Variation — Paper 3 · IGCSE Sciences - Co-ordinated (Double) 0654

7 Polydactyly is an inherited condition which results in the growth of extra fingers or toes. Fig. 7.1 is a drawing of the foot of a baby with polydactyly. Fig. 7.1 • The allele for polydactyly is D. • The allele for non‑polydactyly is d. (a) (i) State the terms that can be used to describe the genotype DD. … and … [2] (ii) State the genotype of a person that does not have polydactyly. … [1] (b) A couple have a child. Complete the genetic diagram to show the possible genotypes of the offspring. mother’s alleles D d D … … father’s alleles d … … [1] (c) Identical twins have identical genotypes, but often have different phenotypes. Explain what causes their phenotypes to be different from each other, and give an example of a possible difference. … … … [2] (d) Humans have 46 chromosomes. Half are inherited from the mother and half from the father during fertilisation. (i) Use words from the list to complete the description of the term fertilisation. Each word may be used once, more than once or not at all. alleles cell DNA eggs genes nuclei sperm zygotes Fertilisation is described as the joining of the … of male gametes called … and female gametes called … . [2] (ii) State the chromosome pairs in the sex chromosomes of a human male and the sex chromosomes of a human female. male sex chromosomes … female sex chromosomes … [1]

9 marks

Mark scheme: 7(a)(i) homozygous; dominant; 2 7(a)(ii) dd; 1 7(b) D d D DD Dd d Dd dd 1 7(c) (phentoype) affected by environment; named example; 2 7(d)(i) nuclei; sperm and egg; 2 7(d)(ii) male chromosomes are XY, female chromosomes are XX; 1

This question in 0654/32 Oct/Nov 2018

10 (a) Describe the difference between phenotypic variation and genetic variation. … … … … [2] (b) A class investigated the number of students that are able to roll their tongues. Fig. 10.1 is a graph of the results. 30 25 20 number of students 15 10 5 0 can roll tongue cannot roll tongue ability to roll tongue Fig. 10.1 Use evidence from Fig. 10.1 to explain why this is an example of discontinuous variation. … … [1] (c) The list shows some examples of different types of variation. Place a tick (3) in the boxes to show all the examples of continuous variation. height foot length sex (gender) types of teeth mass [2] (d) Fig. 10.2 is a photograph of a giraffe, a mammal. Giraffes eat the leaves from branches on trees. Fig. 10.2 The ancestors of giraffes had shorter necks. Describe how giraffes developed long necks by natural selection. Use the words variation, competition and alleles in your answer. … … … … … … [4] [Total: 9]

9 marks

Mark scheme: 10(a) phenotypic variation are differences in the features we can observe ; genetic variation are differences in the genotype ; 2 10(b) there are a limited number of phenotypes (and no intermediates) ; 1 10(c) height ticked foot length ticked mass ticked 1 correct ; 3 correct ; 2 10(d) there is variation in the length of giraffes necks ; there is competition for resources / food ; giraffes with long necks survive ; passing on their alleles (for long necks) to offspring ; 4

This question in 0654/32 May/June 2019

10 (a) Describe the difference between phenotypic variation and genetic variation. … … … … [2] (b) A class investigated the number of students that are able to roll their tongues. Fig. 10.1 is a graph of the results. 30 25 20 number of students 15 10 5 0 can roll tongue cannot roll tongue ability to roll tongue Fig. 10.1 Use evidence from Fig. 10.1 to explain why this is an example of discontinuous variation. … … [1] (c) The list shows some examples of different types of variation. Place a tick (3) in the boxes to show all the examples of continuous variation. height foot length sex (gender) types of teeth mass [2] (d) Fig. 10.2 is a photograph of a giraffe, a mammal. Giraffes eat the leaves from branches on trees. Fig. 10.2 The ancestors of giraffes had shorter necks. Describe how giraffes developed long necks by natural selection. Use the words variation, competition and alleles in your answer. … … … … … … [4] [Total: 9]

9 marks

Mark scheme: 10(a) phenotypic variation are differences in the features we can observe ; genetic variation are differences in the genotype ; 2 10(b) there are a limited number of phenotypes (and no intermediates) ; 1 10(c) height ticked foot length ticked mass ticked 1 correct ; 3 correct ; 2 10(d) there is variation in the length of giraffes necks ; there is competition for resources / food ; giraffes with long necks survive ; passing on their alleles (for long necks) to offspring ; 4

