Evolution of LifeEvolution of LifeHow Organisms How Organisms

SurviveSurvive

What Is Necessary To What Is Necessary To Survive?Survive?

• VariationVariation is an appearance of an inherited trait or behavior that makes one organism differentdifferent from others in the same species.

• AdaptationsAdaptations are variations that make an organism betterbetter able to survive.

VariationsVariations vs. vs. AdaptationsAdaptations

How Does Evolution How Does Evolution Work?Work?

•Natural selectionNatural selection is the process where the organisms that are better better adaptedadapted to their environment are more likely are more likely to surviveto survive and reproduce.

Charles Darwin Charles Darwin Theory of Natural Theory of Natural

SelectionSelection

• Charles DarwinCharles Darwin is credited as is credited as discovering the mechanism, or tool, discovering the mechanism, or tool, for evolution to occur. He called this for evolution to occur. He called this the the theory of natural selection.theory of natural selection.

• His theory can be summarized as His theory can be summarized as “survival of the fittest”.“survival of the fittest”.

Theory of Natural Theory of Natural SelectionSelection

1. Organisms produce more offspring than can survive. Ex. Tree seeds, salmon eggs.

2. Variations exist within populations.3. Some variations are more

advantageous for survival. The struggle to survive results in competition.

4. Over time only those individuals with advantageous variations will survive and reproduce.

Natural SelectionNatural Selection

Species Are Always Species Are Always ChangingChanging

• EvolutionEvolution is the change in the change in the hereditary featureshereditary features of a population of organisms over time.

• When a species changes it is said to have evolvedevolved.

How Do Species How Do Species Change?Change?

• A mutationmutation is a permanent changea permanent change in a gene or chromosome that changes the organism in some way.– Ex. Size, shape, color, behavior, etc.

• Some mutations are harmful.• Some mutations are beneficial.

MutationsMutations

MutationMutation vs. vs. AdaptationAdaptation

• Only beneficial Only beneficial mutationsmutations are are adaptationsadaptations because these provide an advantageadvantage to survival.

MutationMutation vs. vs. AdaptationAdaptation

What Evidence Is There What Evidence Is There Of Evolution?Of Evolution?

• Evolution of species is evident in:• FossilsFossils• Cell StructuresCell Structures• DNADNA• Homologous StructuresHomologous Structures• EmbryosEmbryos• Shared CharacteristicsShared Characteristics

FossilFossil Evidence of Evidence of EvolutionEvolution

• FossilsFossils are remains of life from earlier times.

• FossilsFossils are usually found in rock layers that provide a time reference:– Youngest (most recent) layers are on

top.– Oldest layers are on the bottom.

• FossilsFossils provide evidence about the past climates and/or landscapes.

Fossil EvidenceFossil Evidence

Cell Structure Cell Structure Evidence of Evidence of EvolutionEvolution

• Studying cell structurescell structures shows similarities between organisms.

• A comparison of ancient and modern cells shows similarities in cell membranes and cytoplasms.

Cell Structure EvidenceCell Structure Evidence

DNADNA as Evidence of as Evidence of EvolutionEvolution

• Studying DNADNA shows more similarities between organisms.

• The more similar the DNADNA, the more closely related the species are.

• Ex. The DNADNA of Gorillas and Humans are ~92% similar whereas the DNADNA of any two humans is 99.9% similar.

DNA EvidenceDNA Evidence

Homologous StructuresHomologous Structures as Evidence of as Evidence of

EvolutionEvolution• Homologous structuresHomologous structures are body body

partsparts of different organisms that that areare similar in origin and similar in origin and structurestructure.

• Ex: human arm, bird wing, bat wing, and dolphin flipper all have similar bone structure and function and show the relatedness of the species.

Homologous StructuresHomologous Structures

Homologous

Structures

EmbryoEmbryo Evidence of Evidence of EvolutionEvolution

• Studying the similarity seen in the embryosembryos of vertebrates shows that they share a common ancestor.

Embryo EvidenceEmbryo Evidence

Shared CharacteristicsShared Characteristics as Evidence of as Evidence of

EvolutionEvolution• PrimatesPrimates are a group of

mammals, including monkeys, apes and humans, that share many characteristics.

• For example, they share:– Opposable thumbs– Flexible shoulders– Binocular vision

Opposable ThumbsOpposable Thumbs