Abiotic & biotic factors

In 2018, all the plants were removed from the soil in a 1000 m² area.

A wall was built around this area to keep people out.

In 2019, three species of plants were recorded growing in this area.

Two of these species were indigenous.

State what is meant by the term ’indigenous’.

Name one piece of equipment that could be used to sample the number of indigenous plants in this area.

The area was surveyed every year and the number of plants of each species (A to H) was estimated.

Figure 20 shows the results.

State the trend shown by the data in Figure 20 for plant species C from 2019 to 2023.

A scientist suggested that the decrease in the number of plants of species B in 2021 was caused by competition from one of the other species of plant.

Which species is most likely to have out-competed species B in 2021?

Explain one way that this species could have out‑competed species B.

Give one way that species H could have moved into the area.

*(c) Figure 21 shows some plants growing in a small area of a 1000 m² field.

Devise a plan to estimate the number of named plant species growing in this field.

In 2018, all the plants were removed from the soil in a 1000 m² area.

A wall was built around this area to keep people out.

In 2019, three species of plants were recorded growing in this area.

Two of these species were indigenous.

State what is meant by the term ’indigenous’.

Name one piece of equipment that could be used to sample the number of indigenous plants in this area.

The area was surveyed every year and the number of plants of each species (A to H) was estimated.

Figure 6 shows the results.

State the trend shown by the data in Figure 6 for plant species C from 2019 to 2023.

A scientist suggested that the decrease in the number of plants of species B in 2021 was caused by competition from one of the other species of plant.

Which species is most likely to have out-competed species B in 2021?

Explain one way that this species could have out‑competed species B.

Give one way that species H could have moved into the area.

Plants also need water to grow.

Explain how water is absorbed into the plant.

Figure 13 shows the biomass of each population of organisms in a food chain.

Figure 13

Calculate the percentage efficiency of biomass transfer from the aphids to the ladybirds.

Use the equation:

Give your answer to the nearest whole number.

Give two reasons why the biomass of ladybirds is lower than the biomass of aphids in this food chain.

Aphids are a problem for rose growers as they damage the leaves of rose plants.

Explain how ladybirds could be used to reduce the number of aphids.

As human population rises, food security is an increasing problem throughout the world.

Give three factors that reduce the amount of food available for humans throughout the world.

Figure 4 shows a food chain in an oak woodland.

oak tree aphids ladybirds robins

State what the arrows in the food chain represent.

A robin in this woodland eats 6 g of food in a day.

The robin uses 15% of this food for growth.

Calculate the mass of food that is used for growth.

Temperatures in England have increased over the last 20 years.

State two human activities that have caused this temperature increase.

One new species of moth is now able to live in England because of the increased temperatures.

This moth feeds on oak leaves.

Explain how these moths may affect the number of aphids in the food chain shown in Figure 4.

6 In 2000, a council planted indigenous trees as part of a reforestation programme.

(a) Why were indigenous trees used instead of non-indigenous trees?

(b) The animal biodiversity in this reforested area was measured from 2004 to 2017. Biodiversity is measured on a scale from 0 to 1. 0 = low biodiversity 1 = maximum biodiversity Figure 12 shows the results.

2000 2002 2004 2006 2008 2010 2012 2014 2016 2018 2020 2022

Figure 12

(i) Draw a straight line of best fit on Figure 12 to show the main trend in this data.

(ii) Estimate the animal biodiversity of the reforested area in 2022.

(c) (i) The data to calculate animal biodiversity was collected using the following method.

• a 100 m² area was chosen

• three 1 m² quadrats were placed randomly on the ground

• animals inside the quadrat were counted

• the number of each species of animal was recorded

State two ways that the quality of the results from this method could be improved.

(ii) State why point A on Figure 12 was ignored when considering the trend in animal biodiversity.

(iii) The data shown in Figure 12 was collected during the summer. Explain why animal biodiversity would be different if the data had been collected in the winter.

(d) A scientist observes that trees at the edge of a forest shade part of a field. Describe how a belt transect could be used to see how light intensity affects the biodiversity of plants growing in the field.

Figure 1 shows a stream flowing near a fertiliser factory.

The factory burns coal as a source of energy.

The factory releases waste into the stream and sulfur dioxide into the air.

