Relationships in an ecosystem

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What is an Ecosystem?

An **ecosystem** is a community of living and non-living things interacting with each other.
Living things include plants, animals, and microorganisms.
Non-living factors include water, soil, and climate.
These interactions keep the ecosystem balanced and functioning.

Interdependence in Ecosystems

All organisms in an ecosystem are **interdependent** – they rely on each other to survive.
Plants need sunlight to make glucose through **photosynthesis**.
Herbivores depend on plants for food; predators depend on other animals.
If one part of the chain is disturbed, the whole ecosystem can be affected.

Pollination and Its Importance

**Pollination** is the transfer of pollen from one flower to another, enabling seed and fruit production.
Many plants, including food crops, need insects like **bees** to pollinate them.
Without pollinators, plants struggle to reproduce, affecting animals that rely on them.
Humans depend on insect pollination for fruits, vegetables, and nuts.

Impact of Insecticides

**Insecticides** are chemicals designed to kill insects, but they also harm beneficial insects like bees.
Reduced pollinator populations lead to lower crop yields and disrupt food chains.
This decreases **biodiversity**, making ecosystems less resilient.

Invasive Species

An **invasive species** is a non-native organism introduced to an ecosystem, often causing harm.
They outcompete native species for food and habitat, disrupt food chains, and reduce biodiversity.
Example: **Grey squirrels** introduced to the UK from North America have caused a decline in native red squirrels.
Grey squirrels compete for food and carry a disease deadly to red squirrels.

Human Food Security

Healthy ecosystems directly impact human **food security**.
Decline in pollinators can lead to food shortages and higher prices.
Protecting pollinators and controlling invasive species helps maintain food supply.

Energy pyramid showing trophic levels in an ecosystem.

Diagram illustrating pollination by a bee between two flowers.

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Practice questions

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1.Which of the following is an example of a pollinator?
Easy
- ABee
- BFox
- CRabbit
- DSquirrel
2.What is an ecosystem?
Easy
- AA community of living and non-living things interacting with each other
- BA group of organisms of the same species living together
- CThe non-living parts of an environment
- DA place where only plants grow
3.What is an invasive species?
Easy
- AA non-native organism that causes harm to an ecosystem
- BA native species that is very common
- CA species that lives only in water
- DA species that is always beneficial to the ecosystem
4.Which of the following is an example of an invasive species mentioned in the text?
Easy
- AGrey squirrel
- BRed squirrel
- CBee
- DRabbit
5.What does interdependence mean in an ecosystem?
Easy
- AOrganisms rely on each other to survive
- BOrganisms live independently of each other
- COnly plants depend on animals
- DOnly animals depend on plants
6.How can the use of insecticides affect an ecosystem?
Medium
- AThey can harm beneficial insects like bees, reducing pollination and crop yields
- BThey always increase biodiversity
- CThey only kill harmful insects with no side effects
- DThey improve the health of all plants
7.What would likely happen to human food supply if pollinator populations decrease?
Medium
- AFood shortages and higher prices due to lower crop yields
- BFood supply would increase because fewer insects eat crops
- CThere would be no effect because humans don't rely on pollinators
- DOnly meat would be affected, not fruits and vegetables
8.Why is pollination important for plants?
Medium
- AIt allows plants to produce seeds and fruit
- BIt helps plants absorb water
- CIt protects plants from herbivores
- DIt makes plants grow faster

