Ecosystems & Biodiversity (AQA GCSE Combined Science: Synergy: Life & Environmental Sciences): Exam Questions

A student investigated the number of plants in two fields.

Figure 12 shows the fields.

This is the method used.

1. Place a quadrat randomly in field A.

2. Count the number of plants in the quadrat. Do not count grasses.

3. Repeat steps 1 and 2 another five times.

4. Repeat steps 1 to 3 in field B.

The student used a quadrat to count the number of plants.

What is a quadrat?

Table 4 shows the results.

Table 4

Calculate mean value X in Table 4.

The area of the quadrat used was 1 m².

Field B was 100 m long and 90 m wide.

Calculate the total number of plants in field B.

You should calculate:

• the area of the field

• the total number of plants.

Use the data in Table 4.

The mean number of plants in field A is greater than in field B.

Suggest one reason why.

A student did a different investigation in field A.

Figure 13 shows the areas sampled.

The student sampled:

• an area at the edge of the field next to the hedge, P

• an area at the edge of the field with no hedge, Q.

Table 5 shows the results.

Table 5

Give three conclusions from the results in Table 5.

Suggest one way to increase biodiversity in field A.

A student investigated the number of plants in two different fields.

This is the method used.

1. Place a quadrat randomly in field A.

2. Count the number of plants of each species in the quadrat. Do not count grasses.

3. Repeat steps 1 and 2 another 19 times.

4. Repeat steps 1 to 3 for field B.

Figure 6 shows the two fields.

Why should a random sampling method be used to sample the plants?

The student counted dandelion plants.

The student used a 0.5 m × 0.5 m quadrat.

The mean number of dandelion plants in field A in Figure 6 was 2.8 per quadrat.

Determine the total number of dandelion plants in field A.

The student placed insect traps in the ground in field A and in field B.

The insect traps were used to estimate the total number of insects in each field.

Figure 8 shows the insect trap the student used.

This is the method used.

1. Place the insect traps in the fields as shown in Figure 7 and Figure 8.

2. Leave for 12 hours.

3. Count the number of insects of each species in each trap.

4. Repeat every 2 days for 6 days.

The method for estimating the total number of insects in field A and field B may not give valid results.

Suggest two reasons why.

Table 5 shows the results for all the plants and insects sampled.

Table 5

A student concluded:

'There is greater biodiversity in field B than in field A.'

Give the reason why.

There has been a decrease in the total number of birds in the UK since 1970.

Explain how planting more hedges would affect the number of birds.

The orca is a large animal that lives in the ocean.

Figure 4 shows an orca.

Complete the sentence.

Choose the answer from the box.

The ocean is the orca’s ________________.

Figure 5 shows a food chain.

Draw one line from each organism to the description of that organism in the food chain.

Use information from Figure 5.

Figure 6 shows a food web.

Seaweed and microscopic algae photosynthesise.

Give two factors that affect the rate of photosynthesis.

1

2

The number of fish in the oceans has decreased since 1990.

Suggest one way that human activity has caused the decrease in the number of fish.

Explain how a decrease in the number of fish could affect the numbers of other organisms in the food web.

Use Figure 6.

A farmer removes some of the young trees from the managed forest every year.

Explain why removing some of the young trees allows the remaining trees to grow faster.

Suggest one advantage to the farmer if the remaining trees grow faster.

In managed forests:

• tree seedlings are regularly planted

• some trees are regularly removed

Some of the young trees in a managed forest are removed every year.

The biomass of wood produced by the remaining trees in the forest is increased by removing the young trees.

Explain why.

Planting trees to maintain forests is good for the environment.

Explain the environmental and biological benefits of maintaining forests.

Figure 10 shows a rock pool on a sea shore.

Rock pools are flooded twice a day with fresh sea water.

Figure 10

What is the community of the rock pool?

Tick (✓) one box.

Starfish are animals that live in rock pools.

A scientist investigated the effect that starfish had on the number of species in rock pools.

This is the method used:

1. Count the number of species in rock pool A and in rock pool B

2. Regularly remove all the starfish from rock pool B

3. Count the number of species in rock pool A and in rock pool B each year for 10 years

Figure 11 shows the results.

Figure 11

Figure 12 shows a food web in the rock pools.

Figure 12

Starfish usually prefer to feed on mussels.

Mussels reproduce and grow more quickly than limpets, chitons, and barnacles.

After 10 years the only species left in rock pool B was mussels.

Explain the results shown in Figure 11 for rock pool B.

Use Figure 11 and Figure 12.

Explain the results shown in Figure 11 for rock pool A.

Some species of starfish can reproduce by cloning (asexual reproduction) and also by sexual reproduction.

