Lecture test 1: Prezygotic barriers essay

Question 1

Name all of the prezygotic barriers

Answer 1

1. Habitat
2. Temporal
3. Behavioral
4. Mechanical
5. Gametic

Question 2

What are prezygotic barriers

Answer 2

Egg and sperm never meet. Prezygotic barriers block fertilization from occurring by

1. Impeding different species from attempting to mate
2. Preventing successful completion of mating
3. Hindering fertilization if mating is successful (incompatibilities of the sperm and egg)

Question 3

Habitat isolation

Answer 3

Prezygotic barrier. Two species encounter each other rarely or not at all because they occupy different habitats, even though they are not isolated by physical barriers. Unlikely to encounter each other and therefore unlikely to mate

Question 4

Habitat isolation example

Answer 4

Snake living on land and snake living in the water. Both garter snakes living in the same geographic area but they probably will never encounter each other

Question 5

Temporal isolation

Answer 5

Two species that breed during times of the day, season years etc. Not in heat at the same time periods

Question 6

Temporal isolation example

Answer 6

Skunks go into heat at different seasons. One goes into heat in winter and one goes into heat in the summer. Cannot interbreed. Eastern and western spotted skunk

Question 7

Behavioral isolation

Answer 7

Unique and individual courtship behaviors. Specific behavior attracts specific mates. Behaviors different among different species

Question 8

Behavioral isolation example

Answer 8

Blue footed boobys do a special dance to attract females

Question 9

Mechanical isolation

Answer 9

Very closely related species attempt to mate but fail because there are anatomical differences. Prevents complete transfer of sperm

Question 10

Mechanical isolation example

Answer 10

Direction of spirals on snails. Snails that have opposite spirals cannot mate. They do not line up

Question 11

Gametic isolation

Answer 11

Sperm of one species is unsuccessful at fertilizing the egg of another species

Question 12

Gametic isolation example

Answer 12

Organisms that use external fertilization (sea urchin). Only will match up will egg of same species of the same sea urchin. Will not be able to fertilize other species in the area. Same goes for pollination