Evolution ppt

(1)

Evolution:

Why Are There So Many

Living Things?

(2)

Where Did the Idea of Evolution Come

From?

• Middle Ages:

– “Ladder of Life”

• Complex organisms found at highest rungs • Less complex at lower

rungs

• Everything perfect – no need for evolution

• 1800’s

– Georges Cuvier brought study of fossils to the level of science.

(3)

Where Did the Idea of Evolution

Come From?

• Charles Lyell (French Geologist)

– Proposed theory of uniformitarianism by interpretting fossil evidence. Believed

geological changes take place slowly.

• Jean-Baptiste Lamarck

(4)

Charles Darwin

• Loved nature

• Studied medicine

– Struggled with the inhumane operating procedures

• Switched to religion • Offered position as naturalist on British survey ship, The

(5)

Voyage around the World

• Studied animals and fauna.

• Noticed South American fossils differed from

contemporaries.

• Collected data for 27 years to support his mechanism for

(6)

Fathers of Evolution

• Alfred Wallace studied in Brazil and East

Indies.

• Developed mechanism of evolution

independently of Darwin.

• Sent a copy of it to Darwin.

– Contained same conclusions as Darwin

• Both presented their data at Linnaean

(7)

How Did Darwin Account for

Species?

• In Origin of Species, he developed two main concepts

– Evidence that evolutions has occurred.

(8)

Major points of Darwin’s theories of

evolution and natural selection

• First observation:

– Populations have the potential to increase

exponentially.

(9)

• Second observation:

(10)

• Third observation:

– Natural resources are limited.

• Limited amount of space, nutrients, shelter

(11)

Major points of Darwin’s theories of

• Deduction one:

– Only some organisms survive. There is a struggle for existence among individuals in a population.

• Organisms posses characteristics that enhance survival

(12)

Three Types of Adaptations

•

Morphological-anatomical:

modifications

in form and structure that enhance

survival.

•

Biochemical-physiological:

modifications

in the production and use of chemicals by

organisms.

•

Behavioral Adaptations:

Modifications in

(13)

• Fourth observation:

(14)

• Deduction two:

– Individuals with

favorable variations are more likely to

survive and reproduce.

• Natural Selection:

– “preservation of

(15)

Major points of Darwin’s theories of

• Deduction three:

– Accumulation of

inheritable variation

over many generations is evolution.

• If changes within a

species become great enough, a new

(16)

What is a species?

• Species are considered extinct if they do not interbreed in nature.

(17)

Evidence supporting Theory of

Evolution

• Selective breeding

practices used by farmers result in:

– “improved”

domesticated plants and animals.

(18)

Evidence supporting theory of

evolution

• Fossil record

(19)

evolution

• Homologous structures

– Structures dissimilar in form and function.

• but share underlying structural similarities

(20)

Evidence supporting theory of

evolution

• Analogous structures – Structures similar in

form and function.

(21)

evolution

• Biochemistry

– Organisms are made of molecules and studying the molecules can help us

understand possible relationships.

– Example: Proteins

• Made of amino acids bonded together.

– Similar to a strand of pearls.

(22)

Evidence supporting theory of

evolution

• Comparative Embryology

– Similarities in embryos of organisms help us to identify common ancestors and recognize similarities as organisms develop.

– Example:

• All vertebrates follow a common

(23)

(24)

Patterns in Evolution

• Convergent evolution

(25)

• Divergent evolution

– Closely related species living in different

environments and facing different environmental challenges sometimes evolve dissimilar

(26)

Patterns in Evolution

• Adaptive radiation

– Sometimes, several species will evolve from a single,

(27)

• Coevolution

– Evolution of one species affects the evolution of another species.

• As predators evolve, prey evolves. As prey evolves, predators evolve.

– Example: Cheetahs feed on Thompson’s gazelles

(28)

• Gradualism

– Evolution may occur as a slow, gradual process of change.

(29)

Patterns in Evolution

• Punctuated equilibrium

– Evolution may proceed with long periods of relatively little change (stasis) punctuated with short periods of intense change.

– Examples: House flies, trilobites,

(30)

Evolution does not always occur

• Natural selection can only work on existing variation.

• Variation cannot be created on demand. • Some species lack

(31)

Results of evolution

• Everywhere we look on the Earth, you can

find organisms.

– Scientists have described 1.5 millions species

• Still many species yet to be described.

(32)

Darwin recognizes three special

cases of natural selection

• Sexual selection explained flamboyant appearance amongst birds.

– Sexual selection: female birds choose mates and are attracted to males with extreme features.

(33)

Darwin recognizes three special

cases of natural selection

• Altruism

– Individual behavior

benefits a social group often at the expense of the individual.

• Example: worker bees in a hive

• Kin Selection

(34)

Evolution & Genetics

• Evolution is simply a change of

frequencies of alleles in the gene pool of a

population.

• It is the minor changes within a species

from generation to generation over long

periods of time that can result in the

(35)

Evolution will not occur if these

conditions are met

1. _{mutation is not occurring}

2. _{natural selection is not occurring} 3. _{the population is infinitely large}

4. _{all members of the population breed} 5. _{all mating is totally random}

(36)

Microevolution

– changes within a species

Mutations

Genetic Drift

• Founder Effect • Bottleneck Effect

Gene Flow

• Migration

• Natural Selection • Non-random

(37)

Mutations

can be beneficial or harmful

1.

DNA base substitution, insertion, and

deletion

2.

unequal crossing-over and related

structural modifications of chromosomes

3.

partial or complete gene inversion and

duplication

(38)

(39)

Stabilizing Selection

– favors the norm, the average trait within

populations (i.e. siberian husky weight)

Directional Selection

– favors the extreme variations within populations (i.e. greyhound speed)

Disruptive Selection

– sudden change in environment forces the favor of an extreme variation within a

(40)

(41)

(42)

Gene Flow

genes being transferred from one population to another

Migration/Emigration Migration/Emigration

•Moving into or out of an area

•Ex. If all red haired

individuals left Scotland you would see less of this trait in future

generations and more of it in other area

populations

Non-random mating

•People select mates non-randomly (sexual selection)

•Animal breeders try to improve breeds

(43)

Small Population Size Effects

• In small,

reproductively

isolated populations, special circumstances exist that can produce rapid changes in gene frequencies totally

independent of

mutation and natural selection.

• These changes are due solely to chance factors. The smaller the population, the more susceptible it is to such random

(44)

(45)

Founder Effect

• Small amount of people have many descendants surviving after a number of generations. • Results in high frequencies of

specific genetic traits inherited from few common ancestors (or “founder”)

(46)

Bottleneck Effect

• Some form of

catastrophe occurs

• Large # of population

dies

• Survivors reproduce

in large quantity

(47)

Pinegelap

Island

 Typhoon in 1775 killed 90% of Pinegelap Island(thereby

eliminating most of the genetic variation)

 _{One of the 20 survivors was a}

man named Nahnmwarki Mwanenised. He had

achromatopsia, (rare recessive eye condition of color blindness & extreme sensitivity to light.

 _{6 generations later, nearly 5% of}

the island's population had achromatopsia. (All descendents of Nahnmwarki Mwanenised.)

 By comparison, only 1 in 33,000 people in the United States have it.

mutation

natural selection

random