Evolution Flashcards
Evidence of evolution I evidence of evolution II the selection process I the selection process II origins of species
what is the definition of evolution
descent with modification
what is the plural of genus
genera
what is palaeontology
the study of fossils
what is an adaptation
inherited characteristics of organisms that enhance their survival and reproduction in specific environments
what is 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
the favourable traits are seen at a higher frequency in future generations
what is artificial selection
the process where humans select and breed organisms with desired traits
TRUE/FALSE individuals evolve
FALSE the population evolves over time
TRUE/FALSE evolution by natural selection can only occur when the individuals in the population differ in that trait
TRUE if all the individuals in a population were genetically identical for a trait then evolution by natural selection cannot occur
TRUE/FALSE a trait that is favourable in one place may be useless in another place
TRUE the traits favoured depends on the organisms environment
what is an example of ongoing evolution that dramatically effects humans
the evolution of drug resistant pathogens
how do resistant strains of bacteria emerge
some penicillin strains disrupt the cell wall of bacteria by deactivating their enzymes
bacteria became able to synthesise their cell walls using a different bacteria that penicillin couldn’t attack
these bacteria reproduced at higher rate compared to other bacteria and the resistant individuals become increasingly more common
how can bacteria become resistant to antibiotics so quickly
they can proliferate quickly and can exchange genetic material with members of their own species and other species (a resistant bacteria can pass the resistant gene to other bacteria making them resistant too)
natural selection is a process of ………………., not a creative mechanism
editing
a drug does not create a resistant pathogen it selects for resistant individuals that are already present in the population
what is homology
similarity resulting from common ancestry
what are homologous structures
e.g. the underlying skeletons of arms, forelegs, flippers
these structures are shared due to a presence in their common ancestor
how else can anatomical homologies be compared apart from comparing what is visible in adult organisms
we can compare early development of different organisms
what two structures do all vertebrate embryos have at some stage in their development
a tail behind the anus
pharyngeal aches
both of these develop into different structures in different species and can have very different functions
what are vestigial structures
leftover structures of marginal or no importance to the organism that served a function in the organisms ancestor
e. g. vestiges of leg bones in snakes
e. g. eye remnants in blind species
what molecular similarities suggest that all species descended from common ancestors
they all use the same genetic code and some genes have the same functions in different species
what is an evolutionary tree
a diagram that represents evolutionary relatedness among groups of organisms
what is convergent evolution
the independent evolution of similar features in different lineages
resemblance due to convergent evolution is referred to as ……………. instead of homologous
analogous
what is the difference between analogous and homologous
analogous features - similar function but no common ancestry
homologous features - common ancestry but not necessarily a similar function
where does the evidence of evolution come from
taxonomy
comparative anatomy
fossils and geology
biogeography
what is biogeography
the study of the geographic distribution of species
what does it mean if a plant or animal species is endemic
they are found nowhere else in the world
how do we categorise organisms
by comparing them with potential close relatives
what is phylogeny
the evolutionary history of a species or a group of species (phylogenetic tree)
what is systematics
a discipline focused on classifying organisms and determining their evolutionary relationships
what is taxonomy
the study of naming and classification of organisms
what is a binomial
the 2 part Latin name of an organism
what is the first part of the binomial
the name of the genus
what is the second part of the binomial
the specific epithet and is unique for each species in a genus
what is the order of classification from specific to non specific
species genus family order class phylum kingdom domain
what is a taxon
the named taxonomic unit and any level of the hierarchy
e.g. panthera is the taxon of a leopard at genus level
what does a branch point in a phylogenetic tree represent
the common ancestor of two evolutional lineages diverging from it
what are sister taxa
groups of organisms that share an immediate common ancestor that is not shared by any other group
the members of a sister taxa are each others closest relatives
what does the root of a phylogenetic tree represent
the most recent common ancestor of all the of all the taxa in the tree
what data can systematists use to infer phylogeny
morphology
genes
biochemistry
when does convergent evolution occur
when similar environmental pressures and natural selection produce similar adaptations (analogs) in organisms from different evolutionary lineages
the more complex the two similar structures when comparing organisms the more likely the evolution was convergent/divergent
divergent - they shared a common ancestor
what are molecular homoplasies
coincidental matches in the DNA of two organisms
if more than 25% of DNA bases match it is likely that the organisms are homologous/analogous
homologous
what is cladistics
an approach to systematics in which organisms are placed into groups called clades based primarily on common descent