More questions

9.How do grey squirrels negatively affect red squirrels in the UK?
Hard
- AThey compete for food and carry a deadly disease
- BThey are predators of red squirrels
- CThey destroy red squirrel habitats by cutting down trees
- DThey reproduce faster and take over all nests
10.Which of the following best describes the relationship between bees and flowering plants?
Hard
- AMutualistic: both benefit from pollination
- BParasitic: bees harm plants by taking pollen
- CCommensal: bees benefit, plants are unaffected
- DCompetitive: bees and plants compete for resources
11.Which of the following is NOT a likely consequence of introducing an invasive species?
Hard
- AIncreased biodiversity
- BDisruption of food chains
- CReduction in native species populations
- DOutcompeting native organisms for resources
12.What is the main source of energy for most ecosystems?
Medium
- ASunlight
- BSoil
- CWater
- DWind
13.Which of the following is the best definition of an ecosystem?
Easy
- AA community of living and non-living things interacting with each other
- BA group of organisms of the same species living together
- CThe non-living components of an environment
- DA food chain showing energy transfer
14.In a garden ecosystem, a gardener removes all the flowering plants. Which of the following is the most likely immediate effect?
Medium
- AThe number of bees will decrease
- BThe number of bees will increase
- CThe soil quality will improve
- DThe number of predators will increase
15.In a study of a grassland ecosystem, scientists recorded the following data: producers (grass) have 10,000 kJ of energy; primary consumers (rabbits) have 1,000 kJ; secondary consumers (foxes) have 100 kJ. What percentage of energy is transferred from producers to primary consumers?
Hard
- A1%
- B10%
- C90%
- D100%
16.The graph below shows the population of red squirrels and grey squirrels in a UK woodland over 20 years. Which statement best explains the trend?
Medium
- AGrey squirrels outcompete red squirrels for food and carry a disease harmful to red squirrels
- BRed squirrels are better adapted to the woodland than grey squirrels
- CGrey squirrels are eaten by red squirrels
- DThe climate change favoured red squirrels
17.A farmer uses an insecticide that kills all insects in his field. Which of the following is the most likely long-term consequence?
Medium
- ACrop yields will increase because there are fewer pests
- BPollination of crops will decrease, reducing fruit and seed production
- CThe soil will become more fertile
- DBirds that eat insects will increase in number
18.In an experiment, two identical fields are planted with the same crop. Field A is sprayed with insecticide; Field B is not. After one season, the yield from Field A is 20% lower than Field B. Which of the following is the most likely explanation?
Hard
- AInsecticide killed pests that were damaging the crop
- BInsecticide killed pollinators, reducing fruit set
- CInsecticide increased the growth of weeds
- DInsecticide made the soil acidic
19.A food chain in a pond ecosystem is: algae → water flea → small fish → large fish. If a chemical kills all the water fleas, what is the most likely immediate effect?
Medium
- AAlgae numbers will increase, and small fish numbers will decrease
- BAlgae numbers will decrease, and small fish numbers will increase
- CLarge fish numbers will increase
- DAll organisms will be unaffected
20.The table shows the number of different species in two ecosystems. Which ecosystem is more resilient to change?
Hard
- AEcosystem A because it has higher biodiversity
- BEcosystem B because it has more producers
- CEcosystem A because it has fewer consumers
- DEcosystem B because it has more total individuals
21.Pollination is the process of transferring pollen from one flower to another. What is the main benefit to the plant?
Easy
- AIt allows the plant to produce seeds and fruit
- BIt helps the plant grow taller
- CIt protects the plant from insects
- DIt provides the plant with water
22.Which of the following best describes interdependence in an ecosystem?
Medium
- AOrganisms rely on each other to survive
- BOrganisms compete for the same resources
- COrganisms are independent of each other
- DOnly plants depend on animals
23.A student investigates the effect of an invasive plant species on native plant diversity. She counts the number of native plant species in 10 quadrats in an area invaded by the non-native plant and in 10 quadrats in a nearby uninvaded area. Her results show an average of 4 species per quadrat in invaded areas and 12 species per quadrat in uninvaded areas. What is the most likely conclusion?
Hard
- AThe invasive plant increases native plant diversity
- BThe invasive plant reduces native plant diversity
- CThe invasive plant has no effect on native plants
- DThe invasive plant is eaten by native herbivores
