“Nothing in biology makes

sense except in light

of evolution”

-Theodosius Dobzansky

“Nothing in biology makes

sense except in light of

evolution”

Viewed evolution as "a

change in the frequency of

an allele within a gene pool“

His Idea: that it is through

mutations in genes that

natural selection takes place.

Theodosius Dobzansky

The History of

Evolutionary Thought

Aristotle (384-322 B.C.)

Ladder of Life 2 types of animals

– those w/ blood &

those w/o

Animals classified by their

way of life

Plants by structure

Observation of various

marine life anatomy was

remarkably accurate

Distinguished whales

from dolphins

•Linnaeus was classifying organisms based on what they looked like.

•This made it difficult to classify organisms that seemed to share characteristics with both kingdoms that Linnaeus proposed, Plants andAnimals.

• For example, fungi including mold and mushrooms do not move (or do they?) so they seem to be plants but, unlike plants…..?????

Lion Cat Dog Man Catbird

Phylum Chordata Chordata Chordata Chordata Chordata

Class Mammalia Mammalia Mammalia Mammalia Aves

Order Carnivora Carnivora Carnivora Primata Passeriformes

Family Felicidae Felicidae Canidae Hominidae Minidae

Genus Felis Felis Canus Homo Dymetella

Species leo domesticus carolinensis sapiens familiaris

Classifying organisms often

starts at the cellular level

Cladistics (phylogeny)

A system of classification

based on the study of

evolutionary relationships

history of groups of organisms.

Primate Evolution

An Example of Cladogram Construction for Vertebrates

Trait Outgroup

(lobed-

finned fish)

Frog Turtle Kangaroo Mouse Human

Dorsal

Nerve

Cord

Yes Yes Yes Yes Yes Yes

Legs NO Yes Yes Yes Yes Yes

Nature of

EggRequires

water

Requires

water

Hard shell

prevents

drying

Develops

inside the

mother

Develops

inside the

mother

Develops

inside the

mother

Nature of

developmentIn egg In egg In egg Marsupial Placental Placental

Hair No No No Yes Yes reduced

Presence

of pouch

No No No Yes No No

Bipedal

posture

No No No Yes No Yes

Georges-Louis Buffon

(1707-1788)

Buffon questions a 2,000

yr. dogma 100 yrs. before

Darwin

Openly suggests the earth

is older than 6,000 years

Supported a concept

similar to Lyell’s

uniformitarianism

Multiple Centers of

Creation

Jean-Baptiste Lamarck

(1744-1829)

His name is associated

merely w/ a discredited

theory of heredity – he

died in obscurity &

poverty

Darwin & Lyell give him

great credit

Law of use/disuse

Law of acquired

characteristics

LAMARCK’S THEORY

ACCORDING TO DARWIN…

Thomas Malthus (1766-1834)

1798 wrote “Essay on the Principle of Population”

Humans have the tendency to outgrow their food supply

Forces that work against this, war, famine, and disease

Darwin read essay and thought this reasoning applied more strongly to animals and plants

Sir Charles Lyell (1797-1875)

British geologist

Wrote Principles of

Geology

Showed that the earth was

very old and changed its

form slowly (i.e. erosion)

Dated the age of rocks by

using fossils embedded in

stone as time indicators

How Lyell’s work helped Darwin

Darwin witnessed volcanic eruptions

Darwin witnessed an earthquake that raised a rocky shoreline 3m above its original position

Noted fossils of marine life many feet above sea level

This understanding of geology

influenced Darwin in 2 ways:

First, Darwin asked himself: If the Earth could

change over time, might life change as well?

Second, he realized that it would have taken many,

many years for life to change in the way he

suggested. This would have been possible only if

the Earth were extremely old

James Hutton (1726-1797)

Layers of rock are

moved by forces

beneath the earth’s

surface

Proposed the earth had

to be much older than

a few thousand years

Hutton’s Theory of Geological

Change

Some rocks twist and

bend

Others are buried and

others are pushed up from

the sea floor

Resulting rocks are shaped

by natural forces

These processes operate

extremely slowly over the

course of millions of years

Alfred Wallace (1823-1913)

Studied the way

geography limited or

facilitated the extension of

species range

How ecology influenced

the shaping of adaptations

In 1858, shared with

Darwin on the Theory of

Evolution by means of

Natural Selection

Charles Darwin (1809-1882)

Voyaged around the

world 1831-1836

Wrote On the Origin

of Species which

reveals his ideas on

Evolution by means of

Natural Selection

Natural Selection Summarized:

Darwin’s theory suggests that in a species:

There is a tendency towards overproduction

Variation exists

Variations are inherited

Individuals survive in their environments with varying degrees of success

Best adapted, survive and pass favorable variation on to next generation

In time, great differences arise, until a new species evolved from an old species

Biological Fitness

What is biological fitness???

Survival of the Fittest….

Fitness - the genetic

contribution of an

individual to

succeeding

generations relative to

the contributions of

other individuals in

the population

Coevolution: Mutual evolutionary influence between two species

•Typically evolution of two species totally dependent on each other.

•Exert selective pressure on the other, so they evolve together.

•Extreme example of mutualism.

Homologous Structures

Structures that have different

mature forms in different

organisms but develop from the

same embryonic tissues.

.

A kind of evolution

wherein organisms evolve

structures that have

similar structures or

functions in spite of their

evolutionary ancestors

being very dissimilar or

unrelated.

These structures are

referred to as analogous.