Chapter 4 Evolution and Biodiversity:

Origins of Life Early Earths information comes from chemical & radioactivity analysis of rocks and fossils Earth developed in 2 phases –See fig 4-3 on pg 66 –Chemical evolution – billion years Biological evolution – billion years Prokaryotic bacteria Single cell eukaryotic creatures Multi-cellular organisms

Evolution All species descended from earlier, ancestral species –Micoevolution – small genetic changes that occur in a population –Macroevolution – large-scale evolutionary changes through which new species are formed while other species are lost through extinction

Microevolution Alleles – genes that may have 2 or more molecular forms –Sexual reproduction allows random shuffling or recombination of alleles Mutations – random changes in the structure or number of DNA molecules –Exposure to chemicals or radiation –Random mistakes that sometimes occur in coded genetic instructions during replication

Microevolution (continued) Natural selection – genetically based traits that increase their chances to survive Natural variability –Heritable so they can pass on the trait –Produce more offspring (differential reproduction) Adaptation – hereditary traits that help an organism to survive in new conditions –Natural selection –Migration –Become extinct

Artificial Selection Genetic engineering and all that is! selection ages/evo/mustardselection.jpg

Coevolution Species adapts because of another species adaptation

Ecological Niche Niche is defined as the role in which a species plays within its ecosystem –An understanding of a species niche allows us to be more aware of : The affects we have on the success of that’s species survival The competition for resources that species have within a community (realized niche) General classifications of species

Natural Factors Relating to Extinction Extinction occurs when environmental conditions change, and adaptation or migration can not occur in time for a species to exist. –Large scale movement of the continents (continental drift) –Gradual climate changes –Rapid climate changes

Unnatural Factors Relating to Extinction Humans have played a major role in the unnatural process of extinction. –Clear cutting or burning of forests, woods and grasslands –Over hunting of animals for food, by-products and sport –Population of humans have increased exponentially and have taken over the habitat of other species

Summary See slide show on specific species See film CNN: Costa Rica – Science in the Rainforest