9th Grade Bio Semester 2

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* Charles Darwin
Origin of species by natural selection
Theory of natural selection
1. Over production
More offspring are produced than can survive
2. Variation
There are differences in the traits of these organisms
3. Competition
4. Best adapted survive
select agent
5. Reproduce
Pass on desirable traits to the next generation
Organisms rarely have mutations that can allow the to better adapt to there envirironment.

I. Evidence for evolution
A. Fossils
Remnants of organisms that lived in the past.
Fossil record
1. Bones
2. Petrified
Organic materials are replaced in the fossil (minerals)
3. Animals in tar pits
4. Insects in amber
5. Imprints

*Fossils are found in sedimentary rock.

Dating Fossils
Pay for dinner
Level of soil
Carbon dating
C14 is used because of its long half life

B. Similarities in structure
1. Homologous structure
The have the same anatomy but different structure
Ex: the arm of a man
* leg of a horse
* wing of a bat
* flipper of a whale
* wing of a bird
2. Analogous structure
have the same function but different anatomy
Ex: Wing of insect (made of chitin)
* Wing of bird (made of bone)
3. Vestigial organs
No use today
Ex: Appendix
* Coccyx
* Ear muscles
4. Embryology
Similarities of embryos in development

Geographical distribution of species
Species living in the same region tend to be more closely related to each other. Species that look similar but are from different regions are not often closely related. Convergent evolution
Organisms that aren’t related but have similar traits

Molecular biology
Comparing DNA and protein structure
Universal genetic code
Protein structure
Gas exchange
Protein structure

Natural selection in action
Insecticide and drug resistance
Insecticide didn’t kill all insects
Insects that were resistant to the drug reproduced
Resistance is inherited
Insecticide becomes less and less effective

Inheritance of acquired characteristics
Organisms can change
1. Organisms develop traits out of need (need=bad)
2. If you don’t use an organ, you lose it

*Organisms don’t adapt, they are either adapted or not adapted *Organisms don’t evolve, populations do

Hardy Weinberg principle
No change in the % of genes in a population under the following conditions 1. No mutations
2. No migration
3. Large population
4. Random mating
5. No selection
* *Weismann cut of the tails of mice in order to see if there offspring would be born without a tail Result
Mice were born with tails

What causes change within a population?(disproves/proves Hardy Weinberg) A. Mutations are spontaneous
* Most mutations are recessive (don’t show) and harmfull. B. Gene flow
Opposite of no migration
1 field, half have blue flowers and the other half have yellow flowers. A storm comes and blows the yellow flowers onto the blue side. The yellow flowers reproduce. Now that half of the field has blue and yellow flowers. C. Genetic drift

Changes in the gene pool of a population do to chance rather then natural selection D. Random mating
E. No selection
There is, natural selection

Evolution of a new species

Organisms that can interbreed and produce fertile offspring
Asexually reproducing organisms

How do new species arise?
A. Geographic isolation
Leads to new species forming

*Geographic isolation is the main cause of speciation

If you are reproductively isolated you can’t interbreed
How are species reproductively isolated?
A. Timing
Egg or sperm are produced at different times
B. Behavior
Courtship routines.
Ex: birds display mating dances
C. Habitat
Organisms are adapted to different niches.

Speciation within some area occurs more...
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