evidence for biological evolution. evolution results from 4 factors: potential for a species to...
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Evolution results from 4 factors:
Potential for a species to increase in number
Heritable genetic variation Due to mutations and sexual reproduction
Competition for limited resourcesReproduction of organisms better able to
survive in the environment
Inherited variation & Artificial selection Individuals of each species vary. Darwin argued that variation was important. In artificial selection, humans select from the
naturally occurring genetic variations in a species.
Example: Dogs: all descended from wolves Selective breeding
for color, hair, size, behavior
Interbreeding reduces genetic variation
Artificial SelectionWheat, corn, for
resistance to rust,fungi, etc. USDA spends $ to breed
new resistant varieties.Unintentional artificial selection
Antibiotic resistance in bacteriaPenicillin, Streptomycin, Tetracycline, etc.“Multidrug resistant” tuberculosis
Pesticide resistance in insect pestsDDT, Chlordane, etc.
Remember… Adaptation = any inherited characteristic
that increases an organism’s chance of survival Anatomical, physiological, behavioral Successful adaptations enable organisms to
become better suited to their environment. Fitness = the ability of an individual to
survive and reproduce in its specific environment. Result of adaptation.
Survival of the fittest = individuals with adaptations that make them better suited to their environment survive and reproduce.
Natural Selection Natural selection = the
traits being selected, and increasing over time, contribute to an organism’s fitness in its environment.
Results in changes in the inherited characteristics of a population, which increase a species’ fitness in its environment.
Evolution by Natural Selection
Darwin proposed that a type of artificial selection occurred in nature.
Members of each species compete regularly to obtain food, living space, and other resources. Selection removes (some) individuals with
unfavorable traits. Selection preserves (some) individuals with
favorable traits. The struggle for existence was central to
Darwin’s theory of evolution.
Common Ancestry Homologous “same” structures, different
fucntions Comparing the anatomy of fossils and living
organisms
All tetrapods have similar limb bones
Common Ancestry Embryological evidence suggests common
ancestry Homologous structures develop different functions
Common Ancestry
The early embryonic stages of a (a) lemur, (b) pig, and (c) human show strikingly similar anatomical features.
Darwin’s Concept: Natural Selection Genetic variation exists within a population due
to mutations and sexual recombination Competition for resources yields the survival of
the fittest for a certain environmental condition Adaptations are changes in genetic traits over
time Natural selection favors traits (variations) that
make an organism more fit for its environment, leading to adaptations in a population over many generations.
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