inheritance and variation

Question 1

2 main causes of variation

Answer 1

• genetic material
• organism’s living environment

Question 2

genetic causes of phenotypic variation

Answer 2

• alleles (genes have different alleles. A gene for a particular characteristic has alleles producing different effects)
• mutations (changes to DNA sequence/genes leads to change of proteins which changes physical/metabolic characteristics
• meiosis (genetic material of mother and father mixes up to produce varied gametes)
• sexual reproduction (offspring inherits genes from parents so each individual differs)
• chance (when 2 gametes combine)

Question 3

discontinuous variation

Answer 3

when there are 2 or more discrete values for a characteristic
e.g. blood group, plant colour/seed shape, antibiotic resistance

Question 4

continuous variation

Answer 4

where a characteristic can vary within a range
e.g. height, mass, milk yield, leaves SA, width and length of microorganisms

Question 5

environmental causes of variation

Answer 5

• climate
• food
• lifestyle
  e.g. accents, piercings

Question 6

both genetic and environmental causes of variation examples

Answer 6

e.g.
- height (diet)
- flagellum (genes determine if it grows flagellum, but some will only grow them in certain environments)

Question 7

how to represent discontinuous variation

Answer 7

• bar chart
• pie chart

Question 8

how to represent continuous variation

Answer 8

• frequency table
• plotted onto histogram

Question 9

what is phenotypic variation

Answer 9

variation in an organism’s phenotype

Question 10

genotype

Answer 10

the combination of alleles an organism inherits for a characteristic (genetic makeup)

Question 11

phenotype

Answer 11

the observable characteristics of an organism

Question 12

number of genes that influence continuous variation

Answer 12

many genes- characteristics are polygenic

Question 13

number of genes that influence discontinuous variation

Answer 13

only one gene (or a small number)- characteristics are monogenic