This question in 0654/33 May/June 2019

7 (a) A teacher measured the height of the students in a class to the nearest cm. Table 7.1 shows the results. Table 7.1 height range / cm frequency in class 140–145 2 146–150 6 151–155 8 156–160 12 161–165 5 166–170 2 171–175 1 (i) State the most common height range in the class. … cm [1] (ii) State the type of variation shown by height. … [1] (iii) State the evidence from Table 7.1 that supports your answer in (a)(ii). … … [1] (b) Use words from the list to complete the sentences about natural selection. Each word may be used once, more than once or not at all. alleles cells competition die react survive variety Individuals in a population produce offspring. If there are not enough resources for all the individuals there is increased … . Individuals that are better adapted to the environment … . Individuals that are not adapted … . Individuals that … can reproduce passing their alleles to the next generation. [4] (c) Lack of resources can cause extinction of a species. Suggest two ways humans can cause extinction. 1 … 2 … [2] [Total: 9]

9 marks

Mark scheme: 7(a)(i) 156 – 160 (cm) ; 1 7(a)(ii) continuous ; 1 7(a)(iii) height is a range (between two extremes) / not distinct categories ; 1 Question Answer Marks 7(b) competition ; survive ; die ; survive ; 4 7(c) any two from: pollution hunting deforestation / any change of land use introducing new disease introducing new (competitive) species ;; 2

This question in 0654/31 May/June 2020

7 (a) Students in a school measure their hand-span. Fig. 7.1 is a photograph showing the measurement that each student takes. Fig. 7.1 Fig. 7.2 is a histogram showing the results. 14 12 10 8 number of students 6 4 2 0 17.0–17.9 18.0–18.9 19.0–19.9 20.0–20.9 21.0–21.9 22.0–22.9 23.0–23.9 24.0–24.9 25.0–25.9 26.0–26.9 27.0–27.9 hand-span category / cm Fig. 7.2 (i) Determine which hand-span category has the most students. … cm [1] (ii) Determine the number of students with a hand-span of 19.0–19.9 cm. … [1] (iii) Histograms are used to display data that show continuous variation. What other evidence from Fig. 7.2 shows that hand-span is an example of continuous variation? … … [1] (iv) State the name of one other example of continuous variation. … [1] (b) Fig. 7.3 is an incomplete Punnett square, genetic diagram. (i) Complete Fig. 7.3 to show how sex is inherited in humans. male sex chromosomes X Y female sex chromosomes Fig. 7.3 [2] (ii) Use Fig. 7.3 to determine the ratio of male offspring to female offspring. … male : … female [1] (c) Several structures are involved in inheritance. chromosomes DNA gene nucleus Place structures from the list in order of size from smallest to largest. smallest … … … largest … [2] [Total: 9]

9 marks

Mark scheme: 7(a)(i) 22.0–22.9 (cm) ; 1 7(a)(ii) 4 ; 1 7(a)(iii) there is a range (of hand spans between two extremes) ; 1 7(a)(iv) height / any valid point ; 1 7(b)(i) correct female sex chromosomes ; 2 correct offspring chromosomes ; 7(b)(ii) 1:1 ; 1 7(c) DNA 2 gene chromosome nucleus ;; 1 mark for DNA and nucleus in correct place 1 mark for gene smaller than chromosome (in any position)

This question in 0654/33 Oct/Nov 2022

7 (a) A school investigates variation in one class. Define the term variation. … … [1] (b) A class measures the height of each student. Table 7.1 shows the results. Table 7.1 height range / cm number of students 140.0 – 144.9 2 145.0 – 149.9 5 150.0 – 154.9 8 155.0 – 159.9 6 160.0 – 164.9 3 165.0 – 169.9 1 (i) Identify the most frequent height range shown in Table 7.1. … cm [1] (ii) Complete the sentence to describe how Table 7.1 provides evidence that height is an example of continuous variation. Choose words from the list. Each word can be used once, more than once or not at all. genotypes offspring phenotypes six eight two The results in Table 7.1 show there are a range of … between … extremes. [2] (iii) State one example of discontinuous variation. … [1] (c) Fig. 7.1 is a photograph of a female lion. The lion has very sharp, pointed teeth suitable for catching and eating other animals. Fig. 7.1 (i) State the term used to describe an animal that gets its energy from feeding on other animals. … [1] (ii) Circle the correct words shown in bold to complete the sentences to describe how lions may have developed sharp, pointed teeth. There was a range of different length teeth in the lion population. The lions with sharp, pointed teeth were better at catching and killing other animals for food. The lions without sharp, pointed teeth adapted / died / survived. The lions with sharp, pointed teeth passed on their alleles / cells / sex to their offspring. This occurred over many days / hours / generations until eventually, all the lions had sharp, pointed teeth. [3] (iii) State the name used to describe the process in (c)(ii). … [1] [Total: 10]

