How did people think species arose before Darwin's theory of Natural selection
the earth was young (6000 years old)
each species was created at the same time and species dont change or die out
the number of speices never changes
What is evolution?
the genetic change in a population over time
what is evolution by natural selection?
there is differential survival and reproduction among individuals of a population whose traits vary
mechanism of evolution
explains how genetic change can happen in a population over time
what are the three conditions for natural selection
variation for the trait
variation must be heritable
differential reproductive success (more offspring produced than can survive, competition for resources, some are better competitors, survive and have a change to reproduce
how does genetic variating arise?
heritable trait that allow for greater reproductive success become more common in a population over time
how does genetic variation contribute to differential reproductive success
more offspring produced than can survive
competition for resources
some are better competitors, survie and have and chance to reproduce
what is evolutionary fitness
a measure of relative reproductive success
whats the result of evolution
populations adapted to their current local environment
why doesnt natural selection produce perfect organisms
in each generation, the alleles that code for traits with better fitness tend to increase in frequency
if the environment changes, which alleles are favored may also change
Modes of natural selection: directional
one extreme phenotype is the most fit
Modes of natural selection: disruptive
extreme phenotypes are favored; intermediate phenotype selected against
Modes of natural selection: stabilizing
intermediate phenotype favored; extreme phenotypes less fit
what are the different mechanisms of evolution
sexual selection- greater fitness bc they're attracted to the opposite group , migration, genetic drift- by chance
what is the process of speciation
The process by which one species splits into two distinct species; the first phase of speciation is reproductive isolation, the second is genetic divergence, in which two populations evolve over time as separate entities with physical and behavioral differences.
how do we defin species in different ways?
morphological species concept- A concept that defines species on the basis of physical features such as body size and shape.
phylogenetic species concept- A grouping of organisms in a hierarchical system that reflects the evolutionary history and relatedness of the organisms
biological species concept- Populations of organisms that interbreed, or could possibly interbreed, with each other under certain conditions, and that cannot interbreed with organisms outside their own group.
how does reproductive isolation occur?
The inability of individuals from two populations to produce fertile offspring together.
BSC emphasizes reproductive isolation which makes gene flw between groups impossible
ecological- diff environments, temporal- fertile at diff times, behavioral- diff activities, gametic- gametes cannot unite
pre vs postzygotic isolating mechanism
pre- ecological- diff environments, temporal- fertile at diff times, behavioral- diff activities, gametic- gametes cannot unite
post- hybrid inviability- gametes unite, but development cannot produce a viable embryo (goat sheep)
hybrid infertility- hybrids lack the ability to make or deliver viable gametes (liger, the hybrid offspring of lion and tiger
allopatric vs sympatric speciation
allopatric speciation occurs when a geographic barrier causes one group of individuals ina population to be reproductively isolated from another group (stream and squirrels)
Speciation that results not from geographic isolation but as a result of polyploidy or hybridization and allopolyploidy; this type of speciation is relatively uncommon in animals but is common among plants. [Gk., sun, together with +patris, native land]
what are the different lines of evidence of evolution
comparative anatomy- organisms w/ very diff ways of life often share common anatomical structures
molecular data- all species use the same 20 amino acids DNA
what are vestigial traits?
A structure, once useful to organisms but which has lost its function over evolutionary time; examples include the human appendix and molars in bats that now consume an exclusively liquid diet. [Lat., vestigium,footprint, trace]
how do vestigial traits illustrate that evolution is not perfect
why are science and religion not dichtomous
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