It all depends on barriers that prevent members of two species from producing viable, fertile hybrids.

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1 Name: Date: Theory of Evolution Evolution: Change in a over a period of time Explains the great of organisms Major points of Origin of Species Descent with Modification o All organisms are related through descent from a that lived in the o History of life is a single tree with branches representing Natural selection o populations can evolve if individuals that possess certain that leave more offspring than other individuals. WHICH EQUALS Evolutionary Adaptation An accumulation of inherited that enhance an organisms ability to survive and reproduce in. So how does Natural Selection work, anyways? Observation 1 of offspring o Population sizes would if all individuals born Observation #2: Populations tend to be, except for fluctuations Observation #3: Resources are Inference #1: Production of more individuals than the environment can support leads to a among individuals of a population, with only a of their offspring surviving

2 Observation #4 : Members of a population vary extensively in their characteristics; no two individuals are. Observation #5: Much of this Inference #2: Survival depends in part on ; individuals whose inherited traits give them a of surviving and reproducing are likely to leave than other individuals Inference #3: This unequal ability of individuals to survive and reproduce will lead to a in a population, with characteristics accumulating over generations Summary of Natural Selection In order to occur: o Differences in determined by the Artificial Selection Cross a beagle with a pug and you get a Evidence for all of this? 1) 2) 3) 4) 5) 6) 7) Geographic distribution of species closely related species tend to be found in same. Evolution in the 21 st century Drug pathogens big problem in bacteria and viruses that reproduce quickly o Naturally resistant pathogens not affected by. o All those are killed. o So.the ones with the resistance survive, reproduce, and on to their offspring. What Darwin DIDN T Know: Darwin found a mechanism for change over time He did not know the heritable variations in populations or how organisms actually these variations to their offspring.

3 MENDEL Gregor Mendel discovered that traits (we call them ) are passed from parent to offspring. Population genetics the study of how populations over time. Sources of Genetic Variation a) Mutations any change in the sequence (GGU instead of GCU) Causes: mistakes during replication o Environment b) Gene shuffling result of Genetic Drift traits fluctuate from one generation to the next. Effects of Genetic Drift a) The Effect for some reason the gene pool doesn t reflect the original pool. b) The Effect when a few individuals get isolated from population and establish a new one gene pool may be different from original.

4 Hardy-Weinberg Principle Allele (trait) frequencies in a population will remain stable (genetic equilibrium) if: The result? No evolution! Does it happen? Sometimes. Part III Speciation when can we say we have a new species? It all depends on barriers that prevent members of two species from producing viable, fertile hybrids. a) Habitat Isolation 2 species occupy within the same area. b) Mechanical Isolation - Flowers attract so cross-pollination doesn t occur c) Temporal Isolation Dendrobium orchids open flowers and release pollen at different no cross pollination! d) Behavioral Isolation - Courtship rituals that and unique to a species prevent reproduction e) Gametic Isolation Sperm of one species may not be able to of another species. What happens if 2 different species DO breed? a) genes from different parents interact and impair development (reduces chances of survival) b) offspring of 2 species are sterile they cannot produce offspring themselves c) some first-generation hybrids are viable and fertile, but when they mate with on e another or either parent species, offspring of the next generation are feeble or sterile. Speciation can also occur with or without geographic isolation a) ( other country ) populations divided into subpopulations with no chance of getting back together. b) ( same country ) speciation takes place in overlapping populations

5 Adaptive Radiation - Beak inheritance-speciation The evolution of many diversely adapted species from a common ancestor upon introduction to various new environmental opportunities and challenges. Convergent Evolution resemble one another (maybe live in same environment)

6 Coevolution 2 species evolve in to changes in each other The Tempo of Speciation How fast or slow do new species evolve?

7 Fossil record Importance of Genes Hox genes that control growth of an embryo certain genes turned on may produce wing, those genes turned off = no wings. turned on or off may also affect body plans (short versus long legs, for example).