Evidences of Evolution

Fossils

There are millions of different life forms on earth that have evolved over time.

Some clues to the type and structure of organisms remain in the form of fossils.

Fossils: Remnants or traces of organisms of a past geologic age.

Aging Fossils

Fossils found in deeper, and therefore older, layers of sedimentary rock are generally simpler in body structures than fossils found in younger layers.

Stacking Newspapers.

Comparative Anatomy

Homologous Structures: Structures which come from different organisms yet have the same evolutionary origion.

Forelimbs

The Methods Of Change

Lamarck’s Theory (1809) “Inner need” to change Inheritance of acquired

characteristics (based on use and disuse)

The Methods of Change

Darwins Theory 1859Naturalist on HMS Beagle which

Explored South America (3 1/2 years)

Visits the Galapagos IslandsCame up with the theory of

Natural Selection.

Principles of Natural Selection

1. Living things increase in number geometrically (overproduction).

2. There is no net increase in the number of individuals over a long period of time

3. A “struggle for existence” since not all individuals can survive

Principles of Natural Selection

4. No two individuals are exactly alike (variation)

5. In the struggle for existence those variations which are better adapted to their environment leave behind them proportionately more offspring than those less adapted (Survival of the Fittest)

Species

A group of individuals that LOOK similar and are capable of producing FERTILE offspring in the natural environment.

Population

All of the members of the same SPECIES that live in particular AREA at the same TIME.

Variation in a population

Bell Curve - The distribution of traits (Average is the middle.)

Mode - The number that occurs most often (High pt.)

Range - The lowest number to the highest number

Gene pool

The collection of GENES for all of the traits in a POPULATION

Hardy-Weinberg Principle

Genetic Equilibrium – no CHANGE in the gene pool

Conditions that must exist for genetic equilibrium

1. No MUTATION 2. No MIGRATION3. Large POPULATION 4. Random MATING 5. No NATURAL SELECTION

Natural Selection

Four types of selection1. Stabilizing Selection2. Directional Selection3. Disruptive Selection4. Sexual Selection

Stabilizing Selection

Individuals with the AVERAGE form have the ADVANTAGE.

This type of selection reduces variation in a population

Directional Selection

Individuals with one of the EXTREME forms have the ADVANTAGE

This type of selection favors one of the extreme variations of a trait and can lead to the rapid evolution of a population

Disruptive Selection

Individuals with either of the EXTREME forms have the ADVANTAGE

This type of variation favors both extreme variations of a trait, resulting eventually in no intermediate forms of the trait and leading to the evolution of two new species.

Sexual Selection

Preferential choice of a MATE based on the presence of a specific trait

Speciation

The formation of new SPECIES

Isolation

Separation of a formerly successful BREEDING population

Geographic Isolation

Separated PHYSICALLY from each other

Reproductive Isolation

Can no longer produce FERTILE offspring.

Extinction

When an entire SPECIES dies off.