final exam study guide Flashcards
disruptive selection
favors individuals at both extremes of phenotypic range
directional selection
favors individuals at one extreme end of the phenotypic range
stabilizing selection
favors intermediate variants and acts against extreme phenotypes
characteristics of asexual reproduction
-no single parent
-no fusion of gametes
-usually offspring are genetically identical
strategies of asexual reproduction
-binary fission
-budding
-clonal fragmentation
clone
A group of genetically identical individuals or cells.
sexual reproduction is
reproduction arising from fusion of gametes and allows individuals to combine subsets of their genome with other inviduals
why use both asexual and sexual reproduction
because of the environmental stability: asexual reproduction is advantageous in stable environments and sexual is advantageous in unstable environments
what is the connection between genotype, phenotype and evoution of species
phenotype was the phsyical characteristic of genotype. The phenotype is not necessarily passed down while genotype are heritable traits that drive evolution via natural selection
sources of genetic variation are….
new genes and allles can arise by mutation or gene duplication. Sexual reproduction can add to genetic variation among individuals by recombining existing alleles.
which mutations are passed to offspring
only mutations occuring in gametes
what can extend genome length
duplication of genes due to errors in meiosis
where does most genetic variation come from with sexual reproduction
from recombination of alleles
three mechanisms that can shuffle exciting alleles into new combinations are
-crossing over
-independent assortment
-random fertilization
can individuals evolve
no, only populations
what is evolution at its finest level
a change in allele frequencies in a population over generations
what are the three main mechanisms that cause allele frequency change
-natural selection
-genetic drift
-gene flow
adaptive evolution
traits that increase fitness overtime
what is the only thing that causes adaptive evolution
only natural selevction
Natural selection
A process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits.
Genetic drift
A process in which chance events cause unpredictable fluctuations in allele frequencies from one generation to the next. Effects of genetic drift are most pronounced in small populations.
Gene flow
The transfer of alleles from one population to another, resulting from the movement of fertile individuals or their gametes.
what are mechanisms of genetic drift
-founder effect
-bottleneck effect
does geentic drift have to be associated with a natural disaster
no
How is natural selection more “predictable” than genetic drift?
in that it alters allele frequencies in a nonrandom way: It tends to increase the frequency of alleles that increase the organism’s reproductive success in its environment and decrease the frequency of alleles that decrease the organism’s reproductive success.
what does gene flow tend to do with variation
tends to reduce variation between popualtions and increase variation within a popualtion
natural selection results in…
alleles being passed to next generation in proportions that differ from those in the present generation in a nonrandom way
Why is natural selection the only mechanism that consistently leads to adaptive evolution in a population
Although both gene flow and genetic drift can increase the frequency of advantageous alleles in a population, they can also decrease the frequency of advantageous alleles or increase the frequency of harmful alleles. Only natural selection consistently results in an increase in the frequency of alleles that enhance survival or reproduction. Thus, natural selection is the only mechanism that consistently leads to adaptive evolution.