Samples of water were taken at five points, A, B, C, D and E, as shown on Figure 1.

Figure 2 shows the oxygen concentration in the water at the five points along the stream.

Calculate how many times greater the oxygen concentration is at point E than at point A.

State how the oxygen concentration changes from point A to point E.

Which indicator species would be most likely to be seen in the water at point A?

Explain where the biodiversity will be highest in the stream.

Figure 3 shows rose leaves infected with blackspot fungus.

(Source: © Manfred Ruckszio/Shutterstock)

Figure 3

State why rose plants growing near this factory are not infected with blackspot fungus.

10 A student investigated the width of leaves on nettle plants growing in two areas next to a woodland. Figure 19a shows a nettle plant and Figure 19b shows a map of the woodland showing area A and area B. The woodland caused area A to be in the shade.

(Source: © Alila Medical Media/Shutterstock) Figure 19a Figure 19b The student measured the maximum width of leaves on five plants from each area. The student always measured one leaf from the fourth pair of leaves.

(a) Give one reason why the student always measured a leaf from the fourth pair of leaves.

(b) Figure 20 shows the results.

Figure 20

(i) Why did the student not include the circled width when calculating the mean for area B?

(ii) Explain the difference in the mean width of leaves in the shade and those in the sunlight.

(c) The student also studied some of the animals in areas A and B. The student saw caterpillars eating the leaves of some nettles. The student also saw a toad eating a large beetle. Large beetles eat ladybirds. Ladybirds eat caterpillars.

(i) Give the food chain for these feeding relationships.

(ii) Frogs also eat large beetles. Figure 21 shows the energy transferred between these animals.

Figure 21

Calculate the percentage efficiency of energy transfer from the large beetles to the frog.

(iii) Give two reasons why only some of the energy in the biomass of the large beetles is transferred to the biomass of the frog.

4 A student investigated the width of leaves on nettle plants growing in two areas next to a woodland. Figure 5a shows a nettle plant and Figure 5b shows a map of the woodland showing area A and area B. The woodland caused area A to be in the shade.

(Source: © Alila Medical Media/Shutterstock) Figure 5a Figure 5b The student measured the maximum width of leaves on five plants from each area. The student always measured one leaf from the fourth pair of leaves.

(a) Give one reason why the student always measured a leaf from the fourth pair of leaves.

(b) Figure 6 shows the results.

(i) Why did the student not include the circled width when calculating the mean for area B?

(ii) Explain the difference in the mean width of leaves in the shade and those in the sunlight.

(c) The student also studied some of the animals in areas A and B. The student saw caterpillars eating the leaves of some nettles. The student also saw a toad eating a large beetle. Large beetles eat ladybirds. Ladybirds eat caterpillars.

(i) Give the food chain for these feeding relationships.

(ii) Frogs also eat large beetles. Figure 7 shows the energy transferred between these animals.

Calculate the percentage efficiency of energy transfer from the large beetles to the frog.

(iii) Give two reasons why only some of the energy in the biomass of the large beetles is transferred to the biomass of the frog.

Figure 16 shows an area of woodland with some small plants growing in the ground between the trees.

(Source: © Maksym Holovinov/Shutterstock)

Figure 16

The leaves of the small plants are green.

Describe how these plants make glucose.

Name a group of organisms that break down the dead leaves and release mineral ions into the soil.

The mineral ions are absorbed from the soil into the roots of plants.

Describe how these mineral ions are transported from the roots to the leaves of the plants.

A scientist recorded the mean light intensity and the mean number of small plants per m² for six 25 m² areas of the woodland.

Figure 17 shows the results.

Explain the effect of light intensity on the number of small plants per m².

State one variable the scientist should have controlled to make sure the light intensity measurements could be compared.

The scientist selects an area near the edge of the woodland where many stinging nettles are growing.

This area is partly shaded by the trees.

Describe how the scientist should use a belt transect to investigate how light intensity affects the growth of stinging nettles.

The population of native white‑clawed crayfish in English rivers is decreasing due to an increasing population of American imported signal crayfish.

Figure 1 shows a white‑clawed crayfish.

Which term is used to describe the American imported signal crayfish now that it is living in English rivers?

American imported signal crayfish may eat white‑clawed crayfish.

