EvolutionChapter 13

“A change over time”

http://www.youtube.com/watch?v=-FT3FU2XOgo

http://www.hulu.com/watch/403434#details=expand

The Theory of Evolution Evolution literally means to change over

time. A theory is a well supported, testable

explanation that observes observations from the natural world

Questions that evolution attempts to answer. How do species adapt to changes in the

environment? How do new species develop?

Charles Darwin

1809-1882 Studied to be a doctor

and a minister 1831 sailed around the

world as a naturalist on the HMS Beagle

HMS Beagle

Darwin’s Voyage

Galapagos Islands

Galapagos Islands

15-2 Darwin’s Influences

James Hutton Geologist Proposed that the earth was

millions of years old based on geologic evidence

Sir Charles Lyell

Geologist Proposed that geologic

changes occur slowly over long periods of time.

Darwin read his book, Principles of Geology, on the Beagle

Jean Baptiste Lamarck

French Naturalist

Published his ideas on evolution in 1809 in Philosophie zoologique

Lamarck’s Hypothesis

Organisms Strive for Perfection – all individuals are trying to better themselves

Lamarck’s HypothesisUse and Disuse –

If an individual uses a trait it will be more useful

If an individual does not use a trait it will decrease in usefulness

Lamarck’s Hypothesis

Inheritance of Acquired characteristics

Analyzing Lamarck’s Hypothesis There is no evidence to suggest that plants

and animals are trying to improve themselves

Analyzing Lamarck’s Hypothesis Use and disuse do not change all

characteristics Stretching will not make you taller Reading will not make your eyesight better

Analyzing Lamarck’s Hypothesis Acquired characteristics are not inherited

A mouse that loses its tail will still produce offspring with tails

Erasmus Darwin

Charles Darwin’s Grandfather

Physician and Scientist

'All vegetables and animals now living were originally derived from the smallest microscopic ones.'

Thomas Malthus –

Economist Human Population would be

limited Starvation War (Competition) Disease

15-3 Darwin Presents His Case

Alfred Wallace Developed his own theory

of Natural Selection Contacted Darwin This caused Darwin to

finally publish his theory with Wallace

On Origins of Species After publishing with

Wallace, Darwin submitted all of his ideas in a book titled On Origin of Species, By Means of Natural Selection in 1858

Artificial Selection Darwin was influenced to believe change

was possible because of the humans selecting for traits in plants and animals.

Darwin’s Theory

Evolution “Change” is driven by natural selection

Summary of Darwin’s Theory

Variation There are differences within a population

Mutation and Sexual Reproduction

Competition for resources Not all offspring will survive

Starvation Overcrowding Predation

Fitness Some of the variants will have an

advantage over the others, they will survive and produce more offspring

Reproduction and Inheritance These advantages will be passed on to the

next generations

Descent with Modification Species alive today are descended with

modification from ancestral species

Tree of Life All species are connected on a single tree

of life

Modern Theory Mendel’s discoveries in genetics explained

a great deal in evolution

Evidence for Evolution Fossil Record Anatomy Development Molecular Evidence

Fossil Record Since most of the “ancestor” species are

extinct, fossils are the only evidence that can be examined.

Intermediate “missing link” fossils are very informative

Archaeopterix

A fossil of a bird like creature

Has feathers, teeth and claws in its wings

Whale Ancestors http://www.youtube.com/watch?

v=lx079oEgKKs

Anatomy

Structures similarities in body structure indicates organisms are related

Homologous StructuresStructures that have common function and design (ancestry)

Vestigial Organs

Structures that have reduced size and or function

http://www.youtube.com/watch?v=pbc7ee9u1JE

Developmental Evidence Similarities in embryonic development are

interpreted to mean closer relationships.

Developmental Evidence Similarities in embryonic development are

interpreted to mean closer relationships.

Molecular Evidence

Organisms are considered to be more closely related if

DNA sequences in genes are more similar

Amino acid sequences in proteins is more similar

Molecular Evidence

Organisms are considered to be more closely related if

DNA sequences in genes are more similar

Amino acid sequences in proteins is more similar

Strengths of Darwin’s Theory

Many discoveries in Physics, Geology and Biology have supported and expanded Darwin’s ideas

Strengths of Darwin’s Theory

Many discoveries in Physics, Geology and Biology have supported and expanded Darwin’s ideas

Weaknesses of Darwin’s Theory Researchers still debate how new species

arise and how they become extinct. The origin of life is still very uncertain

Evolution of Populations

Chapter 14

Genes and Variation Variation – differences between individuals

of a species Produced by two processes

Mutation – random changes in DNA Sexual Reproduction- combining genes from two

gametes

Single Gene Traits Several traits are controlled by a single

gene and are either dominant or recessive.