what are the three general modes of natural selecrion that affect quantitative trait/character
-direcional selection
-disruptive selection
-stabilizing selection
what mode of natural selection is this
stabilizing
what mode of atural selection is this
disruptive
what mode of natural selection is this
directional
Quantitative trait/character
A heritable feature that varies continuously over a range rather than in an either-or fashion
Sexual dimorphism
marked differences between the sexes in secondary sexual characteristics
example of sexual dimporphism
elephant seal
which is usually the showier sex
males
intrasexual selection
competition among individuals of one sex (usually males) for mates of the opposite sex
Intersexual selection (aka mate choice)
individuals of one sex (usually females) are choosy in selection of mates
what does intersexual selection depend on
showiness of males behavior/appearnce
what are the reasons why natural selection cannot fashion perfect orgaisms
- selection can act only on existing variations
- evolution is limted by historical constraints
3.adaptations are often compromied
4.chance, natural selection, and the environmnet interact
how will a population’s allele and genotype frequecnues reain if no evolutionary force acts upon them
constant
what doe sthe hardy weinberg equilibrium serve as
a baseline for comparison to data collected from a population
if there is no difference in data collected then
the population is not evolvingif
if there is a difference with data collected
then the poulation is evolving
Hardy-Weinberg Equilibrium
the state of a population in which frequencies of alleles and genotypes remain constant from generation to generation
what are the five conditions that need to be met if a population is not evolving
- no mutations
- random mating
3.no natural selection
4extremely large population size - no gene flow
whne is the gene pool modified
if mutaitons occur or if the entire gnees are deleted or duplicated
how do allele frequecnies fluncuate with small populations
allele frequencies fluncutae by chance over time (a process called genetici dirft)
p with hardy weinberg equation is
dominant allele frequency
q with hardy weinberg equation is
recessive allele frequency
p^2 with hardy weinberg equation is
homozygous dominat (CC)
2pq
heterozygous (Cc)
q^2
homozygous recessive (cc)
what is a specied (macroorganisms)
group of orgaisms that produce viabe, fertile offosroing under natural conditions
reprodutcive isolation
barriers that prevent memevers of two species from producing viable offspring
what is a species (microorganism)
genetically related enough (defined threshold) and fulfill same ecolofical roles
how can speciation take place
with or without geographic isolation
allopatric speciation
a popualtion forms a new species while geographica.y siolated from its parent population
traits of allopatric speciation
-areas with divided barriers have more species (island chain)
-does not have to be a physical wall/barrier
sympatric specaition is
a subset of a population forms a new species without geographic isolation
sympatric isolation charcateristcs
-less common
-driven by sexual selection ot utilization of a different food or habitat
how long does it take for annew species to evolve ad how many genes influence formaiton of new species
highly variabe but on average takes millions of years (much shorter for microbes because of fast geneeration time)
how many genes doe sit take to result in reproductive isoaltion
one, many (eough to cause reproductive isolation)
what is ecolofy
study of the interaction between oragnisms and their environment
what elemnts do environments include
biotic and abiotic
What is the relationship between Ecology and Evolution?
While ecology observes the interactions between organisms and their environment in the present, evolution explains how those interactions have developed over time and continue to change. Both fields are crucial for understanding the complex dynamics of life on Earth.
wha are the interspecific interactions and what can they lead to
-predation
-competition
-symbiosis
can lead to coevolution
what can competition lead to
competitive exlcusion
Competitive exclusion
when populations of two similar species compete for the same limited resources, one population will use the resources more efficiently and have a reproductive advantage that will eventually lead to the elimination of the other population
Can a species’ ecological niche be influenced by competition?
yes
Ecological niche
the specific set of biotic and abiotic resources that an organism uses in its environment
Fundamental niche
what can be used
Realized niche
what is used in nature
given ebough time what can compeition sometimes lead to
resource partititoining and species coexistsence
character displacemnt
The tendency for characteristics to be more divergent in sympatric populations of two species than in allopatric populations of the same two species; the evolutionary divergence in characteristics (morphological, behavioral, or ecological) of two species that are in contact, compared to when these species are isolated
Resource partitioning
the division of environmental resources by coexisting species
how does resource partitioning differ from charcerter displacemnt and how are they related
-resource partitiioning is ecological strat that allows species to coexist by using shared resources in diff ways
-charcter displacemnet is evolutionary response to comp leading to divergence in traist when species are in contact
what does resource partitioning lead to
cgarcater displacement
what causes adaptive radiation
ecological opportuntiy and key innovation
what is ecological opportuntiy
-invasion of unutilized ecological resouces leads to rapid diversificaiton
example of ecological opportunity
colonizing a remote island, surviving a mass extcintion
what is key innovation
acquisiting of a novel adaptive trait that allows orgabisms to exploit previsoulty unavailable ecological resources
example of key innovation
mammals developing molars to help them digest food
can extinction and adaptive radiion be connected
yes, mass exntinction can mark the end of an era and the rise of a new one due to the openended ecological niches which drive adpative radiaiton
