chapter twenty-two/twenty-three Flashcards
2 examples of evidence for natural selection
- natural selection of soapberry bugs in response to introduced plant species
- evolution of drug-resistant bacteria
natural selection in response to introduced plant species
- soapberry bugs use beak to feed on seeds in fruit
- Southern Fl - longer beaks, balloon vine w/ larger fruit
- Central Fl - shorter beaks, golden rain tree w/ smaller fruit
- beak size has evolved in populations depending on size of fruit
- Fl - occurred in less than 35 years
evolution of drug-resistant bacteria
- Staphylococcus aureus found on people
- became resistant to penicillin 1945
- became resistant to methicillin in 1961 - MRSA (dangerous pathogen)
- became resistant to vancomycin
how does methicillin work
it inhibits protein used by bacteria in cell walls
- MRSA bacteria use dif protein in cell walls
- when exposed to methicillin, MRSA strains more likely to survive and reproduce
what does natural selection edit or select?
traits already present in populations
homology
similarity resulting from common ancestry
homologous structures
anatomical resemblances that represent variations on a structural theme present in a common ancestor
what does comparative embryology reveal?
anatomical homilies not visible in adult organisms
vestigial structures
remnants of features that served important functions in the organism’s ancestors
examples of homologies at molecular level
genes shared among organisms inherited from a common ancestor
evolutionary trees
hypotheses about relationships among dif groups
- homologies form nested patterns
- branch points indicate common ancestors
convergent evolution
evolution of similar or analogous features in distantly related groups
how to analogous traits arise?
when groups independently adapt to similar environments in similar ways
what does convergent evolution not provide information about?
ancestry
what do fossil records provide evidence of?
extinction of species, origin of new group, changes within groups over time
- documented transition from land to sea in ancestors of cetaceans
biogeography
geographic distribution of species, provides evidence of evolution
endemic species
species that aren’t found anywhere else in the world
implications of evolution
- philosophy - no purpose/meaning to existence
- religion - no goal, no morality, no ethics
- politics - social darwinism, eugenics
- psychology - human just another animal and is prisoner of animal urges
- biology - links all living things to common ancestor
do organisms evolve during their lifetime?
no
natural selection of medium ground finches on Galapagos Islands
beak size varied on seeds available
microevolution
change in allele frequencies in a population over generations
3 mechanisms that cause allele frequency change
- natural selection
- genetic drift
- gene flow
what is the only thing that causes adaptive evolution?
natural selection
what is a prerequisite for evolution?
variation in hereditable traits
what provided evidence of discrete heritable units/genes?
Mendel’s work on pea plants
what is genetic variation caused by?
differences in genes or other DNA segments
what is phenotype the product of
inherited genotype and environmental influences
discrete characters
- classified on either/or basis
- typically determined by single gene locus
- white/purple flowers
quantitative characters
- vary along continuum within pop
- human heigh, intelligence
what can genetic variability be measured as?
gene variability and nucleotide variability
average heterozygosity
average percent of loci that are heterozygous in population
how is nucleotide variability measured?
by comparing DNA sequences of pairs of individuals
true or false: most species exhibit geographic variation, which includes differences between gene pools of separate populations
true
genetic variation at the whole-gene level can be quantified as the average percentage of loci that are _______________
heterozygous
new genes and alleles can arise by what?
mutation or gene duplication
true or false: phenotypic variation is not always the result of genetic differences
true
mutation
change in nucleotide sequence of DNA
mutations in what type of cells can be passed to offspring?
gametes
effects of point mutations
- in noncoding regions often harmless
- can be neutral because of redundancy in genetic code
- can result in change in protein production (harmful)
- can result in change in protein production (beneficial)
altering gene number/position
- chromosomal mutations that delete or disrupt or rearrange many loci are harmful
- duplication of small pieces of DNA increases genome size and is usually less harmful
- duplicated genes can take on new functions by further mutation
mutation rates in animals/plants
low
- repair systems fix many mutations
- average: 1 mutation per 100,000 genes per generation
comparison of mutation rates in prokaryotes and viruses
lower in prokaryotes, higher in viruses
what can sexual reproduction do to existing alleles?
shuffle them into new combinations
in organisms that reproduce sexually, what is more important that mutation to produce genetic differences?
recombination of alleles
- crossing over
population
localized group of individuals capable of interbreeding and producing fertile offspring
gene pool
consists of all the alleles for all loci in a pop
when is a locus fixed in a population?
if all ind. are homozygous for same allele
total number of alleles at locus in diploid organisms
total number of individuals x 2
p + q =
1
what does the Hardy-Weinberg principle describe?
a population that isn’t evolving
- if pop doesn’t meet criteria, it is evolving
what does the Hardy-Weinberg principle state about the frequencies of alleles and genotypes in a pop?
they remain constant from generation to generation
in a given population where gametes contribute to the next generation randomly, what won’t change?
allele frequencies
5 conditions for non evolving pops that are rarely met in nature
- no mutations
- random mating
- no natural selection
- extremely large population size
- no gene flow
natural selection
differential success in reproduction results in certain alleles being passed to the next generation in greater proportions
genetic drift
allele frequencies fluctuate unpredictably from 1 gen to next
- the smaller a sample, the greater the chance of deviation from a predicted result
- tends to reduce genetic variation through loss of alleles
founder effect
- when few individuals become isolate from larger population
- allele frequencies in dif populations can be dif
bottleneck effect
- severe drop in pop size due to change in environment
- resulting gene pool may no longer reflect original pop’s gene pool
- if pop remains small, it may further be affected by genetic drift
summary of genetic drift
- sig. in small populations
- causes allele frequencies to change at random
- can lead to loss of genetic variation within pop
- can cause harmful alleles to become fixed
gene flow
movement of alleles among populations
- can be transferred through movement of fertile ind./gametes
does gene flow increase or decrease variation over time?
decrease
does gene flow increase or decrease fitness of pop?
decrease - lake erie water snake
increase - insecticide resistance in mosquitos
