Diversity of Life

Species Organisms that can mate and produce fertile offspring

Population Group of the same species living in the same place at the same time

Gene Pool All of the genes in an entire population

Mutation Spontaneous change in DNA sequence Source of new genes/alleles in a population

Variation Naturally occurring differences between members of a species Result of different combinations of genes/alleles

Natural Selection We observe and measure that- 1. There are more organisms born than can survive 2. There is naturally occurring variation in populations

As a result, members of a population with traits that are an advantage to survival (Best Fit) will pass on those traits to the future gene pool. Over time the gene pool changes to contain more of these traits

Evolution Change in heritable traits of the gene pool, over time Populations evolve, not individuals

Evidence for Evolution 1. Fossil Record Deeper rock layers are older then the layers above them.

Fossils from various levels show how organisms have changed over time

2. Homologous Structures Structures with different mature forms develop from the same embryonic tissues.

3. Embryology embryonic cells develop in the same order and in similar patterns to produce tissues and organs in all vertebrates.

4. Biochemical Similarities in DNA, RNA and proteins show relationships Changes in DNA sequence can be used as a molecular indicator or ‘clock’ to determine when divergence occurred

Speciation The formation of new species

Recall that species are defined as organisms that can mate and produce offspring that can mate. If populations are isolated, Natural Selection may affect their gene pools in different ways. If in time, they have changed to the point of not being able to interbreed, new species have evolved.

Isolation can be caused by- Geography- mountains, islands, rivers, highways. Behavior- courtship rituals, songs Temporal- timing