Evolution Darwin 1809 82 n English naturalist wrote

Evolution Darwin (1809 -82) n English naturalist, wrote “On the Origin of Species by Means of Natural Selection” n explain why evolution and how, natural selection

The voyage

Previous 1. Malthus (1798), Essay on the Principle of Population n human populations increases geometrically but the food resources grows arithmetically

2. Lamarck: evolution occurred by the inheritance of acquired characteristics, body and behavior n giraffes evolved long necks because ancestral giraffes tended to stretch their necks and this neck extension was passed on to subsequent generations n

n Darwin variation is not created by experience but already exists when selection acts on it n populations of ancestral giraffes contained variation in neck length individuals who were able to feed higher up on the trees had more food and so were able to survive and reproduce better than their shorter-necked relatives n

n Darwin’s evidence to explain how species evolve rather than remain fixed 1. 2. 3. 4. fossils resemble living organisms Organisms change gradually when move into new habitats, islands have diverse animals and plants related to the mainland sources Comparative Embryology Molecular Biology

Fossils 150 M 230 M 65 M (Extinction)

Elephant Evolution Modifications seen in newer species Older species replaced

Proof of Evolution - Biogeography Four Galápagos finches and what they eat: 1. all the finches shared a common ancestor 2. their beak sizes had evolved to suit their food 3. genetic differences account for the physical differences in the beaks

Proof of Evolution – Comparative Embryology Comparing structures during embryo development Ex: vertebrates and gills

Proof of Evolution – Molecular Biology All cells have same/similar molecules Suggest organisms share similar ancestor

Concepts 1. adaptive radiation: species changes to occupy different habitats: adapt

2. Macroevolution: grand scale evolutionary changes that result in the creation of new species 3. Microevolution: evolutionary change within a species (population) that make that species different from its immediate ancestor

4. Homologous structures: n n derive from the same body part present in an ancestor same bones used for different functions in related species 5. Analagous structures n n similar-looking structures in unrelated lineages parallel evolution or convergent evolution

Forelimbs of Animals – Homologous Structures Same bones and similar structures Different functions

Insect Bird Examples of Analogous Structures Organisms not related!

Agents of Evolution 1. 2. Mutation: change in DNA sequence Migration: movement of individuals between populations, effects based on two factors: • • 3. 4. proportion of migrants in the population difference in allele between migrants-original population genetic drift: genetic changes in populations isolated from one another Selection: some individuals leave behind more progeny than others • • artificial selection, a breeder selects for the desired characteristics natural selection, conditions in nature determine

n Natural selection “survival of the fittest” frequency of favorable characteristics increasing in a population n favorable characteristics are specific to an environment (not the biggest or the strongest) n organisms whose characteristics are best suited to their particular environment survive more often and leave more offspring n

n artificial selection n n Evolution of domesticated animals through selective breeding the resulting differences between breeds of domesticated species are more extreme than what exists in nature

Who Are We? n n Humans are apes Family: Hominidae • Opposable thumbs • 1% DNA difference to chimps 2

Hominid Evolution n n First hominids appeared 5– 7 mya Characteristics of hominids • Large brains • Bipedal • Toolmaking • walked upright © 2009 W. W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e 3

n Oldest Homo fossils are from 2. 4 mya © 2009 W. W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e 6

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n H. sapiens showed primitive technology • Toolmaking • Building shelters • Control of fire © 2009 W. W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e 9

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H. sapiens gave rise to Neandertals and modern humans n 13

Origin and Spread of Humans n n Out-of-Africa hypothesis Multiregional hypothesis © 2009 W. W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e 11

Evolutionary Future of Humans n n n Brain size Agriculture Genetic drift Natural selection Infectious disease Anything else? © 2009 W. W. Norton & Company, Inc. DISCOVER BIOLOGY 4/e 14

Lecture Practice questions 1. Changes in organisms over a long period of time, including the rise of novel organisms and extinction, is known as A) natural selection. B) microevolution. c) macroevolution. D) punctuated equilibrium. 2. One of the major sources of evidence for evolution is in the comparative anatomy of organisms. Features that have a similar look but different origin are called: A) homologous B) analogous c) vestigial structures. D) equivalent 3. Chance events that cause a population to lose some individuals (die), and hence a loss of alleles to the population, results in: A) mutation. B) migration. C) selection. D) genetic drift.