Theory of Natural Selection: Darwin’s explanation for HOW evolution works.

VOYAGE OF THE HMS BEAGLE : 1831 - 1836

7 Steps to Natural Selection Overpopulation (overproduction)- animals produce more offspring than survive. Variation- animals of the same species are different Change in environment- a) Biological - food, predators, shelter, etc. b) Physical…water, oxygen, temp, etc. 4. Struggle for existence- competition for water, food, & shelter 5. Survival of the fittest- the best adapted & strongest tend to survive longer & produce more offspring 6. Inheritance- favored/best fit/selected variations (characteristics) are passed on to offspring. 7. New species arise- “selected” individuals grow in number and become a new species that cannot reproduce with original species

Darwin’s Observation: 13 or so species of finches on different Galapagos islands; these finches resembled the South American (mainland) finches more than say finches in Asia….

Same process for other species!

Jean Baptiste Lamarck: the outcaste! used the fossil record as evidence proposed a theory of evolution where organisms became better and better Mechanism - ”use” and “disuse” leads to: inheritance of acquired characteristics (you ‘acquire’ a phenotype in your lifetime and pass it on to your kids) also means environmental influences can be inherited DON’T BE LAMARCKIAN!

Hugo DeVries & Mutation Theory New Characteristics suddenly appear Mutation These can be passed on and may or may not help a species become more fit Helped to modify Darwin’s Theory

Evidences for Darwin’s theory Fossil record - horse lab Homologous Structures Vestigial structures Artificial selection

Natural selection in action: the evolution of insecticide-resistance occurs in nature - individuals with the best fit genes that can resist the insecticide will survive…. Fig. 22.12

B) HOMOLOGIES – Similarities in characteristics resulting from common ancestry is known as homology. 1) Homologous Structures: Same skeletal elements, but different functions

Human hand, cat limb, whale flipper, bat wing - they all have the same basic bone structure and design; So they have ALL evolved from a common ancestor with a similar ‘limb design’. B) HOMOLOGIES – HOMOLOGOUS STRUCTURES

Some Alleged Vestigial Organs in Man C) Vestigial organs, structures that are not used, but which had important functions in ancestors - still retained in descendents, so evolution/change has occurred. Some Alleged Vestigial Organs in Man Tonsils Adenoids Coccyx (tail bone) Nictitating membrane of eye Thymus Appendix Little toe Wisdom teeth Nipples on males Parathyroid Nodes on ears "Darwin's points" Ear muscles for wiggling Pineal gland Body hair

C) Vestigial organs – spurs in snakes, hind leg bones in whales.

Artificial Selection

Artificial Selection: The selective breeding of domesticated plants and animals to encourage the occurrence of desirable traits. Short period of time needed for Artificial Selection

Heredity: Characteristics that are passed down to offspring Mutations: Changes that occur in the hereditary material Mutant: The new form that survives a mutation and passes this trait on to offspring Adaptation: A favorable variation within a species that may help an organism survive

Natural selection - Predators/famine/space shortage/disease/ environmental changes

Origin of life and Stanley Miller’s Experiment

Abiotic synthesis of organic monomers Stanely Miller - simulated conditions on early Earth (no oxygen, reducing environment with inorganic gases like H2, CO2, NH3, CH4; lightning/UV with no ozone. Favored the synthesis of organic compounds from inorganicmaterial The Miller-Urey experiments produced a variety of amino acids and other organic molecules (monomers).