Natural selection

Which process is involved in the theory of evolution?

Figure 1 shows some stages of the theory of evolution.

overproduction variation survival of the fittest

Figure 1

State two causes of variation in organisms.

Disease is an example of a selection pressure.

Give one other example of a selection pressure that leads to survival of the fittest.

Figure 2 shows the location of the Wallace line, an imaginary line Alfred Wallace suggested, based on his research.

Wallace found that animals to the west of the line were different from animals to the east of the line.

Suggest two possible reasons why animals to the west of the Wallace line are different from animals to the east of the Wallace line.

Give one reason why the work of Alfred Wallace encouraged Charles Darwin to publish his theory of evolution.

Figure 6 shows the bones in the limbs of a bird and a whale.

The bird and the whale have evolved from a common ancestor.

Give one way the structure of these limbs provides evidence for this evolution.

Charles Darwin developed the theory of evolution by natural selection.

Which scientist worked with Darwin on the theory of evolution by natural selection?

DNA is found in bones and stem cells.

Suggest one reason why DNA is found in bones.

Describe how stem cells help animals to grow.

Scientists have transplanted stem cells into the retina of the eye.

Name one type of light sensitive cell found in the retina.

Explain one reason for transplanting stem cells into the retina.

In the 19th century the destruction of wetland habitats caused the extinction of the bittern in the UK.

Figure 10 shows a bittern.

Restoration of the habitats has led to the birds returning to the UK.

Male bitterns make a loud booming sound.

This allows the numbers of male bitterns to be counted.

In 1997, 11 males were counted and this increased to 221 males in 2021.

Calculate the percentage increase in the number of males from 1997 to 2021.

The bitterns are difficult to see in the reeds of the wetland habitat.

Give one benefit of this to the bittern.

There is some concern that the bitterns in the UK are all closely related. This could make them susceptible to extinction.

Explain, using your knowledge of natural selection, why being closely related could make the bitterns susceptible to extinction.

Describe how selective breeding can be used to produce a large population of animals that are not closely related.

Sex determination in birds is different from humans.

Males are homozygous Z and females are heterozygous ZW.

Complete the Punnett square to show how sex is determined in birds.

Stone tools can be found at sites used by our human ancestors.

Describe how tool P was made.

Figure 4 shows tool Q which was found at the same site as tool P.

A scientist stated that tool Q was made by a more evolved human ancestor than tool P.

Which observation supports this statement?

Tools provide evidence for human evolution.

Use words from the box to complete the sentences.

Evolution is the change of inherited characteristics through

_........ selection.

These changes occur because genes_........ .

Fossils were also found in the soil around tool Q.

Describe two ways that stone tools and fossils can be dated to find out how old they are.

The book ‘On the Origin of Species’ was published in 1859.

This book describes the theory of evolution.

Which scientist wrote this book explaining his theory of evolution?

Which statement is supported by this theory of evolution?

One chapter of this book discusses pentadactyl limbs.

Figure 5 shows the bones of the pentadactyl limbs of three mammals.

Describe one difference between the humerus of the whale and the humerus of the human.

Describe one difference between the phalanges of the horse and the phalanges of the human.

Another chapter of the book discusses how the shape of bird beaks has evolved on different islands.

Figure 6 shows two species of finch from two different islands.

(Source: © Kristel Segeren/Shutterstock)
(Source: © Maurizio De Mattei/Shutterstock)

Species A
Species B

Figure 6

These two species of finch evolved from a common ancestor that had a similar shaped beak to species B.

Beak shape is related to the food that the finches eat.

Describe how the thinner beak of species A is a result of evolution.

Alfred Russel Wallace travelled around Malaysia during the 1800s and wrote to Charles Darwin about the animal species he studied.

His main conclusions were very similar to those of Charles Darwin and they both contributed to the current understanding of evolution.

Describe the theory of evolution by natural selection.

Wallace and Darwin did not always agree.

Darwin believed that male birds have feathers that are brightly coloured to make them more attractive to female birds.

Wallace thought that female birds have feathers that are less brightly coloured so they are more likely to survive.

Explain why having feathers that are less brightly coloured increases the survival rate of females.

Suggest why it is more important for the survival of the species that the survival rate is higher in female birds than in male birds.

Figure 7 shows the limbs of five animals.

Describe how the structure of these limbs provides scientists with evidence for evolution.

Figure 5 shows a great tit on a bird feeder.

Scientists have found that great tits living now have longer beaks than great tits living 50 years ago.

Genetic analysis shows changes in the sequence of the bird’s DNA.

Give the complementary strand sequence for this DNA template.

Which statement correctly describes a DNA molecule?

State the term used to describe a change in the sequence of DNA bases.

Scientists think that great tits living now have longer beaks because of the increased use of bird feeders during the last 50 years.

Explain how natural selection could have caused an increase in beak length because of the use of bird feeders.

Birds are classified in the domain Eukarya.

Why are the cells from birds described as eukaryotic?

Give one reason why the three domain classification system was proposed.