EVOLUTION

Jean Baptiste Lamarck - One of the first to propose a hypothesis for how species can change. “Theory of Acquired Characteristics” - If an organism used a part of its body more, it grew bigger (or changed). - Any learned / acquired traits are then immediately passed on to their offspring.

Charles Darwin - Developed his ideas based on his 5 year voyage as a naturalist aboard the HMS Beagle. - Wrote the book: On the Origin of Species - Discovered more than 1500 species on the Galapagos Islands. * What is a species?

- Darwin’s Observations: * Noticed only slight differences between species on each island. - Adaptations: A trait which allows an organism to survive in its environment. * Could be anything!

What can you say about each tortoise’s food supply?

- Darwin’s Theories: 1. Natural Selection - When an individual(s), best suited for its environment, survives, mates & pass on its genes. Factors Involved/Needed: - Overproduction - Variation - Competition - Those who can’t survive, die.

2. Artificial Selection - When a breeder selects which traits are desirable, not the environment.

3. Survival of the Fittest - Who is the most fit? - The one’s who survive to produce the most “fertile” offspring.

III.Evidence for Evolution A. Fossil Evidence - What is a fossil? * Trace of a long dead organism. - How do they form? * Organism dies and is quickly buried by sediment. - How old they are? 1. Relative Dating 2. Absolute Dating (Half-Life)

- Types of Fossils: 1. Petrified - Bone that has been changed to rock. 2. Molds & Casts - Molds are hollow spaces in sediment. - Casts are molds filled in with sediment.

3. Preserved Remains - Organisms which have become fully preserved in materials such as ice or tree sap.

B. Homologous Structures - Similar anatomical features shared between multiple species.

Humerus Radius Ulna Carpals & Metacarpals Phalanges

C. Analagous Structures - Different structures, same function.

D. Vestigial Structures - Features which no longer serve a purpose.

E. Embryological Structures - Similarity seen in early fetal development.

F. Biochemical Evidence - Similarity in genetic material between different organisms. Examples: DNA between Chimps & Humans Proteins amongst various species

G. Transitional Species Ex. Archaeopteryx

H. Bacterial Evolution in Action Bacteria evolves at such a fast rate due to it’s short lifespan. Many generations can be observed over a short period of time. Antibiotic resistant bacteria –MRSA

IV. Conditions which affect Gene Frequencies A. The sum of all genes in a population is referred to as the Gene Pool. B. If a population is in equilibrium, it will not evolve. Gene frequencies are equal. C. 5 Factors that Affect Gene Pools: 1. Mutations - Introduces new alleles which can spread quickly if advantageous.

2.Genetic Drift - Random changes in allele frequencies. - Mainly affects small populations. (Microevolution) - Can result in the “founder effect.”- migration of a small subgroup of a population.

3. Gene Flow / Migration - Genes moving in and out of a population. –Immigration- individuals entering a population –Emigration- ind. leaving a population

4. Non-Random Mating - When organisms mate based on specific traits. Ex: Height, Strength, Blue Eyes, Skin Color, etc.

5. Natural Selection - The environment itself dictates the change in a population. Three Types: a. Stabilizing - Selects the average traits in a population.

b. Directional - Favors one extreme. c. Disruptive - Favors both extremes

Single Gene vs Polygenic Traits Single gene trait- controlled by a single gene with 2 alleles. –You either have it or you don’t. –Ex- widow’s peak, hitch hiker’s thumb Polygenic trait- controlled by 2 or more genes. –Ex- height, hair color

V.Pattern, Speed and Formation of Species A. Patterns: * These mainly occur within large populations (macroevolution). 1. Coevolution - When two or more species evolve closely together.

2. Convergent - The environment selects which traits are beneficial. - Dissimilar and/or similar species evolve similar traits.

3. Divergent - When two or more related species become more and more dissimilar. Two Types: a. Adaptive Radiation - When many species evolve from the same species. Ex: Galapagos Finches b. Artificial selection - When an organism is bred for a specific trait(s). Ex: Dogs from grey wolves

B. Formation of New Species (Speciation) 1. Reproductive Isolation- members of a population can no longer interbreed. a) Geographical- When a population evolves into separate species due to a physical barrier.

b) Behavioral- have ability to interbreed but do not due to different courtship rituals. –Ex- Eastern and Western Meadowlark

Reproductive Isolation Cont. c) Temporal- –When species mate at different times. –Ex- 3 different orchids produce pollen on 3 different days.

C. Speed of Evolution 1. Gradualism (Macroevolution = Large Populations) - Speciation over very long periods of time. - Usually millions of years. 2. Punctuated Evolution (Microevolution = Small Populations) - Speciation occurs quickly - Can take only hundreds to thousands of years.