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LECTURE 6 UNDERSTANDING EVOLUTION Outline 2. Natural selection vs artificial selection 1. Importance of variation 3. The modern synthesis 4. Patterns of selection 5. Processes that cause evolution Darwin’s Theory 1. Variation among individuals 2. Some variation is heritable 3. Over-production of offspring: overpopulation and competition ie. 2000 maple seeds, not all grow, env cant support it all 4. Reproduction: non-random  not equal; some breed, some lose in dominance fight, not all breed in population  NO DNA, chromosomes, Variation Individuals within populations vary: – true of human and non-human populations – variation can include traits such as appearance, blooming time in flowers, etc Figure 10.6 same species in same area but diff fur color ideal color of rose is red; all other organisms try to become ideal; but variation of species have different genetic traits Understanding Variation Example: long necks in giraffes lamarack – first evolution theory(change occurred over lifetime of organisms; passed on to offspring) but proposed mechanism inheritance of acquired characteristics darwin (different in population diff in size of necks but if advantageous; more will survive and reproduce Variation is inherited if beneficial for survival; reproduce and higher survival rate Variation and Natural Selection • among individual organisms of a species, variation is not imperfection, but the material from which natural selection fashions better adapted forms of life  Differences are important ie camaflauge alleles is important dependent on env Reproduction - populations of organisms produce more offspring than will survive - even slow-breeding animals can produce large populations  elephants; max over population; competition for resources Adaptations – a flower’s reproduction is impacted by traits that affect the number of pollinators it attracts – therefore, color or nectar production may be adaptations more pink than white; pink are more adapted; pollinators like pink more; more than one feature Survival And Reproduction Are Not Random – Adaptation: traits that increase individual fitness in an environment Natural selection causes evolution: Some forms are more successful at surviving and breeding than others in a given environment Natural Selection Causes Evolution • Result of natural selection – favorable inherited variations tend to increase in frequency – unfavorable variations tend to be lost – end result is a change in genetic traits of individuals in a population over generations Theory of Natural Selection – favorable alleles = variation • Darwin was familiar with variation in domesticated animals – Breeders: produce animals/plants with particular characteristics Artificial Selection The selective breeding of plants and animals to produce specific desirable traits • selection by …. HUMANS • on ……DOMESTICATED plants and animals • has a ….. SPECIFIC PURPOSE OR GOAL Ie. Breed short legs with shorter legs ie dachshunds all depends on variation to breed specific traits BRASSICA OLERACEA Plants Natural Selection • Darwin proposed that nature or the environment determine which individuals in a population are more fit • Fitness: the genetic contribution of an individual to subsequent generations relative to the contribution of other individuals  Different from artificial selection; nature determines which individual gets to survive Natural Selection • ….  ALL organisms • selection by ….  ENVIRONMENT • …NO purpose or goal • …  NOT predictable Natural Selection In The Lab Increase in percent of fast-metabolizing flies No change in alcohol-metabolizing rate Fly population in normal laboratory environment Fly population in a high-alcohol laboratory environment After 57 generations, all flies in the high-alcohol environment are fast processors of alcohol. As a result, the average rate of alcohol metabolism is twice the rate of the unmodified population. Percent of population that metabolized alcohol rapidly -animals have enzymes to metabolize alcohol - variations in ability to metabolize alcohol exist in populations Natural Selection Since Darwin - The Modern Synthesis • The union of genetics and evolution is called “the modern synthesis” – knowledge of genetics facilitates understanding of the mechanisms of evolution
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