Evolution

Fixed Species Concept

The creator had designed each and every species for a

particular purpose.

Result

No evolution. Created the viewpoint that all species could be identified and

named (Taxonomy). A major factor in the Linnaeus

classification system.

Theory Fossils were the remains of

species lost due to catastrophe.

No new species originated; species could only be lost

over time. Result - No evolution.

James Hutton 1795 - Gradualism

Profound change is the cumulative product of slow, but continuous processes.

Result

Changes on the earth were gradual, not catastrophic.

Charles Lyell

1797 - 1875. Incorporated

Hutton’s gradualism into a theory called Uniformitarianism.

Uniformitarianism

Geological processes have operated at the same rate over the Earth’s history.

Result

The Earth must be VERY old. (much older than 6000 years of the fixed species concept). Idea that slow and subtle

processes can cause substantial change.

Jean Baptiste Lamarck

Published theory in 1809. Theory - Life changed from

simple to complex over

time.

Lamarck

Fossils were the remains of past life forms.

Evolution did occur.

Lamarck’s Mechanisms

1. Use and Disuse - Body parts used to survive become larger and stronger.

Body parts not used to survive deteriorate.

Lamarck’s Mechanisms

2. Acquired Characteristics Modifications acquired by

use/disuse were passed on to offspring.

Lamarck’s Mechanisms

3. Natural Transformation of Species ….species changed with every generation… extinction never occurred, organisms simply changed overtime.

Problems with Lamarck’s Theory

No knowledge of genetics. Acquired traits are not

transmitted offspring.

To Lamarck’s Credits

Did suggest correctly the role of fossils in evolution.

Did suggest that adaptation to the environment is a

primary product of evolution.

Charles Darwin

Father of the modern theory of evolution.

Theory - Descent with Modification.

Darwin's Background

Trained as a Naturalist (after trying religion and medicine).

Voyage of the Beagle

Result

Darwin's training and travel opportunities allowed him to formulate and support his ideas on Natural Selection.

Galapagos Finches

Galapagos Islands

Unique animals

Marine Iguana Tortise

Alfred Wallace - 1858

Paper on Natural Selection identical to Darwin's ideas.

Result - July 1, 1858

Dual presentation of the Wallace-Darwin ideas to the Linnaean Society of London.

Darwin - 1859

Publication of "The Origin of Species”

Comment

Darwin best remembered for the theory because of his overwhelming evidence and because he published.

Darwinian View

History of life is like a tree with branches over time from a common source.

Current diversity of life is caused by the forks from common ancestors.

Example

“The Origin of Species”

Documented the occurrence of evolution.

Suggested that the mechanism for evolution was Natural Selection.

The Facts:

Fact 1 - All species reproduce themselves exponentially.

Fact 2 - Most populations are normally stable in size.

Fact 3 - Natural Resources are limited (finite).

Inference 1

The large number of offspring must compete for the finite resources.

Result - Most offspring die.

More FactsFact 4 - No two individuals in a

population are exactly alike.

Fact 5 - Variation is inheritable.

Inference 2

Those individuals whose inherited characteristics fit them best to their environment survive and reproduce.

Inference 3

Offspring inherit the favorable characteristics. Populations shift over time as the favorable characteristics accumulate.

Nature

Determines which characteristics are favorable.

Determines who survives. Result - “Natural Selection”

Natural Selection in action

Artificial Selection

When man determines the characteristics that survive and reproduce.

Result - the various breeds of animals and plants we’ve developed.

Ex - Mustard Plant

Original Cultivars

Evolution Success Measured By

Survival Reproduction Whoever lives long enough

and has kids is the “winner” in evolution.

Requirements

In order for Natural Selection to work, you must have: Long periods of time. Variations within a population.

Subtleties of Natural Selection

1. Populations are the units of Evolution.

2. Only inherited characteristics can evolve.

Comment

Acquired characteristics may allow a species to evolve "outside" of Natural Selection.

Ex: culture, learning

Evidences of Evolution

1. Biogeography

2. Fossils

3. Taxonomy

4. Comparative Anatomy

5. Comparative Embryology

6. Molecular Biology

Biogeography

The geographical distribution of species.

Problem: Species mixtures on islands Marsupials in Australia

Evolution Viewpoint

Biogeographical patterns reflect descent from the ancestors that colonized that area.

Fossils

Relics or impressions of organisms from the past.

Problem: Show changes over time from

simple to complex. Many fossils don't have

descendants.

Evolution Viewpoint

Life has changed over time.

Many species failed to survive and became extinct.

Comments1. Fossilization is a rare event.2. Only hard parts fossilize well.3. Problem in finding fossils.4. Interpretation.5. Missing Links.

Taxonomy Science of Classification.

Main Categories Kingdom Phylum or Division Class Order Family Genus Species

Comparative Anatomy Problems

1. Homologous Structures - Common "building plan” with divergent functions.

Mammal forelimbs

Comparative Anatomy Problems

2. Vestigial Organs - Rudimentary structures of marginal, if any, use.

Whale Legs

Human Example

Evolution Viewpoint

Remodeling of ancestral structures as their functions or adaptations changed.

Comparative Embryology

Problem - closely related organisms go through similar stages in their embryonic development.

Ex: Gill pouches in vertebrates

Evolution Viewpoint

Ontogeny is a replay of Phylogeny. (Development reflects descent)

Molecular Biology

Study of Evolution at the DNA or protein levels.

Problem - related species have similar DNA sequences.

Evolution Viewpoint

Related species share a common ancestrial DNA. The closer the relationship, the more similar the DNA sequences should be.