Chap. 15 : Darwin’s Theory of Chap. 15 : Darwin’s Theory of EvolutionEvolution

I.I. FossilsFossils

- traces of dead organisms, collect - traces of dead organisms, collect in sediments (dust, mud, etc) to in sediments (dust, mud, etc) to form form sedimentary rocksedimentary rock..

A. Types :A. Types :

1. 1. MoldMold – imprint (living parts maybe left behind) – imprint (living parts maybe left behind) common in limestone rock.common in limestone rock.

2. 2. CastCast – when molds fill in with minerals – when molds fill in with minerals 3. 3. AmberAmber – fossilized sap or petrified rocks – fossilized sap or petrified rocks

B. Law of Superposition – states that layers of B. Law of Superposition – states that layers of succession (called strata) build on top of each succession (called strata) build on top of each other.other.

youngestyoungest

oldestoldest

** all fossils found in same area are from the same time ** all fossils found in same area are from the same time period.period.

** ** relative agerelative age – comparison between fossils. – comparison between fossils.

** ** absolute ageabsolute age - determined by radioisotopes. - determined by radioisotopes.

(carbon dating) (carbon dating)

A

B

C

D

C. Succession layers – shows periods of C. Succession layers – shows periods of boom of certain organisms then periods of boom of certain organisms then periods of mass extinctions. Caused by environmental mass extinctions. Caused by environmental changes.changes.

D. Biogeography – the study of distribution D. Biogeography – the study of distribution of living (or once living) organisms.of living (or once living) organisms.

II. Evolution TheoriesII. Evolution Theories

A. Lamarck – 1A. Lamarck – 1stst to suggest that similar to suggest that similar species arose from common ancestors. species arose from common ancestors.

Suggested the term Suggested the term acquired traitacquired trait ( not passed by ( not passed by genes but changed by habitat or behavior and genes but changed by habitat or behavior and then passed to offspring). Ex. webbed feet – then passed to offspring). Ex. webbed feet – resulted from repeated stretching.resulted from repeated stretching.

B. Darwin – “Origin of Species” – book about the B. Darwin – “Origin of Species” – book about the idea of idea of natural selectionnatural selection (nature selects for the (nature selects for the most fit organisms to survive)most fit organisms to survive)

-- fitness fitness – how well an organism is adapted to its – how well an organism is adapted to its environmentenvironment

III. Evidence of EvolutionIII. Evidence of Evolution A. Homologous/Analogous StructuresA. Homologous/Analogous Structures - - Homologous StructuresHomologous Structures – features that – features that

originated from a shared ancestor. Ex. Different originated from a shared ancestor. Ex. Different beaks, forelimbs of penguins, alligators, bats, and beaks, forelimbs of penguins, alligators, bats, and humans.humans.

** indicates that different species shared a ** indicates that different species shared a common ancestorcommon ancestor

- - Analogous StructuresAnalogous Structures – features that look – features that look somewhat alike and serve similar functions but do somewhat alike and serve similar functions but do not share the same embryo development. Ex. not share the same embryo development. Ex. Birds and moth’s wings.Birds and moth’s wings.

B. Vestigial Structures – structures that B. Vestigial Structures – structures that presently serve no function.presently serve no function. Ex. Appendix and tail bone in humans, 4-Ex. Appendix and tail bone in humans, 4-

chambered stomach in whales, “legs” in boas and chambered stomach in whales, “legs” in boas and pythons.pythons.

--- organisms with similar vestigial structures shared --- organisms with similar vestigial structures shared an ancestoran ancestor

C. Similar Embryo DevelopmentC. Similar Embryo Development

- in the early stages of development all - in the early stages of development all vertebrates are the same. Ex. Fish,rabbits,birds, vertebrates are the same. Ex. Fish,rabbits,birds, and humansand humans

D. Similar Macromolecules – homologous D. Similar Macromolecules – homologous structures have similar amino acid structures have similar amino acid sequences.sequences.The # of differences are related to how recent The # of differences are related to how recent their ancestor was.their ancestor was.IV. Patterns of EvolutionIV. Patterns of Evolution 1. Coevolution – change of 2 or more 1. Coevolution – change of 2 or more

species in close association with each other. species in close association with each other. Ex. Predator/prey , plants/animal pollinatorsEx. Predator/prey , plants/animal pollinators

-- bats and flowers – bats long tongue and -- bats and flowers – bats long tongue and slender nose, flower light in color and smells slender nose, flower light in color and smells fruityfruity

2. 2. Convergent evolutionConvergent evolution – environment selects – environment selects similar phenotypes even though the ancestors were similar phenotypes even though the ancestors were quite different. Ex. Sharks and porpoisesquite different. Ex. Sharks and porpoises

3. 3. Divergent EvolutionDivergent Evolution – 2 or more related populations – 2 or more related populations become more and more dissimilar. Caused by a change of become more and more dissimilar. Caused by a change of habitat.habitat.

--- usually results in new species--- usually results in new species

a. a. Adaptive RadiationAdaptive Radiation – related species evolve from – related species evolve from single ancestor. Ex. Darwin finches.single ancestor. Ex. Darwin finches.

b. b. Artificial selectionArtificial selection – speeding up of divergence by – speeding up of divergence by artificial means. Ex. Domestic dogs, horsesartificial means. Ex. Domestic dogs, horses

-- doesn’t result in new species but rather varieties of -- doesn’t result in new species but rather varieties of species.species.

V. Events that lead to new species :V. Events that lead to new species :

Barrier separating like organisms forms Barrier separating like organisms forms (flood, volcanic eruptions, earthquakes, (flood, volcanic eruptions, earthquakes, forest fires, etc.)forest fires, etc.)

Time passes (thousands of yrs), Time passes (thousands of yrs), environment changesenvironment changes

Natural selection breeds changesNatural selection breeds changes Enough change occur overtime to change Enough change occur overtime to change

DNA significantly so no longer recognized.DNA significantly so no longer recognized.

VI. Primates and Human EvolutionVI. Primates and Human Evolution

45 million years ago45 million years ago

New World Monkeys (tails

that grasp, upward noses)

Old World Monkeys (non-grasping tail,

downward nose)

Some evolved into apes and gorillas

Evolved into humans

monkeys baboons