Year 9 Genetics and Evolution Worksheet - Intermediate

Year 9 Genetics and Evolution worksheet for Year 9 (Key Stage 3 / Year 7-9 (Ages 11-14)). Intermediate level science practice, aligned to the UK National Curriculum. Print-ready with answer key included.

Science•Key Stage 3 / Year 7-9 (Ages 11-14)•Genetics and Evolutionintermediate

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Genes, Inheritance and Evolution

Year 9 Science | Ages 13–14 | Intermediate

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Instructions: Complete the activities in order, using scientific vocabulary and showing your reasoning where asked. Each question includes its mark allocation; use the evidence and data provided rather than relying on guesswork.

DNA, Genes and Chromosomes

Use the word bank to complete each sentence. Choose the most precise term and use each word where it fits. Then explain the relationship between DNA, genes and chromosomes in your own words.

Word bank: allele, chromosome, DNA, gene, nucleus

1. The molecule that carries genetic information is called ___.

2. A short section of DNA that influences a characteristic is a ___.

3. A long, organised structure made from DNA and proteins is a ___.

4. Different versions of the same gene are called ___.

5. In a human cell, most chromosomes are found in the ___.

6. Explain how DNA, genes and chromosomes are related. [3 marks]

Inheritance and Variation

In this model, allele B is dominant and allele b is recessive. Use the allele combinations shown to identify each offspring's genotype and phenotype. For the final question, distinguish inherited variation from variation caused by the environment.

1. A parent cross is Bb × Bb. What is the probability that an offspring will have genotype bb? Give your answer as a fraction. [2 marks]

2. In the same cross, what is the probability that an offspring will show the dominant phenotype? Give your answer as a fraction. [2 marks]

3. A plant has genotype Bb. Which allele will its gametes carry: B, b, or both types? [1 mark]

4. Classify each example as mainly inherited or mainly environmental: blood group; a scar from an accident. [2 marks]

Natural Selection: Reading the Evidence

Study the table. These fictional beetles live on dark soil; birds more easily spot pale beetles. Use the figures to describe the change across generations and explain how natural selection could cause it.

Generation	Dark beetles	Percentage dark
1	20	40%
5	35	70%
10	45	90%

1. By how many percentage points did the proportion of dark beetles increase from generation 1 to generation 10? [1 mark]

2. Which colour beetle was more likely to survive on the dark soil, and why? [2 marks]

3. Explain how the frequency of the dark-colour allele could increase over generations. Include survival and reproduction in your answer. [3 marks]

4. What is the name of the process that explains this change in a population? [1 mark]

Darwin and Mendel

Use the word bank to identify the scientist in each description. Then compare the kind of evidence or ideas associated with their work. Remember that scientific explanations develop through evidence.

Word bank: Charles Darwin, Gregor Mendel

1. Who proposed that species change over time through natural selection? [1 mark]

2. Who studied inheritance using pea plants and described patterns in how characteristics pass between generations? [1 mark]

3. Which scientist’s work is most directly associated with the idea that organisms with advantageous inherited variations may leave more offspring? [1 mark]

4. State one way Darwin’s work and Mendel’s work contributed different but complementary ideas to understanding evolution and inheritance. [2 marks]

Extinction and Gene Banks

Read the information in the table and answer using the figures and your scientific understanding. In your final answer, explain both a benefit and a limitation of gene banks.

Species	Wild population estimate	Seeds stored in gene bank
Mountain flax	120	000
8	000	Silver marsh orchid
35	000	2
500	Blue heath	0
6	000

1. Which listed species has no recorded wild population but does have seeds stored? [1 mark]

2. Which species has the largest estimated wild population? [1 mark]

3. Explain one way a gene bank could help protect a species from extinction. [2 marks]

4. Give one limitation of relying on a gene bank instead of protecting a species in its natural habitat. [2 marks]

Answer Key

Activity 1: DNA ; gene ; chromosome ; allele ; nucleus ; DNA is organised into chromosomes, and genes are sections of DNA found on chromosomes.

Activity 2: 1/4 ; 3/4 ; both types (some gametes carry B and some carry b) ; blood group: inherited; scar: environmental

Activity 3: 50 percentage points ; dark beetles, because they are less visible to birds on dark soil ; dark beetles are more likely to survive, reproduce and pass on the dark-colour allele, so that allele becomes more common over generations ; natural selection

Activity 4: Charles Darwin ; Gregor Mendel ; Charles Darwin ; Darwin explained evolution by natural selection, while Mendel's breeding experiments revealed patterns of inheritance; together these ideas help explain how inherited variation can drive evolution.

Activity 5: Blue heath ; Mountain flax ; stored seeds can preserve genetic material and may be used to grow plants and support future reintroduction ; a gene bank does not preserve the whole habitat or ecological interactions, and stored seeds may not remain viable indefinitely.