Topic 37: Speciation

Question 1

Define a species. What are some limitations to the definition of species we are using?

Answer 1

Species are a group of populations whose memebers are capable to interbreed and produce viable fertile offspring.

They must mate within their species. If two species interbreed a hybrid can occur. Most likely will be unable to produce offsrping.

Question 2

What does it mean when two populations can mate and produce offspring but their offspring are sterile.

Answer 2

This means the offspring is hybrid, meaning its biable but sterile.

Question 3

Describe Allopatric Speciation. Provide some examples.

Answer 3

speciation to occur, two new populations must form from one original population and they must evolve in such a way that it becomes impossible for individuals from the two new populations to interbreed.
**Allopatric Speciation **: involves geographic seperation from a parent species subsequent evolution.

Examples:
River seperates a population
seeds float away
Barriers

Question 4

Describe Sympatric Speciation. Provide the examples.

Answer 4

Sympatric Speciation:Involves speciation occuring within a parent species remaining in one location.

Examples: chromsomal sperations in meiosis
causing polypploidy.

Question 5

Describe each of the 5 pre-zygotic barriers that ead to reproductive isolation.

Answer 5

Reproductive Isolation: biological barriers that prevent two species from interbreeding to produce viable fertile offspring.

5 pre-zygotic Variable:
- **Habitat Isolation: **two species occupy two different habitats where they dont ever encounter nor mate.
- Temporal Isolation: Species are reproductively active in different seasons.
- Behavioral Isolation: different species have different patterns or behaviors. Females will only mate within their species.
- Mechanical Isolation: difference in morphology prevents succesful fertilization.
- Gametic Isolation: gametes incompatible. Proteins on their surface prevent fertilization.

Question 6

Describe each of the 3 post-zygotic barriers that lead to reproductive isolation.

Answer 6

3 post-zygotic barriers:
Reduced Hybrid Viability: Hybrid is more susceptible tp predators, diseases, or parasites that impair its surivival.
Reduced Hybrid Fertility: Hybrids are sterile and cannot producefertile or viable offspring.
Hybrid Breakdown: hybrids in plants can be fertile but in the next generation can sterile.

Question 7

Be able to identify examples for all of the reproductive barriers.

Question 8

What is punctuated equilibrium? Gradualism?

Answer 8

In the gradual speciation model, species diverge gradually over time in small steps. In the punctuated equilibrium model, a new species undergoes changes quickly from the parent species, and then remains largely unchanged for long periods of time afterward