Speciation

Question 1

Define Speciation

Answer 1

The split of a species into 2 or more species

Question 2

What is the most generally accepted species concept? What does it describe?

Answer 2

The Biological Species Concept (BSC) describes that groups that actually or potentially inbreed and produce fertile offspring in nature, and which cannot form fertile offspring with other groups is considered a species.

Question 3

Name the three species concepts you are responsible for on the midterm and their definitions.

Answer 3

1. Biological Species Concept (populations that mate within themselves)
2. Morphological species (groups with similar features)
3. Ecological (groups with similar niches in their environment)

Question 4

Identify the two types of reproductive barrier

Answer 4

Prezygotic/Postzygotic

Question 5

What are the two categories of prezygotic barriers to reproduction? Name the 5 sub categories.

Answer 5

Prezygotic barriers that occur before mating include habitat isolation, temporal isolation, and behavior/pollinator isolation

Prezygotic barriers that occur after mating include mechanical isolation and gametic isolation.

Question 6

What is the difference between mechanical isolation and gametic isolation in prezygotic reproductive barriers?

Answer 6

Mechanical isolation occurs when a physical barrier prevents mating between two species, and gametic isolation is when sperm and eggs come into contact, but no fertilization can happen.

Question 7

Does birth occur in prezygotic or postzygotic reproductive barriers?

Answer 7

postzygotic

Question 8

What are the two types of postzygotic reproductive barrier? Explain them.

Answer 8

Genetic incompatibilities lead to an offspring with reduced survival chances or reproductive ability.
Ecologically-dependent postzygotic barriers occur when the offspring has phenotypes that are not matched to their environment.

Question 9

Define allopatric populations.

Answer 9

Populations that occur in different areas that do not overlap.

Question 10

What is the opposite of an allopatric population?

Answer 10

A sympatric population occurs in the same area.

Question 11

What do we call two partially overlapping populations?

Answer 11

Parapatric populations.

Question 12

What evolutionary variable must change within the population for sympatric speciation to occur?

Answer 12

The gene flow between two groups must decrease or stop completely.

Question 13

What are the three mechanisms of speciation?

Answer 13

Ecological, polyploidization, and reinforcement

Question 14

What drives ecological speciation?

Answer 14

Unique environmental characteristics select species to diverge in two different pathways to fill two different niches. This is also called divergent natural selection.

Question 15

Where is polyploidization found most often? What is it?

Answer 15

Polyploidization is most commonly found in ferns and flowering plants. It is the increase in number of sets of chromosomes.

Question 16

What is the difference between an autopolyploid and an allopolyploid?

Answer 16

Autopolyploids have two or more individual sets of chromosomes from the same species. Allopolyploids have two or more chromosome sets from different species.

Question 17

How can we describe hybrid crosses between two species when reinforcement speciation is present?

Answer 17

We can say hybrid crosses are less fit as the strengthening of the prezygotic barrier is selected in response to decreased fitness of the hybrid cross.

Question 18

In which mechanism of speciation is allopatry present? What about sympatry?

Answer 18

In ecological speciation, any geographical context can be present. Polyploidization occurs in sympatric context, and reinforcement is also expected to be more prevalent in more sympatric contexts.

Question 19

What is a downside of using BSC to describe speciation?

Answer 19

The Biological Species Concept cannot describe asexual taxa, fossils, and some animal species have gene flow within different species but still maintain divergence.

Question 20

What is a cryptic species and why is it important?

Answer 20

Cryptic species are identical in appearance, but do not interbreed within populations. This is important to consider when taking the morphological species concept into account.

Question 21

How would one experimentally study speciation?

Answer 21

With multiple populations of a common ancestor are exposed to separate environmental conditions.

Question 22

How would one test for ecologically-dependent postzygotic isolation of hybrids?

Answer 22

Reciprocal transplants of parents and hybrids into different environments can be done in both habitats.