processes Flashcards
what are the two types of variation in chromosome number?
- change in number of entire sets (polyploidy)
- change in number of single chromosomes within a set (trisomy)
why is variation important?
because there cannot be evolution without variation (it is the fuel of evolution)
what are the different sources of genetic variation?
- chromosome number
- chromosome rearrangements
- point mutation
- homeotic mutation
- transposons
- environmentally induced variation
what are the two levels where mutations are normally expressed?
- changes within a gene product
- changes in the regulation of a gene or its product
what can mutation in regulation affect?
the amount or rate at which a gene product is produced, or whether or not the product is produced at all
what can mutations in a gene product affect?
the amino acid constitution so changes folding
what are homeotic mutations? what genes do they affect?
mutations that transform the identity of one body part into another (affect hox genes)
what are hox genes?
genes that act during the impart identity to regions along the body axis
what are transposons?
sequence that produces special transposase enzymes that allow it to insert copies of itself into various target sites in an organism’s nuclear genome
what can increase transposon activity?
stress
what was Lamarck’s hypothesis on acquired characteristics?
- environment can induce change and we can inherit it
- will can change which characteristics are passed on to the next generation
how can epigenetics change genes?
- increased methylation: turned off
- decreased methylation: turned on
what are two examples of environmentally induced variation? what do these show?
- butterfly experiment: my manipulating temperature, can produce intermediate phenotypes between summer and fall
- ants: by changing nutrition, can induce size changes in ants
are mutations random?
no, they are only random with respect to the environment (internal mutations blind to the external environment), there are preferrable spots (hot spots)
what is the variation equation?
Different types of mutation in different genes regions and different types of genes can lead to different types of genetic and phenotypic evolution
what is an emergent property?
a property that only exists at more complex levels of organization
frequency of alleles is a property of ____, change in frequency is a property of _____, and interpopulation variance is a property of ______
population, population through time (lineage), multiple populations (community)
evolution is a phenomena that occurs at which level of organization?
population and lineage level
what is population genetics?
- concentrates on collections of individuals and their genetic properties
- studies origin, maintenance, and change of genotypic variation in populations and lineages
- utilizes models to study the processes that influence population genetic composition
what causes allele frequencies to change?
- inbreeding
- genetic drift
- natural selection
- mutation
- migration
what are single gene traits and what examples?
they are traits are affected by a single gene (not common)
- ex: cystic fibrosis
- sickle cell anemia
what type of distribution is usually seen for a trait? how is this possible?
-a bell curve (normal distribution)
- possible since have many genes with small additive or subtractive effects that combine with environmental/non-genetic effects
how can selection on population?
- stabilizing selection (more of the middle)
- directional selection (more to one side)
- distributive selection (more of the extremes and less in the middle)
what is breeder’s equation and what does it consider?
R = h^2S (considers the proportion of selection that is actually passed on to the subsequent generation)
what are the effects of reduction in population size?
- demographic threat
- genetic threat
where did conservation genetics originate from?
agriculture and animal husbandry
what are the genetic threats of small populations?
- inbreeding depression: non random assortment of deleterious alleles
- loss of genetic diversity: genetic variation is the “raw-material” for natural selection
- ineffectiveness of selection: natural selection is less effective in small populations
what is inbreeding? what does it lead to? why is it bad?
- breeding with a closely related lineage
- leads to identity by descent (IBD)
- bad since most deleterious alleles are recessive so more chances that they will come together
what is consangunity?
pairing with the same family (or closely related)
what is endogamy?
pairing with other people from a small cultural population
what can cause smaller populations in nature?
habitat destruction and fragmentation
what is the 50/500 rule?
- minimum population size needed
- 50 founding individuals, 500 population size long-term
what is genetic drift?
change due to random probability
does genetic drift affect bigger or smaller populations?
smaller
what accentuates genetic drift?
reproductive success
what is a genetic bottleneck?
special case of severe genetic drift (when goes from big to small population which much different allele distributions by random chance)
what is the founder effect?
special case of genetic bottleneck (when small amount of random people found a new population)
what is the extinction vortex?
- when have small population, will be higher genetic drift and inbreeding
- causes loss of genetic variability, which reduces individual fitness
- causes lower reproduction and higher mortality
- even smaller population…
what is genetic rescue?
- take small, unhealthy population, and have outbreeding with higher diversity population
- there is now increased fertility, which causes lower mortality so increases population growth
- then natural selection can act on the variation
- now have stable population
what are the three types of selection?
artificial, natural, sexual
what is artificial selection usually done for?
for animal and plant breeders, who select for extremes of yield, productivity, or resistance to disease (directional selection)
explain the experiment for color polymorphism in Cepaea.
