Ecology Exam 4 Flashcards
what are the steps of how a species originates from existing species
-populations are connected by gene flow
-a barrier to gene flow is established
-this population begins to diverge genetically
-this population is reproductively isolated, forming a new species
what is speciation
the process by which one species splits into two or more species, is at the focal point of evolutionary theory
what is microevolution
consists of changes in allele frequency in a population over time
what is macroevolution
refers to broad patterns of evolutionary change above the species level
____ form a bridge between microevolution and macroevolution
speciation
The biological species concept emphasizes ____ isolation
reproductive
what is a species
is a group of populations whose members can interbreed in nature and produce offspring; they do not breed successfully with members of other such groups
____ ____ between populations holds a species together genetically
gene flow
The biological species concept is based on the ____ to ____, not on physical similarity
potential to interbreed
what is reproductive isolation
is the existence of biological factors (barriers) that impede two species from producing viable, fertile offspring
what are hybrids
are the offspring that result from mating between different species
what are prezygotic barriers
-habitat isolation
-temporal isolation
-behavioral isolation
-mechanical isolation
-gametic isolation
how do prezygotic barriers block fertilization from occurring
-Impeding different species from attempting to mate
-Preventing the successful completion of mating
-Hindering fertilization if mating is successful
what is habitat isolation
Two species encounter each other rarely, or not at all, because they occupy different habitats, even though not isolated by physical barriers
what is temporal isolation
Species that breed at different times of the day, different seasons, or different years cannot mix their gametes
what is behavioral isolation
Courtship rituals and other behaviors unique to a species are effective barriers to mating
what is mechanical isolation
Morphological differences can prevent successful completion of mating
what is gametic isolation
Sperm of one species may not be able to fertilize eggs of another species
how do postzygotic barriers prevent hybrid zygote from developing into a viable, fertile adult
-Reduced hybrid viability
-Reduced hybrid fertility
-Hybrid breakdown
what is reduced hybrid viability
Genes of the different parent species may interact and impair the hybrid’s development or survival in its environment
can hybrids be sterile
yes, mules
what is hybrid breakdown
Some first-generation hybrids are fertile, but when they mate with each other or with either parent species, offspring of the next generation are feeble or sterile
The biological species concept cannot be applied to ____ or ____ organisms (including all prokaryotes)
fossils or asexual
The biological species concept emphasizes the ____ of gene flow
absence
can gene flow occur between morphologically and ecologically distinct species
yes, grizzly and polar bears
how does the morphological species concept define a species
-structural features
-body shape
-other structures
does the morphological species concept apply to sexual and asexual species
yes
what does the ecological species concept define a species in terms of what
its ecological niche
what role does the ecological species concept emphasize
disruptive selection
does the ecological species concept apply to both sexual and asexual species
yes
what are the two ways that speciation can occur
-allopatric
-sympatric
can speciation take place with or without geographic separation
yes
what happens in allopatric speciation
gene flow is interrupted or reduced when a population is divided into geographically isolated subpopulations
what does the definition of a barrier depend on
the ability of a population to disperse
Separated populations may evolve independently through ____, ____ ____, and ____ ____
mutation, natural selection, and genetic drift
Reproductive isolation may arise as a by-product of ____ divergence
genetic
what is a example of evidence of allopatric speciation
fruit flies taken from the same source population and allowed to adapt to different diets over several generations tend to choose mates adapted to the same diet
Regions with ____ geographic barriers typically have more species than do regions with _____ barriers
many, fewer
when reproductive isolation between populations increases what also increases
the distance between them increases
is physical separation alone a biological barrier
no
reproductive barriers are ____ to the organisms themselves
intrinsic
what occurs in sympatric speciation
speciation occurs in populations that live in the same geographic area
Sympatric speciation can occur if gene flow is reduced by factors including
-polyploidy
-sexual selection
-habitat differentitation
what is polyploidy
is the presence of extra sets of chromosomes due to accidents during cell division
is polyploidy more common in plants or animals
plants
how quickly can polyploidy produce new biological species in sympatry
within a single generation
what is a autopolyploid
