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Evolution

 Galapagos Islands (540 miles west of South America)   Fascinated by the unusual organisms he found

on the Galapagos islands   Noted that groups of animals varied from island

to island   Finches and fauna unique to Island but

resemble mainland   Evolution - The development of new types of

organisms from preexisting types of organisms over time   Darwin formed a theory to explain how evolution could occur

 Darwin formed his theory by studying other ideas about the earth and evolution at this time

 Ideas about Geology   Study of strata = rock layers   Discovered that strata are formed as new layers

of rock are deposited over time   Scientists found that different rock strata hold

fossils of different kinds of organisms

 Cuvier (1769-1832)   Studied fossils (paleontology) – remains or traces

of organisms from the past   Noticed fossil differences in each layer (strata) of

rock as he dug deeper   Noticed that some organisms had become extinct   Found many “sudden” changes in the kinds of

organisms found in one rock strata (layer) compared to the next

  Catastrophism – his view of the earth – changes in species found in each strata were due to major catastrophes or extinctions

 Charles Lyell (1797-1875)   Thought that the geologic processes that have

changed the shape of Earth’s surface in the past continue to work in the same ways today

  Uniformitarianism – geological processes are so uniform and gradual that their rates and effects must balance out over time   Mechanisms of change are constant over time

  Lyell’s ideas strongly influenced Darwin’s thinking   geological change results from slow, continuous actions

rather than sudden events, then the earth must be older than originally thought

  Idea of gradual change – slow accumulation of small changes could ultimately produce profound changes

 Lamark (1744-1829)   Developed a comprehensive theory as to HOW life

evolved over time   Thought that simple organisms could arise from

nonliving matter   Thought that simple forms of life develop into more

complex forms   Proposed that individuals could acquire traits during

their lifetime as a result of experience or behavior and pass these traits on to their offspring….What is wrong with this idea

  Inheritance of acquired characteristics – modifications that an organism acquires during its lifetime can be passed on to its offspring   This idea was rejected by many scientists

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 Darwin developed 2 main concepts:

1.   Descent with modification – every species (living or extinct) must have descended by reproduction from preexisitng species and that species must be able to change over time

  Darwin saw the animals of the Galapagos islands as evidence of descent with modification

  Studies finches – and differences in beak type over time

  Diverse adaptations accumulated as descendants from this common ancestor moved into various habitats over millions of years

  Adaptation – inherited variation that increases an organisms likelihood of surviving to reproduce

 Darwin developed 2 main concepts:

2.   Natural Selection – proposed theory as the mechanism for descent with modification

1.   Overproduction – More offspring can be produced than can survive to maturity. The environment limits the populations of all organisms by causing deaths or limiting births

2.   Genetic Variation – Within a population, individuals have different traits. Some of this variation can be inherited.

3.   Struggle to Survive – Individuals must compete with each other, “struggle for existence.”

  Some variations improve an individual’s chance to survive and reproduce but some variations reduce this change

  Adaptation – a trait that makes an individual successful

4.   Differential Reproduction – organisms with the best adaptations are most likely to survive and reproduce

  Through inheritance the adaptations become more frequent in the populations

  “survival of the fittest” – term used to describe natural selection

  Fitness – the measure of an individual’s hereditary contribution to the next generation

  Ex: thick fur is an advantage for deer living in the mountains – these deer with thick fur are more likely to live long enough to reproduce

  If a certain trait increases an individual’s fitness, the proportion of individuals with that trait is likely to increase over time

  Adaptations are those traits that increase the fitness of individuals

  Galapagos island finches – adapted beak shape depending on food source

1. What are the lines of evidence that support Darwin’s ideas?

Millions of years ago

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Equus

Hyracotherium Mesohippus

Merychippus

Nannippus

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 Fossil – remains or traces of an organism that died long ago   Show that different types of organisms appeared

at different times and places on Earth   Some fossils are of organisms that have become

extinct   Most powerful evidence of evolution

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 Superposition – if the rock strata at a location have not been disturbed, the lowest stratum was formed before the strata above it   Successive strata are newer – most recent on top

 Geological time scale – a timeline for the order in which different groups of rocks and fossils were formed   Can tell the relative age of a fossil. Its age

compared to that of other fossils

 Absolute age – time since formation. Scientists can estimate the absolute age of certain rocks   Radiometric dating – technique scientists use to

determine the absolute age of rocks

 Relative and absolute age dating is used to make history as precise as possible

 Fossil record is incomplete because not all organisms have left fossil evidence

1.  Different organisms lived at different times   Rock strata hold different kinds of fossils in

successive layers

2.  Today’s organisms are different from the past

3.  Fossils found in adjacent layers are more like each other than to fossils found in deeper or higher layers

4.  By comparing fossils and rocks from around the planet, can infer when and where different organisms existed

 Species have differed in gradual sequence of forms over time

 Transitional species – species have features that are intermediate between those of their ancestors and later descendant species   Ex: Scientists think that whales evolved from land dwelling mammals

 Biogeography – study of the locations of organisms around the world.   Darwin saw evidence of evolution in the

distribution of organisms   Observed animals that seemed closely related

but had adapted to different environments   Observed unrelated animals that had developed

similar adaptations to similar environments in regions that were far apart

 Descent with modification predicts the findings of anatomy and embryology  Anatomy – study of body structures of organisms   Embryology – study of how organisms develop

 Forelimbs of human, penguin, alligator and bat   An early ancestor shared by all these vertebrates had a

forelimb with a similar bone structure   After many years different populations adapted to

different environments   Bones inherited from ancestors have become modified

for different tasks

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 Homologous Structures – anatomical structures that occur in different species but originated from a common ancestor   Similar structure, different function!

 Analogous structures – structures with closely related functions, but different ancestors   Ex: birds, bats and moths all have wings, but

their wings have very different structures   The structures are derived from different ancestors

and have evolved independently

 Vestigial Structures – structures that serve no function but resemble structures with functional roles in related organisms   Served a function in the past – no current use for

them today   Ex: human tailbone made up of 4 fused

vertebrae that resemble the bones in an animal’s tail

  Ex: Pelvic bone of whales and human appendix

  In all species DNA and RNA are the molecular basis for inheritance of traits

 DNA affects traits by coding for amino acids  Biologists can compare the DNA, RNA and

proteins of from many different organisms   The greater the number of DNA similarities, the

more closely the species are related

 Phylogeny – the relationships by ancestry among groups of organisms   Phylogenic Tree

 Convergent Evolution – process by which different species evolve similar traits   The independent evolution of similar features in

different lineages   Evolved independently from different ancestors,

yet they have adapted to similar environments in similar ways

 Divergent Evolution – process in which the descendants of a single ancestor diversify into species that each fit different parts of the environment   Same ancestor   Evolved in different environments developed

different traits to fit their environemnt

  Sometimes a new population in a new environment (island), will undergo divergent evolution until the population fills many parts of the environment.   This is called Adaptive Radiation

  Artificial Selection – occurs when a human breeder chooses individuals that will parent the next generation   Ex: choosing a breed of oat plants to yield more

stalk; breeding dogs for favorable traits

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 Evolution is ongoing  In a given environment, many species are

evolving at once  Coevolution – when 2 or more species have

evolved adaptations to each other’s influence   Ex: some species have evolved strategies to

avoid being eaten   Ex: flowering plants evolved that specific insects

carry pollen to other plants   Ex: humans have developed and used antibiotics

to kill disease causing bacteria as antibiotic use has increased, causing resistance to the antibiotics.