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Natural Selection. 4.1.2 Outline the mechanism of natural selection as a possible driving force for speciation. What is evolution? What does it mean to you? Do you think it happens? Evidence? (for or against). http://evolution.berkeley.edu/evolibrary/article/evo_25. DEFINITIONS:.

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natural selection

Natural Selection

4.1.2 Outline the mechanism of natural selection as a possible driving force for speciation.

slide2

What is evolution?

What does it mean to you?

Do you think it happens?

Evidence? (for or against)

http://evolution.berkeley.edu/evolibrary/article/evo_25

slide3

DEFINITIONS:

Evolution are the changes in the gene pool of a population over time.

Natural selection process by which individuals that are better suited to their environment survive and reproduce most successfully.

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

slide5

Darwin

Wolf

Pinta

Genovesa

Marchena

Santiago

Bartolomé

Seymour

Råbida

Baltra

Pin zon

Fernandia

Santa Cruz

Santa Fe

Tortuga

San Cristobal

Española

Floreana

EQUATOR

Galåpagos

Islands

Isabela

slide7

Marine Iguana

Land Iguana

darwin s postulates
Darwin’s Postulates
  • Variation within populations.
  • Overproduction of offspring.
  • Struggle for existence.
  • Unequal survival and reproduction rates. (Those with traits more likely to help them survive will pass traits to their offspring)
what is a species
What is a species?
  • A group of individual organisms that are capable of reproducing and produce viable offspring.
  • When organisms can no longer reproduce or do not produce viable offspring then they are no longer the same species.
slide11

KONA FINCH extinct

KAUAI AKIALAOA

AMAKIHI

LAYSAN FINCH

IIWI

AKIAPOLAAU

APAPANE

MAUI PARROTBILL

fruit and seed eaters

insect and nectar eaters

FOUNDER SPECIES

slide13

Population of organisms

Mutations & Sexual reproduction produces variations among offspring.

Overproduction of offspring

Limited resources leads to a struggle for survival between offspring.

Survivors reproduce more successfully.

Population changes over time.

slide14

The Genetic Makeup of a Population Can Change

  • Populations evolve by becoming genetically different
  • Genetic variations
    • First step in biological evolution
    • Occurs through mutations in reproductive cells
    • Mutations in other cells can happen , but only reproductive cell mutations are passed on
    • Sometimes a mutation can result in a new genetic trait that gives it a better chance to survive, sometimes not.
slide15

Can a fish species willfully grow limbs and fingers if they are needed to crawl out of the water onto dry land?

slide16

Individuals in Populations with Beneficial Genetic Traits Can Leave More Offspring

  • Natural selection: acts on individuals
    • Second step in biological evolution
    • Adaptation may lead to differential reproduction
    • Genetic resistance in bacteria, cockroaches
  • When environmental conditions change, populations
    • Adapt
    • Migrate
    • Become extinct
slide17

A group of bacteria, including genetically resistant ones, are

exposed to an antibiotic

Eventually the resistant strain

replaces the strain affected by

the antibiotic

The genetically resistant bacteria

start multiplying

Most of the normal bacteria die

Normal bacterium

Resistant bacterium

evidence supporting evolution1
Evidence Supporting Evolution

Homologous Structures

evidence supporting evolution2
Evidence Supporting Evolution

Vestigial Structures

activity
Activity:
  • Choose an online natural selection simulation.
  • Work through the simulation and discuss the strengths and weaknesses of the simulation with regard to modeling natural selection.
  • In your own words, explain how a new species forms.

http://www.techapps.net/interactives/pepperMoths.swf (requires flash)

http://www.sciencechannel.com/games-and-interactives/charles-darwin-game.htm

http://phet.colorado.edu/en/simulation/natural-selection (requires shockwave)