3 4 Booklet (pt2) V2 - a level aqa practice PDF

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Name: Teachers:Y12 AQA Biology3 Genetic information, variation and relationshipsbetween organisms (part 2)####### (3.4) Genetic diversity can arise as a result of mutation or during meiosis,####### (3.4) Genetic diversity and adaptation, (3.4) Species and taxonomy,(3.4) Biodiversity within a communi...

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Y12 AQA Biology 3.4 Genetic information, variation and relationships between organisms (part 2) (3.4.3) Genetic diversity can arise as a result of mutation or during meiosis, (3.4.4) Genetic diversity and adaptation, (3.4.5) Species and taxonomy, (3.4.6) Biodiversity within a community, (3.4.7) Investigating diversity.

Lessons outline: 1. Meiosis a. Process b. Crossing Over c. Non-disjunction 2. Genetic Diversity 3. Required Practical 6 4. Selection 5. Species and Taxonomy a. Classification b. DNA and protein comparisons c. Courtship 6. Biodiversity 7. Quantitative investigations of variation

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3.4.3 Genetic diversity can arise as a result of mutation or during meiosis

(a)

Explain what mutations are

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(b)

Explain how mutations can arise spontaneously by chromosome non-disjunction during meiosis

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(c)

Describe base deletions and substitutions

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(d)

Describe the degenerate nature of the genetic code

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(e)

Describe factors that increase the risk of mutation

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(f)

Describe how the process of meiosis produces four haploid daughter cells.

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(g)

Describe how meiosis produces genetically different daughter cells due to independent segregation of chromosomes

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(h)

Describe how crossing over between homologous chromosomes results in further genetic variation

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(i)

Complete diagrams showing chromosome content

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(j)

Compare mitosis with meiosis

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(k)

Recognise where meiosis occurs when given information about an unfamiliar life cycle

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(l)

Explain how random fertilisation of haploid gametes further increases genetic variation within a species

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Content    

Gene mutations Meiosis Independent segregation Crossing over

Learning Outcomes Candidates should be able to:

Page 2

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Meiosis

1. Label on the diagram below: homologous chromosomes, sister chromatids, chromosomes, centromere, DNA replication.

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DNA replication

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2. Complete the cut and stick activity

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3. Label on the completed diagram: A. Formation of homologous pairs B. Independent Assortment of chromosomes C. Crossing over between chromosomes D. Separation of sister chromatids E. Separation of homologous chromosomes 4. Shade in any cells undergoing meiosis I, and any cells undergoing meiosis II in different colours

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In humans, non-disjunction involving chromosome 21 can lead to a child being born with Down’s syndrome; a condition caused by having 3 copies (a trisomy) of chromosome 21. Figure 2 shows two ways in which non-disjunction can take place during meiosis.e 2 Figure 2 Meiosis I

Non-disjunction Meiosis II

Non-disjunction Egg cells

1 4 (a)

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Use Figure 2 to explain what is meant by non-disjunction. ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ (2 marks)

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More than one of the egg cells, numbered 1 to 8, could produce zygotes that would develop into a child with Down’s syndrome. Give the numbers of these cells and explain the reason for your choices. Explain your answer. Cell(s) ................................................................................................................................ Explanation ........................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ ............................................................................................................................................ (3 marks) (Extra space) .....................................................................................................................

5 ............................................................................................................................................ ............................................................................................................................................

Turn over for the next question

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1.

(a)

Apart from increasing genetic variation, explain why meiosis is important in organisms which reproduce sexually. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2)

(b)

Figure 1 shows the chromosomes in a diploid cell. Figure 1 Diploid cell

Gametes

Complete Figure 1 to show the four different combinations of these chromosomes in the gametes produced by meiosis. (2)

(c)

Figure 2 shows the main stages in the production of pollen grains in a flowering plant. Figure 2 Mitosis

Meiosis

Pollen mother cell 2 nuclei Immature pollen grains

Mature pollen grains

Page 9

The diploid number of chromosomes in this plant is sixteen. How many chromosomes would there be in (i)

the nucleus of an immature pollen grain; .................................................................

(ii)

one of the nuclei of a mature pollen grain? ............................................................. (2)

(Total 6 marks) 2.

The diagram shows stages of meiosis in a human testis. Each circle represents a cell. 46 Meiosis I

Meiosis II

(a)

In each empty circle, write the number of chromosomes that would be found in the cell. (1)

(b)

Describe two ways in which meiosis contributes to genetic variation. 1.................................................................................................................................. .................................................................................................................................... 2.................................................................................................................................. .................................................................................................................................... (2)

(c)

Explain the importance of genetic variation in the process of evolution. .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... .................................................................................................................................... (2) (Total 5 marks)

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3.

