Natural Selection

Natural Selection:Natural Selection:

A process by which characteristics that make an individual better suited to it's environment become more common in the species.

Sometimes referred to as “survival of the fittest”

How Does Natural Selection work?How Does Natural Selection work?

1. Those with the unique characteristics best suited for their environment will survive and produce offspring.

2. End result = ADAPTATIONS

English Peppered Moth –Natural English Peppered Moth –Natural selection in actionselection in action

camouflaged mothdark moth - random mutationnot as common

Soot covered treeEngland 1800’s

Shell for protectionShell for

protection

AdaptationsAdaptationsBehaviors or physical characteristics that

allow organisms to live successfully in their environment

Long neck to reach leavesLong neck to reach leaves

Long shallow roots, needles to protect from

animals

Long shallow roots, needles to protect from

animals

NicheNicheAn organisms’ role in an ecosystem = niche.Niche and Habitat are different

◦ Address of an organism = Habitat◦ “Job” or “Profession” = Niche

Habitat = Forest

Niche = produce oxygen provide home for birds

Organism = tree

Explain why two organisms Explain why two organisms cannot occupy the same niche:cannot occupy the same niche:

If two species occupy the exact same niche in nature, one will die off due to competition for limited resources.

http://www.youtube.com/watch?v=D1aRSeT-mQE

Video Link – Niche, Competition, Predation, and Symbiosis

Three major types of Three major types of interactions among organisms:interactions among organisms:

CompetitionPredationSymbiosis

Competition:Competition:

The struggle between organisms to survive as they attempt to use the same limited resources.

Predation:Predation:

An interaction in which one organism kills another for food.

Predator or Prey:Predator or Prey:

Predator - organism that does the killing

Prey – organism that is killed.

Effect of predation on population Effect of predation on population size:size:

What variable is plotted on the x-axis? ______

What two variables are plotted on the y-axis? ________ and __________

years

# of moose

# of wolves

Effect of predation on population Effect of predation on population size:size:

How did the moose population change between 1965 and 1972 ___________

How did the wolf population change between 1973 and 1976? __________

It increased

It increased

Effect of predation on population Effect of predation on population size:size:

How might the change in moose population have lead to the change in wolf population?– The wolf preys on

the moose so more moose meant more food for the wolf.

Effect of predation on population Effect of predation on population size:size:

How might disease in the wolf population one year affect the moose population the next year?– Disease in the wolf

population might cause some to die. With less predators, the moose population would most likely increase.

Examples of Predator AdaptationsExamples of Predator Adaptations

Cheetah speedOwl eyes Jelly fish venom

Defense Strategies of PreyDefense Strategies of Prey

MimicryProtective Covering False ColoringWarning colorCamouflage

Video Link on Predator and Prey Interactions

http://www.youtube.com/watch?v=vZynrBA91fY

Interactions – Three Types Interactions – Three Types

Symbiosis – a close relationship in nature Symbiosis – a close relationship in nature that benefits at least one speciesthat benefits at least one species

Termites

Bacteria from gut of termite

SymbiosisSymbiosis

MutualismMutualismBoth species benefit

CommensalismCommensalism

One species benefits, but the other isn’t harmed or helped.

ParasitismParasitism

One species benefits and the other is harmed.

The one benefiting is the parasiteThe one being harmed is a host