chapter 17 & 18 test Flashcards
(33 cards)
scientific theories
well established explanation of event about the natural world
Species vary globally
nimal species inhabited separated but ecologically similar habitats around the globe.
Species vary locally
animal species often occupied different habitats within a local area
Species vary over time
Explains how some species that have already become extinct resemble those that are living.
Jean-Baptiste Lamarck proposed the 2 hypotheses…
- that organisms could change during their lifetimes by selectively using or not using various parts of their bodies.
- that the individuals could pass these acquired traits on to their offspring enabling the species to “change” over time
why was lamarck wrong
aquired traits are not inherited
artificial selection
When nature provides the variations and humans select those they find useful.
Natural Selection
is the process by which organisms with variations most suited to their local environment survive and leave more offspring with the same variations.
biologocal fitness
how well an organisms adaptations allow it to survive
3 conditions needed for natural selection
over productiuon of offspring, inherrtied variation, and struggle to survive
principal of common descent
all species – living and extinct – are descended from ancient common ancestors.
how old is the earth
4.5 billion years
what is a gene pool
all of the genes present in a population
relative frequency
– Number of times a particular allele occurs in a gene pool, compared with the number of times other alleles for the same gene occur.
do popultions or individuals evolve
popukations
what are the 2 sources of genetic variation
mutation- any change in dna sequence
genetic recombination- due to sex (crossing over)
what are the 4 mechanisms for revolutionary change
genetic drift
gene flow
non random mating
natural selection
what is genetic drift
netic drift occurs in SMALL populations when an allele becomes more or less common simply BY CHANCE. Genetic drift is a random change in allele frequency.
• 2 types
– bottleneck effect
– founder effect
bottle neck effect
is a change in allele
frequency following a dramatic reduction in the
size of a population.
• Ex. A disaster may kill many individuals in a population and the surviving population’s gene pool may contain different gene frequencies from the original pool.
the founders effect
The founder effect occurs when allele frequencies change as a result of the migration of a small subgroup of a population.
• Two groups from a large, diverse population could produce new populations that differ from the original group.
what happpens to the allele frequency in genetic drift
it changes because dome individuals go off to start their own pop.
gene flow
The movement into or out of a population can change the variations in the gene pool.
non random mating
If mate choice is not based on chance or opportunity, but instead mates are chosen due to some characteristic that is more desirable… allele frequencies in a population will change.
how does natural selection effect single genes
Natural selection on single-gene traits can lead to changes in allele frequencies and thus to changes in phenotype frequencies
