Introduction to Evolution

Pre-AP Biology

Bellwork

Ancestors of the polar bear had a brown coat but today they have a white coat. Why? What initiated the change?

Objectives

Explain how Lyell and Malthus contributed to Darwins Theory of Evolution.

Define descent with modification and natural selection

Key Terminology

Inheritance of acquired characteristics Descent with modification Natural selection

Important Dates

Darwin – published his theory of evolution 1859

Mendel –published that parents pass on their offspring discrete heritable factors 1866

Hershey and Chase Experiment – discovery DNA genetic material-1952

Watson and Crick discovery of DNA structure -1953

Jean Lamarck’s Ideas

One of first to develop a theory of evolution

Reasoned that organisms must adapt to their environment

Inheritance of acquired characteristics organisms develop certain characteristics

during their lifetime and pass them on to their offspring.

Example: Giraffe’s long neck due to stretching to reach leaves

Ideas from Geology

Charles Lyell-geologist-suggested Earth far older than originally thought. Evidence: Slow and gradual geological processes

occur over long periods of time cause enormous changes to Earth

Examples building of mountains creation of canyons

Malthus and Population Dynamics Observed more babies born than people

dying Suggests human population growing at a

rapid rate Maintain this pace, eventually run out of

food and living space

TThinkhink-P-Pairair-S-SharehareHow might Malthus ideas

be applied to plants and animals?

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Darwin influenced by Malthus ideas

Applied Malthus ideas to plant and animal populations

Plant and animal populations typically do not become overpopulated. Ex. Orange trees

Suggests certain factors keep population in check disease availability of food and other resources

Charles Darwin

Darwin took a voyage on the HMS Beagle in 1831 Purpose of voyage was to map the

topography of South American coastline As a naturalist, his job was to record and

collect the plants and animals of South America

From these observations developed his theory of evolution which was published in “Origin of Species”

in 1859

Two key ideas published in the

Origin of Species Descent with modification Natural Selection

Descent with modification

Originated from common ancestor Descendants of that ancestor spread into

various habitats and accumulated modifications Modifications were adaptations that allowed

them to live successfully in that environment Occurred over millions of years Descent with modification was driven by

natural selection

Natural Selection

Individuals better suited for the environment Are more fit Survive and successfully reproduce Passing those desirable traits onto their

offspring

Natural Selection requires several factors Genetic variation within the population Environmental selection pressures Ability of the organism to reproduce

TThinkhink-P-Pairair-S-SharehareWhy is reproduction

critical to natural selection and descent with modification?

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Example: Darwin’s Finches

TThinkhink-P-Pairair-S-SharehareExamining the picture of finches,

what was the1. genetic variation2. environmental pressure

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TThinkhink-P-Pairair-S-SharehareWhy is the statement “She

has evolved into a fine pianist” not biologically accurate?

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2 Minute Summary

Over millions of years, the average length of the giraffes’ necks has increased. During the time that this change was taking place, food close to the ground became relatively scarce, but there were always plenty of leaves on the higher branches of trees. Provide the most likely explanation for the giraffes’ long neck

a) according to Lamarckb) according to Darwin