Reproduction (Edexcel IGCSE Science (Double Award): Biology)

Cell division can be by meiosis or by mitosis.

(i) Where are cells dividing by meiosis found in a human?

(1)

(ii) Which part of a flowering plant is usually used to demonstrate cells dividing by mitosis?

(1)

The table lists features comparing the processes of meiosis and mitosis in human cells. Complete the table by giving the missing information.

Cell division can cause variation in offspring.

(i) Describe other causes of variation in offspring.

(3)

(ii) Scientists investigating a drug treatment use rats that are homozygous for many genes.

Suggest the advantages of using rats that are homozygous for many genes.

(2)

All organisms carry out some form of reproduction such as asexual reproduction or sexual reproduction.

Describe how asexual reproduction differs from sexual reproduction.

The diagram shows the structure of the human female reproductive organs.

(i) What is the site of fertilisation? 

(1)

(ii) Where does the fetus usually develop? 

(1)

(iii) Describe the role of the hormones produced by structure B.

(4)

The male reproductive system in humans produces sperm in a liquid called semen.

The production of sperm changes with age.

A scientist investigates how age affects mean semen volume and sperm concentration in one ejaculation.

The table shows the results of the investigation.

(i) Calculate the mean number of sperm released in one ejaculation from men aged 40–43

(1)

(ii) Explain why mean number of sperm released is a better measure of fertility than either mean semen volume or mean sperm concentration.

(2)

(iii) Calculate the percentage decrease in mean number of sperm between men aged 37–39 and men aged 48–72

(2)

The diagram shows an insect transferring pollen grains from flower P to flower Q.

Which structure in flowers contains pollen grains? 

Pollen grains are deposited on the stigma and grow tubes down the style.

(i) Suggest how style tissue helps the tube to grow.

(2)

(ii) The graph shows the change in the length of a pollen tube over a 180 minute period.

Calculate the fastest rate of pollen tube growth in mm per minute.

(3)

A farmer grows apple trees.

The flowers on the apple trees must be pollinated by insects to produce an apple crop.

The farmer is concerned that the use of pesticides may affect the yield of apples.

Design an investigation to find out if pesticides reduce the yield of apples.

Include experimental details in your answer and write in full sentences.

State what is meant by the term menstruation.

A girl starts to ovulate at the age of 12 years and continues to ovulate until she reaches the age of 51 years.

[Assume her menstrual cycle is 28 days and she releases one egg per cycle.]

Estimate the maximum number of eggs she could release in her lifetime.

Give your answer to two significant figures.

Give a reason why a female does not produce as many offspring as the number of eggs she releases.

Flowers are involved in plant reproduction. The diagram shows a section through a flower with parts labelled A, B, C and D.

(i) Which part of the flower makes pollen grains?

(1)

(ii) What part of the flower is the stigma?

(1)

After a pollen grain lands on the stigma of a flower, a pollen tube grows.

Explain the role of the pollen tube.

Describe a method the scientist could use to observe pollen grains

Some scientists have suggested that adding hydrogencarbonate solution to soil, instead of adding water, can increase plant growth.

Design an investigation to discover the effect that adding hydrogencarbonate solution has on the growth of seedlings.

Include experimental details in your answer and write in full sentences.

Scientists investigate the effect of salt (NaCl) concentration on the germination of maize seeds.

Batches of seeds are watered with different concentrations of salt solution.

They count the number of seeds that germinate in each batch 12 days after sowing. They then determined the percentage germination.

(i) Describe how the scientists could tell if a maize seed had germinated.

(1)

(ii) The scientists measured the germination after 12 days.

State two other abiotic variables that the scientists need to control in their investigation.

(2)

The table shows the scientists’ results.

(i) Plot a line graph to show the effect of the concentration of the salt solution on germination.

Use a ruler to join your points with straight lines.

(5)

(ii) Explain the effect of increasing the concentration of the salt solution on germination.

(4)

As plants grow, they produce roots and stems.

(i) Compare the responses of roots and stems to gravity.

(2)

(ii) Compare the responses of roots and stems to light.

(2)