(a)

During meiosis, one chromosome from each homologous pair goes to each of the cells produced. Explain why this is important. ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (2)

(b)

The diagram shows the life cycle of a fern plant. Drawings of the chromosomes during cell division are shown for the stages that give the spore-producing plant and the gamete-producing plant. Stage A

Sporeproducing plant Spores

Zygote Stage B

Male gamete

Female gamete

Gameteproducing plant

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(i)

What is the diploid number of chromosomes in this fern plant? ................................................... (1)

(ii)

Explain the difference in the number of chromosomes at stages A and B. ......................................................................................................................…. ........................................................................................................................... (1)

(iii)

Are the male and female gametes produced by mitosis or meiosis? Explain your answer. ......................................................................................................................…. ......................................................................................................................…. ......................................................................................................................…. (2) (Total 6 marks)

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3.4.4 Genetic diversity and adaptation

(a)

Describe genetic diversity as the number of different alleles of genes in a population

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(b)

Explain why genetic diversity is a factor that enables natural selection to occur

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(c)

Describe the principles of natural selection in the evolution of populations

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(d)

Describe directional selection, exemplified by antibiotic resistance in bacteria

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(e)

Describe stabilising selection, exemplified by human birth weights

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(f)

Explain how natural selection results in species that are better adapted to their environment

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(g)

Use unfamiliar information to explain how selection produces changes within a population of a species

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(h)

Interpret data relating to the effect of selection in producing change within populations

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(i)

Show understanding that adaptation and selection are major factors in evolution and contribute to the diversity of living organisms

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Content    

Genetic diversity Alleles Natural selection and evolution Directional stabilisation

Learning Outcomes Candidates should be able to:

Page 13

Antibiotic Resistance and Natural Selection 1. On the diagrams below, colour in the following:

* Peptidoglycan * Cross-link

* *

Penicillin Enzyme

2. Circle the change in tertiary structure on the enzyme Normal

With antibiotics

Antibiotic resistance

3. Use each of the following keywords in a sentence to explain how natural selection can lead to an antibiotic resistant population of bacteria. Mutation

Selection pressure

Survive

Reproduce

Inherit

Frequency of allele

Application – D Grade Peacocks (Pavo cristatus) have a large iridescent plumage which indicates the fitness of a male peacock to the female peahens. Any alleles (produced by mutations) that negatively affect the quality of a peacock’s plumage remain low in the population. Suggest why?

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Application – C Grade The shovel snouted (Zeros anchietae) lizard lives in the hot sand dunes of Namibia and has a duck-like snout. 1. Suggest the ability this snout gives.

2. Why might that ability be of particular use?

Application – A Grade Mexican blind tetras (Astyanax mexicanus) occupy pitch-black caves in South America and have evolved from tetras that have the ability to see. Their eyes are completely missing and skin tissue covers the regions where the eyes would have been situated. 1. Suggest why it is an advantage for the tetra to not have eyes?

Application – A/A* Grade

The Cane toad (Rhinella marina) was originally introduced to as a pest control the grey-backed cane beetle which devastated sugar cane crops. Adult cane toads are large (over 2 kg) and have a gland behind their ears which produces a toxic milky secretion. Although not fatal for humans, ingestion of the secretion can prove fatal for snakes that predate on cane toads. 1. What effect did the cane toad introduction have on snake population sizes? 2. What structural feature(s) may the presence of the cane toads selected for in the snakes? Why?

3. In an attempt to recover snake populations, small cane toads are given to them as a food source. The smaller dose of secretion is not fatal but ensures the snakes avoid predating cane toads in future. Explain why this behaviour would not be passed on to future generations Page 15

Natural Selection Exam Style Questions 1

The diagram shows the structure of a bacterium and the sites of action of two antibiotics.

(a)

(i)

Use information in the diagram to explain why vancomycin does not affect human cells. ............................................................................................................... ............................................................................................................... (1)

(ii)

Use information in the diagram to explain how tetracycline prevents bacterial growth. ............................................................................................................... ............................................................................................................... (1)

(b)

Frequent treatment with vancomycin can result in resistant strains of bacteria. Explain how. ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ ........................................................................................................................ (2)

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2

Some antibiotics work by binding with specific receptors in the plasma membranes of bacteria. The structure of these receptors is determined genetically. Bacteria can become resistant to an antibiotic because a gene mutation results in an altered receptor. Explain how resistance to an antibiotic could become widespread in a bacterial population following a gene mutation conferring resistance in just one bacterium. ...................................................................................................................... ...................................................................................................................... ...................................................................................................................... ...................................................................................................................... ...................................................................................................................... ...................................................................................................................... ...................................................................................................................... ...................................................................................................................... (...