B18 Biodiversity & Ecosystems

Question 1

One way of measuring the population of an animal is to ask volunteers to count how many they see when driving on roads.

Why might this lead to an inaccurate estimate?

Answer 1

The animal may not always be visible from the road e.g. hidden. So the actual number is probably much higher.

Question 2

What effect does disappearing habitat have on the population of an animal?

Answer 2

It decreases.

Question 3

Lichens are pollution indicators of which gas?

Answer 3

Sulfur Dioxide.

Question 4

Only a small percentage of the Sun’s energy captured by a producer passes to the top of the food chain.

What happens to the rest of the energy?

Answer 4

Examples:

• Respiration releases energy.
• Some energy is lost in animals’ waste.
• Some energy is used for movement.
• Some energy is lost as heat to surroundings.
• Not all parts of an organism are eaten, e.g. bones.

Question 5

What is a quadrat?

Answer 5

A square frame of fixed area placed randomly in a habitat, e.g. a field, in order to estimate the number of individuals of different species in the entire field.

Usually several quadrats are placed randomly and an average count of each species is taken.

Question 6

Rohan calculated a mean of 2.8 dandelions per quadrat. His quadrat had an area of 1 square metre. The field had an area of 5400 square metres.

Calculate an estimate of the number of dandelions in the field.

Answer 6

2.8 x 5400 = 15120.

Question 7

When placing quadrats in a field, you should:

a) Place all the quadrats where there are lots of plants.
b) Place all the quadrats randomly in two different sample areas.
c) Place all the quadrats where all types of plant are growing.

Answer 7

b) Place all the quadrats randomly in two different sample areas.

Question 8

The advantage of increasing the amount of metal recycled is…

Answer 8

fewer quarries are dug to provide raw materials.

Question 9

The advantage of using fewer pesticides is…

Answer 9

less pollution of rivers flowing through farmland
or
less pesticide passed up food chains harming other animals.

Question 10

The advantage of reducing the number of cattle raised for food is…

Answer 10

less methane is added to the atmosphere
or
less habitat is cleared to make way for cattle farming.

Question 11

The advantage of increasing the amount of paper recycled is…

Answer 11

fewer forests are cut down.

Question 12

Why does deforestation take place?

Answer 12

• timber (for building things)
• land for agriculture
• roads and buildings
• land for biofuels

Question 13

What are the effects of deforestation?

Answer 13

• reduction in biodiversity
• increase in carbon dioxide content of atmosphere
• global warming
• climate change
• rising sea levels
• changes in migration patterns of animals

Question 14

Name one human activity that produces sulfur dioxide.

Answer 14

Burning fossil fuels.

Question 15

What effect does sulfur dioxide have on rainwater?

Answer 15

Sulfur dioxide makes acid rain.

Question 16

Acid rain reduces the number of leaves grown on a plant.

Why does this reduce the size of the rest of the plant too?

Answer 16

Fewer leaves means less photosynthesis.

As a result there is less sugar supplied to the rest of the plant for growth.

Question 17

What is the difference between a pyramid of numbers and a pyramid of biomass, and why is biomass a better measure?

Answer 17

A pyramid of numbers indicates the number of individuals in each stage of a food chain.

A pyramid of biomass indicates the amount of biomass in each stage of a food chain.

Biomass takes into account both the number and size of the individuals so better demonstrates the passage of energy and biological matter up the food chain.

Question 18

Why does the total biomass decrease at each new stage of the food chain?

Answer 18

Not all biomass is successfully transferred to the next level because e.g.

1. Some individuals may not be eaten at all.
2. Not all the organism is eaten by the next level, e.g. bones or shells.
3. Some biomass is lost as faeces.
4. Some is converted to waste e.g. carbon dioxide and urea.

Question 19

When using quadrats to estimate the number of plants in a field using quadrats, how can you make your estimate more accurate?

Answer 19

Use more quadrats or larger quadrats.

Question 20

What effect does digging a new quarry have on the environment?

Answer 20

Reduces the land available for wild animals.

Question 21

What effect does spraying pesticides on crops have on the environment?

Answer 21

Pollutes hedges around fields or rivers flowing through farmland.

Question 22

What effect does growing rice have on the environment?

Answer 22

Adds methane to the atmosphere.

Question 23

What effect does driving cars that release sulfur dioxide have on the environment?

Answer 23

Produces acid rain.

Question 24

What effect does global warming have on the environment?

Answer 24

1. Climate change.
2. More extreme weather.
3. Rise in sea level due to melting of ice caps.
4. Reduced biodiversity as animals cannot survive new climate.
5. Changes to migration patterns of animals.

Question 25

It is important to maintain fish stocks high enough for breeding to continue. Why so?

Answer 25

Otherwise species may disappear altogether.

Question 26

Give two ways in which fishermen can conserve fish stocks.

Answer 26

1. Regulate net size or mesh size (so infant fish can escape).
2. Impose fishing quotas (i.e. cannot capture more than a certain number of fish a day).
3. Limit fishing during breeding seasons.
4. Bans on fishing in certain areas.

Question 27

Food chain A transfers about 10 times more energy to humans than food chain B. Why?

Food chain A:
Wheat → humans

Food chain B:
Wheat → pigs → humans

Answer 27

There is an extra stage (pigs) in food chain B and energy is lost by e.g.

the pigs moving, maintaining body temperature and producing waste
or
not all parts of the pig eaten by humans

Question 28

Give methods used in the factory farming of animals. Explain the advantages and disadvantages of these methods.

Answer 28

Methods:

• Kept in cramped conditions (to reduce movement).
• Controlled temperature and feeding.
• Use of growth hormones and antibiotics.

Advantages:
Greater food production as animals are
-well fed (food is high in calories and protein)
-less energy is lost through movement and keeping the animals warm
-stops infections

Disadvantages:

• animals will be stressed due to restricted movement and overcrowding
• risk of diseases spreading faster
• antibiotics can work there way up the foodchain to humans

Question 29

Food chain:
oak tree → caterpillar → blue-tit → hawk

Choose two ways in which biomass (living material) is lost in this food chain out of:

a) As carbon dioxide from the caterpillar
b) As food eaten by the hawk
c) As oxygen from the oak tree
d) As faeces from the blue-tit

Answer 29

a) As carbon dioxide from the caterpillar

d) As faeces from the blue-tit

Question 30

Insecticides are chemicals which kill insects.

Spraying insecticides on crops increases crop yield, why?

Answer 30

Insects are killed so they cannot eat the crop.