what is a clade
a group of species that includes an ancestral species of all its descendants
a clade is equivalent to a monophyletic group
what is a paraphyletic group
consists of ancestral species and some but no all of its descendants
what is a polyphyletic group
includes distantly related species but does not include their most recent ancestor
for mammals, the backbone is what
a shared ancestral character - a character that originated in the ancestor of the taxo
for mammals, hair is what
a shared derived character - an evolutionary novelty unique to a clade
what is an outgroup
a species or group of species from an evolutionary lineage that is closely related but not part of the group of species being studied
what is the ingroup
the group of species being studied
what is the principal of maximum parsimony
the simplest explanation that is consistent with the facts
what is the principal of maximum likelihood
identifies the tree most likely to have produced a given set of data based on probability
what 2 principle need to be used when creating a phylogenetic tree
maximum parsimony and maximum likelihood
what are gene families
groups of related genes within an organisms genome
what are the two types of homologous genes
orthologous and paralogous
what do orthologous genes result from
Orthologous genes are homologous genes that diverged after evolution gives rise to different species, an event known as speciation.
The genes generally maintain a similar function to that of the ancestral gene that they evolved from
e.g. cytochrome c has the same function in humans and dogs
what do paralogous genes result from
Paralogous genes are homologous genes that have diverged within one species. Unlike orthologous genes, a paralogous gene is a new gene that holds a new function. These genes arise during gene duplication where one copy of the gene receives a mutation that gives rise to a new gene with a new function, though the function is often related to the role of the ancestral gene.
e.g. this is how all the different olfactory receptor genes arose
what is a molecular clock
an approach for measuring the absolute time of evolutionary changed based on the observation that some genes appear to evolve at constant rates
what causes the difference in the speed that clock like mutations occur
the more neutral mutations the faster the change in the gene
what are the 3 domains
bacteria
archaea
eukaryotes
what is horizontal gene transfer
genes are transferred from one genome to another though different mechanisms
what is gradualism
profound changes can be the result of small changes over long periods of time
what is catastrophism
recurrent catastrophic events causing widespread extinction and resulting in sharp boundaries between fossil areas
what is Uniformitarism
the same processes seen today that also acted in the past
what are the 5 causes of evolution
natural selection non random mating genetic drift dene flow mutation
for natural selection to occur what 3 conditions must be fulfilled
variation differential selection
inheritance
what is non-random mating/sexual selection
individuals with particular traits are more likely to mate
what is genetic drift
random changes in the frequency of traits due to chance factors
e.g. the founder effect and the bottleneck effect
what is the founder effect
A small group establishes a new population with a different gene pool
what is the bottleneck effect
A small fraction of the population survives that is no longer representative of the original population
what is gene flow
changes due to movement from one place to another
Gene flow is the transfer of alleles from one population to another population through immigration of individuals
how does natural selection work
- Organisms differ from one another i.e. there is variation
- These differences are heritable i.e. passed from generation to generation
- Many more organisms are born than survive and reproduce (mortality)
- Therefore, any variation that makes one offspring more successful than another will have a greater chance of being past to the next generation (survival of the fittest)
what is microevolution
small scale evolution - a change in allele frequencies in a population over generations
what 3 mechanisms cause allele frequency change
natural selection
genetic drift
gene flow
phenotypic variation often reflects ………. variation
genetic
how can gene variation be quantified at the whole gene level
the average percentage of loci that are heterozygous (two different alleles for a locus)
why does nucleotide variation result in less phenotypic change than gene variation
many nucleotides occur within introns so are spliced from the mRNA
of those variations that occur in exons most of them do not result in an amino acid change. however when the amino acid changes this generally alter the protein causing genetic variation and 2 forms of the protein
when does genetic variation result
it can originate from
- gene duplication
- mutation
- other processes that produce new alleles and new genes
genetic variations can be produced rapidly in organisms with short/long generation times
short
what is a point mutation
a change in one base pair
in diploid organisms harmful alleles that are dominant/recessive can be hidden from selection
recessive
point mutations in noncoding regions generally results in …………… variation
neutral
how does redundancy in the genetic code effect the outcome of a point mutation
even though a point mutation occurs the amino acid composition may not be changed due to wobble
how can point mutations that alter an amino acid still be neutral
even if the amino acid was changed it still may not be significant enough that the shape and function of the protein changes
how can mutations be passed to offspring
