Some Evidence of Evolution Geographic Locations Anatomical Similarities Developmental Similarities Molecular (biochemical) Similarities

Some Evidence of Evolution Geographic Locations

Some Evidence of Evolution Anatomical Similarities Homologous Structures = structural features with a common evolutionary origin. Similar in arrangement, function or both.

Some Evidence of Evolution Anatomical Similarities Homologous Structures

Some Evidence of Evolution Anatomical Similarities Homologous Structures http://www.ucmp.berkeley.edu/

Analogous Structure = A structural or functional similarity of a body feature, but not related. Example: Insect & bird wings are similar in function, but not structure

Some Evidence of Evolution Anatomical Similarities Vestigial Structures = a body structure that has no function in a present-day organism but was probably useful to an ancestor.

Some Evidence of Evolution Anatomical Similarities Vestigial Structures http://www.tpwd.state.tx.us

Some Evidence of Evolution Anatomical Similarities Fossils http://www.earthhistory.org.uk/wp-content/crayfish.jpg

1. Trace Fossils https://courseware.e-education.psu.edu/courses/earth105new/graphics/L02_fossil_hpl922.jpg

2. Casts http://www.activityvillage.co.uk/cast-fossils.jpg

3. Imprints http://www.hopefossils.co.uk/Fossil%20photos/Trilobite%20under%20x10%20magnification%20-%20Placoparia%20cambriensis.JPG

4.Amber-Preserved & Frozen http://dsc.discovery.com/news/2007/10/08/gallery/amber_zoom.jpg

5. Petrified http://www.legendsofamerica.com/photos-arizona/PetrifiedWood.jpg

6. Molds http://www.ammonoid.com/mcE-m.jpg

Some Evidence of Evolution Developmental Similarities Comparative embryology Early developmental stages are compared. Related embryos look similar.

Some Evidence of Evolution Developmental Similarities Comparative embryology

Some Evidence of Evolution Molecular (biochemical) Similarities http://www.genome.gov/15515096

Natural Selection 1. Variations exist in a population

Sweet! I’m better at surviving because I blend into my surroundings! Natural Selection 2. Some variations improve the ability to survive and reproduce in the particular environment Sweet! I’m better at surviving because I blend into my surroundings! Boo!

I have more fitness than you! Natural Selection 3. The individuals with the adaptive traits are more likely to pass on their genes to future generations Boo! I have more fitness than you!

Natural Selection 4. Over time, the frequency of adaptive alleles increases = evolution.

Question Break True or False? Individual organisms evolve. Which of the following is NOT needed for natural selection to occur? a. Heritable variation b. Competition c. Fossil evidence d. Different levels of fitness

Speciation One species splits into two due to isolation (geographic, reproductive, etc…) Also known as Divergent Evolution… results in homologous structures between groups

Speciation Hurricane http://evolution.berkeley.edu

Speciation The populations diverge: Ecological conditions are slightly different on the island, and the island population evolves under different selective pressures and experiences different random events than the mainland population does. Morphology, food preferences, and courtship displays change over the course of many generations of natural selection. http://evolution.berkeley.edu

Speciation So we meet again: When another storm reintroduces the island flies to the mainland, they will not readily mate with the mainland flies since they’ve evolved different courtship behaviors. The few that do mate with the mainland flies, produce inviable eggs because of other genetic differences between the two populations. The lineage has split now that genes cannot flow between the populations. http://evolution.berkeley.edu

Speciation http://evolution.berkeley.edu

Speciation The first steps of speciation have been produced in several laboratory experiments involving “geographic” isolation. For example, Diane Dodd took fruit flies from a single population and divided them into separate populations living in different cages to simulate geographic isolation. Half of the populations lived on maltose-based food, and the other populations lived on starch-based foods. After many generations, the flies were tested to see which flies they preferred to mate with. Dodd found that some reproductive isolation had occurred as a result of the geographic isolation and selection in the different environments: “maltose flies” preferred other “maltose flies,” and “starch flies” preferred other “starch flies.”

What is a species? A group of interbreeding populations that cannot breed with other groups. Giraffes and Elephants? German Shepards and Poodles?

Maintaining Species Individuality Ecological (geographic) Isolation – not around each other Behavioral isolation – different species don’t understand each other’s mating rituals Temporal isolation – different breeding seasons Mechanical isolation – structural differences preventing mating

Speciation may lead to extreme genotype survival What is a genotype? Environment may favor extreme genotypes. Over time, extremes thrive, middle genotype extinct.

Direction of Natural Selection and Species Formation Stabilizing – extremes not favored (example – human birth weight) Disruptive – extremes favored (example - short or long beaks not medium beaks) Directional – extremes at one end favored

Convergent Evolution – when species become more alike Animals live apart but in similar environments Desirable traits are same Example – rabbit and squirrel color