1. Speciation: the formation of new species from existing species

2. Read pages
Once you have read the above pages, take the notes on the next few slides.
Add examples of each mechanism where possible

3. Speciation occurs when some members of a sexually reproducing population change so much that they can no longer produce viable, fertile offspring with members of the original population.
Formation of new species is also called macroevolution.
Lack of gene flow between 2 populations may result in the 2 populations becoming reproductively isolated.
A hybrid organism results from the breeding of 2 different species.

4. Reproductive Isolating Mechanisms
Pre-zygotic
Prevention of Mating
Prevention of Fertilizing
Post-zygotic
Prevention of Hybrids

5. Reproductive Isolating Mechanisms
Class A: Pre-zygotic: a barrier that impedes mating between species or prevents fertilization
Prevention of mating
Behavioural Isolation:
Any special signals or behaviours that are species specific prevent interbreeding with closely related species.
Example: differences in the songs of the western and eastern meadowlark
Temporal Isolation:
Species may be kept separate by timing barriers.
Example: 2 species may occupy in the same habitat but mate or flower at different times of the day or in different seasons
Option: Make an extended version of the flowchart on pg 360

6. Ecological/Habitat Isolation:
2 species may live in the same general area but in different habitats, therefore they rarely encounter each other.
Example: the common garter snake lives near water and the northwest garter prefers open areas.

7. Prevention of Fertilization
Mechanical Isolation
Closely related species try to mate but fail to achieve fertilization because they are anatomically incompatible.
Example: genitals may not fit together
Gametic Isolation:
If the gametes from 2 species meet they will rarely fuse to make a zygote
Could be due to how the eggs are fertilized within the female reproductive tract.
In plants, pollen of one species usually do not germinate on the stigma of another species.

8. Read pages 363
Once you have read the above page, take the notes on the next few slides.
Add examples of each mechanism where possible

9. Class B: Post-zygotic: a barrier that prevents hybrid zygotes from developing into viable fertile individuals.
Prevention of Hybrids
Hybrid Inviability:
Genetic incompatibility of the interbred species may stop development of the hybrid zygote during its development.
Due to genetic incompatibility which prevents normal mitosis after the fusion of the gametes.
2. Hybrid Sterility:
2 species mate and produce a viable offspring but the offspring can not reproduce.
Meiosis in these individuals fails to produce normal gametes
Example: mule (female horse x male donkey)

10. Hybrid Breakdown:
The 1st generation hybrids are viable and fertile but when they mate with each other or an individual from the original species, they produce sterile or weak offspring.
Example: cotton
Finch Video

11. Read pages 363-369 Take notes on the following pages
Draw diagrams for:
Sympatric speciation
Allopatric Speciation
Speed of evolutionary change

12. Homework
Pg. 373 # 2-5, 7,9,11,13
Watch this Video on Finches