- they collected snails and found different colors vary in abundance in different habitats
- at anvil rocks, they found shards of rare morphs (birds hunt snails and break their shells at those rocks)
- in deciduous forests the frequency of each morph changes by season
- results: beech-woodland (brown and pink common and green is rare), in meadows (brown and pink rare and green is common), in deciduous (brown and pink common in spring and green is common in summer)
why is sexual selection important?
evolutionary success = reproductive success
what is sexual selection?
when members of one sex compete for the opportunity for preferential mating with members of the opposite sex
what is parental investment? and how does this relate to sexual selection?
in evolutionary terms, eggs are more expensive than sperm, so females will be choosy (sexual selection is weak on females) and there will be male-male competition for access to females (sexual selection strong on males)
what are the two types of male-male competition?
- male-male combat
- sperm competition: some sperm may dislodge or poison sperm from another male
how do females decide which male to chose?
the male will display or show flashy trait in front of females, which displays good genes
explain the barn swallow experiment.
- these birds go to africa in winter and europe to breed
- males set up territories to attract females
- they are sexually dimorphic (males have longer tails)
- experiment 1: shorten tail by cutting
- experiment 2: lengthening tails by gluing
- controls: had a cutting and gluing control
- results: showed that longer tails have greater number of fledglings and shorter have less
explain the guppies experiment.
- guppies in different pools have different life-history characteristics induced by the presence or absence of predators
- experiment 1: lab - stimulate natural conditions and add predators
- experiment 2: wild - swap populations of guppies
- result: was more colourful without predators
what is a species?
a fundamental taxonomic category to which individual specimens are assigned
what is speciation?
the process by which new species arise
what are the three species concepts?
- biological
- morphospecies
- phylogenetic
what is the biologic species concept?
defined as a reproductively isolated community in which all individuals potentially or actually interbreed amongst themselves, but are genetically isolated from other groups
how are speciation and natural selection linked?
the pattern of speciation says something about the pattern of natural selection
what are the advantages and disadvantages of biological species concept?
- advantage: defines species on the basis of criteria important to their evolution (that is reproductive isolation), and members of the species self-define the boundaries of their own species
- disadvantages: exceptions exists (some species interbreed), takes too much time to test, doesn’t apply to asexual organisms, doesn’t apply to dead/extinct
what is the morphospecies concept?
species are composed of individuals that are phenotypically similar, so are distinguishable by phenotypic differences in morphology and embryology
what are the advantages and disadvantages of the morphospecies concept?
- advantage: can be applied easily
- disadvantages: requires arbitrary decisions, no mechanistic definition, and some distantly related species may have similar features
what is the phylogenetic species concept?
defined as a monophyletic group composed of the smallest diagnosable cluster of individual organisms within which there is paternal pattern of ancestry
what are the advantages and disadvantages of the phylogenetic species concept?
- advantage: focuses on operationally defining species
- disadvantages: the method used for construction has effect on outcome, history of different genes can give different results, can’t use fossil record/dead organisms, expensive, no mechanistic definition
what is allopatric speciation?
speciation by geographic isolation
what are the steps to allopatric speciation?
- geographic isolation
- local adaptation
- reproductive isolation
what is reproductive isolation?
obstacles to interbreeding between genetically distinct species
what are the 2 types of reproductive isolating mechanisms?
- pre-zygotic (before fertilization)
- post-zygotic (after fertilization)
what are the pre-zygotic reproductive isolating mechanisms?
- geographic (are in different places)
- ecological (species use different resources in same habitat)
- behavioral (different mating rituals)
- temporal (different mating season)
- mechanical (mating apparatuses don’t fit)
- prevention of gamete fusion
what are the post-zygotic reproductive isolating mechanisms?
- hybrid embryos don’t develop properly
- hybrid adults don’t survive in nature
- hybrids are sterile
evolution and diversity is driven by both ____ and ____.
speciation and extinction
what are living fossils? (give some examples)
found in fossil records continuously (lingula and horseshow crabs)
what are the types of extinction?
- uniform/background
- catastrophic/mass
what is uniform extinction? what causes it?
- members are lost gradually over time periods without abrupt loss of large numbers
- caused by ecological causes
what is the red queen hypothesis?
species must evolve quickly to keep up with competitors and change in environments, when a species falls behind it risks becoming extinct
what are mass extinctions? how many have there been throughout time?
- the loss of species from many different groups (also takes large number of species)
- there are 5
what are the 5 mass extinction?
- end ordovician
- late devonian
- end permian
- end triassic
- end cretaceous
