Speciation Ecology Unit

Speciation Formation of a new species  Species: A group of similar organisms that breed together and produce fertile offspring.  Gene pools must become separated for them to become different species.

Speciation

Phenotype Observable characteristics (green eyes, brown hair, purple flowers, etc.)

Genotype Genetic makeup of an organism determined by a pair of alleles.

All in the Genes commons.wikimedia.org/wiki/Image:DNA_double_helix_vertikal.PNG The genetic make-up of an organism is known as its genotype. An organism’s genotype and the environment in which it lives determines its total characteristic traits.  its phenotype. Phenotype Genotype

DNA Watson and Crick and their model of DNA en.wikipedia.org/wiki/DNA DNA replication The double-helix structure of DNA was discovered in This showed how genetic information is transferred from one cell to another almost without error.

Gene Unit of hereditary information Located on a chromosome Contains DNA Genes are passed from parent to offspring.

Gene Pool Consists of all the genes that are present in a population.

Genetic Variation Mutations  Any change in a sequence in DNA.  Few mutations lead to increased fitness.  Most mutations are harmful. Mutations lead to variations in a population.

Variation majorityrights.com/index.php/weblog/comments/racial_variation_in_so me_parts_of_the_skull_involved_in_chewing/ Variationsof a particular gene are known as alleles.  For example, the one of the genes for hair color comprises brown/blonde alleles. Species with greater genetic variability are more likely to adapt to changing environments

Natural Selection en.wikipedia.org/wiki/Image:Mutation_and_selection_diagram.svg Mutant alleles spread through a population by sexual reproduction.  If an allele exerts a harmful effect, it will reduce the ability of the individual to reproduce and the allele will probably be removed from the population.  In contrast, mutants with favorable effects are preferentially passed on Selection of dark gene

Natural Selection can affect the distribution of phenotypes in any of three ways: Stabilizing Selection Individuals at the middle of the curve have the greatest fitness. Disruptive Selection Individuals at either end of the curve have greater fitness than those in the middle. Directional Selection Individuals at one end of the curve have a higher fitness than those in the middle or other end.

Causes of SPECIATION

Tigon Result of male tiger and female lion mating incaptivity. Offspring are infertile. Separated both geographically and ecologically.

Liger Result of male lion and female tiger mating in captivity. Offspring are infertile.

Fig Four species of leopard frogs: differ in their mating calls. Hybrids are inviable.

Geographic Isolation

These squirrels live on opposite sides of the Grand Canyon. This is an example of allopatric speciation.

Temporal Isolation