Natural Selection and Genetic Diversity

Question 1

What is a model answer for natural selection?

Answer 1

• Random mutation, new alleles
• New allele is beneficial, increased reproductive success
• Alleles passed to offspring
• Over generations, alleles increase in frequency

Question 2

What are three types of Natural Selection?

Answer 2

1) Directional Selection
2) Disruptive Selection
3) Stabilising Selection

Question 3

Describe and explain Directional Selection?

Answer 3

Triggered by a change in environment, desirable allele increases in frequency, passed down generations

(Graph: shift in curve to the right)

Question 4

Describe and explain Disruptive Selection

Answer 4

Extreme traits favoured over intermediate traits, decrease in intermediate traits.

Graph: curve dips in the middle, peaks at two extremes

Question 5

Describe and explain stabilising selection

Answer 5

Population stabilises on a particular phenotype, decrease in diversity.

Question 6

How does deforestation and agriculture reduce biodiversity?

Answer 6

• Habitat reduction
• Food reduction
• Removing plant species
• Prey
• Soil/ Nutrient reduction

Question 7

What is antibiotic resistance?

Answer 7

Antibiotic- kills bacteria only

Bactericidal- kills
Bacteristatic- stops replication and photosynthesis

Caused by a random mutation etc.

Question 8

What is Simpson’s Index?

Answer 8

D = N(N-1)/ Sum of n(n-1)

Question 9

What are different terms for warm-blooded and cold-blooded?

Answer 9

Endotherm and Ectotherm

Question 10

List the sections in a phylogenetic tree

Answer 10

Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species

Question 11

Define species

Answer 11

A set of organisms that can reproduce to produce fertile offspring

Question 12

What do the areas in a phylogenetic tree where points branch off represent?

Answer 12

This shows speciation, the beginning of a new species and the extinction of the previous species.

Question 13

What is the bottle neck effect?

Answer 13

A reduction in allele frequency and variation, followed by a catastrophic event that resulted in a dramatic reduction in the population.

Question 14

What is the founder effect?

Answer 14

A reduction of allele frequency and variation due to the migration of a small subgroup from the rest of its species.

Question 15

What are the three types of variation?

Answer 15

1. Independent segregation
2. Crossing over
3. Mutation

Question 16

Describe independent segregation

Answer 16

When the homologous (same) chromosomes line up randomly in metaphase I
Key thing to remember here is that the chromosomes are lining up randomly. This creates the most variation out of all three.

Question 17

Describe ‘crossing over’

Answer 17

When homologous chromosomes exchange genetic material with each other, thrugh crossing over in a chiasma creating recombinant chromosomes.

Essentially you are shuffling alleles between chromosomes.

Question 18

Example question:

Explain how crossing over can contribute to genetic variation [3]

Answer 18

• Sections of chromatids exchanged (1)
• Sections have different alleles (1)
• New combinations of (linked) alleles (1)

Question 19

How can genetic diversity be compared within or between species?

Answer 19

• Frequency of measurable or observable characteristics
• Base sequence of DNA
• Base sequence of mRNA

Question 20

What is a gene and where is it found?

Answer 20

A gene is a section of DNA found in the locus of a DNA molecule.

Question 21

What is genetic diversity?

Answer 21

Number of different alleles of each gene