what is evolution defined as?
the change in genetic characteristics of a population over time
what is a haploid?
organism that has a single chromosome that has a given gene (so only express one allele)
what is a diploid?
organism that has two chromosomes with the same gene, therefore may have 2 copies of same allele or have two different alleles
what are frequencies of alleles in a population used to determine? what do they show?
used to determine phenotypic variation, changes in these frequencies over generations show evidence of evolution
what are the four processes that can drive evolution?
- natural selection
- genetic drift
- gene flow
- mutation
what is natural selection?
individuals with certain (beneficial) heritable traits that are better suited to their specific environment produce more offspring
what is genetic drift?
random allele frequency changes
what is gene flow?
migration of genes, between separated populations
what is mutation (in terms of processes driving evolution)?
the introduction of new alleles
What drives natural selection? (what is needed for natural selection to occur?)
- competition for limited resources
- phenotypic variation
What does natural selection act on?
A. population
B. individual phenotypes
B. individual phenotypes
what is a phenotype?
observable characteristics or traits of an organism (based on the expression of their genes)
what is phenotypic variation?
random mutation occurs & changes DNA sequence of a gene (or genes (aka genotype))
what types of affects can phenotypic variation result in?
- neutral
- lethal
- beneficial (very rarely)
what is meant by the term “fitness” when discussing biology?
- the survival & therefore reproductive success of an organism.
- leaving more offspring than other individuals in the population
what are possible causes for phenotypic variation to occur?
- inherited (mutation would occur in DNA replication)
- result of environmental conditions (change in response to environment)
what is phenotypic polymorphism?
when a species has two or more distinct phenotypes within a single population
what is an adaptation?
- features that allow an organism to survive in its environment
- traits from natural selection before more prevalent in the population as a whole
what is evolution actually changing?
the allele frequencies in a population over time
why is the idea that “evolution occurs in individuals” wrong?
- evolution is the change of allele frequencies of a population
- individuals can adapt (which is not evolutionary change (change in genotype), rather an interaction between phenotype and environment)
- natural selection, so adaptive advantages would get passed down (eg) giraffes cannot change the length of their necks, but the longer necked versions have adaptive advantage
what are the most common misconceptions of evolution?
- … occurs in individuals
- … is for a purpose, goal, or progressive
- … perfects organism or leads to perfectly adapted organisms
- … is driven by mutation and therefore is random
- … is slow
why is the idea that “evolution is for a purpose, a goal, or progressive” wrong?
inheritance isn’t based off of the organism “wanting it” it is caused by mutations (which can have bad effects), which leads to a degree of randomness
why is the idea that “evolution perfects organism or leads to perfectly adapted organisms” wrong?
- not all traits are adaptive in specific environments
- fitness trade-offs may mean that the trait cannot be optimized (meaning the fitness is more important)
- there can be genetic limitations, as in their DNA just does not allow for specific traits to occur even if in theory they would be beneficial
why is the idea that “evolution is driven by mutation and therefore is random” wrong?
mutations are random, but the other part of evolution is the natural selection that occurs (which is not random)