Polygenic Traits Poly-genic means “many genes” Most traits are controlled by several genes

and can show up in many different forms.

Normal Curve Most individuals are intermediate, extremes

are less common

Microevolution Micro – small Microevolution is change within a species Gene Pool – all of the genes in a population Allele Frequency – how many times a

certain allele shows up in the population

Microevolution

Any change in Allele frequency in a population is considered microevolution

English Peppered MothThe English Peppered MothThe moth was usually white with dark spotsDuring the Industrial Revolution (1850’s) soot

covered many of the white barked treesMore and more dark colored moths appeared

at the same timeKettlewell’s experiments suggested this was

due to natural selection

English Peppered MothThe English Peppered MothThe moth was usually white with dark spotsDuring the Industrial Revolution (1850’s) soot

covered many of the white barked treesMore and more dark colored moths appeared

at the same timeKettlewell’s experiments suggested this was

due to natural selection

Microevolution in Humans

Sickle Cell Anemia is a recessive (hh) disease found mainly in Africa

A carrier (Hh) for the disease has resistance to malaria

Delta 32 Mutation Delta 32 mutation occurs in 10-15% of

whites of European descent This mutation gave resistance to the plague Most of the people without this allele died of

the plague causing the allele frequency to rise

The mutation also gives resistance to HIV infection

Selection Selection can be one of 3 forms

Directional Stabilizing Disruptive

Stabilizing Selection

Both Extremes are selected against The population is stabilized

Directional Selection One of the extremes is selected against,

the population shifts away

Disruptive Selection The most common variation is selected

against spitting the species two groups

Genetic Drift In small population individuals may pass on

more genes by chance. This is called genetic drift.

Large populations are not affected by genetic drift

Genetic Drift

Population 18

9 Heads

9 Tails

Population 18

6 Heads

12 Tails

Can a species stop evolving?

Hardy Weinberg equilibruim

in order for evolution of a species not to occur

(all allele frequencies stay the same)

5 evolutionary forces must not act

Hardy Weinberg Equilibrium

Populations do not evolve if there is

Random Mating

no movement into or out of the population

no genetic drift, large population

no natural selection

no mutation

16-3 The Process of Speciation Speciation –the production of a new

species Species – a group of individuals that

reproduce in nature and produce fertile offspring

Isolation – the factor that prevents the new species from reproducing with the ancestral species

Behavioral Isolation Mating songs or rituals are different, so the

two species don’t interbreed

Behavioral Isolation Groups are not attracted to each other for

mating

Geographic Isolation Groups are physically separated and no

longer interbreed

Temporal Isolation Groups reproduce at different times of day

or year

Mechanical Isolation Structural differences prevent mating

between individuals of different groups

Ecological Isolation Groups are adapted to different habitats,

hybrids aren’t adapted well to either

Reproductive Failure Mating between groups fail to produce

fertile offspring

Speciation Continued Once populations are isolated, different

pressures select different traits When the populations will no longer

interbreed, new species have been formed

Natural Selection - 2 forms Ecological Selection – better suited to

survive in the environment Sexual Selection –

Males compete for access to females Females select males with “good gene” markers

Sexual Dimorphism Dimorphism di-morph-ism

Two forms Males are usually larger Males would have ornaments (antlers, manes,

colors)

Patterns of Evolution

Macro Evolution

Macro – Large

Idea that species can split to form new species

All life forms are related through a common ancestor

Divergent Evolution

Similar species develop different adaptations to different environments

Convergent Evolution

Two species develop similar adaptations to the same environment.

Coevolution Two or more species adapting to each

other

Rate of Evolution Slow and Steady or in Spurts?

Gradualism – the idea that small changes build up slowly over time to produce large changes.

Expectations – many intermediate “missing link” fossils

Punctuated Equilibrium

The idea that populations go through periods of stability followed by short periods of rapid change.

Expectations – fewer intermediate fossils

Endosymbiont Theory

Endo –inside Symbiont – symbiotic “mutualistic”

relationship

Endosymbiont Theory

This theory suggests that mitochondria and chloroplasts were once independent living organisms

These organisms were “eaten” by larger cells, but remained alive

Endosymbiont Theory

Evidence for endosymbiosis Each mitochondrian has its own circular chromosome of DNA Very similar to a bacteria Reproduce on its own Ribosomes are very similar to bacterial ribosomes