Intro to Natural Intro to Natural SelectionSelection

Sept 2008Sept 2008

“Survival of the fittest”

Get set: What have you Get set: What have you learned?learned?

• Survival depends on: Survival depends on: – Being able to obtain adequate amount of Being able to obtain adequate amount of

food and water.food and water.– Being able to protect one’s self from Being able to protect one’s self from

predation.predation.– Having characteristics to deal with the Having characteristics to deal with the

environment (climate, soil, plants, other environment (climate, soil, plants, other animals.)animals.)

– Being able to reproduce to keep the Being able to reproduce to keep the species alive.species alive.

What happened to the animals What happened to the animals in round 1 of the Staying Alive in round 1 of the Staying Alive

simulation?simulation?

• Toothpickta could not obtain enough food Toothpickta could not obtain enough food when climate changes affected their natural when climate changes affected their natural food source.food source.

• Toothpickta became extinct.Toothpickta became extinct.

What happened to What happened to the animals in round the animals in round 2 of the Staying Alive 2 of the Staying Alive

simulation?simulation?• Tweezarian had slight variations in Tweezarian had slight variations in

their pinchers.their pinchers.

• Variations (mutations) are random – Variations (mutations) are random – some are helpful, some are not.some are helpful, some are not.

• Those with the helpful variation thrive Those with the helpful variation thrive and the tweezarian population and the tweezarian population eventually all display the “improved” eventually all display the “improved” variation. variation.

What happened to What happened to the animals in round the animals in round 3 of the Staying Alive 3 of the Staying Alive

simulation?simulation?

•Non-native species can be invasive.Non-native species can be invasive.

•Native plant/animals can be Native plant/animals can be affected when non-native species affected when non-native species are introduced.are introduced.

•Over-feeding can cause a disaster Over-feeding can cause a disaster for the entire ecosystem. for the entire ecosystem.

A scientific ExplanationA scientific Explanation

• A theory is based on a A theory is based on a number of observations or number of observations or experiments.experiments.

• A theory attempts to A theory attempts to explain natural explain natural phenomenon.phenomenon.

Natural SelectionNatural Selection

•the process by which individuals that are better adapted to their environment survive and reproduce more successfully than less well-adapted individuals do.

What does the theory say?

Variations happen by

chance

Some variations are helpful; some

harmful

helpful variations =

survival

Those who survive, pass

traits to young

Charles Charles Darwin Darwin

• An English naturalistAn English naturalist

• studied animals on Galapagos studied animals on Galapagos IslandIsland

• Wrote the famous book: Wrote the famous book: On On the Origin of Species by the Origin of Species by Means of Natural SelectionMeans of Natural Selection..

• Had a major impact on Had a major impact on scientific community.scientific community.

SPECIATIONSPECIATION

• THE THE FORMATION OF NEW SPECIESFORMATION OF NEW SPECIES

• AS NEW SPECIES DEVELOP, AS NEW SPECIES DEVELOP, POPULATIONS BECOME POPULATIONS BECOME REPRODUCTIVELY ISOLATEDREPRODUCTIVELY ISOLATED

• REPRODUCTIVE ISOLATIONREPRODUCTIVE ISOLATION – MEMBERS – MEMBERS OF 2 POPULATIONS CANNOT OF 2 POPULATIONS CANNOT INTERBREED & PRODUCE FERTILE INTERBREED & PRODUCE FERTILE OFFSPRING.OFFSPRING.

Table 23.1aTable 23.1a

These squirrels live on opposite sides of the Grand Canyon. This is an example of allopatric speciation.

Table 23.1bTable 23.1b

Fig. 23.6Fig. 23.6

Four species of leopard frogs: differ in their mating calls. Hybrids are inevitable.

Hawaiian HoneycreepersHawaiian Honeycreepers

FOUNDER SPECIES

An example of adaptive radiation – these species all diverged from a common ancestor (founder species)

SPECIATION IN DARWIN’SSPECIATION IN DARWIN’S

FINCHESFINCHES• SPECIAITON IN THE GALAPAGOS SPECIAITON IN THE GALAPAGOS

FINCHES OCCURRED BY: FINCHES OCCURRED BY:

- - FOUNDINGFOUNDING OF A NEW POPULATION, OF A NEW POPULATION, - - GEOGRAPHIC ISOLATION GEOGRAPHIC ISOLATION which led to which led to -- -- REPRODUCTIVE ISOLATIONREPRODUCTIVE ISOLATION and and

CHANGES IN THE NEW POPULATION’S CHANGES IN THE NEW POPULATION’S GENE POOL due to COMPETITION.GENE POOL due to COMPETITION.

Can species combines in new

and different ways today?

http://www.nps.gov/archive/chis/rm/IslandFox/index.htm

TigonTigonResult of male tiger and female lion mating in captivity. Offspring are infertile.

Separated both geographically and ecologically.

LigerLiger

Result of male lion and female tiger mating in captivity. Offspring are infertile.

Closure: Summarize What Closure: Summarize What you’ve learned:you’ve learned:

•Name 4 parts of Natural Name 4 parts of Natural Selection.Selection.

•Explain how speciation can Explain how speciation can occur.occur.