Chapter 24 continued

There are many types of barriers that can prevent species from interbreeding; these barriers can be broken down into two types: prezygotic: those that prevent species from mating or hinder fertilization and post zygotic barriers: include those that prevent a fertilized egg from becoming a fertile adult.

Isolating mechanisms: mechanism that isolates you, no way to introduce other species or mate.

Examples of prezygotic barriers include:

1. Habitat Isolation- Two species can live in the same geographic area, but if they dont live in the same habitat they can be prevented from mating. ex. two snakes from roberts blog

2. Temporal Isolation- Species may breed at different times of the day, different seasons, or different years, and this can prevent them from mating. ex.Three tropical orchid species of the genus Dendrobium each flower for a single day; the flowers open at dawn and wither by nightfall.

3. Bevavioral Isolation- ex. Blue footed boobies with their foot rituals. An isolating mechanism in which two species do not mate because of differences in courtship behavior. Also known as ethological isolation

4. Mechanical Isolation- PARTS don't FIT :) ex. snails that spiral different directions.

5. Gametic Isolation- Gametes of different species may fail to attract one another and form a zygote ex. Marine animals often discharge their eggs and sperm into the surrounding water, where fertilization takes place

Postzygotic barriers: species mated and formed a zygote.

1. Reduced Hybrid viatlity- when a zygote is formed the fact that the two species are genetically incompatible may cause development to cease. Most of of the hybrids do not complete development and those that do are frail. ex. zygote might not go through all of mitosis.

2. Reduced Fertility Hybrid- Even if the two different species produce a viable offspring, reproductive isolation is still ocurring if the offspring are sterile and can't reproduce.

3. Hybrid animal- If two different species produce offspring that are viable and fertile, the hybrids may mate to produce weak or sterile offspring.

M.C:

1. Species that reproduce and form zygotes can suffer form _______ barriers to reproduction

a)prezygotic

b)postzygotic

c)fertility

d)DNA

2. Behavioral Isolation explains why _____ is important in reproduction.

a)gametes

b)habitat

c)time

d)courtship

3.Mechanical Isolation tells us that _____ potentially do not fit

a)parts

b)gametes

c)zygotes

d)clothes

1.b 2.d 3.a