Speciation and Variation Chapter 16

Learning Goals 1. Compare microevolution to macroevolution 2. Describe the 2 different types of speciation 3. Analyze the effects of genetic drift on a gene pool. 4. Examine how founder effect and the bottle neck effect are similar/different.

What is a species anyway? A species is a group that only mates with each other. When two organisms can not interbreed, they are different species. Ex. Homosapiens (human), diceros bicornis(rhino), and drosophila malagastar (fruit fly). Can new species be created???? yes!!

Types of Speciation 1. Prezygotic: prevents zygote forming. Sperm and egg never meet up! Ex..reproductive isolation: the species is isolated and mating does not occur. a.geographic b. temporal c. behavioral

2. Postzygotic: after mating occurs, sperm and egg do meet but zygote is no good, “not viable”. Ex. Hybrid sterility : species interbreed, but offspring are sterile. Donkey horse mule

What is a zygote anyway? A zygote is formed when a sperm and egg meet during fertilization and a diploid single cell is formed. 1N egg 1N sperm 2N Zygote

1. Temporal isolation: when organisms can’t successfully mate due to different mating ritual, mating times, or mating location. Frog A: mate in Frog B: mate in early April late April, early May. Is this reproductive isolation? explain

Geographic Isolation: two populations are separated by a geographical barrier, like river, mountain or ocean. Can the Grand Canyon cause geographic isolation? Explain.

Darwin observed finches on different islands, and concluded that adaptive radiation occurred causing finches to develop different beaks.

Behavioral Isolation : rituals or behaviors cause species to no longer interact. Ex. The Eastern meadowlark bird and the Western meadowlark are in the same area but using different songs to attract mate.

Genetic Drift …genes move away! Occurs when a small group from a larger population leaves, the gene/allele frequencies may change. Genetic drift is NOT natural selection. It is simply RANDOM CHANCE. Explain diagram.

Bottle Neck effect: an example of genetic drift Bottle Neck: when small group are left over due to a natural disaster. Example, a large group of pecanaries (wild pig) are affected by drought. The surviving member don’t carry that same gene pool as before. Explain the diagram… Gene pool before gene pool after

Founder effect: another type of genetic drift Genetic drift when a small group migrate away from the original population. The new population will be different than the original. Ex. A small group of 12 Germans move to another country…3 of them are related and have polydactylism. After 250 years the gene frequency increases from 25 to 75%. What this because having an extra finger made them “better suited” for their new environment?

Microevolution = visible change from one generation to next small changes in the genes/chromosomes of a population Ex.1 House sparrow is larger in the Northern U.S, associated with colder temps. Ex. 2 Peppered Moth of London went from 90% light colored to 90% dark when the forest became polluted.

Marcoevolution = mutation + genetic drift + gene flow + natural selection billion years major changes affecting many species at once. Indicate a change in the time period. Ex. 1. KT event end the Cretateous period, causing Dinosaurs, along with 65 % of species to disappear. Ex. 2 End of Permian period caused by volcanic eruptions killing 95% of life on earth. Survivors fill in gaps and flourish!!

Geologic Time Scale Identify the KT event and the end of the Permian time. Put a star and label. In what period do we have the origin of birds? In what era and period do We currently live?