only mutations in cell lines that produce gametes can be passed to offspring
in animals the majority of mutations that occur in somatic cells are/are not passed to offspring
are not
give an examples of how gene duplication can occur
errors in meiosis such as unequal crossing over
slippage during DNA replication
activities of transposable elements
how can small gene duplications that currently confer no effect cause harm in the future
they can persist over generations allowing mutations to accumulate
it results in an expanded genome with new genes that may take on new functions
how did we develop 380 functional olfactory receptor genes
the olfactory gene duplicated many times and the duplicated genes developed new functions
mutation rate in prokaryotes is higher/lower than in plants and animals
lower - but they have many more generations per unit time so mutations can quickly create genetic variation
RNA has a higher/lower mutation rate than DNA
higher because it lacks the proofreading systems of DNA
what mechanisms contribute to shuffling of alleles in sexual reproduction
crossing over
independent assortment
fertilisation
does the presence of genetic variation guarantee that a population will evolve
no - more factors that influence evolution need to be present
what is a population
a group of individuals in the same species that live in the same area and interbreed, producing fertile offspring
what is a gene pool
all the copies of every type of allele at every locus in all members of the population
when is an allele said to be fixed in the gene pool
if only one allele exists for a particular locus in a population and all individuals are homozygous for that allele
if a population is not evolving what happens to allele and genotype frequencies
they will remain constant from generation to generation (hardy-weinburg equilibrium)
what 5 conditions must be met for a population to be in hardy-weinburg equilibrium
- no mutations - gene pool is not modified
- random mating
- no natural selection
- extremely large population size - genetic drift occurs in small populations
- no gene flow - no alleles moving in or out of populations
an allele that confers resistance to an insecticide will increase/decrease in frequency in a population exposed to that insecticide
increase
what is adaptive evolution
a process in which traits that enhance survival or reproduction tend to increase in frequency over time by natural selection
genetic drift affects smaller/larger populations more
smaller
what two circumstances can result in genetic drift
founder effect
bottleneck effect
what is genetic drift
a process in which chance events cause unpredictable fluctuations in allele frequencies from one generation to the next
how can genetic drift lead to a loss of genetic variation in a population
it can eliminate alleles from a population decreasing the variation
how can genetic drift cause harmful alleles to become fixed
it happens by chance
why does gene flow occur
either due to the movement of fertile individuals or their gametes
how can gene flow result in 2 populations combining with a single gene pool
because alleles are transferred between populations, gene flow tend to reduce the genetic differences between populations
is the outcome of natural selection random
no - it involves a chance event i.e. a mutation but the events that follow are not by chance
what is relative fitness
the contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals
does selection act directly on the genotype or phenotype of an organism
it acts directly on the phenotype but indirectly on the genotype via how the genotype affects the phenotype
what are the 3 types of selection depending on which phenotypes in the population are favoured
directional
stabilising
disruptive
when does directional selection occur
when conditions favour individuals exhibiting one extreme of a phenotypic range (often occurs when a populations environment changes e.g. larger beak favoured for larger seeds)
what is disruptive selection
when conditions favour both extremes both extremes of a phenotypic range over individuals with an intermediate phenotype (if there are very soft and very hard seeds available, intermediate beak is inefficient for both cases)
what is stabilising selection
when conditions favour intermediate variants (e.g. birth weights - intermediate weights have higher chance of survival)
what is the only evolutionary mechanism that consistently leads to adaptive evolution
natural selection
what is sexual selection
a process in which certain individuals with inherited characteristics are more likely than other individuals of the same sex to obtain mates
sexual selection can result in sexual dimorphism what is this
a difference in secondary sexual characteristics between males and females of the same species (e.g. size, colour behaviour)
what is Intrasexual selection
selection within the same sex
individuals of one sex compete directly for mates of the opposite sex (e.g. male deer fighting)
what is intersexual selection
also called mate choice (e.g. females prefer male traits that are corelated with good genes
what is balancing selection
natural selection that maintains two or more phenotypic forms in a population
includes:
frequency dependent selection
heterozygote advantage
what is heterozygote advantage
recessive alleles persist because they are hidden from selection
individuals that are heterozygous have more of an advantage than either homozygote and natural selection maintains heterozygosity
what is frequency dependent selection
selection in which the fitness of a phenotype depends on how common the phenotype is in a population
give an example of heterozygote advantage
heterozygotes for sickle cell anaemia are protected from malaria
selection can act only on existing ……….
