1
Q
Define community
A
Populations of different species interacting.
2
Q
Define population
A
A species that occupy the same habitat.
3
Q
Define ecosystem
A
The interactions between the biotic and abiotic factors in an area.
4
Q
What do food chains show?
A
Food chains show the feeding relationships of different organisms and the flow of energy between the organisms.
5
Q
Define biomass
A
The total mass of living material.
6
Q
Why are producers the first trophic level?
A
Producers provide all biomass for the food chain (production of glucose via photosynthesis).
The rest of the food chain involves the transfer of this biomass.
7
Q
Describe the carbon cycle
A
Plants take in CO₂
• Plants “breathe in” carbon dioxide from the air during photosynthesis.
• They turn it into organic molecules like sugars.
2. Animals eat plants
• Animals (and humans) eat the plants.
• The carbon from the plants now becomes part of the animals’ bodies.
3. Respiration releases CO₂
• Both plants and animals breathe.
• This releases carbon dioxide back into the air.
4. Decomposition
• When plants and animals die, decomposers (like bacteria and fungi) break them down.
• This releases carbon back into the soil and air.
8
Q
Why is the carbon cycle important?
A
The carbon cycle is important because it recycles carbon through the environment,
Needed for carbon containing molecules like glucose which are essential for growth and respiration.
9
Q
Describe the water cycle
A
- Water from lakes and oceans evaporates.
- The evaporated water condenses into clouds and returns to earth as precipitation.
- The water from precipitation is useful for life on land.
- The water then returns to rivers and oceans through surface runoff. WATER RUNS ON LAND RATHER THAN BEING ABSORBED.
•
10
Q
Why is the water cycle important?
A
The water cycle is important because it provides a continuous supply of water to living organisms. Water is essential for photosynthesis, and transporting substances around organisms.
11
Q
Why are microorganisms important for the cycling of materials through an ecosystem?
A
Microorganisms (bacteria and fungi) return carbon to the environment by releasing carbon dioxide through respiration while they decompose dead matter. The decomposition of dead matter in soil returns mineral ions to the environment for other organisms
12
Q
What is meant by decomposition?
A
The breakdown of dead materials into simpler organic matter
13
Q
How do decomposers break down dead matter?
A
Decomposers release enzymes which catalyse the breakdown of dead material into smaller molecules.
14
Q
What are the two types of decomposition?
A
Aerobic decomposition (with oxygen)
Anaerobic decomposition (without oxygen)
15
Q
What factors affect the rate of decomposition?
A
- Temperature – Decomposers work faster in warmer conditions because their enzymes have more kinetic energy increasing activity; too hot or too cold slows decomposition.
- Oxygen availability – Aerobic decomposers need oxygen to respire; less oxygen slows decomposition.
- Water availability – Decomposers need moist conditions to survive and secrete enzymes
16
Q
Why can decomposition still occur in the absence of oxygen?
A
Some decomposers respire anaerobically.
However, the rate of decomposition is slower as anaerobic respiration produces less energy.
17
Q
How does soil water content affect the rate of decomposition?
A
Decomposers require water to survive:
In moist conditions the rate of decomposition is high.
In waterlogged soils there is little oxygen for respiration so the rate of decomposition decreases.
18
Q
Why does decomposition require water?
A
Water is required for the secretion of enzymes and absorption of dissolved molecules.
19
Q
What is compost?
A
The nutrient-rich product of the rapid decay of waste biological material (dead plants and animal waste) in optimum conditions set by gardeners and farmers.
20
Q
Describe how biogas generators work
A
Biogas generators provide methane gas for fuel through anaerobic decomposition that occurs in animal waste.
21
Q
Describe how environmental conditions affect communities
A
22
Q
What detrimental impacts can sulfur dioxide have on the environment?
A
- Formed when fossil fuels containing impurities are burnt.
- Sulfur dioxide can dissolve in water to form acid rain which can erode buildings and pollute water sources.
23
Q
Give 3 human activities that contribute to greenhouse gases
A
- Burning fossil fuels
- Deforestation.
- Large scale livestock farming
24
Q
How do greenhouse gases lead to global warming?
A
- Greenhouse gases allow heat from the sun to enter the atmosphere.
- The gases act as a ‘blanket’ and trap the heat in the atmosphere.
25
Roughly how much biomass is transferred to the level above it why is that?
10%
Because some food passed out in faeces large amounts of glucose used in respiration
some material lost in excretion
26
what are extremophiles
organisms living in extreme enviroments like those with high temperature pressure or salt concentration
27
What is a stable community
A stable community is a community where the biotic and abiotic factors are in balance, so that population sizes remain fairly constant over time.