10 marks

Mark scheme: 7(a) differences between individuals (of the same species) / AW ; 1 7(b)(i) 150.0–154.9 (cm) ; 1 7(b)(ii) phenotypes ; two ; 2 7(b)(iii) tongue rolling / AVP ; 1 7(c)(i) carnivore ; 1 7(c)(ii) died ; alleles ; generations ; 3 7(c)(iii) natural selection ; 1

This question in 0654/32 May/June 2023

7 (a) A school investigates variation in one class. Define the term variation. … … [1] (b) A class measures the height of each student. Table 7.1 shows the results. Table 7.1 height range / cm number of students 140.0 – 144.9 2 145.0 – 149.9 5 150.0 – 154.9 8 155.0 – 159.9 6 160.0 – 164.9 3 165.0 – 169.9 1 (i) Identify the most frequent height range shown in Table 7.1. … cm [1] (ii) Complete the sentence to describe how Table 7.1 provides evidence that height is an example of continuous variation. Choose words from the list. Each word can be used once, more than once or not at all. genotypes offspring phenotypes six eight two The results in Table 7.1 show there are a range of … between … extremes. [2] (iii) State one example of discontinuous variation. … [1] (c) Fig. 7.1 is a photograph of a female lion. The lion has very sharp, pointed teeth suitable for catching and eating other animals. Fig. 7.1 (i) State the term used to describe an animal that gets its energy from feeding on other animals. … [1] (ii) Circle the correct words shown in bold to complete the sentences to describe how lions may have developed sharp, pointed teeth. There was a range of different length teeth in the lion population. The lions with sharp, pointed teeth were better at catching and killing other animals for food. The lions without sharp, pointed teeth adapted / died / survived. The lions with sharp, pointed teeth passed on their alleles / cells / sex to their offspring. This occurred over many days / hours / generations until eventually, all the lions had sharp, pointed teeth. [3] (iii) State the name used to describe the process in (c)(ii). … [1] [Total: 10]

10 marks

Mark scheme: 7(a) differences between individuals (of the same species) / AW ; 1 7(b)(i) 150.0–154.9 (cm) ; 1 7(b)(ii) phenotypes ; two ; 2 7(b)(iii) tongue rolling / AVP ; 1 7(c)(i) carnivore ; 1 7(c)(ii) died ; alleles ; generations ; 3 7(c)(iii) natural selection ; 1

This question in 0654/33 May/June 2023

7 Pea colour and shape are inherited characteristics that are controlled by a single gene. (a) Define the term gene. … … … [2] (b) A farmer recorded the colour and shape of a sample of 14 peas. Fig. 7.1 shows a graph of the results. 9 8 7 6 5 frequency 4 3 2 1 0 wrinkled smooth wrinkled smooth green green yellow yellow pea colour and shape Fig. 7.1 (i) Identify the most frequent pea colour and shape in Fig. 7.1. … [1] (ii) State the frequency of wrinkled green peas in Fig. 7.1. … [1] (iii) Describe evidence from Fig. 7.1 that shows that pea colour and shape are examples of discontinuous variation. … … [1] (iv) State one example of continuous variation in humans. … [1] (c) The farmer found that smooth green peas were the most popular with food buyers. Describe how the farmer uses selective breeding to increase the number of smooth green peas. … … … … … [3] (d) Name the type of selection that results in species being adapted to the environment they live in. … [1] [Total: 10]

10 marks

Mark scheme: 7(a) length of DNA ; 2 that codes for a protein ; 7(b)(i) wrinkled yellow ; 1 7(b)(ii) 3 ; 1 7(b)(iii) there are, a limited number of phenotypes / no intermediates / AW ; 1 7(b)(iv) height / AVP ; 1 7(c) any two from: 3 farmer selects smooth green peas plants ; uses these plants to breed ; observes / selects, offspring (for smooth green peas) ; repeats the process (for many generations) ; 7(d) natural (selection) ; 1

