AQA GCSE Trilogy Biology Paper 2 Higher November 2020 question paper 8464/B/2H

This question is about DNA and genes.

Which diagram represents a DNA molecule? Tick (✓) one box.

Describe the structure of a DNA molecule.

A gene is a small section of DNA on a chromosome. Complete the sentences.

A gene codes for a particular sequence of. This sequence makes a specific.

What is meant by the term genome?

The complete human genome is now known. Which important scientific advance was made using knowledge of the human genome? Tick (✓) one box.

A student found six different snails of one species in his garden. Figure 1 shows the snails.

All the snails are different. What scientific term describes differences in characteristics between individuals of a species?

A change in DNA has caused snail P to be very different from the other five snails. Suggest why there might be an increasing number of snails similar to snail P in each future generation.

Human reactions are a response to an external change.

Reflex actions help to protect the body against damage. Figure 2 shows the nervous pathway for a reflex action.

A stimulus from the hot pan will cause the muscle in the arm to contract and move the finger away. Describe how the stimulus from the hot pan reaches the muscle in the arm.

A student investigated whether using the right hand or the left hand had an effect on reaction time. The student only tested right-handed people. Describe a method for the student’s investigation. Include details of the test you would use for reaction time.

A different student carried out an investigation to see if playing tennis improved reaction time. The student used two groups of six people. Table 1 shows the results.

Calculate mean value X in Table 1.

What is the dependent variable in the student’s investigation?

The student concluded: ‘Playing tennis improves reaction time.’

Give one piece of evidence which supports the conclusion.

Give one piece of evidence which does not support the conclusion.

There is a need to grow enough food for all the people in the world. Growing enough food affects habitats and biodiversity.

What is meant by the term biodiversity?

Peat bogs are being destroyed because peat is used by humans. Destroying peat bogs also reduces biodiversity.

Give one use of peat taken from peat bogs.

Explain why the use of peat is harmful to the environment. Do not refer to biodiversity in your answer.

Intensive farming, where a single crop is grown on a large area of land year after year, is more cost effective for farmers. It is efficient to use fertilisers and to burn the waste so the land is ready to use the next year. Planting a single crop reduces biodiversity. Suggest two ways that this type of farming can damage the environment. Do not refer to biodiversity in your answer.

Most of the world’s production of antibiotics is used in farming. Antibiotics are given to animals to prevent the spread of disease.

Explain how the widespread use of antibiotics in farming is a threat to human life.

In sexual reproduction, cells divide by meiosis to form gametes. Which two statements are true for cell division by meiosis? Tick (✓) two boxes.

Hormones are released from endocrine glands. Each hormone travels in the bloodstream to a target organ. Figure 3 shows the position of endocrine glands in a female.

Label the endocrine glands on Figure 3.

Complete Table 2.

Millions of geranium plants are sold each year in garden centres. Geraniums can be reproduced asexually or sexually. Figure 4 shows a potted geranium plant.

Garden centres usually grow new geranium plants by asexual reproduction.

Suggest two advantages for garden centres of growing geraniums by asexual reproduction compared with sexual reproduction.

Suggest two disadvantages for garden centres of growing geraniums by asexual reproduction compared with sexual reproduction.

This question is about inheritance. Humans have 23 pairs of chromosomes in each body cell. One pair of chromosomes determines sex.

Complete Figure 5.

Figure 5

In some families all children are the same sex. Give the reason why.

Cystic fibrosis (CF) is an inherited disorder.

A man and a woman do not have CF. The man and the woman have a child who has CF.

Draw a Punnett square diagram to find the probability that their next child will have CF. Use the symbols: T = dominant allele t = recessive allele Draw a ring around the genotype of any children with CF.

Embryo screening for CF can be done by two methods. Method 1

• The woman becomes pregnant by sexual intercourse.

• After 10 weeks of pregnancy a fine needle is inserted into the uterus.

• A sample of the fluid surrounding the embryo is taken.

• The DNA of the embryo is tested for CF.

The screening is done free by specialist hospitals for couples who are at risk of having a child with CF. There is a small risk of miscarriage.

Method 2

• The couple use In Vitro Fertilisation (IVF) to produce a small number of embryos.

• Each embryo is tested for CF.

• One or two embryos without CF are implanted in the woman’s uterus.

In 2017 the success rate for having a baby by IVF for women under 35 years was 30% IVF is a stressful, invasive procedure. In most UK areas the free public health service does not provide IVF for all women asking for it.

Suggest three reasons for choosing Method 1 instead of Method 2.

Suggest one advantage of Method 2.

Scientists believe that the first life on Earth was primitive anaerobic bacteria which first appeared billions of years ago.

Which domain of the three-domain classification system do these primitive anaerobic bacteria belong to?

Scientists have identified five periods of mass extinction since the fossil record began. Figure 6 shows the timeline of the five mass extinction events.

Ammonites were organisms that first appeared in the oceans 415 million years ago. Ammonites disappeared in the 5th mass extinction. Draw a horizontal line on Figure 6 to show the time period that ammonites existed on Earth. Label the line ‘ammonites’.

Another type of organism that existed in the oceans was called trilobites. Trilobites existed from 544 million years ago until 278 million years ago. How many more years did ammonites exist than trilobites?

There was an increase in the percentage of species which became extinct in the third mass extinction compared to the first mass extinction. Calculate the percentage increase.

Human activities affect the environment.

Describe the reasons why deforestation takes place and the effects deforestation has on the environment.

Forests have been called: ‘The lungs of the planet.’

Describe one way forests being called ‘The lungs of the planet’ can be considered to be a correct statement.

Trees do not have lungs. Describe one other way forests being called ‘The lungs of the planet’ is an incorrect statement.