CHAPTER 15 DARWIN’S THEORY

OF EVOLUTION

Before Darwin?

“Natural Theology”

Began to explain the origins of fossils

1. Use and disuse of parts

2. Inheritance of “acquired characteristics”

Mechanism for evolution adaptations:

“Stretching” Problem?

Jean Baptiste Lamarck (1809)

“change linked to physical changes in environment”

CHARLESDARWIN

-Father of Modern Evolutionary Theory

-21 years old:“naturalist”

HMS BEAGLE

1831-1836

5 year Mapping expedition

“Collect specimens”

GALAPAGOSISLANDS

Support a great biodiversity

Giant Tortoise Marine Iguana

Sally Light Foot Crab

Blue Footed Booby

Finch

Penguin

While on the Beagle, Darwin read Charles Lyell’s Principles of Geology??

Life?

Earth has “changed” slowly over a “long period of time”

Endemic, but resemble species on SA mainland

“Volcanic”

Colonized from mainland Diversified on different islands

13 types of FinchesBeak adaptations to food available

In 1844, he wrote a long essay on the origin of species and natural selection

Reluctant to publish

Continued to compile evidence to support his theory (22 years).

In June 1858, Alfred Russell Wallace sent

Darwin a manuscript containing

a theory of natural selection essentially

identical to Darwin’s.

“Darwinism”

November 24, 1859

Within a decade: “Science = Biological diversity due to evolution”Avalanche of Evidence

Darwin envisioned the diversity of life as evolving by

1. A gradual accumulation of minute changes

2. Through the actions of natural selection

3. Operating over vast spans of time.= Darwinism

The Darwinian view of life has two main features.

(1) The diverse forms of life have arisen by descent with modification from ancestral species.

(2) The mechanism of modification has been natural selection working over enormous tracts of time.

1. “Descent with modification”

Common Ancestor

= all present day organisms are related through descent from unknown ancestors in the past

Common Ancestor

“Dead Ends”

About 99% of all species thathave ever lived are extinct

Descendents accumulated diverse modifications/ adaptations that fit them to specific ways of life/ habits

Essay on human population by Thomas Malthus in 1798.

Suffering - disease, famine, homelessness, war

Population > food supply/ resources =

“Struggle for Existence”

“Competition” for?

Food, Space, Predation, Mates

2. The theory of Natural Selection

Unique mechanism of evolution

“Adaptation”

“Individuals that have physical or behavioral traits that bettersuit their environment are more likely to survive/reproduce”

Driven by?

Artificial Selection

Selecting individuals with the desired traits as breeding stock.

Natural selectionNature?

Nature selects for the “strong” phenotype

Less FavorableVariations =EXTINCT

Struggle for Existence

Genetic Variation

Adaptation

Evolution

Population

Natural Selection

Gene Pool

Speciation

Competition

Reproductive Isolation

Mutations

EVOLUTION KEY TERMS

Evolution

EXAMPLES OF NATURAL SELECTION?

MUTATIONS!!!!

Alexander Flemming 1952

Physiological Adaptation = changes in metabolic processes Penicillin

Resistant Bacteria

Evolution of drug resistance in HIV

3TC affects viral enzymes “reverse transcriptase”

Evolution of insecticide resistance in insect populations

Initial?

Gene Frequency?

What helps?

Enzymes

Not Creating!!

Mimicry = copy the appearance of another species

Palatable Unpalatable

Camouflage = blend in with surroundings

Cephalopod

Frogfish

Homology?

Similarity in characteristics resultingfrom common ancestry

Homologous StructuresSame structure but different function (modified)

ANATOMICAL HOMOLOGIES:

Anatomical imperfections

Back and knee problems

Boa and Python Families

Whales and Dolphins

Vestigial Organs

Why reduced in use?

Mole-Rat

Continues to be inherited

Embryological Homologies

Molecular Homologies

“Genetic Code”

BiogeographySpecies of close local are more closely related than similar species (way of life) elsewhere

ANALOGOUS STRUCTURE

Same Function =Different Structure

Sugar glider marsupial mammal (Australia)

Flying squirrel eutherians/placental mammal (North America)

Adapted to same way of life, but different ancestors.

= Kangaroo

Convergent Evolution= distantly related organisms evolve similar traits

Steam-line bodies

Occupy similar environment

Divergent Evolution= species once similar become more and more distinct

Small extremitiesRetain heat

Large extremitiesLose heat

“ADAPTIVE RADIATION”

END

EVOLUTIONOF

SPECIES

Species = look alike, interbreed, produce fertile offspring

Speciation = evolution of a new species

“Transitional Forms”

Geographic Isolation• = a physical barrier separates a

population into groups

Prevent Interbreeding

Tree frogs in Amazon Basin

Deforestation

Gene Pool Changes

KaibabAbert

Grand Canyon

Reproductive Isolation

= past interbreeding organisms are preventedfrom producing fertile offspring

Mating Behavior

ZebroidsSterile

Gene Pool Closed

Major episodes that shaped life as a phylogenetic tree

Fossil Record?

“Tetrapods”Fins Limbs

Lobed-Fin FishesGills and Lungs (underdeveloped)

Fleshy Lateral Fins

Coelacanth

Amphibian Reptile

Tim

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“Genetic Variation”

“Competition”

WOLF (like) WHALE

“Limited Resources”

“Struggle for Existence”

“Differential reproduction”

“Gene Frequency”

“Survival of the Fittest”“Adaptation”

“Natural Selection”

Transitional/ Intermediate forms

?

“Just a theory”?

“There is grandeur in this view of life;with its several powers having been originallybreathed by the Creator into a few forms orinto one; and that, whilst this planet has gonecycling on according to the fixed law of gravity,from so simple a beginning endless forms most wonderful and most beautiful have been,and are being evolved.”