28
Explain how the different fur colour increases the chance of survival
Allows to camouflage from predator in order to not be killed / eaten.
29
Give two ways the biomass is lost.
Lost through respiration
Lost in waste (faeces)
30
What type of acid is produced by digestion of fats in the milk?
Fatty acids
31
The lipids are broken down when the milk decays.
Explain why the pH changes more quickly when the temperature is higher.
enzymes more active at higher temperatures meaning lipids are broken down more quickly and fatty acids are produced more quickly which changes pH.
32
It is more energy-efficient to rear cows indoors than to rear cows outdoors.
Give two reasons why.
less energy lost as heat
less energy lost in movement
33
Suggest two possible disadvantages of rearing cows indoors.
Increased spread of disease
Possible aggressive behaviour (causing harm)
34
What is a mutation?
A change in DNA
35
As the numbers of green algae in the river increase, the concentration of dissolved oxygen increases.
Explain why the concentration of dissolved oxygen increases.
Algae carries out photosynthesis
(which) produces oxygen
36
Name three harmful substances that could cause water pollution.
fertiliser
sewage
toxic chemicals (like sulfur)
37
Chickens can use 80% of the biomass. What happens to the remaining 20% of the biomass?
lost via egestion / faeces
38
Suggest three reasons why some people are concerned about the use of
GM soya bean plants.
do not know effects on animals / humans (when eaten)
may affect flavour / taste (of product)
increased cost to consumer (for product)
39
Give three factors that the weeds and crop plants compete for.
Sunlight
Water
Minerals/ions
40
Suggest why the production of millions of antibiotic-resistant bacteria is a problem for farmers.
Many animals will become ill and may die or become inactive from this disease.
41
Suggest why diseases spread more quickly when the cows are kept indoors.
cows are kept closer together
42
What is interdependence?
Interdependence is the way different species in a community rely on each other for survival. (For food, seed dispersal, shelter)
43
Required practical - measure the population size of a common species in a habitat
44
Explain how conditions for decay are optimised by farmers
Farmers optimise decay by keeping compost warm, because higher temperatures increase the rate of enzyme activity in decomposers. They keep it moist, as water is needed for microorganisms to survive and carry out chemical reactions. They also provide oxygen by turning the compost, allowing aerobic respiration to release energy. These conditions together make decay happen faster.
45
Describe how methane gas can be produced from decaying materials for use as fuel
Methane gas can be produced from decaying materials using anaerobic digestion. Organic waste such as food scraps, manure or plant material is placed in a digester where microorganisms break it down in the absence of oxygen. During this process, the microbes carry out anaerobic respiration, which produces methane gas. This methane can then be collected and used as a fuel for heating, cooking, or generating electricity.
46
Required practical - investigate the effect of temperature on the rate of decay
47
Why is biodiversity important?
Biodiversity is important because it ensures the stability of ecosystems. A wide variety of species means that organisms can interact and depend on each other for food, shelter, and pollination, making the ecosystem more resilient to changes.
48
Explain the consequences of peat bog destruction
Peat bogs are wetlands where partially decomposed plant material (peat) accumulates over thousands of years.
Consequences of peat bog destruction:
1. Release of carbon dioxide – decomposition of peat releases stored carbon, contributing to global warming.
2. Loss of habitat – many plants, animals, and microorganisms that live in peat bogs are destroyed, reducing biodiversity.
3. Reduced water regulation – peat bogs normally store water and prevent flooding, so their destruction can increase flood risk and alter local ecosystems.
49
What is deforestation?
Deforestation is the large-scale removal of trees from an area of land. This is usually done to clear land for farming, urban development, or logging.
50
Describe programmes that aim to reduce the negative effects of humans on ecosystems
1. Breeding programmes – endangered species are bred in captivity and then reintroduced into the wild to increase their populations and maintain biodiversity.
2. Protection and regeneration of habitats – areas such as peat bogs, forests, and coral reefs are protected, restored, or replanted to provide habitat for organisms and maintain ecosystem balance.
3. Recycling programmes – materials such as plastic, glass, and metals are recycled to reduce the need for raw resources and minimise damage to ecosystems.
51
Describe the use of genetically modified organisms in food production
Genetically modified (GM) organisms are organisms whose genes have been altered to give them characteristics ( for example, GM crops can be modified to resist pests, diseases, or herbicides, which increases crop yields).
52
Describe how modern biotechnology is used in food production
1. Fermentation – microorganisms like yeast or bacteria are used to make products such as bread, cheese, yogurt, and alcohol.
2. Genetic modification (GM) – crops are genetically modified to resist pests, tolerate herbicides, survive harsh conditions, or increase nutritional value, which improves yield and food quality.
