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