variations
give an example of frequency dependent selection
fish with right mouths always attack from the left and so prey species begin to guard against this so the next year left mouth fish are favoured
what is the result of speciation
one species splits into 2 or more species
what is macroevolution
the broad pattern of evolution above the species level
e.g. new groups of organisms through a series of speciation events
what is the biological species concept
a species is a group of populations whose members have the potential to interbreed in nature and produce viable fertile offspring
…….………. occurs between different populations of a species and the ongoing exchange of alleles tends to hold populations together genetically
gene flow
a reduction or lack of gene flow can play a key role in …….….
speciation
what is reproductive isolation
the existence of barriers that impede members of 2 species from interbreeding and producing viable fertile offspring
barriers block gene flow between the species and limit the formation of hybrids. what are hybrids
offspring that result from interspecific mating
give examples of reproductive barriers
prezygotic: habitat isolation temporal isolation behavioural isolation mechanical isolation gametic isolation postzygotic: reduced hybrid viability reduced hybrid fertility hybrid breakdown
what are prezygotic barriers
they block fertilization from occurring
what are postzygotic barriers
errors after the hybrid zygote is formed
does the biological species concept apply to organisms that reproduce asexually all or most of the time
no
species are designated by the absence of ……………….
gene flow
what is the morphological species concept
distinguishes a species by body shape and other structural features
can the morphological species concept be applied to organisms that reproduce sexually and organisms that reproduce asexually
yes
what is the ecological species concept
it defines a species in terms of its ecological niche, the sum of how members of the species interact with the non-living and living parts of the environment
can the ecological species concept accommodate sexual and asexual species
yes
what is allopatric speciation
speciation that results when gene flow is interrupted when a population is divided into geographically isolated subpopulations
give an example of allopatric speciation barriers
- when water level in a lake subsides resulting in 2 or more smaller lakes that are home to separate populations
- a river may change course and divide a population of animals that cannot cross it
once geographic isolation has occurred the separated gene pools may …….
