Chapter 11: Evolution and Its Processes Flashcards
define evolution
- descent with modification
- any change in heritable traits within a population across a generation
define natural selection
- mechanism to explain evolution
- differential reproductive success
- process when population’s heritable variations are exposed to environmental factors that favor success of some over others
define variation
- differences in a population
- must have some genetic basis
- mutations, crossing over/independent assortment during meiosis, sexual reproduction
define adaptation
- match of organism to environment
- aids in survival and reproduction of organism in its present environment
define divergent evolution
- structures that evolve from a common ancestor
- wings of a hummingbird and ostrich
define convergent evolution
- structures that did not evolve from a common ancestor; evolved independently
- wings of bats and insects
define homologous structure
- result of divergent evolution
- structure from common ancestor
define analogous structure
- result of convergent evolution
- structure not from common ancestor; evolved independently
define evolutionary theory
- modern synthesis
- genetics and evolution integrated into one theory
- from work of Mendel and Darwin
define microevolution
- small-scale
- within single species
- short period of time
- changes in allele frequency in a population; changes phenotype
- ex: beaks of finches after 1977 drought
define macroevolution
- large-scale
- long period of time
- formation of new species and higher taxonomic groups
define population genetics
- field of study examining what happens to alleles in a population
- defines evolution in terms of genetic change that underlies phenotypic change; changes in frequency of an allele
define allele frequency
- describes how common an allele is in a population
define Hardy-Weinberg equilibrium
- a population allele and genotypic frequencies are stable unless some kind of evolution force is acting on the population
- if no factors are acting on a population, the allele frequencies with remain constant
how old is the idea of evolution
- very old: B.C., pre-Socratic era
what were Plato’s ideas on evolution
- thought species were static and unchanging
describe the ideas of evolution in the 18th century
- accepted idea of extinct species
- idea that geology of the planet was consequence of catastrophic events OR geological change occurred gradually
describe Lamarck’s idea of evolution
- inheritance of acquired characteristics
- if an organism changes to adapt to its environment then those changes will be passed onto offspring
- now known to be incorrect
how did August Weissman disprove Lamarck’s idea of the mechanism of evolution
- cut tails off 22 generations of mice
- observed that all offspring had tails
how did Charles Darwin and Alfred Wallace create a new idea on the mechnaism of evolution
- both went to different parts of the world and observed species on separate islands
- separately and simultaneously explained natural selection
what is the actual mechanism for evolution and who discovered it
- natural selection
- Darwin and Wallace
what animal did Charles Darwin study to determine natural selection as the mechanism of evolution
- finches of the Galapagos islands
- observed how beak shape adapted to different food sources
what three principles of nature are needed for natural selection to occur
- individuals have to vary within a species
- variation has to be heritable
- organisms have to have more offspring than resources can support
what are the consequences of natural selection
- more likely to survive
- higher reproduction rates
- traits passed to offspring; greater proportions in following generation
- changes in population over generations
do individuals evolve
- no
- populations of organisms evolve
is evolution always a result of natural selection
- no
- many other driving factors including mutations, genetic drift, and migration
describe how to 1977 drought affected finch beak length
- 1976: smaller beaks
- 1978: larger beaks
are mutations always bad
- no
- may have no effect, negative effect, or positive effect
why are the same traits not always advantageous in every population or throughout time
- environmental conditions favor certain traits
- different conditions for different organisms
- conditions change over time
is the dominant allele more frequent
- not always
why might a dominant allele not increase in frequency in a population until it eliminated all other alleles
- recessive allele is advantageous in the environment
what are the 5 assumptions of Hardy-Weinberg equilibrium
- no mutations
- no selection pressures
- no gene flow (migration)
- infinite population size
- random mating
what do the p and q represent in Hardy-Weinberg equilibrium equations
- p=allele frequency of dominant allele
- q=allele frequency of recessive allele
what are the 4 equations in the Hardy-Weinberg equilibrium
- p + q = 1
- p^2 and q^2 = frequency of each homozygote
- 2pq = frequency of heterozygote
- p^2 + 2pq + q^2 = 1
what 5 evolutionary forces disrupt the Hardy-Weinberg equilibrium
