Speciation

Question 1

species

Answer 1

a population that can breed and produce offspring that can also breed, but it is not able to breed successfully with other populations

Question 2

speciation

Answer 2

• process by which an existing population gives rise to a new 
population that no longer has the 
potential to recombine with it as a single 
gene pool.
• the key to this is reproductive isolation.
• As long as individuals can share genes freely in a gene pool, that gene pool may 
change over time, but we would not consider it to be a new species unless it had 
changed enough that present members of the population would be unable to 
breed with past members.

Question 3

reproductive isolation (what is it)

Answer 3

Reproductive isolation can occur as a result many different 
changes in genetic compatibility that may lower fitness of 
hybrids or changes in phenotype that may provide a barrier 
to successful mating. can happen through post or pre zygotic methods.

Question 4

Post-zygotic isolation

Answer 4

occurs when hybrids are formed but have 
reduced fitness.

a) - hybrid viability: offspring dies young
b) - hybrid sterility: when you can’t reproduce with another member of the population is not hybrid
c) - Hybrid Fitness: fitness is reduced because it is not going to survive. it is a mix between the best of the both parents but because it is a mix, it is eaten. if poisonous mates with camouflage, it will be half camouflaged and half poisonous. it doesn’t do either well so it gets eaten

Question 5

prezygotic isolation

Answer 5

prevents the formation of hybrids in the first 
place

Question 6

gametic isolation (prezygotic isolation)

Answer 6

sperm and egg can’t form zygote. they just don’t fertilize

Question 7

mechanical isolation (prezygotic isolation)

Answer 7

parts don’t fit

Question 8

termporal isolation (prezygotic isolation)

Answer 8

fertile periods don’t match. ex. one animal is only fertile in spring, others only in fall

Question 9

behavioural isolation (prezygotic isolation)

Answer 9

behaviours don’t match. the mating activity they do is different from the mating that the organism is attracted to so they don’t recognize each other as mates

Question 10

habitat isolation (prezygotic isolation)

Answer 10

they live so far away that they will never encounter each other. ex. tigers in asia vs lions in africa

Question 11

allopatric speciation

Answer 11

• Speciation requires reproductive isolation. It usually also involves divergence as the two populations become 
different phenotypically.
• The standard model of speciation assumes that a gene pool MUST BE physically 
split before the two sub-populations can diverge enough to speciate.

Question 12

geographic isolation

Answer 12

causes all gee flow to stop between two subpopulations:

- natural disasters, colonization, fragmentation, physical barrier, continental drift

Question 13

microevolution

Answer 13

causes two gene pools to diverge from one another.

- genetic drift, natural selection, differential mutation, sexual selection

Question 14

steps in model

Answer 14

1) geographic
2) microevolution
3) reproductive isolation

Question 15

types of prezygotic isolation

Answer 15

gametic, temporal, behavioural, mechanical and habitat

Question 16

sympatric speciation

Answer 16

sympatric (sym = same) speciation, in which reproductive isolation occurs between two sub-groups of a single population before divergence.

Question 17

divergence

Answer 17

when two populations start to become different (they are still same species). If they diverge enough, they will speciate