is an individual with more than two chromosome sets derived from a single species
The offspring resulting from mating between polyploids and diploids have ____ fertility
reduced
what is allopolyploid
is a species with multiple sets of chromosomes derived from different species
Allopolyploids can successfully mate with each other, but cannot interbreed with either ____ species
parent
____ selection can drive sympatric speciation
sexual
what type of selection contributed to speciation in cichlid fish in Lake Victorie
sexual
____ speciation can also result from the appearance of new ecological niches
sympatric
what is a hybrid zone
a region in which members of different species mate and produce hybrids
____ are the result of mating between species with incomplete reproductive barriers
hybrids
A hybrid zone can occur in a ____ ____ where adjacent species meet
single band
Hybrids often have reduced ____ compared with parent species
fitness
The distribution of hybrid zones can be more complex if parent species are found in ____ within the same region
patches
what can result in the relocation of existing hybrid zones or the production of novel hybrid zones
change in environmental conditions
Breeding between hybrids and parent species can result in the transfer of ____ from one parent species to the other
alleles
In a changing environment: the transfer of novel alleles may help parent species do what with changing conditions
cope with changing conditions
If hybrids do not become reproductively isolated from their parent species, then three alternate outcomes are possible:
-reinforcement
-fusion
-stability
what does reinforcement do
strengthens reproductive barriers
when does reinforcement of reproductive barriers occur
when hybrids are less fit than parents
what does fusion do
weakens reproductive barriers
when does fusion occur
if hybrids are as fit as parents, there can be substantial gene flow between species
how does fusion occur
reproductive barriers weaken, fusion occurs and the two species become one. The hybrids are as fit or more fit than the parents, the two species may fuse back into one species
what does stability do
continued formation of hybrid individuals
what causes stability
Barriers remain the same if hybrids are fit and reproductive. Two species will remain separate but also continue to interact to produce some hybrid individuals
how can the rate of speciation be studied
using the fossil record, morphological data, or molecular data
what does punctuated equilibria describe
these periods of apparent stasis punctuated by sudden change
what are speciation rates
The punctuated pattern in the fossil record and evidence from lab studies suggest that speciation can be rapid
how many genes influence the formation of new species
Depending on the species in question, speciation might require change in a single gene or many genes
macroevolution is the cumulative effect of what
of many speciation and extinction events
The fossil record shows macroevolutionary changes over large time scales, for example:
-the emergence of terrestrial vertebrates
-the impact of mass extinctions
-the origin of key adaptations, such as flight
what is abiogenesis
the original evolution of life or living organisms from inorganic or inanimate substances
when did earth form
4.6 billion years ago
what did Oparin and Haldane hypothesize about the early atmosphere
is was a reducing environment
where did the first organic compounds may have formed in reducing conditions
near the openings of volcanoes
Some evidence suggests that the early atmosphere was neither ____ or ____
reducing, oxidizing
Organic compounds could have been produced in deep-sea ____ ____
hydrothermal vents
what was another source of organic molecules
meteorites
what is the abiotic synthesis of macromolecules
-RNA monomers have been produced spontaneously from simple molecules
-RNA polymers form spontaneously when a solution of monomers is dripped onto hot sand, clay, or rock
-Such abiotically synthesized polymers could have acted as weak catalysts on early Earth
how were vesicles formed
-Adding montmorillonite, a soft mineral clay common on early Earth, greatly increases the rate of vesicle formation, and some can self replicate.
-They can absorb organic molecules attached to montmorillonite particles through a selectively permeable bilayer
where did replication and metabolism first appear
protocells
where did protocells form from
from fluid-filled vesicles with a membrane-like structure
what was the first genetic material
RNA
what did RNA provide the template for
the formation of DNA
how does DNA differ from RNA
-more chemically stable
-replicated more accurately
what species is the fossil record biased towards
-existed for a long time
-were abundant and widespread
-had hard parts, such as shells or skeletons
how is the age of older fossils estimated
by using isotopes with long half-lives to date the rock layers above and below the fossil
can we find out the actual ages of fossils
no
how can the age of a fossil be determined
radiometric dating
can fossils contain isotopes
yes, they accumulated in the organisms when they were alive
how can the age of some fossils be estimated by measuring what
ratio of the radioactive isotope carbon-14 to the stable isotope carbon-12
