EvolutionEvolution• The processes that have

transformed life on earth from it’s earliest forms to the vast diversity that characterizes it today.

• A change in the genes!!!!!!!!

The one scientist who is most well known for evolution is

Charles Darwin

He did not reach this conclusion on his own…

Ideas that helped shape Ideas that helped shape DarwinDarwin’’s thinkings thinking

• James Hutton – Theory of geological change. • He proposed that the earth is shaped by geological forces

that took place over extremely long periods of time. He estimated the earth to be millions of years old, not thousands (as previously thought).

• This idea led Darwin to realize that if the earth was millions of years old (not thousands), it would mean there was enough time for organisms to evolve.

Ideas that helped shape Ideas that helped shape DarwinDarwin’’s thinkings thinking

• Charles Lyell published “Principles of Geology”.

• Explained that the processes occurring now have shaped earth’s geological features over long periods of time. These processes are still changing earth today.

• This idea led Darwin to realize that if the earth could change then so could life

Ideas that helped shape Ideas that helped shape DarwinDarwin’’s thinkings thinking

• Jean Baptiste Lamarck (early 1800’s) proposed:“The inheritance of acquired characteristics”

• He proposed that by using or not using its body parts, an individual tends to develop certain characteristics, which it passes on to its offspring.

Ideas that helped shape Ideas that helped shape DarwinDarwin’’s thinkings thinking

• First scientist to propose a mechanism for how organism change.

• HE WAS

WRONG!!!

Ideas that helped shape Ideas that helped shape DarwinDarwin’’s thinkings thinking

• Thomas Malthus – Predicted that the human population will grow faster than the space and food supplies needed to sustain it.

• This same prediction applies to organisms in nature as well and leads to competition among them

Charles DarwinCharles Darwin• With this information in his mind Darwin set sail

on the H.M.S. Beagle (1831-1836) to survey the south seas to collect plants and animals.

• On the Galapagos Islands, Darwin observed species that lived nowhere else in the world.

Charles DarwinCharles Darwin• Even though the islands are fairly close

together they have different environments. Varying from lush jungle to bare volcanic land.

Charles DarwinCharles Darwin• In these different environments Darwin

found different types of animals– Finches were very different on each island– Tortoises had very different necks on each

island

• Charles Darwin is credited with the theory of evolution, but scientists knew that organisms change over time before Darwin…..what Darwin really came up with is the mechanism for change (HOW organisms changed over time)

Darwin’s observations on the Galapagos and his knowledge that things change over time led him to write a book….

Charles DarwinCharles Darwin

Charles DarwinCharles Darwin• Wrote in 1859: “On the Origin of Species

by Means of Natural Selection”

• Two main points:1. Species were not created in their present form, but evolved from ancestral species.

2. Proposed a mechanism for evolution: NATURAL SELECTION

Natural SelectionNatural Selection• Individuals with favorable traits are

more likely to leave more offspring better suited for their environment.

Example: Peppered moth•Has both dark and light types

Natural SelectionNatural Selection• Overtime, natural

selection results in changes in the inherited characteristics of a population.

• These changes increase a species fitness (survival rate)

Natural SelectionNatural Selection• Natural selection is also sometimes called “survival of

the fittest". In this case, “fittest” does not necessarily mean fastest, strongest, etc… “Fittest” simply means the organism has a trait that helps it survive and reproduce (called an adaptation)

• If you are a turtle “fittest” might mean strongest shell

• If you are a chameleon “fittest” might mean best camouflage

Artificial SelectionArtificial Selection• The selective breeding of domesticated The selective breeding of domesticated

plants and animals by man.plants and animals by man.• nature provides variation, humans select nature provides variation, humans select

variations that are useful. variations that are useful. • Example - a farmer breeds only his best Example - a farmer breeds only his best

livestocklivestock

Evidence of EvolutionEvidence of Evolution

1. Fossil Record:1. Fossil Record:

Fossils, and the order in which they appear in layers of sedimentary rock, show the history of life on earth and how different groups of organisms have changed over time

Evidence of EvolutionEvidence of Evolution2.2. Biogeography: Biogeography:

Geographical distribution of Geographical distribution of species. species. Similar animals in different locations were the product of different lines of descent

Evidence of EvolutionEvidence of Evolution3. Homologous Structures: 3. Homologous Structures: Structures that are similar because of common ancestry.

e.g. Wing of bat, human arm, leg of turtle

Provides strong evidence that all four-limbed animals have descended, with modifications, from a common ancestor

Evidence of EvolutionEvidence of Evolution3. Homologous Structures:3. Homologous Structures:.Not all homologous structures serve important functions. The organs of many animals are so reduced in size that they are just vestiges, or traces, of homologous organs in other species. These vestigial organs are organs that serve no useful purpose in an organism

e.g. pelvic bones in whales, appendix, wisdom teeth and coccyx in humans

Evidence of EvolutionEvidence of Evolution4. Comparative embryology:4. Comparative embryology:

In their early stages of development, chickens, turtles and rats look similar, providing evidence that they shared a common ancestry.

Evidence of Evidence of EvolutionEvolution

Evolution can be observed all around us…..