cloning**
**Process:**
1. Sterilize a Petri dish.
2. Use a scalpel to cut an explant from a plant with desired traits.
3. Transfer the explant into an agar gel containing auxins and nutrients.
4. Provide light and water to stimulate growth.
5. The explant develops roots and grows into a complete plant, producing many identical copies.
232
What are the stages involved in cloning a mammal (4 points)?
1. Remove a diploid nucleus from a body cell.
2. Enucleate an ova (remove its nucleus).
3. Insert the diploid nucleus into the enucleated ova and stimulate it (often by an electric shock) to start dividing into an embryo by mitosis.
4. Implant the embryo into the uterus of a surrogate mother.
