Paper 2

Question 1

Wong length in fruit flies is controlled by two alleles
Vestigial( short) wings are caused by the allele n
Normal length wings are caused by the allele N
Vestigial wing allele is recessive to the normal wing allele
What does it mean it allele is recessive?

Answer 1

Two copies of the allele to be present for the characteristic to be displayed.

Question 2

Two fruit flies with Normal length wings are crossed. Complete the Pinnett in figure 1 to show this cross.

Answer 2

Question 3

Two fruit flies with Normal length wings are crossed. Complete the Pinnett in figure 1 to show this cross.

Answer 3

Question 4

The two fruit flies crossed in figure 1 have 200 offspring’s. Compare how many of the offspring would be expected to have vestigial wings?

Answer 4

Proportion of offspring expected to have vestigial wings =
25%/0.25/1 in 4
So out of 200 fruit flies, the expected number of offspring with vestigial wings = (200 ÷ 100) × 25 / 200 × 0.25 / 200 ÷ 4 = 50 [2 marks for the correct answer, otherwise 1 mark for the correct proportion of offspring expected to have vestigial wings)
Remember, the allele for vestigial wings is recessive, so only offspring with the genotype ‘nn’ will have vestigial wings.

Question 5

Fruit flies are eukaryotic organisms. Describe how the genetic material of fruit fly is stored in its cells.

Answer 5

Genetic material is stored as DNA molecules which are arranged into chromosomes. The chromosomes are found in the nucleus of each cell.

Question 6

Quadrats can be used to investigate the distribution of organisms in a habitat.
A group of students used 1 m? quadrats to investigate the plant species that live in a small field next to their school.

They placed three quadrats at random in each section of the field and counted the number of buttercups, clover and dandelions in each quadrat.
Their results are shown in Table 1.
Explain why the quadrats were placed randomly?

Answer 6

To make sure the result were representative of the whole population in each section.
To prevent bias

Question 7

What is the median number of buttercups per m2 in section A

Answer 7

52

Question 8

What is the mean number of of clover per m2 in section B. Give you answer in 2 significant figures.

Answer 8

90.333
90

Question 9

Section C measures 5m by 3m
Use the data in table 1 to estimate the total population of dandelions in section C

Answer 9

Area of section C=5x3=15m2
12x15=180
All you have to do is to multiply the number of dandelions found in 1m2 by the total area of section C

Question 10

Use the data in table 1 to give a conclusion about the distribution of the three plant species across the field.

Answer 10

The number of plants per m2/ density of plants/ frequency of plants of all three species increases with the increasing distance from the school.

Question 11

Give three examples of abiotic factors that may affect the number of plants of each species growing at different locations in the field.

Answer 11

Any three from: e.g. differences in temperature / differences in the mineral content of the soil / differences in the soil pH / differences in the light intensity received by the plants / differences in the moisture level of the soil / differences in the wind intensity/direction 3 marks — 1 mark for each correct answer|
Remember, abiotic factors are non-living parts of an ecosystem.

Question 12

Students carried out an experiment to investigate the effect of age on reaction time.
This is the method they used.
1. They recruited 35 volunteers with ages between 20 and 60.
2. The volunteers were asked to complete a task on a computer. In the task they had to press the enter key every time a certain shape appeared on the screen.
Each volunteer completed the task 10 times and the mean reaction rate for each volunteer was calculated.
4. The students then divided the volunteers’ results into four age groups and calculated a mean reaction time for each group.

The results of the experiment are shown in Table 2.

The student’s experiment tested a nervous response in the volunteers.

The effector in the response is muscle in the hand. Describe how muscles respond when they are stimulated by a nervous impulse.

Answer 12

They contract.

Question 13

A motor neurone is involved in this nervous response. Describe the role of the motor neurones in the human body.

Answer 13

Motor neurones carry Electrical/ nervous impulses from the central nervous system to effectors.

Question 14

Calculate the percentage increase in mean reaction time between the 20-29 age group and the 50-60 age group.

Answer 14

Percentage increase= final value-original value/original value X100
0.39-0.30/0.30X100=30%

Question 15

Use data from Table 2 to draw a bar chart on Figure 3, showing the mean reaction time for each age group.
Complete the y-axis. Include a label and use a suitable scale.
Plot the mean reaction time data.

Answer 15

Question 16

From their results, the students concluded that as age increases, reaction time slows down.
Suggest two ways in which the students could have improved their method in order to have more confidence in their conclusion.

Answer 16

Any two from: e.g. they could have used volunteers with a wider range of ages. / They could have used more volunteers. / They could have used the same number of volunteers in each age group.

Question 17

A hospital patient has a suspected brain injury. Doctors have been running tests to determine which area of the patient’s brain may have been damaged.
The patient is breathing normally without any medical assistance.
Using this information, suggest what part of the brain remains undamaged.
Explain your answer.

Answer 17

The medulla because this part of the brain controls unconscious activities suck as breathing.

Question 18

Which part is cerebral cortex

Answer 18

A

Question 19

Give two activities which are associated with cerebral cortex

Answer 19

Consciousness
Memory
Intelligence
Language

Question 20

Another patient in the hospital has OPCA.
OPCA (OlivoPontoCerebellar Atrophy)is a condition that affects the function of particular areas of the brain.
Symptoms include clumsiness, difficulty walking and loss of balance.
Using the information given above, suggest a region of the brain that may not be functioning normally in people suffering from OPCA. Explain your answer.

Answer 20

Cerebellum as this is the region responsible for muscle coordination.

Question 21

Give two methods scientists can use to work out the function of particular parts of the brain.

Answer 21

Studying patients with brain damage
Electrically stimulating different parts of the brain
MEI Scans

Question 22

Plant hormone control aspects of a plant’s growth. Some plant hormones are affected by factors outside the plant such as light
Name the response shown by shoot A after 2 days.

Answer 22

Phototropism

Question 23

Give one variable that the student should have controlled during the experiment.

Answer 23

E:g the type of plant shoots used. / The intensity of the light source. / The temperature the plants were kept at. / The medium (e.g. soil) the shoots were grown in. / The amount of water the shoots received. [1 mark)