Adaptation
What are the 4 main aspects of Natural Selection?
Overproduction: more offspring produced than can survive
Variation: individuals have different phenotypes and genotypes. Best ones survive and reproduce.
Selection: results from competition for limited resources (food, water, shelter, mates, etc)
Adaptation (Inheritance): Variations (both favorable and unfavorable) get passed to offspring. Proportion of those with favorable phenotypes will be higher.
What is speciation?
Formation of new, distinct species.
Divergent evolution
When two or more species evolve from a common ancestor.
Divergent evolution looks at longer time spans.
What is extinction?
death of entire species
Three examples of adaptation
Better suited to its environment making it possible to better exploit its niche.
Examples: Body Structure or Function, Physiological, Behavior
Species
a group of organisms capable of interbreeding to produce fertile offspring.
Adaptive radiation
One common ancestor gives rise to multiple species, occupying different niches. Adaptive radiation is shorter term change.
Mass Extinction
Widespread and rapid decrease in life on Earth, not only loss of species, but entire families (made up of genera and species).
Evidence indicates we are possibly in a 6th mass extinction.
Examples of adaptive features that promote fitness
hummingbird's specialized beak
north american beaver adapted to aquatic and terrestrial environment
giraffe's neck
What is reproductive isolation?
When some members of a population stop breeding with other members.
Causes gene pool to split. Leads to speciation.
Phyletic Gradualism
Populations diverge slowly by accumulating adaptive features in response to different selective pressures.
What does each fork represent in the hominim cladogram?
Each “fork” represents an event that separated common ancestors.
Organisms that are not related develop similar traits.
Result from adapting to similar environment or niches.
What 3 mechanisms lead to reproductive isolation?
Geographical: when 2 populations are separated by geographical barriers (mountains, rivers, etc).
Behavioral: differences in courtship rituals or other behaviors (mating calls, dances, etc).
Temporal: when 2 or more species reproduce at different times (seasons, day/night, etc).
Punctuated Equilibrium
Populations stable but interrupted by brief periods of more rapid change.
What are Analogous Structures?
Structures that have the same function in unrelated taxa. Not the result of shared ancestry.
What type of reproductive isolation is the gray wolf in N. America and Eurasia?
Geographical
What does this tell us about the process of species formation?