Ch 04 Origins of Life/ Natural Selection Ch 04 Section 1 Section 2

Animation: Stanley Miller’s Experiment PLAY ANIMATION

Variety of multicellular organisms form, first in the seas and later on land Biological Evolution (3.7 billion years) Chemical Evolution (1 billion years) Small organic molecules form in the seas Large organic molecules form in the seas First protocells form in the seas Single-cell prokaryotes form in the seas Single-cell eukaryotes form in the seas Origins of Life First was Formation of the earth’s early crust and atmosphere ThenThen ThenThen PLAY ANIMATION

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 4-4

B. Natural Selection and Adaptation 1.Evolution is the change in a population’s genetic makeup over time a)Populations evolve by becoming genetically different b)All species descend from earlier, ancestral species 2.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

Natural Selection PLAY ANIMATION

Gene Flow or Migration SHOW LINK

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.

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.

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.

Animation: Moth Populations PLAY ANIMATION

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 other a)This often happens between predators and prey species.

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!

Horizontal Gene Transfer PLAY ANIMATION

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