Evolution!

Evolution

A process that results in heritable changes in a population spread over generations.

Adaptation

An inherited characteristic that improves an organism's ability to survive and reproduce in a particular environment.

Fitness

The contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals.

Natural Selection

A process by which individuals with inherited characteristics that are well suited to the environment leave more offspring than do other individuals; main mechanism of evolutionary change.

Charles Darwin

A British naturalist who introduced the concept of natural selection which is the main mechanism for how evolution occurs.

Darwin's Concept of Natural Selection

1. There are variations within every population.

2. Organisms compete for limited resources.

3. Organisms produce more offspring than can survive due to there being limited resources leads to competition.

4. The organisms with the favorable characteristics or adaptations for that environment survive better and reproduce more often, thus transmitting those favorable traits to the next generation.

Adaptive Radiation

A rapid evolutionary event in which one ancestral species evolves into an array of different species due to them adapting to different environments.

Evidence to Determine Evolutionary Relationships

1. Fossil Record

2. Anatomical Evidence

3. Embryological Evidence

4. Molecular Evidence

Radiometric Dating

A procedure that determines the age of rocks and fossils based upon the half-life of radioactive isotopes.

Homologous Structures

Have a similar structure, similar embryological development, may have different functions, but the evidence proves that the trait evolved from a shared common ancestor, and branched off from a common 4 limbed ancestor.

Divergent Evolution

The process by which two or more related but reproductively isolated populations become more dissimilar.

Analogous Structures

Have similar functions, similar external forms, but different internal structures and development, different origin, the trait is not found in a common ancestor of those organisms, the trait developed independently in each lineage after the last shared common ancestor, and evolves from convergent evolution.

Convergent Evolution

The process whereby organisms not closely related, independently evolve similar traits as a result of having to adapt to similar environments.

Phylogenetic Tree

A branching pattern that shows the evolutionary relationships of organisms.

Nodes

Common ancestors (where the lines meet).

Clade

Each evolutionary branch.

Cladistics

A way in which biologists determine the sequence of branching in a phylogenetic tree.

Derived Characters

Unique homologous features that unite the group of organisms.

Cladogram

Phylogenetic diagram that specifies the derived characters of clades.

Gene

DNA instructions for building proteins.

Allele

Variations of a specific gene.

Mutation

A change in the DNA instructions of a particular gene.

Gene Pool

Consists of all the alleles of genes found in all the individuals that make up a population.

Allele Frequency

The percent of the population that contains a specific allele of a gene.

Why do traits vary?

1. Mutation

2. Genetic Recombination

3. Random fertilization of a sperm or egg between partners

Natural selection can only act on traits that contain....

1. Heritability

2. Variability

3. Reproductive Advantage

Artificial Selection

Selective breeding of domesticated plants and animals to produce offspring with desired genetic traits.

Sexual Selection

Non-random mating.

Coevolution

Two or more species having a close ecological relationship evolve together such that one species adapt to the changes of the other thereby affecting each other's evolution.

Microevolution

Refers to allele frequency changes within a population.

Macroevolution

Evolutionary change at the species level.

Species

A population whose members can interbreed and produce viable fertile offspring.

Specialization

The formation of a new species. In order for speciation to occur there needs to be reproductive isolation.

Fertilization

The union of a sperm and an egg cell forming a zygote.

Zygote

The first cell of an offspring formed from the union of a sperm and egg cell.

Geographic Isolation

A physical barrier separates a population and they eventually evolve differently.

Ecological Isolation

Species occur in the same area by occupying different habitats so they rarely encounter each other.

Temporal Isolation

Species that breed during different times of day, different seasons, or different years cannot mix gamete.

Behavioral Isolation

Unique behavioral patterns and rituals isolate species.

Mechanical Isolation

Morphologic differences can prevent successful mating.

Gametic Isolation

Sperm of one species may not be able to fertilize the eggs of another species.

Prezygotic Barrier

An obstacle to mating or fertilization if mating occurs.

Postzygotic Barrier

Prevents hybrid offspring from developing into a viable, fertile adult.

Reduced Hybrid Fertility

Chromosomes of parents may differ in number or structure and meiosis in hybrids may fail to produce normal gametes.