Who developed the theory of natural selection?
Charles Darwin
What are the two main principles of natural selection?
- there is variation within a population of organisms and this variation can be inherited
- individuals with inherited traits that are better suited for growth and reproduction in a given environment can contribute disproportionately to the next generation
Who is Georges Cuvier?
- did not believe species changed over time (no evolution)
- after a catastrophe, a different species simply moved into the area (catastrophism)
What is natural selection?
a process in which individuals with favorable inherited traits are more likely to survive and reproduce.
What is decent with modification?
describes the origin of new species (speciation) from ancestral species.
- natural selection is the mechanism for “decent with modification”
What is genotypic variation?
- the difference in DNA among individuals in populations.
- Genotype = genetic makeup of an organism
- genotypic variation is heritable.
What are the two observations of evolution by natural selection?
- members of a population vary in their inherited traits.
- populations produce more offspring than the environment can support, and many of these offspring fail to survive and reproduce.
What is phenotypic variation?
the variability in phenotypes that exist in a population.
- phenotype = an organisms observed characteristics
- an organism’s phenotype is determined by interaction of environmental factors and its genotype.
What is a selective agent?
- environmental factors acting on populations to effect the survival and/or reproduction of individuals in the populations
What is a selective pressure?
when a selective agent consistently causes differences in survival and/or reproduction in a population
- selective pressures act on individuals, but only populations evolve.
consistent selection pressure leads to…
… a directional change in the population, known as natural selection.
- if the selection pressure changes, the direction of natural selection will change.
What is an adaptation?
an inherited characteristic of an organism that enhances its survival and reproduction in a specific environment.
What does natural selection increase?
The adaptation of populations.
Natural selection acts on…
Existing variation. (genetic diversity)
- natural selection does not create new variation.
