G4 Speciation

Question 1

Define Species (2)

Answer 1

• population of reproducing organisms isolated from other populations
• Group of individuals with common ancestor, capable of interbreeding and producing a FERTILE offspring

Question 2

if the there is NO gene flow, does that indicate species are different?

Answer 2

· If there is no GENE flow it doesn’t necessarily mean the species are different, for example there is 5 subspecies of Giraffes but and they’re aesthetically different in patterns, this doesn’t indicate a different species, because they do not live near each other so of course there will be no gene flow.

Question 3

In which way can speciation occur?

Answer 3

• In time along lineage= humans/chimpanzee
• geographical isolation
• genetic factors like genetic bottleneck/genetic drift

Question 4

Different species can be identified using GENE comparison, die there have to be a SPECIFIC amount of gene differences to indicate speciation?

Answer 4

Different species can be identifies by comparing GENES of the population, there is not a specific amount of different genes that divides two species, it could be 1 gene as it could be 1000s as long as they can reproduce.

Question 5

What is allopatric speciation?

Answer 5

-Species are geographically isolated
- leads to REPRODUCTIVE ISOLATION (no gene flow)
- resulting in 2 different species
-

Question 6

What id directional selection

Answer 6

• ONE extreme is favours

Question 7

What is stabilising selection?

Answer 7

• Middle/ mean is favoured
• e.g cat with long tail cannot balance
  cat with short tail cannot balance properly either, MEDIUM sized tail is favoured

Question 8

What is disruptive selection

Answer 8

both EXTREME are favoured
EX. Short tails help keep predators
from catching you on the ground.
Long tails are good for balance in
the trees. Medium tails don’t help.

Question 9

What other ways beside natural selection can speciation occur?

Answer 9

GENETIC DRIFT

Question 10

WHAT is GENETIC BOTTLENECK

Answer 10

Genetic Bottleneck:
-When an event causes big reduction
in a population’s size & gene pool.
Certain alleles may be due to
the event & population will also be
subject to genetic drift.

Question 11

what is FOUNDER EFFECT?

Answer 11

When a new pop. Is established by small number of
Individuals -> founding population will have low genetic diversity -> heavily influenced by genetic drift.

Question 12

What is sympatric speciation?

Answer 12

Speciation that occurs within a a population that id NOT due to geographical isolation

Question 13

What is Parapatric speciation?

Answer 13

Speciation that occurs between species that are not completely geographically isolated, they’re somewhat isolated.

Question 14

How does sympatric speciation supposedly occur?

Answer 14

• Most common scenario involves DISPRUPRTIVE SELECTION
• 2 Species diverege, where extreme are favoured
• so if hybridisation occurs within these species, the hybrid is in-between and wont survive and reproduce to pass on genes
• speciation can then occur if the species EXCLUSIVELY mate with the same extreme individuals

Question 15

Why is SYMPATRIC SPECIATION so hard to achieve?

Answer 15

because of the GENETIC RECOMBINATION between species

Question 16

What 4 conditions are required for SYMPATRIC speciation?

Answer 16

• Species must be largely sympatric ( while species have separated sympatrically but then were affected by allopatric it is hard to prove it was due to sympatric)
• Species must show REPRODUCTIVE isolation
• sympatric taxa must be close relatives
• Biogeographic must make ALLOPATRIC speciation very unlikely

Question 17

Can you give example of species tin which sympatric speciation occurred?

Answer 17

• Cichlid Fish
• Palm trees on lord howe island
• Polyploidy in plants

Question 18

What is poliploydi in plants?

Answer 18

polyploidy in plants is
a type of sympatric speciation
in which two sympatric species
having different chromosome
numbers or morphologies form a
hybrid, and that hybrid produces
offspring with a doubled number
of chromosomes (one full genome
from each parental species).
This yields a new lineage that
is reproductively isolated from
both ancestral species. Polyploid
speciation is quite common in
plants, perhaps accounting for up
to 4% of new angiosperm species.

Question 19

What is ASSORTATIVE mating?

Answer 19

Sexual selection in which individuals with similar phenotypes/genotypes interbreed more frequently than expected under a random mating pattern
e.g. Blackcap Birds -> breed in Germany -> some overwinter fly in Spain, others fly in UK
This leads to Assortative mating – Spanish birds mating with Spanish birds, UK with UK -> due to arrival time on breeding grounds (UK closer to Germany) -> Reproductive Isolation between 2 groups so over time= Genetic Change

Question 20

What is PREYGOTIC barrier?

Answer 20

eggs of an organism fail to be fertilized

Question 21

What is POSTZYGOTIC barrier?

Answer 21

• mechanism that blocks reproduction after fertilization and zygote formation
• POSTZYGOTIC barriers which occur after fertilization. In this case, the offspring are produced but they are sterile or not viable

Question 22

What is HYBRID zone?

Answer 22

area where two different population meet and breed

Question 23

Describe and explain the outcome the 3 of hybrid zones?

Answer 23

Reinforcement: Hybrids/ Offspring which are a less fit to survive, the hybrids are less likely to survive and pass on genes: so therefore species diverge until hybridization can no longer occur.