Variation

Evolution of new species occurs by mutation and natural selection.

What is a mutation?

Describe the process of natural selection.

Which scientists suggested the theory of evolution by natural selection?

Tick (✓) one box.

The hoverfly and the wasp are insects with bright yellow and black markings.

Figure 12 shows a hoverfly and a wasp.

The wasp has a sting to defend itself against predators.

The hoverfly does not have a sting.

Hoverflies and wasps live in the same habitat.

Explain how having yellow and black markings helps the hoverfly survive.

Evolution of new species occurs by mutation and natural selection.

What is a mutation?

Describe the process of natural selection.

Which scientists suggested the theory of evolution by natural selection?

Tick () one box.

The hoverfly and the wasp are insects with bright yellow and black markings.

Figure 1 shows a hoverfly and a wasp.

The wasp has a sting to defend itself against predators.

The hoverfly does not have a sting.

Hoverflies and wasps live in the same habitat.

Explain how having yellow and black markings helps the hoverfly survive.

Reproduction can produce offspring which are:

• genetically different or

• genetically identical.

Farmers grow tomato plants in greenhouses.

The tomatoes are sold in supermarkets.

Suggest one advantage of growing tomato plants that are genetically different.

Suggest one advantage of growing tomato plants that are genetically identical.

Scientists can grow genetically identical tomato plants using tissue culture.

What is tissue culture?

Genetically identical tomato plants growing in the same garden do not all grow to the same height.

Give one reason why.

The sex of dogs is determined by X and Y chromosomes in the same way as in humans.

Complete the Punnett square diagram in Figure 15 to show the inheritance of sex in dogs.

Use the symbols X and Y.

Figure 15

A female dog gave birth to six offspring.

Why would you expect there to be three male offspring and three female offspring?

Use your answer to Question 09.5.

Farmers keep chickens for:

• meat production

• egg production.

Some varieties of chicken grow more quickly and are more suitable for meat production.

Other varieties of chicken produce more eggs.

A farmer keeps two varieties of chicken, A and B.

The farmer investigated the growth rates and egg-production rates of both varieties.

Figure 16 shows the results.

Suggest two control variables the farmer should have used in this investigation.

Figure 16 shows mean values from 500 chickens of each variety.

Give the reason the farmer used a large number of chickens.

The farmer wants to produce a new variety of chicken that is good for both meat production and egg production.

Describe how selective breeding of chicken varieties A and B can produce the new variety of chicken.

Reproduction can produce offspring which are:

• genetically different or

• genetically identical.

Farmers grow tomato plants in greenhouses. The tomatoes are sold in supermarkets.

Suggest one advantage of growing tomato plants that are genetically different.

Suggest one advantage of growing tomato plants that are genetically identical.

Scientists can grow genetically identical tomato plants using tissue culture. What is tissue culture?

Genetically identical tomato plants growing in the same garden do not all grow to the same height. Give one reason why.

The sex of dogs is determined by X and Y chromosomes in the same way as in humans.

Complete the Punnett square diagram in Figure 4 to show the inheritance of sex in dogs. Use the symbols X and Y.

Figure 4

A female dog gave birth to six offspring. Why would you expect there to be three male offspring and three female offspring? Use your answer to Question 03.5.

Farmers keep chickens for:

• meat production

• egg production.

Some varieties of chicken grow more quickly and are more suitable for meat production. Other varieties of chicken produce more eggs. A farmer keeps two varieties of chicken, A and B. The farmer investigated the growth rates and egg-production rates of both varieties. Figure 5 shows the results.

Suggest two control variables the farmer should have used in this investigation.

Figure 5 shows mean values from 500 chickens of each variety. Give the reason the farmer used a large number of chickens.

The farmer wants to produce a new variety of chicken that is good for both meat production and egg production. Describe how selective breeding of chicken varieties A and B can produce the new variety of chicken.

A scientist found a polluted pond which had a new type of blue algae in the water. The blue colour of the algae was caused by a mutation.

What is a mutation?

The scientist measured the number of blue algal cells in a sample of the pond water.

The scientist used a special slide which has a counting grid.

This is the method used.

1. Dilute 2.5 cm³ of pond water to a volume of 10 cm³ with distilled water.

2. Place a drop of the diluted pond water on the special slide, as shown in Figure 8.

3. Place a thick coverslip over the diluted pond water to give a depth of 0.1 mm of

pond water.

4. Use a microscope to count the number of algal cells in a 0.2 mm 0.2 mm square on the counting grid.

Figure 8 shows a side view of the special slide.

Figure 9 shows the view of the counting grid through a microscope.

How many algal cells are in the 0.2 mm × 0.2 mm square in Figure 9 ? Use the following procedure:

• Count all cells that are completely within the 0.2 mm × 0.2 mm square in the counting grid.

• Count cells that are touching the left side or the lower side of the square.

• Do not count cells that are touching the right side or the top side of the square.

One week later the scientist repeated the test and counted 14 cells on the 0.2 mm × 0.2 mm counting grid. Calculate the number of algal cells in 1.0 mm³ of undiluted pond water. Use the scientist’s second count of 14 cells.

Suggest why the scientist diluted the pond water before placing it on the special slide.

A student repeated the scientist’s method. The student used a thin coverslip over the diluted pond water instead of the thick coverslip. The liquid pulled the thin coverslip downwards slightly. Explain how the use of the thin coverslip would affect the results for the cell count.

