Reproduction (Edexcel IGCSE Biology (Modular): Unit 2)

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.

Separate: Biology Only

The table gives information about some hormones involved in the menstrual cycle.

Complete the table by giving the missing information.

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.

Separate: Biology Only

A scientist investigates the effect of three different solutions on the growth of pollen tubes using this apparatus.

This is the scientist’s method.

• Place a different solution in three different flasks 

• Add pollen grains to the solution in each flask

• Leave the grains in each solution for three hours

• Take a sample of pollen grains from each solution

• Measure the length of the pollen tubes in each sample

The graph shows the scientist’s results.

(i) Calculate the difference between the mean rate of pollen tube growth in the control solution and the mean rate of pollen tube growth in the actinomycin D solution.

Give your answer in μm per hour.

(2)

(ii) Actinomycin D prevents transcription and cycloheximide prevents translation.

Use this information and your own knowledge to explain the results of this investigation.

(4)

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) Explain the responses of roots and stems to gravity.

(2)

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

(2)

Separate: Biology Only

Read the passage below. Use the information in the passage and your own knowledge to answer the questions that follow.

Suggest why the men in the study had to be able to produce sperm with no abnormalities in shape or movement (lines 8 and 9).

Separate: Biology Only

(i) The contraceptive injection contained the drug progestin (lines 15 and 16).

Progestin is similar in structure and function to progesterone.

Describe the roles of progesterone in the human female body.

(2)

(ii) Suggest why the injections also contain the hormone testosterone (lines 15 and 16).

(1)

(iii) State where in the male body testosterone is produced.

(1)

Separate: Biology Only

(i) Give the purpose of the initial suppression phase of the study (line 13).

(1)

(ii) State why the sperm count is monitored during the suppression phase (lines 18 and 19).

(1)

(iii) State why alternative contraception was used during the suppression phase (lines 19 and 20).

(1)

Separate: Biology Only

Suggest why sperm count continues to be monitored during the testing phase (lines 25 and 26).

Separate: Biology Only

Calculate the number of men whose partners became pregnant during the study (lines 6 and 28).

Separate: Biology Only

Evaluate the use of progestin and testosterone injections as a method of contraception.

Separate: Biology Only

Read the passage below. Use the information in the passage and your own knowledge to answer the questions that follow.

Explain how cross-pollination can lead to an increase in genetic variation. (Lines 2–3)

Separate: Biology Only

(i) Explain the advantages of the seeds germinating away from the parent plant. (Line 8)

(3)

(ii) Give one advantage of a seed germinating close to the parent plant. (Line 11)

(1)

Separate: Biology Only

Explain the conditions needed for seed germination.

Separate: Biology Only

Explain why some seeds are surrounded by a brightly-coloured and sweet-tasting fruit. (Lines 13–14)

Separate: Biology Only

Large numbers of tomato plants are often found growing along the sides of drains and settling beds on sewage farms.

Suggest a reason for this observation.

Separate: Biology Only

Give the reason why sunlight is required for lupin seeds to be dispersed. (Lines 21–24)

Separate: Biology Only

Describe an experiment you could carry out to investigate how the presence of fluff on dandelion seeds affects how fast they fall. (Lines 30–31)