This question in 0654/32 Feb/March 2024

4 (a) Fig. 4.1 is a diagram of the female reproductive system in humans. A B D C Fig. 4.1 The boxes on the left show the letters of some of the parts in Fig. 4.1. The boxes on the right show some functions. Draw one line from each letter to its function. release of female gametes A site of fertilisation B where fetus develops C ring of muscle at opening of uterus D produces semen receives penis during sexual intercourse [4] (b) A survey records the length of the menstrual cycle in a sample of females. Fig. 4.2 shows a bar chart of the results. 14 12 10 8 number of females 6 4 2 0 23 24 25 26 27 28 29 30 31 32 33 length of menstrual cycle / days Fig. 4.2 (i) State the most frequent length of the menstrual cycle shown in Fig. 4.2. … [1] (ii) State the number of females that have a 26‑day menstrual cycle shown in Fig. 4.2. … [1] (c) State the name of the female gamete in humans. … [1] (d) The list shows several processes that occur before the development and birth of a baby. Put the stages in the correct order. Two have been done for you. fertilisation formation of embryo formation of zygote implantation release of female gamete release of female gamete … formation of zygote … … [2] (e) State where fertilisation occurs in plants. … [1] [Total: 10]

10 marks

Mark scheme: 4(a) release of female gametes A site of fertilisation B where fetus develops C ring of muscle at opening of uterus D produces semen receives penis during sexual intercourse ;;;; 4(b)(i) 27 (days) ; 1 4(b)(ii) 9 ; 1 Question Answer Marks 4(c) egg / ovum ; 1 4(d) release of female gamete fertilisation formation of zygote formation of embryo implantation 1 or 2 correct ; 3 correct ; 2 4(e) ovule ; 1

This question in 0654/32 May/June 2024

10 (a) Scientists record the mass of each baby at birth in one country. The results are shown in Fig. 10.1 frequency 0 500 1000 1500 2000 2500 3000 3500 4000 mass at birth / g Fig. 10.1 (i) Complete the sentences about the mass of babies at birth as shown in Fig. 10.1. The lowest mass at birth was … g. The most frequent mass at birth was … g. Fig. 10.1 shows that mass of babies at birth is an example of continuous variation. This is because there is a … of phenotypes between two extremes. A phenotype is defined as the … features of an organism. [4] (ii) State one other example of continuous variation in humans. … … [1] (b) The statements A–E describe stages of natural selection. They are not in the correct order. A There is competition for resources. B Those with adaptations best suited to their environment survive and reproduce. C This process is repeated over several generations. D There is variation in a population. E Alleles are passed on to the next generation. Complete the answer spaces to show the correct order. One has been done for you. … A … … … [2] (c) Alleles are made of DNA. (i) Define the term allele. … … [1] (ii) State where alleles are found in a cell. … [1] [Total: 9]

9 marks

Mark scheme: 10(a)(i) 800 (g) ; 4 2400 (g) ; range / AW ; observable / AW ; 10(a)(ii) height / AVP ; 1 10(b) D in first box ; 2 B, E, C ; 10(c)(i) a version of a gene ; 1 10(c)(ii) nucleus ; 1

This question in 0654/32 Oct/Nov 2024

10 (a) Scientists record the mass of each baby at birth in one country. The results are shown in Fig. 10.1 frequency 0 500 1000 1500 2000 2500 3000 3500 4000 mass at birth / g Fig. 10.1 (i) Complete the sentences about the mass of babies at birth as shown in Fig. 10.1. The lowest mass at birth was … g. The most frequent mass at birth was … g. Fig. 10.1 shows that mass of babies at birth is an example of continuous variation. This is because there is a … of phenotypes between two extremes. A phenotype is defined as the … features of an organism. [4] (ii) State one other example of continuous variation in humans. … … [1] (b) The statements A–E describe stages of natural selection. They are not in the correct order. A There is competition for resources. B Those with adaptations best suited to their environment survive and reproduce. C This process is repeated over several generations. D There is variation in a population. E Alleles are passed on to the next generation. Complete the answer spaces to show the correct order. One has been done for you. … A … … … [2] (c) Alleles are made of DNA. (i) Define the term allele. … … [1] (ii) State where alleles are found in a cell. … [1] [Total: 9]

9 marks

Mark scheme: 10(a)(i) 800 (g) ; 4 2400 (g) ; range / AW ; observable / AW ; 10(a)(ii) height / AVP ; 1 10(b) D in first box ; 2 B, E, C ; 10(c)(i) a version of a gene ; 1 10(c)(ii) nucleus ; 1

This question in 0654/33 Oct/Nov 2024