How did humans evolve?
I. Early Theories
A. Jean Baptiste de Lamarck (1809)- thought that these evolutionary changes in animals were caused by their need to adapt to changes in the environment; his theory involved 2 principles
1. the law of use & disuse- assumed the more a body part is used, the stronger & better it becomes; just the opposite for body parts that are not frequently used
2. inheritance of acquired characteristics- assumed that the characteristics an organism developed through use & disuse could be passed on to its offspring
B. August Weismann (1870's)- scientists don't know for sure but genes are not affected by an individual's life experiences or activities; Weismann best proved this
1. cut tails of mice for 22 generations; hence, acquired characteristics of shortened tails were not inherited
II. Modern Theory- based partially on Darwin's concept of natural selection
A. Charles Darwin (1830's) made several observations; the most significant were on the Galapagos Islands (1000 miles off the coast of Ecuador) and develop his theory of evolution
1. Natural Selection- organisms with favorable variations would be better able to survive & reproduce than organisms with less favorable variations
2. Overproduction- species population remain constant because only a small fraction survive long enough to reproduce
3. Competition- living space & food are limited organisms have to compete with their own species and others
4. Variation- differences that exist within a species; such as, shape, strength, resistance to disease, & others
5. Adaptations- because of variations some organisms are better adapted to survive & then reproduce which would then perhaps pass on that trait to improves that individuals chances for survival
6. Speciation- formation of a new species; one of the most important factors involved in speciation is isolation caused by
a. Geographic isolation- occurs when a population is divided by a natural barrier, hence, a mountain, river, desert or ocean
B. Problems with Darwin's theory
1. it doesn't explain how variations originate
2. doesn't distinguish between variations caused by hereditary differences & variations caused by the environment, which are not inherited
III. Rates of Evolution- today scientists are not sure on a rate which evolution or species formation
A. Gradualism- according to Darwin, evolution occurs slowly & continuously over millions of years
B. Punctuated Equilibrium- according to Steven J. Gould & Niles Eldredge (newer theory), species remaining in constant or in Equilibrium over a long period of time and then the Equilibrium is interrupted, or punctuated by a short period of rapid evolution
1. fossil records supports this idea
2.
IV. The Synthetic Theory of Evolution- modern biologists have combined Darwin's basic theory with the findings of genetics & population biology to form this theory which states evolution happens to populations, not individuals. "EVOLUTION IS NOW DEFINED AS A CHANGE IN THE ALLELE FREQUENCY WITHIN A POPULATION OVER TIME."
A. Population- a group of organisms of the same species living together in a given region and are capable of interbreeding
1. Gene frequency- in a certain population, there are a certain number of alleles of each kind. All individuals may have a copy of some allele in a population; therefore, 100% is the frequency. Mutations sometimes occur & the gene frequency will account for this.
2. Gene Pool- total of all alleles present in a population
B. according to the Synthetic theory, evolution is the gradual change of the allele frequencies found in a population
C. Hardy-Weinberg Law- the principle that sexual reproduction alone does not affect allele frequencies in a population
V. Speciation (finish this Gabriel)
1. In the event of a nuclear catastrophe, what creature, able to withstand up to approximately 60, 000 roentgens of radiation, could likely take over the earth? (Humans can safely absorb no more than 200 roentgens.) answer
2. How did humans evolve? answer
3. Why do humans have wisdom teeth? answer
