mechanisms of evolution and speciation Flashcards
define “founder effect”
a random reduction in a population that occurs when a few individuals become isolated from a larger population and form a new population that does not carry all the alleles that were present in the original population. when a small group of individuals migrates and establishes a population in a new location, the founder effect may occur
define “genetic drift”
a change in the pool of a population as a result of chance; it usually occurs more noticeably in small populations.
how does the bottleneck effect occur?
the bottleneck effect occurs when there is a disaster of some sort that reduces a population to a small handful, which rarely represents the full makeup of the initial population.
what’s the difference between a gene and an allele?
a gene is a sequence of DNA that codes for a specific characteristic. the different variants of a gene is known as an allele.
define “evolution”
evolution is defined as the process that results in cumulative, inheritable changes in a population, spread over many generations
recite the theory of evolution
the theory of evolution states that all organisms have developed from previous organisms and that all living things have a common ancestor in some initial form of primitive life. it also states that all organisms are fundamentally similar because their basic chemistry was inherited from the initial organism
define “mutation”
a mutation is a permanent change in the DNA sequence of a gene; a source of new alleles in a population’s gene pool; the process of generating a mutation
what are selection pressures?
a selection pressure is an abiotic or biotic environmental factor that enhances the survival and reproduction of the individuals in a population that possess a beneficial trait, and reduce survival and reproduction in individuals that do not have that trait. t can contribute to allele frequencies in a gene pool and also drive natural selection.
describe the process of allopatric speciation
- two groups are separated by geographical isolation which prevents gene flow between the two populations
- selection pressures on both sides of the barrier are different and both populations change due to natural selection (mutation/genetic drift)
- differences will increase/accumulate over time until the two groups are unable to interbreed and produce fertile offspring
describe the process of genetic drift
- changes in allele frequencies
- changes are random or occur by chance
- causes loss of diversity /alleles from a population
- causes differences between populations
define “artificial selection”
artificial selection (selective breeding) is the intentional breeding or reproduction by humans of individuals with desireable traits, resulting in chnages in allele frequencies in gene pools over time; the traist are beneficial to humans
when did life first form on earth?
3.5 billion years ago
what is natural selection
natural selection in the process in which organisms that have traits that better enable them to adapt to specific environmental pressures will tend to survive and reproduce in greater numbers than others, enabling the continuation of those traits in succeeding generations
how does variation occur?
variation is created by mutation and in increased within a population by sexual reproduction
what are the 3 main types of selection pressures?
resource availability, environmental conditions, biological factors
