Flashcards in Ch. 6 Evolution And Ecology Deck (30)
Biological evolution -
Change in populations of organisms over time
Genes can have two or more forms called ___.
___ is the genetic makeup, and can be represented by letters, one for each allele.
___ is a change in allele frequencies over time.
Evolution can be defined more broadly as ___ ___ ___.
Descent with modification
Who used the phrase "descent with modification?"
Proposed populations change over time through ___ ___.
Individuals with certain __ __ survive and reproduce more successfully than individuals with other ___ ___.
Natural selection requires three attributes:
- genetic variation
- variation must be heritable
- differential reproductive fitness related to this variation
Natural selection causes the two populations to ___ genetically over time.
Natural selection acts only as a ___ ___.
Populations may evolve, but ..
Individuals do not evolve
Four key processes influence evolution:
- natural selection
- genetic drift
- gene flow
Observable characteristics of individuals that are determined by the genotype
Why is variation so important?
Natural selection acts upon variation
Different alleles arise by __.
Mutation results from:
- copying errors during cell division
- mechanical damage
- exposure to certain chemicals
- exposure to high energy radiation
Lack genetic variation
Mutation is the "___ ___" of variation.
__ is essentially a random process.
Individuals in a population differ genetically because of both mutation and ___.
Mutations occur too rarely to be direct cause of ___ ___ change.
Allele frequency change
Natural selection -
Occurs when individuals with particular heritable traits tend to leave more offspring than individuals with other heritable traits
What is the only process that consistently results in adaptive evolution?
Natural selection can be categorized into three types:
- directional selection
- stabilizing selection
- disruptive selection
Directional selection -
Individuals with one extreme of a heritable phenotypic trait are favored
Ex: drought favored large beak size in medium ground finches -> eating larger seeds
Stabilizing selection -
Individuals with an intermediate phenotype are favored
Ex: parasitic wasps select against small gall size, birds select against large gall size -> medium size galls
Disruptive selection -
Individuals at both phenotypic extremes are favored
Ex: African seedcrackers have two food sources -> really small seeds and really big seeds -> caused disruptive selection -> some birds got big beaks and some birds got small beaks
Helping others when it costs you