Evolution:Evolution:

Evidence of Change & How Change Occurs

Evidence of Change & How Change Occurs

EvolutionEvolution- Change over time- Process where modern organisms have descended from ancestors with modifications

Early Evolutionary

IdeasEarly Evolutionary

Ideas1.1.LamarckLamarck

- among the first to explain how organisms

change over time

- later disproved

- relied on 2 assumptions:

1.Use and disuse2.Inheritance of

acquired traits- both later disproved

LamarckLamarck

2. Charles Darwin(1809-1882)

2. Charles Darwin(1809-1882)

- developed the theory of evolution by natural

selection

- traveled around the world as a naturalist (1831-1836)

Galapagos wildlife

Darwin’s Finches & their Darwin’s Finches & their foodfoodDarwin’s Finches & their Darwin’s Finches & their foodfood

Large seeds Small seeds

Insects

Leaves

Evolution by Natural SelectionEvolution by Natural Selection- Natural

Selection is the result of 3 natural processes:

1. Natural Variation:1. Natural Variation:- all organisms produced sexually

are genetically different due to gene recombination and mutations

Variation in Human Height

2. AdaptationThis natural variation or mutation may be an adaptation that helps them outcompete others to survive and reproduce.

Male caribou competing for mates.Male caribou competing for mates.

2. Competition2. Competition- resources (food, space,

water) - mates- constant struggle for

existence - winners reproduce

Gazelles struggling to reach food.Gazelles struggling to reach food.

.Natural Selection or survival of the fittest.Natural Selection or survival of the fittest

- Those best suited will survive longer and reproduce.

- Those not suited will not survive or reproduce as often.

3. Heredity3. Heredity- Those that survive

will pass on the very traits that helped it survive.

WoodpeckerWoodpecker

Artificial SelectionArtificial Selection- similar to natural selection

- domestic crops and animals vary a lot

Artificial SelectionArtificial Selection

Artificial SelectionArtificial Selection- only the best animals or

plants are allowed to produce offspring

Artificial SelectionArtificial Selection

Recent Examples of EvolutionRecent Examples of Evolution

1.Peppered Moths1.Peppered Mothsa. Before industrial

revolution, most moths were grayish and well camouflaged.

b.During the industrial revolution, soot stained the bark black.- Rarer dark moths were then better camouflaged.

- The more common light mothswere easily seen and eaten.

c.Dark moths had greater fitness and became more common.

2.Resistant Diseases & Pests

2.Resistant Diseases & Pestsa.Increased resistance to

antibiotic by bacteriab.Insects have become more

resistant to pesticides

Resistant Pests

C. SpeciationC. Speciation- development of one

species from another species

C. SpeciationC. Speciation

Kaibab Squirrel Abert Squirrel

1. Process of Speciation1. Process of Speciation

a.Separation of original population by a geographic barrier

b.Changed environmentc. Gene pool changesd.Reproductive isolation

- two populations can no longer interbreed

e.New species arises

Barrier removed; mix but don’t interbreed

Genetic drift; tan vs white mice

Geographical barrier;isolated populations

Single species; Same habitat Speciati

on

(a)

(b)

(c)

(d)

2.Divergent Evolution (Adaptive Radiation)

2.Divergent Evolution (Adaptive Radiation)- ancestral population

evolves into several different species

2. Adaptive Radiation2. Adaptive Radiation

Hawaiian Honeycreepe

rs

2. Adaptive Radiation2. Adaptive Radiation

3. Convergent Evolution3. Convergent Evolution

- different organisms evolve similar adaptations to survive in similar niches- develop analogous structures

(similar function with different underlying anatomy)

3. Convergent Evolution3. Convergent Evolution

3. Convergent Evolution3. Convergent Evolution

European Hare(lagamorph))

Patagonian “Hare”(rodent)

Banded Wallaby(marsupial)

3. Convergent Evolution3. Convergent Evolution

Tasmanian “Wolf” Coyote

Placentals MarsupialsPlacentals Marsupials

Tasmanian“Wolf”

Wolf

QuollOcelot

NumbatAnteater

FlyingPhalanger

FlyingSquirrel

Wombat

Marmot

3. Convergent Evolution3. Convergent Evolution

American CactusAmerican Cactus African EuphorbAfrican Euphorb

D. Evolutionary Theory Evolves

1.Genetic Drift- random changes in allele

frequency produce new traits

D. Evolutionary Theory Evolves

1. Genetic DriftMasai Giraffe Rothschild Giraffe

Reticulated Giraffe

Chambered Nautilus

D.Evolutionary Theory Evolves2.Unchanged Gene Pools

- "living fossils": sharks, horseshoe crabs, coelacanth

Coelacanth

Horseshoe CrabHorseshoe Crab

3. Gradualism:3. Gradualism:- slow change over time

4.4.Punctuated EquilibriumPunctuated Equilibrium- periods of little change, followed by abrupt change

Gradualism Punctuated Equilibrium