Summary: The video Speciation defines and describes what a species is, what speciation means and the different types of speciation and what causes them. The two types are allopatric speciation, which is a geographic barrier that keeps the populations separate and allows them to evolve independently, and sympatric speciation, which have prezygotic and postzygotic barriers that keep the two from producing offspring. It also provides examples of the different barriers and how they cause speciation.

Why watch this video?

1. Have you ever wondered how different species come to be?
2. Would you like to know how one species can become two (or more) different species over time?
3. Have you ever been confused by why certain animals that are similar and live in the same environment and geological area (like mule and white tail deer) don’t mate and produce offspring?

Key Terms:

• Speciation: The formation of new species
• Allopatric speciation: Speciation caused by the separation of a species by a geographic barrier
• Sympatric Speciation: A barrier that keeps two species from producing a zygote

Loose Ends:

Loose end #1: There are 5 types of prezygotic barriers/isolation. Mechanical – parts don’t fit together, Temporal – different mating seasons, Behavioural – different mating behaviours, Habitat isolation, and Gametic isolation – sperm and egg are incompatible

Loose end #2: The definition of a species is that the two can interbreed AND produce viable offspring that can also reproduce. So just because two animals can breed and have an offspring does not mean they are the same species if that offspring is unable to reproduce. (the zonkey example – a zonkey is sterile)

Loose end #3: If a species is isolate it doesn’t mean that it will for sure turn into two different species. It would have to have different types of natural selection occurring to become two separate species. Ex: white tail deer in BC are the same species as the white tail deer in Manitoba even though they are isolated by distance.

Self-Test Questions:

Question 1: A type of speciation that has a geographic barrier keeping the species from producing offspring and allowing them to evolve independent of each other

a: Sympatric speciation

b: Natural selection

c: Continental drift

d: Allopatric speciation

Answer: D is the answer because b and c aren’t a type of speciation and a isn’t the right type of speciation

Question 2: What is an example of a prezygotic barrier?

a: Different breeding seasons

b: Different mating behaviours

c: Incompatibility of sexual organs

d: All of the above

Answer: D is the answer because all of the answers are types of prezygotic barriers that keep the two species from mating and creating a zygote

Question 3: For something to be a species it has to:

a: Be able to interbreed

b: Be able to produce viable/fertile offspring

c: a and b

d: Live in the same area

Answer: C is the answer. D is not true, domestic dogs live all over the place and have come from different parts of the world and are all the same species. And a species needs to be able to do both a and b to be considered a species.

Question 4: If two different species mate and fertilization occurs what is the barrier called that keeps the offspring from being viable?

a: Postzygotic barrier

b: Speciation barrier

c: Prezygotic barrier

d: After fertilization barrier

Answer: A is the answer because the barrier happens POST (after) zygotic formation

Question 5: Prezygotic and Postzygotic barriers are an extension of what type of speciation?

a: Natural speciation

b: Sympatric speciation

c: Allopatric speciation

d: Evolution

Answer: B is the answer because allopatric speciation has geographical barriers so the two species wouldn’t be able to come in contact in order to produce a zygote.