3. 2. 4 - speciation

Question 1

What is speciation?

Answer 1

The formation of a new species

- happens as a result of the isolation of parts of a population

Question 2

Explain speciation in terms of reproductive isolation

Answer 2

Key factor: reproductive isolation

• two isolated populations experience different conditions
• natural selection will occur in different directions on the 2 populations
• therefore, genotype and phenotype of the populations will change over time
• can continue to the point where even if members of the split population reunite, they will not be able to successfully interbreed

Question 3

What is hybridisation?

Answer 3

The production of offspring as a result of sexual reproduction between individuals from two different species

Question 4

Explain speciation in terms of hybridisation

Answer 4

• sometimes two closely related species can breed and produce fertile hybrids
  (May be better adapted to the niche)
• in some cases they will not produce fertile offspring so a new species is formed
  (These may outcompete the original species)

Question 5

What is geographical isolation?

Answer 5

Occurs when a physical barrier such as a river or a mountain range separates individuals from two different species

Question 6

What is ecological isolation?

Answer 6

Occurs when two populations inhabit the same region, but develop preferences for different parts of the habitat

Question 7

What is seasonal isolation?

Answer 7

Occurs when the timing of flowering or sexual receptiveness in some parts of a population drifts away from the norm for the group
- can eventually lead to the two groups reproducing several months apart

Question 8

What is behavioural isolation?

Answer 8

Happens when changes occur in the courtship ritual, display or mating pattern so that some animals do not recognise others as being potential mates
- might be due to a mutation that changes the colour or pattern of markings

Question 9

What is mechanical isolation?

Answer 9

Happens when a mutation occurs that changes the genitalia of animals, making it physically impossible for them to mate successfully with only some members of the group
- or it changes the relationship between the stigma and stamens in flowers, making pollination between some individuals unsuccessful

Question 10

What is allopatric speciation?

Answer 10

Speciation that takes place when populations are physically or geographically separated and there can be no interbreeding or gene flow between the populations

• the main evolutionary process
• e.g endemic species found isolated on an island (geographical isolation)

Question 11

What does it mean if a species in endemic?

Answer 11

A species that evolves in geographical isolation and is found in only one place

Question 12

What is adaptive radiation?

Answer 12

Process by which one species evolves rapidly to form a number of different species that all fill different ecological niches
- usually occurs after allopatric speciation

Question 13

Give an example of adaptive radiation.

Answer 13

Australian marsupials and monotremes

Question 14

What are marsupials?

Answer 14

Mammals that give birth to very immature young and then protect them in pouches

Question 15

What are monotremes?

Answer 15

Primitive mammals that lay eggs and feed their offspring with milk from mammary glands

Question 16

What are placental mammals?

Answer 16

Mammals that provide for the developing fétus during gestation through a placenta

Question 17

What is sympatric speciation?

Answer 17

Speciation that takes place between populations of a species living in the same place

• they become reproductively isolated by mechanical, behavioural or seasonal mechanisms
• gene flow continues between the populations to some extent as speciation takes place