how far can radiocarbon dating be used to date fossils
75,000 years old
do organisms take up isotopes with long half-lives
no
The evolution of unique mammalian features can be traced in the ____ ____
fossil record
Mammals belong to the group of animals called ____
tetrapods
what eons is the geologic record divided into
-hadean
-Archaean
-Proterozoic
-phanerozoic
what eon includes the last half billion years
Phanerozoic
what era did the Cambrian explosion occur
paleozoic
what periods are in the paleozoic era (oldest to youngest)
Cambrian, Permian
what periods are in the Mesozoic era (oldest to current)
Triassic, Jurassic, cretaceous
what period is in the Cenozoic era
-quaternary
what time frame is the holocene epoch
11.7 Ka to today
what epoch is in the quaternary period
holocene
what eras is the Phanerozoic divided into (oldest to youngest)
Paleozoic, Mesozoic, and Cenozoic
Major boundaries between eras correspond to major ____ events in the fossil record
extinction
when were dinosaurs abundant
Triassic, Jurassic, Cretaceous
what are the oldest known fossils
stromatolites (rocks formed by the accumulation fo sedimentary layers on bacterial mats)
what time do stromatolites date back to
3.5 billion years ago
when were prokaryotes Earth’s sole inhabitants
for more than 1.5 billion years
is most atmospheric oxygen of biological origin
yes
when did oxygen accumulate gradually in the atmosphere
2.7-2.4 billion years ago
what did the oxygen revolution cause
the extinction of many prokaryotic groups
the oldest fossils of eukaryotic cells date back to when
1.8 billion years
what did eukaryotes originate from
endosymbiosis
what is endosymbiosis
when a prokaryotic cell engulfed a small cell that would evolve into a mitochondrion
what is an endosymbiont
is a cell that lives within a host cell
All eukaryotes have mitochondria or remnants of mitochondria, but not all have ____ (chloroplasts and related organelles)
plastids
Mitochondria and plastids likely descended from ____ cells
bacterial
A hypothesis for the origin of mitochondria and plastids through serial ____
endosymbiosis
what is the evidence supporting an endosymbiotic origin of mitochondria and plastids
-Inner membranes of both organelles are similar to plasma membranes of living bacteria
-DNA structure and cell division are similar to bacteria
-Both organelles transcribe and translate their own DNA
-Ribosomes are more similar to bacterial than to eukaryotic ribosomes
what period did dinosaurs evolve and radiate
triassic
what period did dinosaurs go extinct
end of the cretaceous period
what did the evolution of eukaryotic cells allow for
a greater range of unicellular forms
A second wave of diversification occurred when ____ evolved and gave rise to algae, plants, fungi, and animals
multicellularity
what are the oldest fossils of multicellular eukaryotes
red algae
when did the mesozoic era end
66 Ma
when did the creataceous period end
66 Ma
when did the permian period end
252 Ma
when did the paleozoic era end
252 Ma
when did the mesozoic era begin
252 Ma
when did the triassic period begin
252 Ma
when did the cambrian period begin
541 Ma
when did the paleozoic era begin
541 Ma
when did the phanerozoic eon begin
541 Ma
what are the eras in order from oldest to youngest
paleozoic, mesozoic, cenozoic
what are the periods of the paleozoic from oldest to youngest
cambrain, permian
what are the periods of the mesozoic era from oldest to youngest
triassic, jurassic, cretaceous
what are the eons from oldest to youngest
-hadean, archean, proterozoic, phanerozoic
when did the hadean eon begin and end
4.56 Ga to 4.0 Ga
when did the archean eon begin and end
4.0 Ga to 2.5 Ga
when did the proterozoic eon being and end
2.5 Ga to 541 Ma
what are the ediacaran biota
an assemblage of larger and more diverse soft-bodied organisms that lived 635 to 541 mya
what was the Cambrian explosion
refers to the sudden appearance of fossils resembling modern animal phyla in the Cambrian period
when did the trilobtes appear
during the cambrian explosion
what animals appear before the Cambrian explosion
sponges, cnidarians, and mollusks
what event provides evidence of predator-prey interactions
Cambrian explosion
Molecular and fossil data suggest that the Cambrian explosion had a ____ ____
long fuse
Fungi, plants, and animals began to colonize land about ____ million years ago
500
what adaptations did plants evolve to survive on land
reproduction and avoiding dehydration
____ and ____ are the most widespread and diverse land animals
arthropods, tetrapods
what did tetrapods evolve from
lobe-finned fishes
when did tetrapods evolve from lobe-finned fishes
365 mya
what did the human linage evolve from
tetrapods
when did the human lineage evolve from tetrapods
6-7 mya
when did the modern human originate
195,000
The rise and fall of groups depend on ____ and ____ rates within the group
speciation, extinction
how many times have the landmasses of Earth formed a supercontinent
three times
what causes continental drift
movements in the mantle cause the plates to move over time
when did Pangaea form
350 mya
what effects did Pangaea have
-a deepening of ocean basins
-a reduction in shallow-water habitat
-a colder and drier climate inland
what effects does continental drift have on living organisms