24.A student sets up two identical garden plots. Plot A is left open to natural pollination. Plot B is covered with fine netting that excludes all insects but still allows sunlight and rain. After one growing season, the student counts the number of fruits produced by each plot. Which of the following is the most likely result?
Medium
- APlot A produces more fruits than Plot B.
- BPlot B produces more fruits than Plot A.
- CBoth plots produce the same number of fruits.
- DNeither plot produces any fruits.
25.In an experiment, a student uses a sweep net to collect insects from two areas: a wildflower meadow and a wheat field that has been sprayed with insecticide. The student counts the number of bees caught in each area. Which of the following is the most likely outcome?
Medium
- AMore bees are caught in the wildflower meadow than in the wheat field.
- BMore bees are caught in the wheat field than in the wildflower meadow.
- CThe same number of bees are caught in both areas.
- DNo bees are caught in either area.
26.A researcher studies a food chain: grass → rabbit → fox. She estimates that the grass contains 20,000 kJ of energy. Approximately how much energy is available to the fox?
Hard
- A200 kJ
- B2,000 kJ
- C20 kJ
- D20,000 kJ
27.A student uses a quadrat to sample the number of daisy plants in a lawn. She places the quadrat in five random locations and counts 12, 8, 15, 10, and 5 daisies. What is the mean number of daisies per quadrat?
Medium
- A10
- B12
- C50
- D8
28.A scientist is investigating the effect of an invasive plant species on native plant diversity. She sets up 10 quadrats in an area invaded by the species and 10 quadrats in an uninvaded area. She counts the number of native plant species in each quadrat. Which of the following is the independent variable?
Hard
- AThe presence of the invasive plant species
- BThe number of native plant species
- CThe size of the quadrat
- DThe location of the quadrat
29.A team of researchers wants to estimate the population of grey squirrels in a woodland. They capture 20 grey squirrels, mark them with ear tags, and release them. One week later, they capture 30 grey squirrels, of which 5 are marked. What is the estimated population size?
Medium
- A120
- B100
- C150
- D55
30.Which of the following is a method used to measure the population size of a plant species in a field?
Easy
- AUsing a quadrat
- BUsing a pitfall trap
- CUsing a sweep net
- DUsing a pooter
31.A farmer sprays insecticide on his crop to kill pest insects. Which of the following is the most likely long-term effect on the ecosystem?
Hard
- ADecreased biodiversity due to loss of pollinators and natural pest predators
- BIncreased crop yield because all insects are eliminated
- CImproved soil fertility from the insecticide
- DNo change to the ecosystem
32.The diagram shows a food web in a woodland ecosystem. Which organism is a primary consumer?
Medium
- ARabbit
- BFox
- COak tree
- DHawk
33.A student investigates the effect of temperature on the rate of pollination. She places potted plants in three different temperature-controlled rooms: 15°C, 20°C, and 25°C. She introduces the same number of bees to each room and counts the number of flowers pollinated after 2 hours. Which of the following is a controlled variable in this experiment?
Hard
- AThe number of bees introduced
- BThe temperature of the room
- CThe number of flowers pollinated
- DThe type of plant used
34.Which of the following statements best describes why the introduction of grey squirrels to the UK has led to a decline in red squirrel populations?
Medium
- AGrey squirrels compete with red squirrels for food and carry a disease that is deadly to red squirrels.
- BGrey squirrels are prey for red squirrels, reducing their numbers.
- CRed squirrels are an invasive species that outcompete grey squirrels.
- DGrey squirrels do not affect red squirrel populations.
35.Which of the following is an example of a non-living (abiotic) factor in an ecosystem?
Easy
- ASunlight
- BBees
- COak trees
- DRabbits
36.True or false: Invasive species are needed to keep ecosystems balanced.
Medium
- ATrue
- BFalse
- CIt depends on the species
- DOnly if they are native
37.A farmer sprays insecticide on his crop. Which of the following is the most likely long-term effect on the ecosystem?
Hard
- AIncreased biodiversity as pests are removed
- BDecreased crop yields due to reduced pollination
- CNo effect because insecticides only target pests
- DHigher populations of beneficial insects
38.What is pollination?
Easy
- AThe transfer of pollen from one flower to another
- BThe process of a seed growing into a plant
- CThe production of glucose by plants
- DThe movement of insects from plant to plant
39.Which of the following is a non-living (abiotic) factor in an ecosystem?
Medium
- ASoil
- BBees
- CTrees
- DBacteria
40.Grey squirrels carry a disease that is deadly to red squirrels but not to themselves. This is an example of:
Hard
- ACompetition
- BPredation
- CParasitism
- DMutualism

