Reproduction | Edexcel IGCSE Biology: Double Science Paper 1 2019

1a

3 marks

The diagram shows an insect-pollinated flower called a lily.

jan-22-1b-q2a-flower

(i)

Which of these is the name of structure P?

(1)

☐	A	Anther
☐	B	Filament
☐	C	Stigma
☐	D	Style

(ii)

Which of these is the name of structure Q?

(1)

☐	A	Leaf
☐	B	Petal
☐	C	Stem
☐	D	Style

(iii)

On which structure do pollen grains germinate?

(1)

☐	A	P
☐	B	Q
☐	C	R
☐	D	S

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1b

3 marks

Describe how the structures of P, Q and S would differ in a wind-pollinated flower.

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1c

4 marks

Plants can also reproduce by asexual reproduction.

(i)

Give one natural method that plants use to reproduce asexually.

(1)

(ii)

Give one artificial method that a plant grower may use to reproduce a plant asexually.

(1)

(iii)

Suggest why a plant grower may choose to reproduce a plant asexually rather than allowing the plant to reproduce sexually.

(2)

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2a

8 marks

The passage describes reproduction in flowering plants. Complete the passage by writing a suitable word in each blank space.

Flowers are organs that allow plants to carry out .............................. reproduction. The male gamete is contained within the .............................. grains. These grains are released from the .............................. , which is found on top of the filament. These grains need to land on the .............................. , the female part of the flower. Grains can be transferred by wind or by animals. These animals are often insects such as .............................. or butterflies. The petals of insect-pollinated plants are often .............................. and brightly coloured. After pollination, the grains germinate and a tube grows down the ..............................to reach the ovary. In the ovary, the gametes fuse. This process is known as.............................. .

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2b

2 marks

Once the seed has been produced it can then germinate, but only in the correct conditions.

Temperature is one factor that affects the rate of germination.

Name two other factors.

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2c

2 marks

A student investigated the speed of seed germination at different temperatures.

To do this they placed 20 cress seeds on a layer of moist cotton wool in a petri dish.

They set up three of these plates and placed them in different temperature conditions: one at 10 °C, one at 30 °C, and one at 50 °C.

They recorded how long it took for 15 of those seeds to germinate.

The results were as follows:

Temperature (°C)	Time taken for 15 seeds to germinate (hours)
10	26
30	13
50	15 seeds did not germinate after 5 days

Explain the results shown in the table.

(2)

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2d

2 marks

The diagram below shows the seeds shortly after germination. zt-CpwZr_germinating-seed-sq

Name part X and part Y of the germinating seed.

(2)

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1a

3 marks

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)

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1b

9 marks

The table shows the scientists’ results.

Concentration of salt solution in mmol	Percentage germination (%)
0	89
20	83
40	81
80	73
120	68
160	55
200	52
240	49
280	43
320	38

(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. edexcel-igcse-1b-jan-21-q7b

(5)

(ii)

Explain the effect of increasing the concentration of the salt solution on germination.

(4)

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1c

4 marks

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)

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1a

2 marks

Cell division can be by meiosis or by mitosis.

(i)

Where are cells dividing by meiosis found in a human?

(1)

☐	A	kidney
☐	B	penis
☐	C	skin
☐	D	testis

(ii)

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

(1)

☐	A	anther
☐	B	cotyledon
☐	C	root tip
☐	D	xylem

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1b

6 marks

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

Feature	Meiosis	Mitosis
Number of chromosomes in each original cell	46
Number of daughter cells produced from each original cell		2
Number of chromosomes in each daughter cell
Ploidy level of daughter cells produced		diploid
Genetic differences in daughter cells	present
Type of cell produced		body cell

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1c

5 marks

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)

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In one ejaculation	Age in years
In one ejaculation	16–30	31–33	34–36	37–39	40–43	44–47	48–72
Mean semen volume in cm³	3.45	3.44	3.35	3.30	3.22	2.92	2.49
Mean sperm concentration in millions per cm³	61.5	64.2	64.1	61.1	62.1	62.4	56.9
Mean number of sperm released in millions	212	221	215	202		182	142

Reproduction (Edexcel IGCSE Biology: Double Science)

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