Chapter 4 Flashcards
forces in evolution are those that happen….
forces in evolution are those that happen in natural populations that cause change in gene frequencies over multiple generations
is natural selection the only force of evolution
natural selection is not the only force of evolution
what are the 5 forces of evolution
mutation, natural selection, gene flow, genetic drift and nonrandom mating
Where does Variation Come From?
point mutation—
chromosomal mutations
what are chromosomal mutations
entire chances of chromosomes are transposed with one another
what are point mutation—
change in a base in a DNA molecule
des natural Selection operate on the genotype or the phenotype
operates on the phenotype of an individual organism
how does the environment influx the traits that are expressed
the environment is the filter in which traits—and genes that control their expression— are selected for or against
do individuals evolve
populations evolve as the frequency of certain genes changes; individual organisms do not evolve
what is directional selection—
natural selection that drives the evolutionary change by selecting for greater or lesser frequency of a given trait in a population
e.g. the finches and how their beak change dramatically when the drought hit, then changed again when rain came
what is stabilizing selection—
selection that maintains a certain phenotype by selecting against deviations from it
basically the opposite of directional selection
what are Other Ways by Which Evolution Happens
gene flow
genetic drift
what is gene flow
movement of genes between populations
what is migration—
when animals are on the move… this is different than gene flow but related in the sense that gene flow only happens when migration does
the production of offspring between people of different laces and characteristics results in this
what is admixture—
when a population receives genetic contribution (from other population for a long period of time)
this creates one large gene pool spread across 2 areas through extensive interbreeding
if for some reason the interbreeding stops (war, geographical barrier like a flood between populations), the lack of gene flow between populations means that random mutations that were passed between them are now confined to only one populations
as they accumulate, the 2 populations will diverge genetically and perhaps anatomically as well
what is inbreeding—
mating between close relatives
it has been believed that this is bad for the health of the population, but very limited amounts of gene flow can eliminate the harmful effects of inbreeding… this is not normal or healthy but apparent low levels of immigration can offset the harmful effects in a population
what is genetic drift—
random changes in gene frequency in a population
basically says that all the changes are by chance… the alleles that are passed down and stuff
even though Mendel says differently, that does not always happen and this theory says it is completely random
what are the subcategories of genetic drift
founder effect
genetic bottleneck
what is founder effect—
another aspect of genetic drift; stating that new populations that become isolated from the parent population carry only the genetic variation of the founders
meant that the offspring will only ever have the variation of the parents
real life e.g; amish people remain closed off from the American culture and many genetic diseases that are rare in the main population are common for the amish because their ‘founders’ had it when they migrated and the mutation have not had a chance to be eliminated
what is genetic bottleneck—
temporary dramatic reduction in size of a population or species
phenomenon associated with the founder effect
when the population declines, a large amount of alleles are lost and after the bottleneck, only the accumulation of mutations will being back diversity
e.g.when humans hunt specific looking seals into extinction… if there is no diversity then the population will not be able to survive something like a disease… it would wipe all of them out
who came up with sexual selection
darwin
what are the 2 components in sexual selection;
the struggle between males to gain access to mates and the struggle by a female to choose the right mate
females choose based on natural variation in the male
what drives the traits of males
it is the female choice that drives the traits of males, the results certain male traits (they pick only the ones they like)
what is sexual dimorphism—
difference in size, shape or colour between the sexes
cased by females
Why does she choose the ones she does?
