Theory of Evolution

Chapter 15

TheoryScienceScience = Hypotheses that = Hypotheses that

pass testing. Highest honor in pass testing. Highest honor in science.science.

Common UsageCommon Usage = An idea, = An idea, not necessarily supported not necessarily supported with facts or tests.with facts or tests.

How did living things achieve so much

variety?

Answer:

Changes in DNA (mutations!)

Gradualism vs. Punctuated Equilibrium

GradualismGradualism- small mutations that occur - small mutations that occur frequently.frequently.

Punctuated EquilibriumPunctuated Equilibrium- many mutations that - many mutations that occur all at onceoccur all at once

Jean Baptiste Lemarck

Use and disuse.Use and disuse.

A giraffe’s neck is long after many generations of A giraffe’s neck is long after many generations of giraffe’s stretching their necks.giraffe’s stretching their necks.

Can you see what is Can you see what is wrongwrong with this???? with this????

Endler• Experimented with GuppiesExperimented with Guppies..• Without predators… Without predators…

• increaseincrease in male guppies with large in male guppies with large and brightly colored tails, because and brightly colored tails, because they are favored by females.they are favored by females.

• With predators…With predators…• decreasedecrease in male guppies with large in male guppies with large

and brightly colored tails, because and brightly colored tails, because the flashier fish are eaten by the flashier fish are eaten by predators.predators.

Charles Darwin Rode in Rode in HMS HMS BeagleBeagle along coastal along coastal

South America.South America.

Noticed Noticed varietyvariety in tropical life. in tropical life.

Survival of the fittest.Survival of the fittest.

All life is linked from a common All life is linked from a common ancestor. ancestor.

Darwin never used the word ‘evolution.’

Did you know…

Darwin’s Voyage

Galapagos Islands

Galapagos Islands--A laboratory for evolutionary biology

DARWIN‘S

FINCHES

Darwin’s Theory of

Natural Selection There is There is variationvariation within a population. within a population. Some variations are Some variations are goodgood (helpful). (helpful). Not all young produced in a Not all young produced in a

generation can survive!generation can survive! This leads to a This leads to a strugglestruggle for existence. for existence. Survival of the fittest.Survival of the fittest. Those that survive and reproduce are Those that survive and reproduce are

those with the those with the bestbest variations for variations for thatthat specific environment.specific environment.

Species Group of Group of similarsimilar organisms. organisms.

Can Can interbreed successfullyinterbreed successfully in nature. in nature. Offspring are healthyOffspring are healthy Offspring are fertile (can reproduce)Offspring are fertile (can reproduce)

These organisms are not new species…Why?

MuleMule LigerLiger

Answer…

They are sterile! (Cannot produce children.)

Speciation Evolution of Evolution of severalseveral species species

from 1 ancestor species. from 1 ancestor species.

Can be from isolation.Can be from isolation.Geographic isolationGeographic isolationReproductive isolationReproductive isolation

Geographic Isolation Organisms are separated by a barrier. Organisms are separated by a barrier.

Islands that have broken apart.Islands that have broken apart. Earthquake produces a large crack.Earthquake produces a large crack.

Reproductive Isolation

Organisms that used to Organisms that used to breed breed don’t any longerdon’t any longer..

Many Reasons…Many Reasons… They now make They now make

sterile offspring.sterile offspring. They now mate in They now mate in

different seasons.different seasons.

Mutations are Mutations are successfulsuccessful if if they help the organism they help the organism

survive and produce survive and produce fertile offspringfertile offspring!!

Evidence for Evolution

FossilsFossils DNA similaritiesDNA similarities Homologous StructuresHomologous Structures Similar embryo Similar embryo

developmentdevelopment

Fossil Evidence The age of fossils can be determined by radioactive The age of fossils can be determined by radioactive

decay OR by dating rocks around them.decay OR by dating rocks around them. Fossils of Fossils of simplersimpler organisms are found in organisms are found in olderolder rocks. rocks. Fossils of Fossils of more complexmore complex organisms are found in organisms are found in newernewer

rocks.rocks.

