evidences of evolution. fossils zthere are millions of different life forms on earth that have...
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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.