may use physical features to judge his reproduction ability or protection against predators
what is runway sexual selection—
in this process, female preference for this trait and males evolution of this trait so they constantly reinforce each other and result in elaborate traits
what is costly signalling (derived from handicap principle)—
males may have such outlandish traits in order to prove to the female that he can survive even with the elaborate trait they have
what is reproductive potential—
the possible output of offspring by one sex
why do females choose and male compete; the belief if that the sex with more investment get to choose (aka parental investment)
what is reproductive variance— a measure of variance from the mean of a population in the reproductive potential of one sex compared to the other
males and females differ greatly in terms of their reproductive variance
a measure of variance from the mean of a population in the reproductive potential of one sex compared to the other
males and females differ greatly in terms of their reproductive variance
how did Linnaeus classified things
based oh psychical observation
what is systematics—
branch of biology that describes patterns of organismal variation
what do systematics rely on
systematics rely on homology— similarity of traits resulting from shared ancestry
what is analogous—
having similar traits due to similar use, not shared ancestry
what is convergent evolution—
similar form or function brought about by natural selection under similar environments rather than shared ancestry
what is anatomical character—
physical features (to categorize the organisms)
what is derived characters—
features that they alone possess that distinguishes them from all other organisms
what is phylogeny—
family tree of evolutionarily relatedness of one form or another
what is cladistics—
branch of evolutionary classification, method of classification using ancestral and derived traits to distinguish patterns of evolution within lineages
what is clade—
cluster of species linked by a set of unique traits
what is cladogram—
`cladogram— branching diagram showing evolved relationships among members of a lineage
does not depict the difference in time between clades
at least one problem with the approach; what if a trait (a monkey’s tail for example) has evolved twice, or disappeared then reappeared? that would be highly unlikely! This is called the law of parsimony (aka Occam’s razor)— always use the simplest explanation
what is anther approach to systematics— phenetics
numerical taxonomy, uses all traits that link 2 organisms together, regardless of homology or analogy… relies strictly on numerically describing degrees of similarity and difference between organisms… without bias created by knowing some are closer related to others
problem; unrelated animals sometimes clumped into groups
this approach is largely out of fashion now
what is species—
an interbreeding group of animals or plants that are reproductively isolated through anatomy, ecology, behaviour or geographic distribution from all other such groups… this is actually very hard to define! and the question of “what is a species” remains
what is speciation—
formation of one or more new species via reproductive isolation
what is biological species concept—
defines species as interbreeding populations reproductively isolated from other such populations
this definition refers to natural populations only… tiger and lion are different species yet when they are put in a cage together, they readily breed
this is not the only definition of a species
what is evolutionary species concept—
defines species as evolutionary lineages with their own unique identity
people who use this definition typically study fossils and cannot observe the reproductive isolation mentioned int he above definition
what is ecological species concept—
defines species based on the uniqueness of their ecological niches
what is recognition species concept—
defines species based on unique traits if behaviours that allow members of one species to identify each other for mating
goes along with the biological species concept
what are Reproductive Isolating Mechanisms (RIMs)
any factor— behavioural, ecological or anatomical— that prevents a male and female of 2 different species from hybridizing
have been built into the phenotypes of animals
what are the 2 categories of Reproductive Isolating Mechanisms (RIMs)
2 categories; premating isolation mechanisms and postmating isolation mechanisms
what is anagenesis—
evolution of a trait of species into another over a period of time
what is cladogenesis—
evolution through the branching of a species of a lineage
what is allopatric speciation—
speciation occurring via geographic isolation
natural selection favours what kind of isolating mechanisms
premating isolation mechanisms
what is parametric speciation—
another form of speciation, occurring when 2 populations have continuous distributions and some phenotypes in that distribution are more favourable than others
what is sympatric speciation—
speciation occurring in the same geographical location
what is gradualism—
Darwinian view of slow, incremental evolutionary change
there is evidence of this, but how do we explain the gaps in the fossil record? scientists point out that fossils are fragmented so if it were completed, it would should the gradualism… creationists say that a divine being had to have made at least some of the organisms so thats why they have no ancestral evidence
what is macroevolution—
alternative explanation for gaps in records; evolution of major phenotypic changes over relatively short time periods
what is punctuated equilibrium
most cited mode of macroevolution is punctuated equilibrium— model of evolution characterized by rapid bursts of change, followed by ing periods of stasis
what is an adaptation
Some evolutionary biologist consider any well-designed trait in organism possesses to be an adaptation. Use the stricter definitions, they consider an adaptation to be a trait that evolved for a purpose and is still serving that purpose. A trait that evolved for a purpose other than what it does today would not be considered an adaptation
what is adaptationism—
a premise that all aspects of an organism have been molded by natural selection to form optimal for enhancing reproductive success
what is reductionism
adaptationists tend toward reductionism— paradigm that an organism is the sum of many evolved parts and that organisms can best be understood through an adaptationist approach
what is the Hardy-Weinburg Equilibrium used for
what would populations look like if they never evolved? that is not a realistic question to test, but it is testable in a mathematician’s lab
the theoretical distribution of alleles in a given population in the absence of evolution, expressed as a mathematical equation
what is Null hypothesis—
a starting assumption for scientific inquire, that one’s research results occur by random chance. One’s hypothesis must challenge this initial assumption
what did Hardy put to rest
any ideas of “blending” inheritance that people once thought occurred
what is group selection—
notion, largely discredited by the ride of Darwinian theory. proposing that animals act for the good of their social group or of their species
basically that when animals overcrowd, they regulate their reproduction rather than overpopulate and outstrip their food sources
why is altruism surprising
individual selection leads us to believe that all behaviour should be selfish; altruism should be very rare
but social animals tend to behave in the benefit for their relatives, often in the detriment of their non-relatives
what is kin selection—
principle that animals behave preferentially toward their genetic kin; formulated by William Hamilton
part of a larger concept named inclusive fitness
what is inclusive fitness—
reproductive success of an organism plus the fitness of its close kin
close kin should behave less competitively with one another
