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Biology questions, chapter 12
Nama / NameKelas / ClassTarikh / Date

Variation

41 marks. Use Practice to check each answer as you go, or Exam to answer everything against the clock first.

Section A: objective questions

12 marks
Choose the best answer for each question.
1

Question 1

What is variation?
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A
Variation is the difference in characteristics found within the same population or species (p. 256).
For the teacher: Remembering, low difficulty, standard 12.1.1
Textbook p. 256
2

Question 2

Dark Biston betularia moths survived better than light ones in polluted areas. Which statement explains this?
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B
Variation in colour allowed natural selection: the darker moths were not easily seen by predators and survived (p. 256).
For the teacher: Understanding, low difficulty, standard 12.1.2
Textbook p. 256
3

Question 3

Which characteristic shows continuous variation?
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C
Body mass can be measured and graded, so it is continuous. The other three fall in distinct groups (discontinuous).
For the teacher: Applying, low difficulty, standard 12.1.3
Textbook p. 258
4

Question 4

Which statement is true of discontinuous variation?
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A
Discontinuous variation is qualitative, controlled by a single gene and shows distinct groups with no intermediates (p. 259-260).
For the teacher: Understanding, low difficulty, standard 12.1.4
Textbook p. 260
5

Question 5

In which stage of meiosis does crossing over occur?
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A
Crossing over between non-sister chromatids of homologous chromosomes happens in prophase I (p. 261).
For the teacher: Remembering, low difficulty, standard 12.1.5
Textbook p. 261
6

Question 6

Which process causes gametes to receive different mixtures of maternal and paternal chromosomes?
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B
Homologous pairs arrange randomly in metaphase I (independent assortment), so each gamete has a different mixture (p. 262).
For the teacher: Understanding, low difficulty, standard 12.1.5
Textbook p. 262
7

Question 7

Hydrangea plants of the same genotype grow in different soils. Those in acidic soil have blue flowers and those in alkaline soil have pink flowers. What kind of variation is this?
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C
Soil pH changes the phenotype only, not the genotype, so the variation is environmental and not inherited (p. 264).
For the teacher: Applying, medium difficulty, standard 12.1.6
Textbook p. 264
8

Question 8

Which pair shows a dominant trait followed by a recessive trait in humans?
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D
Right-handed is dominant and left-handed is recessive. In the other pairs the order is recessive then dominant (Table 12.1, p. 266).
For the teacher: Remembering, low difficulty, standard 12.2.1
Textbook p. 266
9

Question 9

Which is a biological mutagen?
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D
Viruses and bacteria are biological agents. X-rays and ultraviolet are physical agents; benzene is chemical (p. 269).
For the teacher: Remembering, low difficulty, standard 12.3.1
Textbook p. 269
10

Question 10

A base is inserted in the middle of a gene. What is the effect on the polypeptide?
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D
Insertion shifts the reading of every codon after the point, so many new amino acids are made (Figure 12.15, p. 270).
For the teacher: Understanding, medium difficulty, standard 12.3.2
Textbook p. 270
11

Question 11

A chromosome has the gene order A B C D E F. After mutation it is A B C F E D. Which type of chromosomal mutation is this?
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B
The segment D E F is reversed end to end, which is inversion (p. 271).
For the teacher: Applying, medium difficulty, standard 12.3.3
Textbook p. 271
12

Question 12

A man has 44 autosomes plus the sex chromosomes XXY. What is his condition and why does it arise?
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D
44 + XXY is Klinefelter syndrome (47 chromosomes), caused by nondisjunction giving a gamete with an extra sex chromosome (p. 272-273).
For the teacher: Analysing, medium difficulty, standard 12.3.3
Textbook p. 273

Section B: structured questions

29 marks
Answer all questions.
13

Question 13

The tables show two characteristics of 35 pupils in a class.
Body mass (kg)40-4445-4950-5455-5960-64
Number of pupils57986
EarlobesAttachedFree
Number of pupils629
[2 marks] (a)State the type of variation shown by body mass and by earlobes.
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[2 marks] (b)State two differences between the two types of variation.
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Any 2 points
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[1 mark] (c)What percentage of the pupils have free earlobes? Give your answer to the nearest whole number.
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For the teacher: Applying, low difficulty, standard 12.1.3
Textbook p. 276
14

Question 14

A normal chromosome has the gene segments A B C D E F. The table shows the gene segments of four mutant chromosomes, K, L, M and N.
MutantGene segments
KA A B C D E F
LA B C D E
MA B C F E D
NA B C X Y Z
[4 marks] (a)Name the type of mutation in K, L, M and N.
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[1 mark] (b)State one difference between gene mutation and chromosomal mutation.
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[1 mark] (c)Name one agent that can cause mutation.
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For the teacher: Applying, low difficulty, standard 12.3.3
Textbook p. 277
15

Question 15

Plot X has trees grown from one tissue culture. Plot Y has trees grown from seeds. A disease infects the farm. All the trees in plot X die but only some in plot Y die.
[2 marks] (a)Explain why all the trees in plot X died.
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[2 marks] (b)Explain why some trees in plot Y survived.
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For the teacher: Evaluating, medium difficulty, standard 12.1.1
Textbook p. 276
16

Question 16

Identical twins J and K were separated in childhood. After 18 years K is obese but J has an ideal body mass. J eats a low-fat diet and is active; K eats a high-fat diet and is inactive.
[1 mark] (a)Why do the twins have the same genotype?
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[1 mark] (b)Name the factor that caused the difference in their body mass.
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[2 marks] (c)Will K's obese children inherit the body mass of K? Explain.
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For the teacher: Understanding, low difficulty, standard 12.1.6
Textbook p. 265
17

Question 17

A diploid cell of an organism has 4 chromosomes (2n = 4). During meiosis I the homologous pair of one chromosome type fails to separate (nondisjunction).
[2 marks] (a)Give the number of chromosomes in each of the four gametes formed.
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[1 mark] (b)One of the abnormal gametes with 3 chromosomes is fertilised by a normal gamete. How many chromosomes does the zygote have?
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[2 marks] (c)A human zygote formed this way has three chromosome 21. State the total number of chromosomes and name the syndrome.
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For the teacher: Applying, medium difficulty, standard 12.3.3
Textbook p. 272
18

Question 18

In sickle cell anaemia a base substitution in the haemoglobin gene replaces glutamic acid with valine, so red blood cells are crescent-shaped. The disease is common in parts of Africa where malaria is common.
[1 mark] (a)State the type of mutation that causes sickle cell anaemia.
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[2 marks] (b)Explain why the disease can be inherited.
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[2 marks] (c)Suggest why the sickle cell trait remains common where malaria occurs.
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For the teacher: Creating, high difficulty, standard 12.3.2
Textbook p. 277