3. Enzyme use – enzymes are added to process food more efficiently, e.g., amylase in bread-making
53
Explain some methods that can help conserve fish stocks
1. Fishing quotas – limits are set on the amount and type of fish that can be caught to prevent overfishing and allow populations to reproduce and recover.
2. Net size regulations – using larger mesh nets allows younger, smaller fish to escape and grow, maintaining future breeding populations.
3. Fishing bans in certain areas or seasons – some areas are protected or closed during breeding seasons, ensuring fish have time to spawn
54
Explain the importance of maintaining fish stocks
Maintaining fish stocks is important to ensure the long-term sustainability of marine ecosystems and human food supply. If fish stocks are overfished, populations may decline, which can disrupt food chains and reduce biodiversity. Maintaining stocks ensures there are enough fish to reproduce, so future generations can continue to be harvested for food. It also helps to support the livelihoods of people who rely on fishing and prevents economic losses
55
Explain the term factory farming
Factory farming is the intensive rearing of large numbers of animals in small, confined spaces to produce food efficiently. In factory farms, animals such as chickens, pigs, and cattle are kept in controlled conditions to maximise growth rates and increase food production.
56
What is food security and biological factors that threaten it
Food security is having enough reliable, safe, and nutritious food to meet the dietary needs of a population.
Biological factors that threaten food security include:
1. Increasing human population – more people need more food, putting pressure on existing resources.
2. Pests and pathogens – diseases in crops or livestock can reduce yield and food availability.
3. Overfishing – depletes fish stocks, reducing a key food source.
57
Why should you RANDOMLY place quadrats?
To ensure the sample is unbiased and representative of the whole area.
58
What are parasites?
Organisms that live in or on a host organism. For example fleas which leave on the skin of other animals and such their blood to which feeds the flee.
59
Describe how plants are adapted to live in deserts
1. Reduced leaves or spines – many desert plants, like cacti, have spines instead of leaves to reduce water loss by transpiration.
2. Thick, waxy cuticle – leaves and stems have a waxy layer to prevent water evaporation.
3. Widespread roots – Shallow, widespread roots collect surface water from rain quickly.
4. Small or no leaves – reduces surface area for water loss.
60
Describe how animals are adapted to live in deserts
1. Water conservation – many desert animals, like camels, can store water in their bodies or survive on very little water.
2. Body temperature regulation – animals may be nocturnal (active at night) to avoid daytime heat, or have large ears to radiate heat.
3. Insulation and body coverings – some animals have thick fur or fat to protect against temperature extremes, or light-coloured fur to reflect sunlight.
61
How is Marram grass adapted?
Found in coastal regions and close to the sea:
Adaptation 1) Rolled leaves so stomata faces inwards. This prevents airflow over the lead and reduces surface area.
Adaptation 2) Waxy leaves which prevent water loss and conserve water.
Adaptation 3) Stiff hairs on inside of ledge to trap humid air against the leaf.
62
Adaptations of a cactus
Found in deserts in Sonora and Arizona
Adaptation 1) Thick, waxy coating which reduces water loss and keeps plant hydrated.
Adaptation 2) Spikes which act as a deterrent against predators and gives plant smaller surface area reducing water loss.
Adaptation 3) Shallow, widespread roots which allow plant to quickly absorb rainflow
63
The student placed the quadrat at regular intervals at a sea along a transect rather than placing quadrat at random positions. Why?
To investigate how the population changes with distance from the sea.
64
Explain why carbon dioxide levels in the atmosphere are changing
1. Burning fossil fuels – combustion of coal, oil, and gas releases carbon dioxide into the atmosphere.
2. Deforestation – cutting down trees reduces the amount of CO₂ absorbed during photosynthesis.
3. Agriculture – activities such as rice farming and livestock production release CO₂ and other greenhouse gases.
65
Behavioural structural and functional adaptations
1. Behavioural adaptations – actions or behaviours that help an organism survive.
• Example: Nocturnal activity in desert animals to avoid daytime heat.
2. Structural adaptations – physical features of an organism’s body.
• Example: Thick waxy cuticle on cactus stems to reduce water loss.
3. Functional adaptations – internal processes that help an organism survive.
• Example: Concentrated urine in desert animals to conserve water.
66
What is an apex predator?
An apex predator is an animal that sits at the top of a food chain and has no natural predators.
67
The sand gazelle feeds only at dawn and at dusk. At other times it stays in the shade.
Suggest how this helps the animal to conserve water.
The sand gazelle feeds at dawn and dusk when temperatures are cooler, reducing water loss through sweating and breathing.
