Evolution

Theory of Evolution

Daniel Garvey

What is “evolution”?

• Change in the gene pool of a population from generation to generation by such processes as mutation, artificial/natural selection, and genetic drift.

1785 James Hutton

postulated that the earth was formed by an

ancient progression of natural events,

including erosion,

disruption, and uplift.

Early 1800’s George Cuvier suggested that the earth was

6,000 years old- based on his calculations.

1830 Charles Lyell published

evidence pushing the age of earth

back several million years.

1838 Charles Darwin starts to

theorize on evolution.

1858 Alfred Russell Wallace

publishes similar theory of evolution.

Timeline of Theory

Mutation

• A sudden departure from the parent type in one or more heritable characteristics, caused by a change in a gene or a chromosome.

Natural Selection

• The process where organisms better adapted to their environment tend to survive and produce more offspring.

Artificial Selection

The practice of choosing individuals from a population for reproduction, usually because these individuals possess one or more desirable traits

Genetic Drift

• Process that causes allele frequencies to fluctuate unpredictably from one generation to the next.

Charles Darwinwas a British scientist who laid the foundations of the theory of evolution and transformed the way we think about the natural world.

Wrote the book Origin of Species which established evolution by common descent as the dominant scientific explanation of diversification in nature.

Where did he get this theory?

• A man by the name John Henslow asked Darwin to accompany him (Was in need of a naturalist)

• Went on a voyage on the ship H.M.S Beagle• Which was a five year trip all around the world.• Found evidence to propose a revolutionary

hypothesis about how life changes over time• Evidence included fossils, invertebrates,

vertebrates and closely related species such as plankton and turtles.

H.M.S Beagle Route

The Voyage

• Darwin collected specimens from each place they stopped.

• Included shells, animals, fish, plants and fossils.

• Compared specimens of different origins and realized they had similar structures.

The Galapagos Islands• Darwin was particularly fascinated by this area.• Low, smaller islands are:

-hot and dry -very little vegetation

• Higher, larger islands have:-a variety of plants and animals-more rainfall

• Focused on the native tortoises and marine iguanas.• Tortoises’ shells directly reflected which island they

inhabited.

Patterns of Diversity

• Darwin realized many places have similar ecosystems, but different inhabitants.

• He studied the correlation between fossils found and the organisms alive today.

Glyptodon - lived 2,500,00 to 10,000 years ago

Armadillo - presently lives in the Americas

Thought Process

• He pondered why some plants and animals are extinct; whilst others are emerging from currently unknown origins.

• Theorized that not all of the species were dying but actually adapting and evolving.

Who helped Darwin?

James Hutton: • 1795 Theory of

Geological change– Forces change earth’s

surface shape– Changes are slow– Earth much older than

thousands of years

Who helped Darwin?

Charles Lyell:• Book: Principles of

Geography- Geographical features

can be built up or torn down Darwin thought if earth changed over time, what about life?

Who helped Darwin?

Thomas Malthus 19th century English economist• If population grew (more Babies

born than die)– Insufficient living space– Food runs out– Darwin applied this theory to

animals

Evolution via Natural Selection

• “Survival of the Fittest”

• Some individuals are better suited for the environment.

• Members of each species have to compete for food, water and shelter.

Descent

• Two types– Descent with modification- Each living organism

has descended with changes from other species over time.

– Common Descent- Derived from common ancestors.

Evidence of Evolution

• The Fossil Record– Where fossilized artifacts are embedded into the

Earth’s stratum

Evidence of Evolution

• Geographic Distribution of Living Species– When the world had one main landmass

(Pangaea) and the species migrated to specific areas as the landmass shifted apart.

Evidence of Evolution

• Homologous Body Structures– Body parts that are similar because the said

species share a common ancestor.

Evidence of Evolution

• Similarities in Early Development– Various species have similar structures when in

infancy.

Fish Reptile Bird Human

Evolution of the Skull

Australopithecus(man-ape)

Homo erectus (java man)

Homo sapiens neanderthalensis

(neanderthal man)

Homo sapiens sapiens

(L’homme sage)

Between 2 and 3 million years

ago

750,000 years ago Between 100,000 and 400,000 years ago

40,000 years ago to the

present