Speciation

Question 1

Definition of speciation?

Answer 1

• forms bridge between evolution of populations and taxonomic diversity
• diversity of organisms is consequence of cladogenesis (where they form and diverge, tree splits off)

Question 2

What is linnaean classification?

Answer 2

• all species have a name conforming to binomial/trinomial system
• groups of similar sorts are a genus, within the genus there’s species, within that there could be subspecies

Question 3

What’s the biological species concept?

Answer 3

• species is a group of individuals fully fertile inter se
• barred from interbreeding with other similar groups by its physiological properties (whether they can breed together and provide fertile offspring)

Question 4

What’s the phylogenetic species concept?

Answer 4

• irreducible cluster of organisms that’s diagnosably distinct from other clusters
• within which there’s a parental pattern of ancestry and descent

Question 5

How do species form?

Answer 5

• allopatric
• peripatric
• sympatric
• parapatric

Question 6

What is the allopatric way of forming species?

Answer 6

• original population but barrier emerges which splits poopulation in 2
• evolve in reproductive isolation from each other
• when they come into contact again they’re distinct species and unable to breed with each other

Question 7

What is the peripatric way of forming species?

Answer 7

• from original population a new niche enters
• that niche becomes isolated and the speciation occurs within that area
• closely related species in isolated, nearby but unconnected area
• like allopatric but one population is smaller, there’s limited pool of genetic variability

Question 8

What is the sympatric way of forming species?

Answer 8

• occurs when species overlap with one another
• evolution of new species within same habitat due to reproductive isolation
• caused by life cycle becoming interrupted at some point
• likely to occur through pre-zygotic or post-zygotic barriers

Question 9

What is the parapatric way of forming species?

Answer 9

• new niche enters original population but doesn’t become isolated or separated, connected partially at least
• within the niche different selective pressures act on them
• leads to them becoming reproductively isolated and distinct from founder population

Question 10

What are pre-zygotic barriers?

Answer 10

• prevent/reduce likelihood of transfer of gametes to members of another species
• stop them from being able to breed
• ecological isolation (physical barriers)
• behavioural isolation
• pre-mating barriers (limited dispersal that prevent them from mixing and isolating behaviours that one sex won’t respond to)
• post-mating pre-zygotic barriers (if they can breed there’s barriers that prevent zygote from forming) (due to morphology they can’t link gametes or they can’t penetrate egg resulting in gamete isolation)

Question 11

What are post-zygotic barriers?

Answer 11

• consist of reduced survival or reproductive rates of hybrid zygotes
• hybrid unviability (hybrids have lower survival rates, mortality is intrinsic)
• hybrid sterility (survival to maturity but can’t produce viable gametes so are infertile)