Fossil Evidence

How fossils are “made”…

Fossil Evidence

Dating Fossils

Fossil Evidence

1. Amount is constant (100% 14C) while alive.

2. Organism dies.

3. 14C amount declines (due to radioactive decay) when organism dies.

Fossil Evidence

14Carbon Dating

DNA Similarities

DNA Evidence

The more similar the DNA, the more The more similar the DNA, the more closely related organisms are.closely related organisms are. Your DNA is closer to your sister’s than Your DNA is closer to your sister’s than

your cousin’s.your cousin’s. Your DNA is closer to a pig than a duck.Your DNA is closer to a pig than a duck.

Similarities in DNA show how closely

related organisms are to each other.

DNA Evidence

ComparinComparing g chromosochromosomes of mes of humanshumans and and chimpanzchimpanzeeee

DNA Evidence

Chromosomes:

Human

Chimpanzee

Gorilla

Orangutan

DNA Evidence

Hominoid Cladogram: Hominoid Cladogram: Lengths and positionsLengths and positions of arrow lines reflect the: of arrow lines reflect the:

# of chromosome changes# of chromosome changes relative timingrelative timing likely relationship likely relationship

‘‘A’ refers to the A’ refers to the AncestralAncestral origin. origin. DNA

Evidence

Humans did NOT evolve from apes!

We had a We had a similar ancestorsimilar ancestor and BOTH of us and BOTH of us evolved from that ancestor.evolved from that ancestor.

It’s no wonder that we have many of the It’s no wonder that we have many of the same DNA sequences!same DNA sequences!

DNA Evidence

Homologous Structures

Similar bone structures.Similar bone structures.

Homologous Evidence

Similar Embryo Development

Embryos in all animals go Embryos in all animals go through similar stages.through similar stages.

Humans even produce Humans even produce pharyngeal slits that are pharyngeal slits that are not seen later.not seen later.

Embryo Evidence

Other Stuff…

Analogous Structures

Similar function evolves Similar function evolves separatelyseparately!!

2 Versions of the Hominoid Family Tree

                                 

Lucy Discovered in 1974.Discovered in 1974. 3.2 million year old 3.2 million year old

bones.bones. Almost half of her Almost half of her

bones were found!bones were found!

Ethiopia (in Africa)Ethiopia (in Africa)

3 feet, 8 inches tall!3 feet, 8 inches tall!

Evolution Observed: Peppered Moths

Light moths

Dark moths

Less pollution More pollution

Opposition to the Theory of Opposition to the Theory of EvolutionEvolution

• Evolutionary theory, more than Evolutionary theory, more than any other scientific theory, is any other scientific theory, is regularly challenged.regularly challenged.

• Much of the objection comes Much of the objection comes from a from a mistaken viewmistaken view of what a of what a scientific scientific theorytheory represents. represents.

– Some of the evidence for evolution is historical in nature, and cannot be demonstrated experimentally.

– Consistency in the evidence derived from many sources, using many methods, from within biology (e.g., embryology, biochemistry) and from other disciplines (geology, nuclear chemistry), for more than a hundred years has convinced most scientists that the core principles of evolution accurately describe the story of life on Earth.

The End

Observation #5 Much of this variation is heritable.Much of this variation is heritable.

Survival is not random, but depends in part on Survival is not random, but depends in part on the hereditary constitution of the surviving the hereditary constitution of the surviving individuals. Those individuals whose inherited individuals. Those individuals whose inherited characteristics fit them best to their characteristics fit them best to their environment are likely to leave more offspring environment are likely to leave more offspring than less fit individuals.than less fit individuals.

This unequal ability to survive and reproduce This unequal ability to survive and reproduce will lead to a gradual change in a populationwill lead to a gradual change in a population