Explain one other reason why the increasing population of American imported signal crayfish may have caused the decrease in white‑clawed crayfish.

The Environment Agency is developing methods of increasing the population of white‑clawed crayfish in English rivers.

Which term describes these methods?

White‑clawed crayfish cannot survive in rivers with a low concentration of oxygen.

Explain how eutrophication can cause the population of white‑clawed crayfish to decrease.

Figure 2 shows an area of woodland with some small plants growing in the ground between the trees.

(Source: © Maksym Holovinov/Shutterstock)

Figure 2

Name a group of organisms that break down the dead leaves and release mineral ions into the soil.

The mineral ions are absorbed from the soil into the roots of plants.

Describe how these mineral ions are transported from the roots to the leaves of the plants.

A scientist recorded the mean light intensity and the mean number of small plants per m² for six 25 m² areas of the woodland.

Figure 3 shows the results.

Explain the effect of light intensity on the number of small plants per m².

State one variable the scientist should have controlled to make sure the light intensity measurements could be compared.

The scientist selects an area near the edge of the woodland where many stinging nettles are growing.

This area is partly shaded by the trees.

Describe how the scientist should use a belt transect to investigate how light intensity affects the growth of stinging nettles.

Figure 8 shows an area of nettle plants.

Grass does not grow among the nettles.

Explain why grass does not grow where there are nettles.

Figure 9 shows caterpillars eating nettle leaves.

A caterpillar has a body mass of 6.0 grams. One week later, its body mass had increased to 7.5 grams. Caterpillars convert 10% of food eaten into body mass.

Calculate the mass of nettles that the caterpillar ate.

Describe what happens to food eaten that is not converted into the body mass of the caterpillar.

Devise a method a scientist could use to investigate how temperature affects nettle growth.

Since 2003, in France, people have been buying Siberian chipmunks as pets but then releasing them into the wild when they are no longer wanted.

They are now classified as an invasive species.

Figure 25 shows a Siberian chipmunk (Tamias sibiricus).

Figure 25

Siberian chipmunks eat acorns, which are the seeds of oak trees.

In Siberia, the natural predators of Siberian chipmunks are wild dogs.

Figure 26 shows the biomass of three organisms in a food chain from one area of Siberia.

Draw a pyramid of biomass for this food chain.

In France, Siberian chipmunks have very few natural predators.

Describe how this affected the Siberian chipmunk population in France.

The percentage of energy transferred from the acorns to the chipmunks is 9.5%.

The energy contained in the acorns is 97 500 kJ.

Calculate the amount of energy transferred to the chipmunks.

Give your answer to the nearest whole number.

The black-legged tick (Ixodes scapularis) is a parasite that feeds on the blood of animals including Siberian chipmunks and humans.

The tick transmits the Lyme disease pathogen.

Figure 27 shows the number of cases of Lyme disease in humans in France in 2003 and 2015.

Calculate the percentage increase in the number of cases of Lyme disease in humans in France from 2003 to 2015.

Explain why there has been an increase in the number of cases of Lyme disease in humans in France.

Since 2003, in France, people have been buying Siberian chipmunks as pets but then releasing them into the wild when they are no longer wanted.

They are now classified as an invasive species.

Figure 7 shows a Siberian chipmunk (Tamias sibiricus).

Siberian chipmunks eat acorns which, are the seeds of oak trees.

In Siberia, the natural predators of Siberian chipmunks are wild dogs.

Figure 8 shows the biomass of three organisms in a food chain from one area of Siberia.

Draw a pyramid of biomass for this food chain.

In France, Siberian chipmunks have very few natural predators.

Describe how this affected the Siberian chipmunk population in France.

The percentage of energy transferred from the acorns to the chipmunks is 9.5%.

The energy contained in the acorns is 97 500 kJ.

Calculate the amount of energy transferred to the chipmunks.

Give your answer to the nearest whole number.

The black-legged tick (Ixodes scapularis) is a parasite that feeds on the blood of animals including Siberian chipmunks and humans.

The tick transmits the Lyme disease pathogen.

Figure 9 shows the number of cases of Lyme disease in humans in France in 2003 and 2015.

Calculate the percentage increase in the number of cases of Lyme disease in humans in France from 2003 to 2015.

Explain why there has been an increase in the number of cases of Lyme disease in humans in France.