Interdependence

5 (a) A scientist decided to study the variety of living organisms in a garden.

(i) The scientist wanted to use a random sampling technique. Devise a plan the scientist could use to randomly sample the number of plant species in the garden.

(ii) The scientist also measured abiotic factors in the garden. The pH of the soil was measured using a pH meter. Describe how three other abiotic factors could be measured in the garden.

(iii) Mistletoe is a parasite that grows on some trees. Figure 6 shows a tree with mistletoe growing on it.

(Source: © NagyDodo/Shutterstock)

Figure 6

Describe the feeding relationship between the mistletoe and the tree.

(b) Nitrate fertilisers are used in the garden. Explain why nitrate fertilisers are used in gardens.

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

(Source: © Jaromir Chalabala/Shutterstock)

(a) (i) 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?

(ii) 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.

(iii) 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.

(b) 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 13 shows part of a food web of organisms found in the cold Antarctic Ocean.

Which term describes phytoplankton in this food web?

Humans are removing large numbers of cod from the Antarctic Ocean.

State why the removal of cod could lead to a decrease in the numbers of squid and penguins.

Explain why the removal of cod could lead to an increase in the numbers of squid and penguins.

Figure 14 shows information about the biomass of some organisms in one part of the Antarctic Ocean.

Draw and label a pyramid of biomass for this food chain.

Seals are mammals.

Explain why the conversion of biomass from phytoplankton to shrimps is more efficient than the conversion of biomass from cod to seals.

Cod are being overfished in the Antarctic Ocean.

Suggest two actions that could be taken by humans to increase the number of cod in the Antarctic Ocean.

5 (a) Figure 8 shows a cross-section of a root nodule on a leguminous plant. Bacteria in the root nodule provide the leguminous plant with nitrogen compounds. The leguminous plant provides the bacteria with sugars.

(Source: © Nigel Downer / Science Photo Library)

Figure 8

(i) Which term describes the relationship between this leguminous plant and the bacteria?

(ii) The width of this root nodule is 7.5 mm. Give the width in µ m.

(b) Figure 9 shows part of the nitrogen cycle.

(i) Identify the types of microorganism involved in process X and process Y.

(ii) Explain how crop rotation increases nitrate levels in the soil.

(iii) Explain why increased nitrate levels in the soil improve crop yield.

There are three levels of organisation in an ecosystem.

Which order shows the levels of organisation from lowest to highest?

Figure 3 shows food webs for two gardens.

Slug pellets are put on the soil around the lettuce plants in garden A and garden B.

Slug pellets kill slugs.

A scientist predicts that the number of caterpillars will decrease in garden A.

Give one reason why the number of caterpillars will decrease in garden A.

The scientist predicts that the number of caterpillars will increase in garden B.

Give one reason why the number of caterpillars will increase in garden B.

Figure 4 shows the population of slugs in garden A for five years.

Slug pellets were used during the first year.

slug

Describe the trend in the slug population from year 1 to year 5.

Flatworms from New Zealand that eat slugs are now living in the UK.

Which term describes a species from one country that is living in another country?

Figure 5 shows tiny white animals called mites on the skin of a slug.

The mites feed on blood.

Explain why these mites are classed as parasites.

The animal shown in Figure 3 is a tick burrowing into the skin of a human.

Use words from the box to complete the sentences.

The tick burrows into the skin to obtain_........ .

When a tick burrows into human skin the tick benefits but the human is harmed.

This means that ticks are classed as_........ .

When skin is cut a blood clot forms.

Which part of the blood starts the clotting process?

Figure 4 shows a bird called an oxpecker eating ticks that are living on a zebra.

Name the type of relationship where both the oxpecker and the zebra benefit.

Zebras eat grass.

Complete the food chain that includes zebras, ticks, oxpeckers and grass.

Figure 5 shows the maximum numbers of oxpeckers observed on four types of mammal.

Describe the difference in the maximum number of oxpeckers on the white rhino and on the hippo.

Give one reason why more oxpeckers were observed on giraffes than on zebras.

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

Figure 15 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 2 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 11 shows a British glow-worm.

Read the following extract before answering the questions.

Female glow-worms produce bright lights in the summer to attract males. Glow-worm larvae are predators of slugs and snails, but adult glow-worms do not feed. Females only have a few weeks to attract a mate and lay eggs, before the females die.

What will happen if the population of snails decreases?

Female glow-worms have an enzyme called luciferase. The glow is produced when this enzyme catalyses a reaction between oxygen and a protein.

A scientist devised a plan to investigate the effect of oxygen concentration on this reaction.

The scientist had:

• five flasks of water each with a different concentration of dissolved oxygen

• a solution of the protein

• a solution of the enzyme.

The first step of this plan is:

Step 1. Add some of the protein solution to each of the five flasks.

Describe the next two steps that should be in this plan to obtain results for this investigation.

Which procedure would improve the investigation?

The enzyme luciferase works best at pH 8.

Explain why the activity of the enzyme decreases at pH 5.

Female glow-worms are found attached to grass plants in a large field.

Describe a sampling technique to find the mean number of female glow-worms in 1 m² of the field.

The mean number of female glow-worms in 1 m² of the field is 5.

The field has a total area of 800 m².

Estimate the number of female glow-worms in the whole field.

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.