Pyramids of number, biomass & energy

Tubifex are worms that live in mud at the bottom of rivers and lakes. The diagram shows some Tubifex worms living in river mud.

Bacteria live in the mud and feed on dead plant material. Tubifex worms bury their heads in the mud to feed on these bacteria. Tubifex worms are eaten by fish.

Use this information to draw a food chain that includes Tubifex worms.

A scientist investigates the relationship between the mass of dead plant material in the river mud and the population size of Tubifex worms. The graph shows the scientist’s results.

Explain the relationship shown by the graph.

Tubifex worms contain haemoglobin. Some other species of worms do not contain haemoglobin. When the mass of dead plant material in river mud is very high, the population size of the other species decreases but the Tubifex population size continues to increase. Explain why the Tubifex population continues to increase while populations of other species decrease.

Suggest how a scientist could measure the mass of organic material in a sample of river mud.

This food web comes from an African ecosystem.

What is meant by the term ecosystem ?

Identify all the producers in this food web.

Give the trophic level of the lion in this food web.

Name an organism that occurs at two different trophic levels in this food web.

Give the food chain from this web that contains four different organisms including the baboon.

Explain why the number of organisms usually decreases along a food chain.

Read the passage below. Use the information in the passage and your own knowledge to answer the questions that follow. Omega-3 Excess lipids (fats and oils) in the human diet can increase the risk of health problems such as obesity, heart disease and strokes. However, a balanced diet needs to contain fats and oils because they are needed in the human body for many important functions. Scientists have recently discovered that a type of fatty acid contained in oils can also benefit human health. The fatty acids that provide benefits to human health are called omega-3 fatty acids. A diet rich in these fatty acids is thought to lower blood pressure and reduce the risk of heart disease. Fish oils are known to contain high levels of omega-3 fatty acids. Fish farmers know that the fish they produce are of more value to the consumer if they contain oils rich in omega-3. As a result, about 80% of the fish oil produced globally from the oceans is used as food in fish farms. Small fish called anchovies live in our oceans. They eat microscopic plants called plankton that contain high levels of omega-3. As the anchovies grow, they also contain high levels of omega-3 in their oil. Fishing boats catch billions of these small fish, that are then ground up to be fed to bigger fish such as salmon, on fish farms. Fish farms consume vast quantities of anchovies. The increase in the number of fish farms is one reason why wild fish stocks of anchovies are declining. It takes about 5 kg of anchovies to produce 1 kg of farmed salmon. The high cost of this source of fish oil has encouraged fish farmers to use less, so the fish they produce contain lower levels of omega-3 in their oil, which is not good for human health. Recently, scientists have discovered another way to obtain high levels of omega-3 to feed to fish on fish farms. The scientists genetically modified a plant called Camelina to produce seeds containing omega-3 fatty acids. This discovery will enable these seeds to be fed to salmon in fish farms and could reduce overfishing of the oceans.

Suggest how excess lipids (fats and oils) increase the risk of heart disease (lines 1 and 2).

Fats and oils are large, insoluble molecules needed in a balanced diet (lines 2 and 3). Give the names of two small, soluble molecules needed in a balanced diet.

State a function of lipid in the human body.

Fatty acids are one component of a lipid molecule. Name another component.

Use the information in the passage to draw a food chain that includes anchovies (lines 13 to 17).

Suggest why wild fish stocks are declining.

Explain why 5 kg of anchovies only produce 1 kg of farmed salmon (line 20).

The genetic modification of Camelina plants involves the use of enzymes and a vector (lines 24 and 25).

Explain how enzymes are used in genetic modification.

Describe the role of a named vector in genetic modification.

The diagram shows a food web from a forest.

Use information from the food web to complete the table. The first one has been done for you.

Plant cell walls are made of cellulose. Cellulose is an insoluble molecule made from the same simple sugar as starch. The rabbit’s intestine contains bacteria that can digest cellulose. Suggest why this is an advantage for the rabbit.

The deer runs away when it sees the wolf.

Name the effector in this response.

The deer releases a hormone when it sees the wolf. Explain how this hormone helps the deer to run away.

The owl uses its eyes to find prey. The diagram shows a section through the owl’s eye.

Name the parts labelled A and B.

Describe the function of part A.

Describe the function of part B.

When trees lose leaves, they fall to the ground and form leaf litter. The leaf litter provides food for many animals. The diagram shows a food web that includes leaf litter.

Use information in the food web to complete the table. The first one has been done for you.

The following apparatus is called a Tullgren funnel. It is used to sample the number of animals living in leaf litter. The animals move away from the light and fall into the collecting pot.

A student used a Tullgren funnel to sample the number of millipedes living in leaf litter in two areas of a forest. The student took leaf litter from 5 quadrats in the centre of the forest and from 5 quadrats near the edge of the forest. The table shows the student’s results.

One stimulus that the millipedes respond to in the Tullgren funnel is light. Suggest two other stimuli that might cause millipedes to fall into the collecting pot.

State the difference in the number of millipedes found in the leaf litter samples from the two areas of the forest and suggest two reasons for this difference.

The student collects leaf litter using a quadrat. Draw a quadrat in the space below.

The diagram shows part of a food web in an oak forest.

Use the information in the food web to complete the statements in the table. The first one has been done for you.

What effect would a decrease in the population size of caterpillars have on the population size of blue jays?

What is meant by the term population ?

The tick feeds on deer by sucking their blood. Name two different molecules that are found in the blood of deer that the tick could feed on.

In fruit flies, the length of the wings is controlled by a gene with two alleles. The allele for long wings (L) is dominant to the allele for short wings (l). The diagram shows a long-winged fruit fly and a short-winged fruit fly.

Complete the table by writing the genotype, the description of genotype and the phenotype of the fruit flies.

Two heterozygous fruit flies mated. The number of long-winged and short-winged offspring produced are shown below.

Tick one box to show the number of these offspring that is likely to be heterozygous.

Yeast cells feed on rotting fruit. Fruit flies feed on these yeast cells. Use this information to draw a food chain in the space below.

A student wanted to find out if fruit flies are attracted to rotting fruit. He set up this apparatus.

He released 20 fruit flies into the glass tank. After ten minutes, he counted the number of fruit flies found near the fresh fruit and the number found near the rotting fruit. The table shows his results.

Name two factors that the student should control in this investigation.

Do you think the student’s results are reliable? Give a reason for your answer.

The photograph shows a bird called a parakeet.

Parakeets eat seeds. Parakeets can be eaten by birds of prey called raptors. Use this information to draw a food chain.

Many seeds contain starch. Suggest what happens to starch in the gut of a parakeet.

The graph shows the volume of oxygen used by a resting parakeet compared to a flying parakeet.

Calculate the extra volume of oxygen used in litres per gram per hour when flying compared to the volume used at rest. Show your working.

_........ litres per gram per hour

Like humans, parakeets need to keep their body temperature constant. Suggest how the volume of oxygen used by a parakeet at rest would change if it was moved to a colder environment.