Selective breeding

Figure 7 shows the times when Homo sapiens (modern humans) and some of their ancestors are thought to have lived.

Which term is used to describe changes in species over time?

Estimate the length of time Homo habilis is thought to have lived on Earth.

Describe two methods scientists used to date the fossils of Ardi or Lucy, as shown in Figure 7.

The ancestors of modern humans used selective breeding to improve the plants they used for food.

Complete the sentences using words from the box.

Selective breeding involves choosing parents with

desirable_........ .

The best offspring are bred together and this process is repeated over

many_........ .

Suggest one feature of a banana that could be improved by selective breeding.

The DNA of fruit can be modified to produce new varieties.

Figure 8 shows part of a method used to extract DNA from fruit.

State the purpose of both step 1 and step 2.

State why the cold ethanol was added in step 3.

Figure 4 shows fossils in different layers of rock.

Which layer of rock is likely to contain the most recent fossils?

Figure 5 shows some stone tools from two different periods of time.

Explain one difference between tool A and tools B, C and D.

Our human ancestors domesticated animals.

Animals were domesticated to use as working animals and to keep as pets.

Use words from the box to complete the sentences.

Animals with the most desirable_........ were bred together.

This is called_........ breeding.

Scientists have analysed the genomes of domestic animals.

Which is the definition of a genome?

Give one advantage of domesticating animals.

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.

Figure 9 shows a plant with plantlets growing from it.

If a plantlet touches soil, it will grow roots and become a new plant.

This is an example of asexual reproduction.

State one advantage of asexual reproduction for this plant.

Scientists investigated how temperature affected the number of plantlets produced by this type of plant in 10 weeks.

The scientists grew one of these plants in each of six temperatures.

Figure 10 shows the results.

Describe the effect of temperature on the number of plantlets produced by these plants.

Which of these would improve the results of this investigation?

The plant in Figure 9 also produces flowers for sexual reproduction.

Explain one advantage of sexual reproduction.

Figure 11 shows the characteristics of three different varieties of this plant.

A gardener wants to use selective breeding to produce a plant with large green and white striped leaves and large white flowers.

Explain which plants the gardener should use.

3 (a) Sickle cell disease is a recessive genetic disorder in humans.

(i) Two parents are heterozygous for sickle cell disease. Complete the Punnett square to show the possible genotypes of their children.

(ii) State the percentage probability that their children could have sickle cell disease.

(iii) A father with the genotype dd and a mother with the genotype DD plan to have several children. Explain why none of their children will have sickle cell disease.

(b) Figure 4 shows some information about two types of cattle.

Describe how these types of cattle could be selectively bred to produce cattle that can survive high temperatures and have good meat quality.

(c) Figure 5 shows the leaf of a wheat plant with a fungal disease.

(Source: © Kazakov Maksim/Shutterstock)

Figure 5

Give two benefits of breeding wheat plants that are resistant to fungal disease.

7 Hipparion is an extinct genus of horse that lived between approximately 20 million and 0.8 million years ago. Figure 10 shows the skeletons of a Hipparion and a modern horse.

Hipparion modern horse (Sources: © Morphart Creation/Shutterstock and © Hein Nouwens/Shutterstock)

Figure 10

(a) (i) Give one method that can be used to date a fossil of a Hipparion.

(ii) Give one reason why scientists have concluded that the modern horse has evolved from Hipparion.

(b) Describe how racehorses alive today have been selectively bred to run faster.

* (c) Discuss the advantages and disadvantages of sexual reproduction and asexual reproduction.

Farmers selectively breed chickens to produce larger chickens.

Figure 9 shows how the size of chickens has changed over time.

Explain how farmers have used selective breeding to produce larger chickens.

Describe one benefit and one risk of selectively breeding chickens.

The body cells of chickens have 78 chromosomes in their nuclei.

State the number of chromosomes found in each sex cell of a chicken.

Name the type of cell division which produces sex cells.

What is the correct definition of a genome?

A new project called the Earth BioGenome Project aims to discover the sequence of bases in the DNA for all plants and animals.

State two benefits of discovering the sequence of bases for all plants and animals.

Figure 11 shows two potato chips.

Figure 12 shows some information about each potato chip.

Calculate the total surface area of potato chip B using the formula,

Total surface area = 2XY + 2XZ + 2YZ

The potato chips were placed in distilled water for 20 minutes.

Figure 13 shows the increase in mass of each potato chip.

Explain why potato chip B has a greater increase in mass than potato chip A.

Potato chip A is transferred from the distilled water into a concentrated salt solution.

Explain what will happen to the cells in potato chip A.

*(b) Figure 14 shows two varieties of potato plant.

• large potatoes • small potatoes

• few potatoes • many potatoes

• slow growing plant • fast growing plant

Figure 14

New varieties of potato plant can be produced by selective breeding.

Explain how selective breeding of the two varieties of potato plants can produce new potato plants that are all faster growing and produce many, large potatoes.