Sickle cell anaemia is an inherited condition that affects red blood cells. Sickle cell anaemia is caused by a mutation in the gene for haemoglobin. Haemoglobin is the red pigment found in red blood cells. A person who is homozygous for the normal haemoglobin allele (H^A) produces normal red blood cells. A person who is homozygous for the mutated allele (H^S):

• produces red blood cells with abnormal haemoglobin

• has red blood cells that can form an altered shape

• has sickle cell anaemia and becomes ill.

A person who is heterozygous:

• has both normal and abnormal haemoglobin in the red blood cells

• has sickle cell trait

• is generally healthy but can become ill in certain circumstances.

Give the reason why a mutation in the gene coding for haemoglobin could be harmful.

Figure 13 shows some red blood cells from the blood of a person with sickle cell trait.

Calculate the proportion of cells in Figure 13 that have an altered shape.

Figure 14 shows the inheritance of sickle cell anaemia in one family.

Persons 8 and 9 in Figure 14 are expecting a second child. Determine the probability that the child will be a girl with sickle cell trait. You should:

• draw a Punnett square diagram

• identify the phenotype of each offspring genotype

• use the symbols: H^A = normal haemoglobin allele H^S = mutated haemoglobin allele.

Without medical treatment, people with sickle cell anaemia are frequently ill and have a reduced life expectancy. The malarial parasite cannot live in the red blood cells of a person who has

A scientist stated: ‘It is an advantage for people to have the H^S allele in countries where malaria occurs.’ Evaluate the scientist’s statement.

The Galapagos Islands are located in the Pacific Ocean. Several species of birds called finches live on the Galapagos Islands. These finches are very similar to each other. Figure 15 shows two modern species of Galapagos finch and their classification.

Figure 15

Medium ground finch Small ground finch

Complete Figure 15 to give the names of the missing classification groups.

Give the binomial name of the medium ground finch. Use information from Figure 15.

In each species of finch, there is a variation in beak depth.

Figure 16 shows how beak depth is measured.

Figure 17 shows the relationship between the beak depth of parent birds and the beak depth of their offspring.

Give evidence from Figure 17 that beak depth is an inherited characteristic.

Scientists suggested that more than one gene controls beak depth. Give evidence from Figure 17 to support the scientists’ suggestion.

Figure 18 is a map of the Galapagos Islands.

On Isabela Island, the medium ground finch and the small ground finch are found. On Daphne Island, only the medium ground finch is found. On Crossman Island, only the small ground finch is found. Figure 19 shows how the beak depth of each species varies on each island.

The medium ground finch and the small ground finch both feed on seeds.

The size of seeds eaten by each bird depends on the depth of the bird’s beak.

The range of beak depth of medium ground finches on Isabela Island is different from the range on Daphne Island. Explain what might have caused this difference.

Figure 19 shows:

• the two species of finch live on Isabela Island

• only one of the species lives on Daphne Island

• only one of the species lives on Crossman Island.

Suggest why both species of finch are able to live on Isabela Island.

Sperm cells and egg cells are formed by meiosis.

During meiosis a cell divides twice.

How many sperm cells are formed when a cell divides by meiosis?

Human body cells contain 46 chromosomes.

How many chromosomes are in each human egg cell?

Dupuytren’s is a disorder that affects the hands.

One form of Dupuytren’s is caused by a dominant allele (D).

The allele for not having Dupuytren’s is recessive (d).

What is an allele?

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A man with Dupuytren’s has the genotype Dd.

Which word describes the man’s genotype?

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The man with Dupuytren’s (Dd) and a woman who does not have Dupuytren’s (dd) plan to have a child.

Complete the genetic diagram in Figure 4 to show the possible genotypes of the child.

Draw a ring around the genotype of a child in Figure 4 who will have Dupuytren’s.

What is the chance of the child having Dupuytren’s?

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A genetic disorder develops as a result of a change in a gene.

What scientific term describes a change in a gene?

People with a family history of some genetic disorders are offered embryo screening.

Suggest one way embryo screening can help people with a family history of a genetic disorder.

Figure 6 shows the production of sperm cells in humans.

Cell A is a normal body cell.

How many chromosomes are there in cell A ?

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What is the mass of DNA in cell E ?

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What type of cell division produces sperm cells?

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Sometimes there are errors in copying the genetic material.

What term describes an error in the genetic material?

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A woman has three children, aged 4, 6 and 9 years.

Why are the children not genetically identical?

In sexual reproduction, a sperm cell fuses with an egg cell to form a new single cell.

An embryo develops from the single cell.

The cell divides three times to produce the embryo.

How many cells are there in the embryo after three cell divisions?

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Figure 7 shows a different human embryo.

Measure image length X on Figure 7.

Give your answer in millimetres (mm).

The image in Figure 7 has been magnified 500

Calculate the real length of the embryo.

Use the equation:

Give your answer in micrometres (m).

The embryo may not implant in the lining of the uterus.

The embryo will then be lost from the woman’s body several days later.

Explain why the woman may not notice this has happened.

Fossils give evidence about organisms that lived a long time ago.

Scientists have found very few fossils of the earliest life forms.

Give one reason why.

Figure 3 is a photograph of a fossilised fish.

Suggest how the fossil in Figure 3 was formed.

The species of fish shown in Figure 3 is now extinct.

Give two possible causes of extinction.

Modern fish species have evolved from fish that lived a long time ago.

Evolution is caused by mutation and natural selection.

What is a mutation?

Tick one box.

Describe the process of natural selection.