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