ch 04 origins of life/ natural selection ch 04 section 1 section 2
TRANSCRIPT
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Ch 04 Origins of Life/ Natural Selection
Ch 04 Section 1Section 2
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Variety ofmulticellular
organismsform, firstin the seasand lateron land
Biological Evolution(3.7 billion years)
Chemical Evolution(1 billion years)
Small organic
moleculesform inthe seas
Large organic
molecules form in the seas
First protocells
form in the seas
Single-cell prokaryotes
form in the seas
Single-celleukaryotes
form inthe seas
Origins of LifeOrigins of Life
First was Formation of the earth’s early crust and atmosphere
Then
Then PLAY
ANIMATION
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How Do We Know Which Organisms Lived in the Past?
4. Our knowledge about past life comes from fossils, chemical analysis, cores drilled out of buried ice, and DNA analysis.
Figure 4-4Figure 4-4
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B. Natural Selection and Adaptation1. Evolution is the change in a population’s
genetic makeup over timea) Populations evolve by becoming genetically
differentb) All species descend from earlier, ancestral
species2. Microevolution describes the small
genetic changes that occur in a population over time
3. Sexual reproduction leads to random recombination of alleles from individual to individual
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Natural Selection
PLAYANIMATION
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Gene Flow or MigrationGene Flow or Migration
SHOWLINK
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4. Over time, a population’s gene pool changes when mutations in DNA molecules are passed on to offspring.
a) Mutations are random changes in the structure/number of DNA molecules in a cell.
b) Mutations occur in two ways.• Gene DNA is exposed to external agents like X rays,
chemicals (mutagens) or radioactivity.
• Random mistakes that occur in coded genetic instructions.
c) Only mutations in reproductive cells are passed to offspring.
d) Many mutations are neutral, some are deadly; a few are beneficial.
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5. For natural selection to evolve in a population, three conditions are necessary:
a) The population must have genetic variability.b) The trait must be heritable, capable of being
passed from one generation to another.c) The trait must enable individuals with the trait
to produce more offspring than individuals without the trait; this is differential reproduction.
6. Adaptations are heritable traits that help organisms to survive and reproduce better under prevailing environmental conditions.
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7. Environmental changes require adaptations also. Organisms must:
a) Adapt to the new conditions.
b) Migrate to an area with more favorable environment.
c) Organisms that cannot adapt become extinct.
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Animation: Moth Populations
PLAYANIMATION
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8. Coevolution is the interactions of species will cause them to engage in a back and forth genetic contest in which each gains a temporary genetic advantage over the othera) This often happens between predators and
prey species.
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9. Hybridization can occur when individuals off two distinct species crossbreed to produce fertile offspring.
a) New species can arise. [ i.e. dog breeds]10. Horizontal gene transfer is when species (mostly
microorganisms) exchange genes without sexual reproduction
11. A population’s ability to adapt to new environmental conditions through natural selection is limited by its existing genes and how fast it can reproduce.
a) Humans have a relatively slow generation time (decades) and output (# of young) versus bacteria which can reproduce millions in hours!
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Horizontal Gene Transfer
PLAYANIMATION
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12. Common myths about evolution through natural selection.
a) Natural selection can only act on existing genes and is limited by reproductive capacity.
b) There is no such thing as genetically perfect organism; the purpose is to leave the most descendants