By staying in the shade during the hottest part of the day, it avoids evaporation of water from its body, helping it to conserve water
68
Explain, as fully as you can, how natural selection leads to evolution.
Natural selection is the process by which organisms with advantageous characteristics are more likely to survive and reproduce.
In a population, individuals show variation in their characteristics due to mutations and genetic differences. Those with beneficial adaptations are more likely to survive environmental pressures and pass these adaptations to the next generation, while losing the unhelpful characteristics.
69
What is natural selection?
Natural selection is the process by which organisms with advantageous characteristics are more likely to survive and reproduce.
70
When fertiliser goes into the river, the concentration of oxygen dissolved in the water decreases. Explain why the concentration of oxygen decreases.
When fertiliser enters a river, it contains nitrates and phosphates which act as nutrients for microorganisms. This causes the growth of algae. When the algae and plants die, decomposers such as bacteria break them down through aerobic respiration, which uses up oxygen dissolved in the water. As a result, the oxygen concentration decreases.
71
A plant dies. The carbon in the dead leaves is recycled through the carbon cycle.
Explain how the carbon is recycled into the growth of new leaves.
Decomposers, such as bacteria and fungi, break down the dead plant material, releasing carbon dioxide through aerobic respiration.
This carbon dioxide enters the atmosphere and can be absorbed by living plants during photosynthesis, where it is used to make glucose and other organic molecules that form new leaves.
72
Give three possible reasons that may have caused a strawberry to decay.
1. Microorganisms – bacteria or fungi can infect the fruit, breaking down its tissues.
2. Enzyme activity – natural enzymes in the strawberry can break down cells over time.
3. Environmental conditions – warmth, moisture, or oxygen can speed up decay.
73
Give one way in which food production might be more efficient from battery chickens than from free-range chickens.
Battery chickens are kept in confined spaces, so less energy is wasted on movement. This means more of the energy from food is converted into body mass or eggs, making food production more efficient compared with free-range chickens that use more energy moving around.
74
The best temperature for anaerobic digesters is about 35 °C.
Explain why the volume of biogas produced would be less at higher temperatures.
At higher temperatures, their enzymes become denatured, so the microbes cannot carry out anaerobic respiration efficiently. As a result, less biogas is produced because the rate of decomposition decreases.
75
Name three products of anaerobic respiration.
1.Lactic acid
2.Ethanol
3.Carbon dioxide
76
Explain how the control of mesh size of fishing nets has helped to conserve stocks of herring.
Controlling the mesh size of fishing nets allows smaller, younger herring to escape and continue to grow and reproduce. This reduces overfishing, ensuring that enough herring survive to maintain the population and replenish the stocks
77
Suggest two ways that the hawk is adapted to catch and kill blue tits.
1. Sharp talons and beak – used to grip, kill, and tear the prey efficiently.
2. Keen eyesight – allows the hawk to spot small birds from a distance.
78
What is golden rice?
A gene is added to wild rice which makes it produce beta carotene. This changes the rice to a golden colour. Beta carotene is needed by humans in order to make vitamin A which is essential for good vision.
79
Describe how mycoprotein is produced
Mycoprotein is produced by growing the fungus Fusarium in large fermenters under aerobic conditions. The fungus is supplied with a carbohydrate-rich nutrient medium and oxygen, which allows it to undergo aerobic respiration and grow rapidly, forming hyphal biomass. The temperature and pH of the fermenter are carefully controlled to optimize growth. After sufficient growth, the fungal biomass is harvested, purified, and sometimes flavoured or textured to produce the final mycoprotein product.
80
Advantages for producing cultured meat instead of farmed meat
1. Reduced land use – Cultured meat doesn’t require large areas for grazing or growing animal feed
2. Lower greenhouse gas emissions – Producing meat in a lab produces less methane and CO₂ than raising livestock.
3. Animal welfare – No need to raise and slaughter animals.
4. Controlled conditions – Less risk of disease and contamination.
81
State two rules to help conserve fish stocks
1. Fishing quotas – Limiting the number or weight of fish that can be caught.
2. Minimum mesh size for nets – Ensuring young fish can escape and grow to maturity.
82
Why is it more energy efficient to rear cows indoors?
1. Controlled environment – Indoor housing protects cows from extreme weather, so less energy is wasted keeping them warm in winter or cool in summer.
2. Efficient feeding – Farmers can provide a balanced, concentrated diet that meets nutritional needs exactly, reducing the energy cows use to forage and digest lower-quality food.
3. Reduced movement – Cows don’t need to walk long distances for food or water, so more energy goes into growth or milk production
83
2 uses of water in plants
1. Photosynthesis
2. Transport of nutrients and minerals
