B7 - Further Biology (Learning from Ecosystems)

Question 1

a) In a perfect, stable ecosystem, what would there be none of?
b) Why is this?

Answer 1

a) Waste

b) Because the output from one part of the system becomes the input to another part

Question 2

What are the waste materials from one part of the ecosystem used as by another part of the ecosystem?

Answer 2

As food or reactants

Question 3

When waste materials from one part of the ecosystem used as by another part of the ecosystem as food or reactants, what is this type of system called?

Answer 3

A closed-loop system.

Question 4

Define what a closed-loop system is

Answer 4

When the output from one part of the system becomes the input to another part.

Question 5

In stable ecosystems, what must any output (loss) be balanced by?

Answer 5

Input (gain)

Question 6

In stable ecosystem, what must any input (gain) be balanced by?

Answer 6

Output (loss)

Question 7

In any natural ecosystem (e.g. a rainforest), the waste products include what? (3 things)

Answer 7

• Oxygen from photosynthesis
• Carbon dioxide from respiration
• Dead matter of living things

Question 8

In any natural ecosystem (e.g. a rainforest), the waste products can include oxygen from photosynthesis. How can this be used?

Answer 8

In respiration

Question 9

In any natural ecosystem (e.g. a rainforest), the waste products can include carbon dioxide from respiration. How can this be used?

Answer 9

In photosynthesis

Question 10

In any natural ecosystem (e.g. a rainforest), the waste products can include dead matter of living things. How can this be used?

Answer 10

Either directly as food or decomposed by microorganisms

Question 11

Give some examples of dead matter of living things, that can be waste products from a natural ecosystem (e.g. a rainforest).

Answer 11

• Remains of bodies
• Fallen leaves
• Petals
• Fruits
• Pollen
• Sperm
• Eggs
• Faeces

Question 12

In order to survive, what do many organisms do?

Answer 12

Produce large quantities of reproductive structures (e.g. eggs, pollen and fruit)

Question 13

Why do so many organisms produce large quantities of reproductive structures (e.g. eggs, pollen and fruit) in order to survive?

Answer 13

To ensure successful reproduction

Question 14

Many organisms produce large quantities of reproductive structures to ensure successful reproduction. Is the excess wasted? Why?

Answer 14

No it isn’t wasted - it acts as input to other processes (e.g. the food chain)

Question 15

What are 2 examples of how microorganisms are extremely important in the recycling of waste?

Answer 15

Carbon and nitrogen cycles

Question 16

Why are microorganisms so important in the process of recycling waste? (2 things)

Answer 16

• They digest and break down many different materials
• They have many digestive enzymes that other organisms lack, e.g. for breaking down cellulose and wood, which couldn’t be reused in the system otherwise

Question 17

Is it likely that there are any perfectly sustainable ecosystems? Why is this?

Answer 17

No - in practise, no system is perfect. Even in our most stable systems, there is always some output lost (e.g. migration of animals leaving an ecosystem, nutrients being washed away in rivers)

Question 18

Why are natural ecosystems so important to humans? (Provision of 3 things)

Answer 18

• Provide food (e.g. fish, game animals, pollination of crop plants by bees and moths)
• Provide clean air and oxygen from the actions of plants and microorganisms
• Provide clean water

Question 19

How can human activity upset the natural balance?

Answer 19

By changing the inputs and outputs of an ecosystem.

Question 20

Human activity can upset the natural balance by changing both inputs and outputs of an ecosystem.

Give some examples of input change.

Answer 20

• Using fertilisers – the minerals found in fertilisers (e.g. phosphates and nitrates) can be washed into rivers and streams, which can make water stagnant and unable to support life
• Burning fossil fuels – adds carbon dioxide to the atmosphere and increases climate change
• Domestic and industrial waste – releases chemicals into the ecosystem, which may be harmful

Question 21

Human activity can upset the natural balance by changing both inputs and outputs of an ecosystem.

Give some examples of output change.

Answer 21

• Removal of non-recycled waste
• Timber harvesting – removing trees for use in paper and furniture
• Fishing – depleting stocks of fish for food
• Agriculture – removing natural vegetation for crops (e.g. palm oil) or livestock (e.g. cattle)

Question 22

How can we tell that human activity in systems isn’t closed?

Answer 22

Because input and output aren’t balanced.

Question 23

What 4 things can removing vegetation cause?

Answer 23

• Soil erosion
• Loss of biodiversity
• Build-up of carbon dioxide
• Changes in the weather

Question 24

Removing vegetation can cause soil erosion. How?

Answer 24

Natural vegetation binds the soil together by the root systems and foliage protects the soil from direct rainfall. Without these, the soil can be washed away leading to desertification. The soil that is eroded can silt up rivers causing them to change course or to lose flow rate, affecting the aquatic life.

