Theory of Evolution

““Nothing in biology makes sense Nothing in biology makes sense EXCEPT in the light of evolution.” EXCEPT in the light of evolution.”

--Theodosius DobzhanskyTheodosius Dobzhansky

Early Evolutionary Thought

James Hutton Suggested

Gradualism Gradual change

over a long period of time leads to species formation

Early Evolutionary Thought

Gould and Eldredge Suggested Punctuated

Equilibrium A successful species may

stay unchanged for long periods of time.

Major environmental changes may have caused evolution to occur in spurts

Early Evolutionary Thought

Jean-Baptiste Lamarck, 1809 Suggested the Law of Use and

Disuse One Of First Scientists To

Understand That Change Occurs Over Time

Organisms Could Change The Size Or Shape Of Organs By Using Them Or Not Using Them

Early Evolutionary Thought Lamark

Stated that Changes Are Adaptations To Environment acquired in an organism’s lifetime

Said acquired changes were passed to offspring If body part NOT used, it deteriorated

Early Evolutionary Thought

Thomas Malthus Wrote that human

populations are able to increase faster than what the food supply can.

We do not because of disease, war and famine.

Early Evolutionary Thought

Charles Darwin Naturalist aboard the HMS Beagle

Traveled for 5 years around the world Made observations and collected

samples Eventually landed on the Galapagos

Islands where he made several observations that impacted his Theory of “Descent with Modification”.

The Galapagos Islands

Small Group of Islands 1000 km West of South America

Very Different Climates

The Galapagos Islands

Animals On IslandsTortoisesIguanasFinches

Natural Selection

When visiting on the Galapagos Islands Darwin noticed: Individuals that have physical or

behavioral traits that better suite their environment are more likely to survive and reproduce.

This theory is called Natural Selection

Natural Selection Finches

Darwin noticed that there were a number of different types of finches

All finches had physical traits that allowed them to adapt to their environment.

For example if a finch lived on a part of the island that was abundant in flowering plants then the finches beak would be long and thin so that it could drink nectar.

Natural vs. Artificial Selection

Natural Selection A mechanism for change in populations. Occurs when organisms with favorable variations

survive, reproduce, and pass their variations to the next generation.

Organisms without these variations are less likely to survive and reproduce.

Artificial Selection Breeding organisms with specific traits in order to

produce offspring with identical traits

Evidence of Evolution

Anatomy Homologous

Structures Structural features with

a common evolutionary origin

Can be similar in arrangement, in function, or in both.

Evidence of Evolution

Analogous StructuresBody parts of

organisms that do not have a common evolutionary origin but are similar in function

Evidence of Evolution

Vestigial Structures Body structure in a

present-day organism that no longer serves its original purpose, but was probably useful to an ancestor.

Evidence of Evolution Embryology

Study of the earliest stage of growth and development of both plants and animals

The embryos of a fish, a reptile, a bird, and a mammal have a tail and pharyngeal pouches

suggest evolution from a distant, common ancestor

Fish Reptile Bird Mammal

Pharyngealpouches

Pharyngealpouches

Tail Tail

Evidence of Evolution

Biochemistry Provides strong

evidence for evolution. Comparing the same

hemoglobin protein in several species reveals a pattern.

Species that share a common ancestor more recently have fewer amino acid differences.

Adaptations

Three major adaptations exist in nature: Mimicry

A structural adaptation that enables one species to resemble another species.

Because a yellow jacket looks so much like a honeybee it’s predators often mistake it for it’s twin and stay away.

Adaptations

Camouflage Adaptation that enables

species to blend with their surroundings

Because well-camouflaged organisms are not easily found by predators, they survive to reproduce.

Adaptations

Physiological Adaptations Changes in an organism’s metabolic

processes Evolve much more rapidly. For example, some of the medicines

developed during the twentieth century to fight bacterial diseases are no longer effective

Antibiotic Resistance

When the population is exposed to an antibiotic, only the resistant bacteria survive.

The bacteria in a population vary in their ability to resist antibiotics.

The resistant bacteria live and produce more resistant bacteria.

Formation of a New Species Speciation

Process by which new species form Reproductive Isolation

Two populations of the same species do not breed with one another because:

Geographic separation Difference in mating periods Other barrier to reproduction.