Genetic Info, Variation and Relationships Between Organisms

Question 1

How does genetic variation occur in a species?

Answer 1

1. Crossing over - exchange of sections of genetic material, alleles can be exchanged
2. Independent assortment/segregation - how the chromosome pairs are arranged during metaphase 1
3. Random fertilisation - produces new maternal and paternal chromosome combinations

Question 2

What are the differences between mitosis and meiosis?

Answer 2

One division in mitosis 2 in meiosis
Daughter cells genetically identical is mitosis, genetically different in meiosis
Crossing over only in meiosis
Separation of homologous chromosome pairs in meiosis

Question 3

Define genetic diversity

Answer 3

The number of different alleles of genes in a population

Question 4

Define evolution

Answer 4

The change in allele frequency over many generations in a population.

Question 5

Describe the process of natural selection

Answer 5

1. New alleles for a gene are created by random mutations
2. If the new alleles increases the individual to survive in that environment, then they are more likely to survive and reproduce.
3. This reproduction passes on the advantageous allele to the next generation
4. As a result over many generations the new allele increases in frequency in the population

Question 6

What is directional selection?

Answer 6

One of the extremes has the selective advantage
Occurs when there is a change in the environment
Modal trait changes
E.g. antibiotic resistance in bacteria

Question 7

What is stabilising selection?

Answer 7

The modal traits (middle of graph) have the selective advantage
Occurs when there is no change in environment
Modal trait remains the same
E.g. human birth weights

Question 8

Define species

Answer 8

A group of organisms that can interbreed to produce fertile offspring

Question 9

What is a hierarchy?

Answer 9

Smaller groups arranged within larger groups
No overlap between groups

Question 10

How are organisms classified?

Answer 10

DNA sequence
mRNA sequence
Amino acids sequence
Immunological

Question 11

What is phylogenetic classification

Answer 11

Arranges species into groups according to their evolutionary origins and relationships
Shows how closely related species are