Speciation and Macroevolution Unit 4, Topic 2

Question 1

What is speciation?

Answer 1

• the evolution of one or more new species from an ancestral species
• a single species can diverge and produce several new species
• formation of new species following an event that splits lineage

events include geographical, morphological, behavioral, or reproductive isolation of a population.

Question 2

What is macroevolution?

Answer 2

• the accumulation of small changes in phenotypes over time (essentially microevolution overtime)
• can result in a new species being formed.

Question 3

What are the 4 types of diversification/patterns?

Answer 3

1. divergent evolution
2. convergent evolution
3. parallel evolution
4. coevolution

Question 4

what is divergent evolution?

Answer 4

• related species evolve new traits over time, away from the common ancestor, to give rise to new species

groups from the same species become isolated -> isolation stops gene flow between separated populations -> two groups evolve differently (diverge and become new species)

Question 5

What is convergent evolution?

Answer 5

• unrelated organisms evolve similar adaptations in response to similar environmental pressures.

Question 6

what is parallel evolution?

Answer 6

• when two species with a common ancestor evolve similar features independent of each other.

Question 7

What is coevolution?

Answer 7

• evolutionary change in one species influences the evolution of another species.

Question 8

What are the 5 types of mechanisms?

Answer 8

• mechanisms of isolation
• geographic mechanisms
• reproductive mechanisms
• spatial mechanisms
• temporal mechanisms

Question 9

What is the mechanisms of isolation?

Answer 9

all reduce gene flow because of the two new populations can’t/don’t breed with each other, restricting the number of genes flowing between two populations - can lead to speciation (formation of new species)

Question 10

What is the geographic mechanisms?

Answer 10

when physical barriers separate a population; a habitat is broken into smaller fragments of an environmental disaster decreases a population’s size, shrinks the habitat, and increases the mutation rate.

Question 11

What is the reproductive mechanism?

Answer 11

There are two types of reproductive mechanisms:

pre-reproductive isolating mechanisms: prevent organisms from being able to interact to reproduce.
- geographic
-temporal - breed during different - seasons
- behavioural - different courtship - patterns
- morpholigical - different reproductive structures
- location - makes mates physically impossible

Post - reproductive isolating mechanisms: prevent fertilisation occurring or an embryo developing into viable offspring if fertilisation does occur
gamete mortality - gametes do not survive
zygote mortality - zygote forms but does not survive
hybrid sterility - adult offspring are formed but are infertile because they are unable to produce viable gametes.

Question 12

what is spatial mechanism?

Answer 12

• occurs between two populations that are separated by a great distance.
• members will never meet and mate resulting in no gene flow between the populations

Question 13

What is temporal mechanisms?

Answer 13

A mechanism that prevents species from mating due to the different times they breed.

Question 14

What is reduced genetic diversity?

Answer 14

• when small number of individuals survive a major catastrophic event/quickly changing adverse environmental conditions
• surviving population is unlikely to carry all the alleles that were present in the original population
• resulting in low genetic diversity (smaller gene pool, reduced allele frequency)
• inbreeding reducing gene pool
• when there is low genetic variation, there is less chance of there being alleles that suit the selection pressure
• if no species has the right genetic variation, the species becomes extinct.
• the more genetically diverse a species is, the more readily they can adapt to changes because they have a greater range of genes and alleles suited for different environments.