Figure 13 shows what happens when starfish P reproduces by each type of reproduction.

Figure 13

During cloning a small piece of the starfish develops into a new starfish.

Before cell division, chromosomes replicate and the number of organelles increases.

Describe the stages in the process of cell division that produces offspring X.

Figure 1 shows a food chain.

Which of the organisms in Figure 1 is the primary consumer?

Name the predator of the fish in Figure 1.

Draw one line from each term to the definition of the term.

Complete the sentence.

Choose the answer from the box.

A decrease in the number of polar bears would cause the number of seals to _________________________.

Food chains and food webs can be used to predict the effect of a decreasing number of polar bears.

Why is a food web more useful than a food chain?

Krill eat algae.

Algae store a mass of 68 arbitrary units of carbon in 1 year.

8% of the carbon stored in algae becomes part of the carbon stored in krill.

Calculate the mass of carbon that becomes stored in krill.

Use the equation:

$\text{mass of carbon stored in krill}=\text{mass of carbon stored in algae}\times \frac{8}{100}$

Mass of carbon stored in krill = ______________ arbitrary units

The minerals in sea water are one abiotic factor that affects algae.

Which are two other abiotic factors that affect algae?

Biodiversity is the variety of species within an ecosystem.

A student investigated the biodiversity in a field. In part of the field, the living grass had been replaced with plastic grass. Other plants grow between living grass plants and between pieces of plastic grass.

Figure 11 shows the field.

The student used quadrats to randomly sample the biodiversity of plants in:

• the area with living grass

• the area with plastic grass.

Describe how the student could decide where to randomly place the quadrats in the area with plastic grass.

How would a greater number of different plant species affect the biodiversity of animals in the area?

Another student used a transect to place quadrats in the field.

Figure 12 shows the position of the transect.

The student placed a quadrat every 5 metres from point A to point B.

Table 6 shows the results.

Table 6

Complete the sentence.

The relationship between the distance from point A and the number of plant species cannot be represented by the equation:

$y=mx+c$

This is because the relationship is not_____________________ .

Describe the relationship between the type of grass and the number of plant species.

Which of the following are two improvements to the investigation that used a transect?

Tick (✓) two boxes.

Small pieces of plastic break off plastic grass and enter rivers and oceans.

Leaves from trees take longer to decompose on plastic grass than on living grass.

Other plants can grow between pieces of plastic grass.

Plastic grass cannot be recycled.

Explain how plastic grass affects biodiversity of ecosystems.

Ecosystems with low biodiversity may have small populations of some species.

Why are small populations more likely to become extinct than large populations?

Tick (✓) one box.

Suggest two ways biodiversity in and around fields can be increased.

Do not refer to plastic grass.

Figure 7 shows part of a food web from one ecosystem:

Define the term 'ecosystem'.

Describe the difference between a population and a community in one habitat.

Humans kill narwhals for meat and skin.

Killing more narwhals can cause the number of seals to increase or decrease.

Explain why killing more narwhals can have two different effects on the number of seals.

The algae in Figure 7 store a mass of 68 arbitrary units of carbon in 1 year.

8.4% of the carbon in each stage of the food web is passed to the next stage.

Calculate the mass of carbon stored in tertiary consumers in 1 year.

Mass of carbon = _________________ arbitrary units

In the last 200 years the concentration of carbon dioxide in the Earth's atmosphere has risen.

Explain how a rise in carbon dioxide concentration in the atmosphere can decrease biodiversity.

A student investigated the number of ribwort plants in a field using a quadrat and a tape measure.

The student used the apparatus shown in Figure 5.

This is the method used.

1. Place the quadrat in an area where there are lots of ribwort plants in the field.

2. Count the number of ribwort plants inside a quadrat.

3. Repeat steps 1 and 2 four more times.

How could the student improve his method so that he can collect valid results?

Tick two boxes.

The student calculated that the mean number of ribwort plants per m² was 3.2.

The area of the field was 8250 m².

Calculate the total number of ribwort plants in the field.

Total number of ribwort plants = __________________

Another group of students did an investigation in the field.

Figure 6 shows how the students placed their quadrats in this investigation.

What is the name given to the line in Figure 6?

Figure 7 shows the students' results.

Describe the relationship shown in Figure 7.

What is one reason why there are no ribwort plants next to the path?

Tick one box.

Feeding relationships can be shown using food chains.

Figure 1 shows a food chain for organisms in a habitat.

What is the producer in the food chain?

Tick one box.

Name the primary consumer in the food chain.

What is the group of leaves, beetles, mice and owls in a habitat called?

Tick one box.

What are two abiotic factors that can affect the food chain?

Tick two boxes.