Speciation: the formation of new species from existing species

Read pages 360-362 Once you have read the above pages, take the notes on the next few slides. Add examples of each mechanism where possible

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.

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

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

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.

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.

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

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)

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 https://www.youtube.com/watch?v=mcM23M-CCog&feature=youtu.be

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

Homework Pg. 373 # 2-5, 7,9,11,13 Watch this Video on Finches https://www.youtube.com/watch?v=mcM23M-CCog&feature=youtu.be