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