17.3. Evolution

Question 1

Evolution (general theory)

Answer 1

change in the characteristics of a population of a species over time

Question 2

Molecular evidence for evolutionary relationships

Answer 2

• large quantity of evidence to support theory of evolution
• comparison of base sequences in DNA, or amino acid sequences in proteins
• mitochondria contain a single DNA molecule that is passed on down the female line
• analysis of mitochondrial DNA can be used to determine how closely related two species are
• the more similar the sequence of bases in their DNA, the more closely related they are considered to be

Question 3

Species

Answer 3

a group of organisms with similar morphological and physiological characteristics, which are able to breed together and produce fertile offspring
- they are reproductively isolated

Question 4

Speciation

Answer 4

the production of one or more new species from an existing species
- must become reproductively isolated from different species

Question 5

Allopatric Speciation

Answer 5

when two populations of the same species become isolated from each other due to geographic changes
- different selection pressures from both sides of geographical barriers

Question 6

Sympatric Speciation

Answer 6

Populations can become reproductively isolated without being physically separated
- most common way is due to polyploidy

Question 7

Polyploidy

Answer 7

A polyploid organism is one with more than two
complete sets of chromosomes in its cells.
- happens when meiosis goes wrong when forming gametes
- tetraploidy: 2+2 = 4; tetraploids are often sterile as 4 sets of chromosomes try to pair up during Meioisis I and get muddled up –> can reproduce asexually; usually happens in plants
- triploidy: 1+2 = 3; triploidy are always sterile as 3 sets of chromosomes can not be shared evenly between daughter cells
- the original diploid plant and tetraploid plant can no longer interbreed –> new species formed

Question 8

Autoploidy

Answer 8

all sets of chromosomes from the same species

Question 9

Alloploidy

Answer 9

different sets of chromosomes from different but related species

Question 10

Reproductive Isolation

Answer 10

the inability of a species to breed successfully with related species due to geographical, behavioral, physiological, or genetic barriers or differences

Question 11

Prezygotic isolation

Answer 11

isolation before a zygote is formed

1) Spatial - selecting different places in the environment to live so never come into contact during breeding season
2) Temporal - different times for breeding
3) Behavioural - e.g. not responding to mating calls or other courtship behaviour, different food preferences
4) Mechanical - due to anatomical differences e.g. penis can’t enter the vagina
5) Gametic - gametes are unable to meet (chemically incompatible)

Question 12

Post-zygotic Isolation

Answer 12

isolation after a zygote forms

1) Hybrid sterility - offspring produced but is unable to reproduce itself
2) Hybrid inviability - offspring doesn’t survive to sexual maturity
3) Hybrid breakdown - first generation is reproductively successful but the second fails

Question 13

Extinction

Answer 13

permanent loss of all members of a species

Question 14

Cause of Extinction

Answer 14

1) Climate change - some species are not able to find habitats to which they are adapted for survival
2) Competition - a newly evolved species or migrated species may out-compete a resident species
3) Habitat Loss - rainforest cut down destroys habitats
4) Hunting by humans