The carbon cycle

Figure 1 shows a bird called an egret on the back of a buffalo.

(Source: © Jaromir Chalabala/Shutterstock)

Figure 1

The egret eats parasites that live on the skin of the buffalo.

Which term describes this relationship, where the buffalo and the egret both benefit?

The buffalo is part of the carbon cycle.

Use words from the box to complete the sentences.

The buffalo gains carbon from the_........ in the plants that it eats.

Bacteria will_........ the waste from the buffalo.

Figure 2 shows part of the carbon cycle.

Draw and label an arrow on Figure 2 to show the process plants use to make glucose from carbon dioxide.

Enzymes are used to digest proteins.

Figure 3 shows an enzyme and a protein.

Explain how boiling the enzyme stops the protein being digested.

Figure 9 shows a photomicrograph of two stomata in a leaf.

The length of one guard cell in this image is 6 mm.

Convert the length of this guard cell into micrometres (µ m).

The image has been magnified 150×.

Calculate the actual size of the guard cell.

Give your answer in standard form in mm.

_........ mm

Explain the role of denitrifying bacteria in the nitrogen cycle.

*(c) Describe how carbon is cycled through the biotic and abiotic components of an ecosystem.

Figure 1 shows part of the carbon cycle.

Name the process that transfers carbon from plants to animals.

Use words from the box to complete the sentences.

Plants use carbon dioxide from the atmosphere for_........

Animals release carbon dioxide and energy during_........

Which of these can be a decomposer?

The water cycle is the movement of water through an ecosystem.

Which process is used to obtain freshwater from seawater?

Water from rivers can be filtered and then treated with chemicals to make it suitable for drinking.

Give one reason why water is filtered.

Give one reason why water is treated with chemicals.

Figure 9 shows an area of woodland with some small plants growing in the ground between the trees.

(Source: © Maksym Holovinov/Shutterstock)

Figure 9

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 10 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 1 shows an area of woodland with some small plants growing in the ground between the trees.

(Source: © Maksym Holovinov/Shutterstock)

Figure 1

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 2 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.

(a) A student was investigating the populations of organisms in a garden.

Figure 9 shows the estimates of the number and biomass of some of the organisms in the garden.

Calculate the biomass of the population of earthworms in the garden.

Hedgehogs eat slugs and earthworms. Slug pellets were used to kill the slugs.

Explain how killing the slugs would affect the population of earthworms in this garden.

Describe a method that could be used to estimate the population of slugs in the garden.

Explain how cabbages, earthworms and squirrels contribute to the carbon cycle.

State three ways the concentration of nitrates in soil can be increased.

(a) A student was investigating the populations of organisms in a garden.

Figure 1 shows the estimates of the number and biomass of some of the organisms in the garden.

Calculate the biomass of the population of earthworms in the garden.

Hedgehogs eat slugs and earthworms. Slug pellets were used to kill the slugs.

Explain how killing the slugs would affect the population of earthworms in this garden.

Describe a method that could be used to estimate the population of slugs in the garden.

Explain how cabbages, earthworms and squirrels contribute to the carbon cycle.

Figure 6 shows the global movement of carbon into or out of the atmosphere.

Calculate the net mass of carbon added to the atmosphere each year.

_........ gigatonnes

Joseph Priestley was a scientist who investigated how green plants and combustion affected the carbon cycle.

Figure 7 shows his first experiment.

State why the candle was not burning after three minutes.

Joseph Priestley continued the investigation but placed a plant inside the bell jar as shown in Figure 8.

He observed that the candle stayed alight for two minutes more than the candle in the bell jar in the first experiment.

Explain his observation.

State two variables that would need to be controlled to compare these two experiments.

Nitrogen is cycled through the environment.

Describe the roles of bacteria in the nitrogen cycle.