Variation

Genes control natural hair colour in humans.

Which term describes the differences in hair colour?

Genes are found on chromosomes.

Name the part of the human cell where chromosomes are found.

The hair colour of 24 students was recorded.

Figure 1 shows the results.

Complete Figure 2 to show the tally and the total for brown hair.

Complete the bar chart to show the totals in Figure 2 and label the x ‑axis.

In the 19th century, Gregor Mendel studied genetic inheritance in pea plants.

Mendel made the conclusion that characteristics in organisms were determined by the inheritance of ‘units’.

What are these ‘units’ of inheritance known as today?

Figure 20 shows one of Mendel’s experiments on the inheritance of pea shape.

plants that produced plants that produced

State the conclusion that Mendel was able to make about the wrinkled pea characteristic.

A scientist crossed two pea plants that were heterozygous for pea shape.

Complete the Punnett square to show the inheritance of the alleles for pea shape and the percentage probability of producing a plant with wrinkled peas.

Use the letter R for the allele for round shape.

Use the letter r for the allele for wrinkled shape.

percentage probability of producing a plant with wrinkled peas_........

Plants used to study inheritance are grown in controlled environmental conditions.

Suggest two ways of controlling these environmental conditions.

Some plants can reproduce asexually and sexually.

Complete the table by writing yes or no in each box to show the features of asexual and sexual reproduction.

A zygote with a diploid nucleus is formed by sexual reproduction.

State what is meant by a diploid nucleus.

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.

Apple trees show genetic variation.

State one possible cause of genetic variation in apple trees.

The colour of an apple is an observable characteristic.

Which is the term for an observable characteristic?

Name the type of reproduction that produces genetically identical organisms.

Grafting is a technique used to grow some varieties of apple tree.

Figure 16 shows apple tree shoots grafted on to a rootstock.

Grafting can be used to produce apple trees that are genetically identical.

Give one advantage and one disadvantage of growing genetically identical apple trees.

advantage

disadvantage

As apples ripen, enzymes convert starch into sugars.

Devise a method to find the optimum pH of an enzyme that breaks down starch.

You may use standard laboratory equipment and the solutions listed in the box.

The optimum pH of an enzyme is pH 6.

Explain why this enzyme would not work at pH 10.

A person’s mass is partially influenced by the alleles they inherit from their parents.

Give two other factors that can influence a person’s mass.

Figure 14 shows the data obtained from a patient by a doctor doing a health check.

The guidance used by the doctor is also listed in Figure 14.

Comment on the data and the health risks to this patient.

* (c) The doctor also tested the reaction time of the patient.

Describe the structure and function of a reflex arc.

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.

Figure 15 shows a method of producing plants.

Step 1. Cells taken from parent plant.

Step 2. Cells placed on agar growth medium.

Step 3. Cells develop into tiny plantlets.

Step 4. Plantlets grown in compost.

Figure 15

Some cells in each plantlet develop into root cells.

Name the process occurring as these cells develop into root cells.

Describe the advantages of producing plants by the method shown in Figure 15.

An autoclave is used to prepare the agar growth medium used in Step 2.

Explain why the agar growth medium is autoclaved.

One of the plantlets had different coloured leaves.

Give one reason why this plantlet had different coloured leaves.

Crop plants provide a source of energy in the form of carbohydrates such as starch and sugars.

Describe the test to identify starch.

The amount of energy in the sugars extracted from crop plants can be measured using the calorimeter shown in Figure 16.

Explain why the calorimeter has a lid.

State why it is important to stir the water in the calorimeter.

(a) Figure 8 shows a method of producing plants.

Step 1. Cells taken from parent plant.

Step 2. Cells placed on agar growth medium.

Step 3. Cells develop into tiny plantlets.

Step 4. Plantlets grown in compost.

Figure 8

Some cells in each plantlet develop into root cells.

Name the process occurring as these cells develop into root cells.

Describe the advantages of producing plants by the method shown in Figure 8.

An autoclave is used to prepare the agar growth medium used in Step 2.

Explain why the agar growth medium is autoclaved.

One of the plantlets had different coloured leaves.

Give one reason why this plantlet had different coloured leaves.

Crop plants provide a source of energy in the form of carbohydrates such as starch and sugars.

Describe the test to identify starch.

The amount of energy in the sugars extracted from crop plants can be measured using the calorimeter shown in Figure 9.

Explain why the calorimeter has a lid.

State why it is important to stir the water in the calorimeter.