EvolutionEvolution

OverviewOverview

EvolutionEvolution

Evolution is change over timeEvolution is change over time It was first studied by Charles Darwin (1831)It was first studied by Charles Darwin (1831)

He travelled on the HMS Beagle to the Galapagos He travelled on the HMS Beagle to the Galapagos Islands and came back with many samples of the Islands and came back with many samples of the diverse speciesdiverse species

He noticed that the species varied from island to He noticed that the species varied from island to islandisland

This lead to his theory of evolutionThis lead to his theory of evolution

EvolutionEvolution

One of Darwin’s most important insigts was One of Darwin’s most important insigts was that members of each species vary from one that members of each species vary from one another in important ways.another in important ways. Ex.) some plant species bear larger fruit than Ex.) some plant species bear larger fruit than

othersothers From breeders, he learned that some of that idea From breeders, he learned that some of that idea

was was heritable variationheritable variation- meaning differences are - meaning differences are passed from parents to the offspring passed from parents to the offspring caused by caused by variation in the genesvariation in the genes

Artificial SelectionArtificial Selection

This idea came from the idea that breeders This idea came from the idea that breeders select only the “best”select only the “best”

Artificial SelectionArtificial Selection nature provides the nature provides the variation and humans select the variations they variation and humans select the variations they find the most useful.find the most useful. Ex.Ex.: horses, dogs, crops, etc. : horses, dogs, crops, etc.

Natural SelectionNatural Selection

A process that takes place without humans A process that takes place without humans controlling it or the direction of itcontrolling it or the direction of it

Involves the idea of “Involves the idea of “survival of the fittestsurvival of the fittest”, ”, ““struggle for existence”struggle for existence”, , adaptationadaptation, and , and fitnessfitness..

Struggle for ExistenceStruggle for Existence

High birth rates among animals and a shortage of life’s basic High birth rates among animals and a shortage of life’s basic needs forces organisms into a competition for resourcesneeds forces organisms into a competition for resources

This includes: food, living space, and other necessitiesThis includes: food, living space, and other necessities Predator-Prey relationshipPredator-Prey relationship

FitnessFitness

A key factor in the A key factor in the struggle for existence is struggle for existence is how well suited an how well suited an organism is to its organism is to its environment.environment.

The ability of an The ability of an individual to survive individual to survive and reproduce in its and reproduce in its specific environment is specific environment is called fitness.called fitness.

AdaptationAdaptation

Any inherited characteristic that increases an Any inherited characteristic that increases an organism’s chance of survival.organism’s chance of survival.

Enable organisms to become better suited to Enable organisms to become better suited to their environment and this better able to their environment and this better able to survive and reproducesurvive and reproduce

Can be anatomical, structural characteristics, Can be anatomical, structural characteristics, physiological process, and behavior physiological process, and behavior

Survival of the FittestSurvival of the Fittest

Idea that individuals with characteristics that Idea that individuals with characteristics that are no well suited to their environment (low are no well suited to their environment (low levels of fitness) either die or leave few levels of fitness) either die or leave few offspring. Individuals that are better suited to offspring. Individuals that are better suited to their environment (have adaptations that their environment (have adaptations that enable fitness) survive and reproduce most enable fitness) survive and reproduce most successfullysuccessfully

Main Point of Natural SelectionMain Point of Natural Selection

Overtime, natural selection results in changes Overtime, natural selection results in changes in the inherited characteristics of a population. in the inherited characteristics of a population. These changes increase a species’ fitness in its These changes increase a species’ fitness in its environment.environment.

Descent with ModificationDescent with Modification

Over long periods of time, natural selection produces Over long periods of time, natural selection produces organisms that have different structures, establish organisms that have different structures, establish difference niches, or occupy different habitats. As a difference niches, or occupy different habitats. As a result, species today look different from their result, species today look different from their ancestors. ancestors. Each living species has descended, with Each living species has descended, with changes, from other species over time.changes, from other species over time.

This idea leads to the other idea that all living This idea leads to the other idea that all living organisms are related to one another and is known as organisms are related to one another and is known as common descentcommon descent. .

Evidence for EvolutionEvidence for Evolution

Darwin suggests that all living things have Darwin suggests that all living things have been evolving on Earth for millions of years.been evolving on Earth for millions of years.

Evidence can be found: Evidence can be found: Fossil record, Fossil record, geographical distribution of living species, geographical distribution of living species, homologous structures of living organisms, homologous structures of living organisms, and similarities in embryology.and similarities in embryology.

Fossil RecordFossil Record

By comparing fossils from older rock layers with By comparing fossils from older rock layers with fossils from younger rock layers, you can document fossils from younger rock layers, you can document the fact that life on Earth has chaged over time. the fact that life on Earth has chaged over time.

Youngest fossils are found closest to the top of the Youngest fossils are found closest to the top of the earth’s crust, and oldest farther downearth’s crust, and oldest farther down

There are gaps in the fossil record, but that proves the There are gaps in the fossil record, but that proves the idea that we still don’t know how certain organisms idea that we still don’t know how certain organisms have evolved. This changes everyday that new fossils have evolved. This changes everyday that new fossils are found. are found.

Geographic DistributionGeographic Distribution

Species now living on difference continents Species now living on difference continents had each descended from different ancestors. had each descended from different ancestors. However, because some animals on each However, because some animals on each continent were living under similar ecological continent were living under similar ecological conditions, they were exposed to similar conditions, they were exposed to similar pressure of natural selection. Because of those pressure of natural selection. Because of those similar pressures, different animals ended up similar pressures, different animals ended up evolving certain striking features in common.evolving certain striking features in common.

Homologous Body StructuresHomologous Body Structures

Amongst species, certain structures have Amongst species, certain structures have different forms but develop from the same different forms but develop from the same embryonic tissues. They have the same basic embryonic tissues. They have the same basic structure but different functions.structure but different functions. Ex. Bird Wings and Reptile limbs or Bat Wings Ex. Bird Wings and Reptile limbs or Bat Wings

and human Handsand human Hands

Vestigial StructuresVestigial Structures

Not all homologous structures serve important Not all homologous structures serve important functions. The organs of some animals are so functions. The organs of some animals are so reduced in size that they are traces of reduced in size that they are traces of homologous organs in other species. These are homologous organs in other species. These are known as known as vestigial structuresvestigial structures. .

EmbryologyEmbryology

The embryos of many animals with backbones The embryos of many animals with backbones is very similar. is very similar.

It is clear that the same groups of embryonic It is clear that the same groups of embryonic cells develop in the same order and in similar cells develop in the same order and in similar patterns to produce the tissues and organs of patterns to produce the tissues and organs of all vertebrates. These common cells and all vertebrates. These common cells and tissues, growing in similar ways, produce the tissues, growing in similar ways, produce the homologous structures!homologous structures!

SpeciationSpeciation

Isolating MechanismsIsolating Mechanisms

Reproductive IsolationReproductive Isolation Behavioral IsolationBehavioral Isolation Geographical IsolationGeographical Isolation Temporal IsolationTemporal Isolation