Theory of Evolution Ch 15 15 1 Evolution

Theory of Evolution Ch. 15

(15 -1) Evolution • Change of organisms over generations w/ a strong natural modification process • “Change over time”

Scientific Theories • Explain data • Generations of predictions • Falsifiable

Lamarck’s Theory • Use & Disuse: parts of body that are used extensively become larger & stronger while those that are not used deteriorate – Acquired traits

Lamarck (cont. ) • Ex: – Webbed foot = stretching of membrane b/w toes (water birds) • 1 st to say: – Organisms change over time – New organisms are modified descendants of older types

Darwin & Wallace’s Theory • Natural Selection: organisms best suited to their environment reproduce more successfully than others • “Survival of the fittest”

Charles Darwin’s • Voyage on the Beagle

Darwin’s Studying Ground

Darwin’s Observations • 13 similar but separate species of finches – Specialized for food • Similarities lead to belief of a common ancestor

Darwin’s Conclusions 1. Descent w/ modification 2. Modification by natural selection

Descent w/ Modification • Newer species are modified descendants of older species • All species descended from 1 of a few original types of life

Modification by Natural Selection • How evolution occurs • Environment limits pop. ’s growth • Not all individuals in a pop. are identical & environment affects them differently

Natural Selection (cont. ) • Individuals w/ favorable traits reproduce more often than those w/ unfavorable traits • Thus favorable traits will be passed down more often

Adaptation • Inherited trait that inc. an organism’s chance of survival in a particular environment – Based on genes

Fitness • Ability to survive to propagate their genes (have babies)

Lamarck vs. Darwin

(15 -2) Evidence of Evolution 1. Biogeography • Geographical distribution of species 2. Fossil Record • Type & order of fossils

Evidence (cont. ) 3. Homologous structures • Similar b/c of common ancestry 4. Comparative embryology • Study of structures that appear during embryonic development 5. Molecular biology • DNA & proteins

Biogeography • New organisms arise in same geographic area where similar forms already lived • Ex: kangaroos only in Australia

Fossil Record • Fossils: impressions of organisms from the past mineralized in rock • Links b/w modern forms & ancestors

Distribution of Fossils • Law of superposition: lowest layers of rock are oldest • Fossil-bearing strata show when organisms became extinct • Mass extinction: brief period in which large #’s of species disappeared

Homologous Structures • May have different functions but have similar anatomy • Shows a common ancestor • Ex: bird beaks & forelimbs

Common Ancestor

Analogous Structures • Similar look & function, but different embryological development & anatomy • Ex: bird & insect wings

Vestigial Structure • Part of an organism w/ little or no function, but had a function in an ancestral species • Ex: human tailbone & appendix

Comparative Embryology • All vertebrate embryos go through a stage in which they have gill pouches & tails

Molecular Biology • The more similar the sequence, the more closely related 2 species are to each other • DNA, RNA, proteins (amino acids)

Amino Acid Chart

(15 -3) Patterns of Evolution 1. Coevolution 2. Convergent Evolution 3. Divergent Evolution • Pattern & speed result from changes in the environment

Coevolution • Change of 2 or more species in close association w/ each other • Ex: – Predator-prey – Parasite-host – Plant-animal pollinator

Convergent Evolution • Organisms appear to be similar but are not closely related • Environment selects similar phenotypes • Ex: shark & porpoise

Divergent Evolution • 2 or more related populations become more dissimilar in response to different habitats • Adaptive radiation – Galapagos finches • Artificial selection – Domestic dogs

Divergent evolution of Grand Canyon squirrels

Peppered Moth Evolution