Revision notes

## Relationships in an Ecosystem An **ecosystem** is a community of living and non-living things interacting. All organisms are **interdependent**—they rely on each other for survival. For example, plants need sunlight for photosynthesis, animals eat plants, and predators eat other animals. Disrupting one part affects the whole ecosystem. **Pollination** is the transfer of pollen between flowers, enabling seed and fruit production. Many plants, including food crops, depend on insects like bees for pollination. Without pollinators, food production drops, causing shortages and higher prices. **Insecticides** kill insects but can harm beneficial pollinators like bees. This reduces crop yields, disrupts food chains, and lowers biodiversity, making ecosystems less resilient. **Invasive species** are non-native organisms that cause harm. They outcompete natives for resources and reduce biodiversity. Example: Grey squirrels introduced to the UK outcompete red squirrels and carry a deadly disease, causing red squirrel decline. ### Key Points - Ecosystems are balanced by interactions. - Interdependence means all organisms depend on each other. - Pollination is vital for plant reproduction and food supply. - Insecticides can harm pollinators and disrupt ecosystems. - Invasive species upset ecosystem balance.

Ecosystem: A community of living and non-living things interacting with each other.
Interdependence: The reliance of organisms on each other for survival.
Pollination: The process of transferring pollen from one flower to another, allowing the plant to produce seeds and fruit.
Insecticide: Chemicals designed to kill insects.
Invasive species: A non-native organism introduced to an ecosystem, often causing harm.

Flashcards

What is an ecosystem?

An ecosystem is a community of living and non-living things interacting with each other.

What does interdependence mean in an ecosystem?

Interdependence means that all organisms rely on each other to survive.

What is pollination?

Pollination is the process of transferring pollen from one flower to another, allowing the plant to produce seeds and fruit.

Why are bees important to ecosystems?

Bees are pollinators that help plants reproduce by transferring pollen. Many plants, including food crops, depend on bees for pollination.

How does insecticide use affect pollinators?

Insecticides can harm beneficial insects like bees, reducing pollinator populations and leading to lower crop yields and disrupted food chains.

What is an invasive species?

An invasive species is a non-native organism introduced to an ecosystem that often causes harm by outcompeting native species and reducing biodiversity.

Give an example of an invasive species in the UK.

The grey squirrel, introduced from North America, is an invasive species that competes with native red squirrels and carries a disease deadly to them.

How can a decrease in pollinators affect human food supply?

Fewer pollinators lead to lower crop yields of fruits, vegetables, and nuts, causing food shortages and higher prices.

What are the non-living components of an ecosystem?

Non-living components include water, soil, and climate.

Why are plants important in an ecosystem?

Plants produce glucose through photosynthesis, providing food for animals that depend on them.

What happens if one part of an ecosystem is disturbed?

It can impact the entire ecosystem because organisms are interdependent.

How do invasive species disrupt food chains?

Invasive species can outcompete native organisms for resources like food and habitat, disrupting food chains and reducing biodiversity.

What is the relationship between pollinators and food security?

Pollinators are essential for many food crops; without them, crop production declines, threatening food security.

What is the effect of reduced biodiversity on ecosystems?

Reduced biodiversity makes ecosystems less resilient to threats.

How do grey squirrels affect red squirrels?

Grey squirrels compete with red squirrels for food and carry a disease that is deadly to red squirrels but not to themselves.

What are insecticides designed to do?

Insecticides are chemicals designed to kill insects.

Why might insecticide use lead to lower crop yields?

Insecticides can kill pollinators like bees, reducing pollination and thus crop yields.

What is an example of interdependence in an ecosystem?

Plants need sunlight for photosynthesis, animals eat plants, and predators eat other animals.

How do invasive species reduce biodiversity?

They outcompete native species for resources, leading to declines or extinctions of native organisms.

What is the role of microorganisms in an ecosystem?

Microorganisms are part of the living community and interact with other organisms and the environment.

True or false: Bees are an example of a pollinator.

True.

True or false: Invasive species are needed to keep ecosystems balanced.

False.

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