Question 25

Removing vegetation can cause loss of biodiversity. How?

Answer 25

Plants form the basis of many food chains, so loss leads to lack of food for animals. It also results in lack of shelter and habitat, reducing animal diversity.

Question 26

Removing vegetation can cause build-up of carbon dioxide. How?

Answer 26

As less photosynthesis occurs, less carbon dioxide is removed from the atmosphere. It accumulates in the atmosphere, causing climate change (the greenhouse effect).

Question 27

Removing vegetation can cause changes in the weather. How?

Answer 27

Temperature and rainfall are both affected by vegetation such as rainforests. The trees lose water, which causes cloud formation and leads to rain (a freshwater supply) in other areas. Rainforests help to prevent temperature extremes as the density of vegetation keeps temperatures stable.

Question 28

What could over-fishing cause? (2 things)

Answer 28

• Loss of biodiversity, leading to a reduction in food resources
• Accumulation of organisms that would have been eaten by fish may have harmful effects on the resources availiable.

Question 29

Explain the process called eutrophication. (HT)

Answer 29

Minerals might get washed away (leached) from fields into rivers and streams. In slow or non-flowing waters (like lakes), the build-up of minerals allows algae to grow at a fast rate:

• At first, the fast growth of algae promotes life as more food is avaliable.
• As the algae die, the microorganisms of decay use up oxygen in the water in respiration
• The process leads to oxygen levels so low that life can’t exist and the water is stagnant.

Question 30

How does bioaccumulation occur? (HT)

Answer 30

• Small amounts of toxic waste may be taken up by plants and stored in their leaves, fruits or seeds
• Animals eat these plants and, as they eat a lot of plants, the amount of chemical stored in their bodies is higher than in a single plant.
• These animals are eaten by other animals, so their bodies accumulate even higher levels of chemical
• The animals at the top of the food chain can become badly affected as the chemical reaches a harmful levels in their bodies

Question 31

Give some examples of the effect bioaccumulation can have at the top of food chains. (HT)

Answer 31

• Sparrowhawk egg-shells becoming brittle and breaking when the female sits on them, causing the number of sparrowhawks to reduce
• High mercury levels in some humans, which have been linked to psychological problems and even death

Question 32

Fill in the gap.

Using natural resources can only be __________ if the materials are replaced at the same rate they’re used.

Answer 32

Sustainable

Question 33

Why can’t using oil be sustainable? (2 things)

Answer 33

• Crude oil takes millions of years to form from the decay of dead organisms
• The energy released from burning oil was ‘fossil sunlight energy’ as it originated from the Sun when the organisms were alive

Question 34

How can the removal of trees can be sustainable?

Answer 34

If new trees are replanted as older ones are felled.

Question 35

How can fish stocks be kept at a sustainable level?

Answer 35

By the use of quotas (i.e. restricting the amount of fish allowed to be caught), so that the remaining fish can reproduce to replace those caught

Question 36

Through the removable of trees and over-fishing, what can humans try to do?

Answer 36

They can try to ‘close the loop’ to create a more sustainable, closed-loop system

Question 37

True or False?

Fish can be grown in artifical areas and used to re-stock over-fished areas.

Answer 37

True.

Question 38

There will always be conflict between the needs of local human communities and the need to conserve the natural ecosystems. So it’s important that compromises are reached because…

Answer 38

…they support the livelihoods of local people and at the same time, maintain the balance of the ecosystem.

Question 39

What three things is it important to remember about sustainable development?

Answer 39

• Sunlight energy is the input energy to all systems on Earth (but this is only likely to last another 5 billion years)
• Energy needs to be ever-present as it’s one thing that can’t be recycled
• Energy can only be transformed or transferred: it can’t be created or destroyed.

Question 40

When cows die in India, they’re sometimes eaten by vultures or wild dogs. Vultures will also eat dead dogs. To stop cows from catching certain diseases, a drug, called diclofenac, is given to them. Later on, some of these cows die of natural causes.

Explain why, when tested, vultures contain a higher concentration of diclofenac than cows. (HT)

Answer 40

Cows containing diclofenac are eaten by vultures, and, as they eat more cows, the drug accumulates in their bodies.

Question 41

When cows die in India, they’re sometimes eaten by vultures or wild dogs. Vultures will also eat dead dogs. To stop cows from catching certain diseases, a drug, called diclofenac, is given to them. Later on, some of these cows die of natural causes.

Some vultures die as a result of high drug levels. Why might this be important for humans? (HT)

Answer 41

Because the drug may accumulate in humans and cause harm if they eat cows/beef.