- natural selection
- mutations
- genetic drift
- migration
- non-random mating
define mutation
- source of new alleles
- change in allele frequency is very small
- new allele may be selected for, selected against, or selectively neutral
- ultimate source of variation
define genetic drift
- effect of chance
- mortality of individual, fidning a mate, which gametes are fertilized
- most important in small populations
- influenced by bottleneck effect and founder effect
define bottleneck effect
- influences genetic drift
- disaster reduces population size
- genetic makeup of survivors becomes genetic makeup of entire population
define founder effect
- influences genetic drift
- small group leaves to start new population in a new location
- population gets divided by physical barrier
define gene flow/migration
- flow of alleles in and out of a population resulting from the migration of individuals
- some population are fairly stable, others experience more flux
what do fossils do for biology
- show evolution of form through time
- sold evidence that organisms from the past differ from those today
define vestigial structures
- structures that exist but have no apparent function
- leftover form past ancestor
- legs in snakes, wings in flightless birds
define convergence of form
- similar characteristics in organisms in similar environments
- occurs from similar selection pressure NOT common ancestry
- fox and birds having temporary white covering during the winter
define embryology
- study of the development of the anatomy of an organism to its adult form
- provides evidence of relatedness between now widely divergent groups of organisms: gill slits and tail in early development
define biogeography
- geographic distribution of organisms on the planet
- follows patterns of evolution and movement of tectonic plates
examples of biogeography
- islands created from tectonic plate movement and species diverge
- diversification of marsupials in australia
define species
- group of actually or potentially interbreeding individuals
- must be able to mate and produce fertile offspring
define allopatric speciation
- speciation in other homelands
- geographic separation
- two kinds: dispersal and vicariance
define sympatric speciation
- speciation in the same homeland
- occurring within parents species while remaining in one location
- two mechanisms: autopolyploidy and alloploidy
define adaptive radiation
- populations disperse through an area and each finds a distinct niche or habitat
- multiple speciation events originating from a single species
define autopolyploidy
- mechanism of sympatric speciation
- error in meiosis where all chromosomes move into one cell instead of separating
- common in plants
define alloploidy
- mechanism of sympatric speciation
- results when two species mate to produce viable offspring
- occurs in cultivated forms of wheat, cotton, and tobacco
define dispersal allopatric speciation
- when few members of a species move to a new location
define vicariance allopatric speciation
- when a natural situation arises to physically divide the organisms
describe the process of speciation with geographic separation
- initial population with relatively homogenous gene pool
- populations are separated and alleles aren’t free-flowing
- populations evolve as different alleles become predominant and new alleles arise through mutations
- divergence may affect reproduction and create speciation
describe an example of speciation without geographic separation in fish in a lake
- fish live in a lake
- competition for food increases as population grows
- some fish are able to feed of another resource
- those fish breed with each other
- eventually, speciation may occur
what are the 6 misconceptions of evolution
- evolution is just a theory
- individuals evolve
- evolution explains the origin of life
- organisms evolve on purpose
- evolution is controversial among scientists
- other theories should be taught
describe this misconception of evolution: evolution is just a theory
- there is lots of evidence to support evolution
- is a scientific theory, not everyday definition of theory
describe this misconception of evolution: individuals evolve
- individuals are born with their genes
- individual changing over time in development, not changing genes
- evolution is change in genetic composition of POPULATIONS over time
describe this misconception of evolution: evolution explains the origin of life
- no, just explains how populations change over time
describe this misconception of evolution: organisms evolve on purpsoe
- evolution in response to environment changing
- not intentional
- variation already exists within the population
describe this misconception of evolution: evolution is controversial among scientists
- was only controversial in the 1860s
- scientific arguments were resolved, religious arguments still persist although many denominations accept evolution and their own theories
- 97% of scientists believe species evolve
describe this misconception of evolution: other theories should be taught
- no other theories are scientific