diverge
describe the steps in allopatric speciation
- a population is separated into subpopulations by a geographical barrier
- different mutations arise in each subpopulation
- natural selection and genetic drift may alter allele frequencies in different ways in the subpopulations
- genetic divergence results and reproductive isolation may evolve
reproductive isolation between 2 populations generally increases/decreases and the geographic distance between them increases
increases
what is sympatric speciation
speciation that occurs in populations that live in the same area
what is more common sympatric or allopatric speciation
allopatric - the ongoing gene flow in sympatric speciation makes it less common to occur
sympatric speciation can occur if gene flow is reduced by factors such as:
polyploidy
sexual selection
habitat differentiation
what is polyploidy
a chromosomal alteration in which the organism possesses more than 2 complete chromosome sets. it is the result of an accident in cell division
polyploid is most common in animals/plants
plants
what are the 2 forms of polyploidy
autopolyploid
allopolyploid
what is an autopolyploid
an individual that has more than 2 chromosome sets that are all derived from the same species
what is a tetraploid
an organism that has double the number of chromosomes due to failure of cell division
can tetraploid organisms produce fertile offspring
yes but they are also tetraploid
they produce the offspring by self mating or by mating with other tetraploids
why are tetraploids reproductively isolated from 2n plants of the original population
because the triploid (3n) offspring of such unions have reduced fertility
how does an allopolyploid occur
when 2 different species interbreed and produce hybrid offspring and in subsequent generations a sterile hybrid can turn into a fertile polyploid called an allopolyploid
why are most hybrids sterile
the set of chromosomes from one species cannot pair during meiosis with the set of chromosomes from the other species (they are not homologous with each other)
how can an infertile hybrid reproduce
it may be able to asexually propagate itself
allopolyploids are fertile when mating with each other but can they mate with their parent species
no
why do allopolyploids and autopolyploids represent new species
because in both cases there is a reproductive barrier preventing gene flow
describe the gametes of tetraploid organisms
diploid
give examples of polyploid plants
potato, tobacco, wheat
how can polyploids be generated in the lab
by using chemicals that promote errors in meiosis and mitosis
how can sympatric speciation be driven by sexual selection
e.g. mate choice based on male breeding colouration can act as a reproductive barrier that keeps the gene pools of the 2 species separate
how can sympatric speciation occur from habitat differentiation
can happen when a subpopulation exploits a habitat or resource not used by the parent population
give examples of processes that produce genetic changes that result in allopatric speciation
natural selection under different environmental conditions
genetic drift
sexual selection
what is a hybrid zone
a region in which members of different species meet and mate producing at least some offspring of mixed ancestry
when do hybrid zones form
when 2 species lacking complete barriers to reproduction come into contact
what can alter the location of a hybrid zone
changes in environmental conditions such as temperature
how can a hybrid zone be a source of novel genetic variation that improves the ability of one or more species to cope with changing environmental conditions
an allele found in only one parent species is transferred to hybrid individuals. it is then passed to the other parent species when the hybrids breed with the second parent species
if the hybrids don’t become reproductively isolated and form a new species from the parent species, what are the other possible outcomes for the hybrid zone over time
reinforcement barriers
fusion of species
stability
hybrids are often less/more fit than members of their parent species
less
what is reinforcement
when hybrid are less fit than the parent species natural selection should strengthen prezygotic barriers, reducing thee formation of unfit hybrids (it involves reinforcement of the barriers)
if reinforcement is occurring then barriers to reproduction between species should be stronger for sympatric/allopatric populations
sympatric
what is fusion
the weakening of reproductive barriers - reverse speciation -hybridizing species fuse into a single species
what is stability
continued production of hybrid individuals
what are the 5 steps in hybrid zone formation and outcome
- populations of a species are connected by gene flow
- a barrier to gene flow is established
- the populations begin to diverge
- gene flow is re-established in a hybrid zone
- reinforcement/fusion/stability
what is punctuated equilibria
in the fossil records, long periods of stasis in which a species undergoes little or no morphological change interrupted by brief periods of sudden change
a punctuated pattern indicates that a species occurred rapidly/slowly
rapidly
what is the difference between punctuated and gradual speciation
punctuated - new species change most as they branch from parent species then change little for the rest of their existence
gradual - species diverge from one another more slowly and steadily over time
are there specific traits that cause reproductive isolation
yes - scientists are researching which genes influence the formation of new species e.g. the gene that controls snail shell spiral can change the spiral direction preventing mating
what can happen as speciation occurs over and over again
differences accumulate and become more pronounced eventually leading to the formation of new groups of organisms that differ greatly from their ancestors (e.g. origin of whales (cetacean) from terrestrial mammals)
what does the time between speciation event include
- the length of time that it takes for populations of newly formed species to begin diverging reproductively from one another (can take ages)
- the time it takes for speciation to be completed once divergence begins (can be fast or slow)
what are the 2 types of barrier
geographic - allopatric
temporal (behavioural) - sympatric
what is co-speciation
when the speciation of one species due to a geographic barrier causes the speciation of another species
