Variation and Classification - Variation

Question 1

define interspecific variation

Answer 1

variation between species

Question 2

define intraspecific variation

Answer 2

variation within species

Question 3

what are the two causes of variation

Answer 3

• genetic variation
• environmental variation

Question 4

how do genes affect variation

Answer 4

the mixture of alleles of genes inherited affect the phenotype of an organism

Question 5

what causes genetic variation

Answer 5

• random mutations
• recombination of alleles
• random fertilisation of genetically different haploid gametes

Question 6

what are random mutations that can occur

Answer 6

• chromosome mutations
• DNA mutations

Question 7

what recombination of alleles can occur

Answer 7

• crossing over during prophase 1 meiosis
• independent assortment of chromosomes during metaphase 1 meiosis
• independent assortment of chromatids during metaphase 2 meiosis

Question 8

how does the environment cause variation

Answer 8

phenotypic variation can be caused by differences in the environment

Question 9

what can cause environmental variation

Answer 9

diet, lifestyle, climate

Question 10

give examples of environmental variation

Answer 10

• etiolation
• chlorosis

Question 11

what is etiolation

Answer 11

changes in the growth of a plant due to being grown in the dark (tall, spindly, yellow leaves)

Question 12

what is chlorosis

Answer 12

plants may develop chlorosis due to a lack of chlorophyll

Question 13

why may a plant lack chlorophyll

Answer 13

• lack of magnesium or iron ions in soil
• lack of light
• viral infection

Question 14

how can diet cause environmental variation

Answer 14

may interact with genes to affect many characteristics e.g height, body mass

Question 15

what are the types of variation

Answer 15

• discontinuous
• continuous

Question 16

what is discontinuous variation

Answer 16

phenotypes fall into distinct and discrete categories with no (or very few) intermediate values

Question 17

how can discontinuous variation be displayed

Answer 17

bar chart

Question 18

how is discontinuous variation controlled

Answer 18

• by one gene (monogenic)
• may be controlled by two genes which are epistatic

Question 19

what does discontinuous variation include

Answer 19

codominance and multiple alleles

Question 20

with discontinuous variation, is the environment likely to have an effect on the phenotype

Answer 20

likely to have little or no effect of the phenotype

Question 21

what is continuous variation

Answer 21

a continuous range of values between two extremes, usually forming a normal distribution curve

Question 22

how is continuous variation usually controlled

Answer 22

by several genes (polygenic). they tend to provide an additive effect on the phenotype

Question 23

what do the smaller effects of each allele cause

Answer 23

quantitative variation in phenotype

Question 24

are polygenic characteristics influenced by the environment or genes, or both

Answer 24

both, but influenced by environment more than monogenic characteristics

Question 25

give examples of discontinuous variation

Answer 25

- blood type - tongue rolling

Question 26

give examples of continuous variation

Answer 26

- skin colour - birth weight