-Organisms must adapt, move, or risk extinction as the climate changes in response to continents moving toward or away from the equator
-Separation of landmasses can lead to allopatric speciation
what is evidence reflects the historic movement of continents
the distribution of fossils and living groups
The fossil record also shows that most species that have ever lived are now ____
extinct
Extinction can be caused by changes to a species’ ____ or ____ environment
biotic or abiotic
At times, the rate of extinction has increased dramatically and caused a ____ ____
mass extinction
when did the Permian extinction occur
between the Paleozoic and Mesozoic Eras 252 mya
what factors contributed to the Permian extinction event
-extreme volcanism
-global warming and ocean acidification
-anoxic conditions
what percentage of the marine animal species went extinct during the Permian extinction
96%
what caused the cretaceous mass extinction
-meteorite impacts the earth
-dust clouds block sunlight and disturb global climate
Scientists estimate that the current rate of extinction is ____ to ____ times the typical background rate seen in the fossil record
100 to 1,000
why are many species declining rapidly
-habitat loss
-introduced species
-overharvesting
Climate change may ____ declines in species
hasten
Mass extinctions can change the ____ of organisms found in ecological communities
types
what is adaptive radiation
is the rapid evolution of diversely adapted species from a common ancestor
what can cause adaptive radiation
-mass extinctions
-the evolution of novel characteristics
-the colonization of new regions (islands)
when did mammals undergo an adaptive radiation
after the extinction of terrestrial dinosaurs
when opened up when the dinosaurs disappeared
ecological niches for mammals
what allows organisms to adaptive radiate in a new environment
when they have little competition
Major changes in body form can result from changes in the ____ and ____ of developmental genes
sequences and regulation
Studying genetic mechanisms of change can provide insight into large-scale ____ ____
evolutionary change
Genes that program development control the ____, ____, and ____ ____ of changes in an organism’s form as it develops to adulthood
rate, timing, and spatial pattern
what is heterochrony
is an evolutionary change in the rate or timing of developmental events
what can heterochrony have an impact on
body shape and sexual development
what is an example of heterochrony
the contrasting shapes of human and chimpanzee skulls
what occurs in paedomorphosis
the rate of reproductive development accelerates compared with somatic development
Substantial evolutionary change can also result from alterations in genes that control the ____ and ____ of body parts
placement and organization
what do homeotic genes determine
basic features as where wings and legs will develop on a bird or how a flower’s parts are arranged
what information do Hox genes provide
positional information during animal embryonic development
what are Hox genes a class of
homeotic genes
what happens if Hox genes are expressed in the wrong location
body parts can be produced in the wrong location
what do new morphological forms come from
gene duplication events that produce new developmental genes
Changes in the ____ of ____ ____ have likely contributed more to changes in the form of organisms than sequence changes
regulation of developmental genes
what is phylogeny
a hypothesis of the evolutionary history of a species or group of related species
what discipline classifies organisms and determines their evolutionary relationships
systematics
what shows evolutionary relationships
phylogenies
The two-part scientific name of a species is called a ____
binomial
what is the first part of a scientific name
genus
what is the second part of a scientific name
specific epithet
what are the taxonomic groups
-domain
-kingdom
-phylum
-class
-order
-family
-genus
-species
A taxonomic unit at any level of hierarchy is called a ____
taxon
The broader taxa (i.e. the number of species) are not always ____ between lineages
comparable
The evolutionary history of a group of organisms can be represented in a branching ____ ____
phylogenetic tree
what does each branch point on a phylogenetic tree represent
represents the divergence of two evolutionary lineages from a common ancestor
what are sister taxa
groups that share an immediate common ancestor that is not shared by any other group
A ____ tree includes a branch to represent the most recent common ancestor of all taxa in the tree
rooted
A ____ ____ diverges early in the history of a group and originates near the common ancestor of the group
basal taxon
what do phylogenetic trees show
patterns of descent
do phylogenetic trees show phenotypic similarity
no
do phylogenetic trees indicate when species evolve or how much change occurred in a lineage
no
To infer phylogenies, systematists gather information about the ____, ____, and ____ of living organisms
morphologies, genes, and biochemistry
Phenotypic and genetic similarities due to shared ancestry are called ____
homologies
Organisms with similar ____ or ____ ____ are likely to be more closely related than organisms with different structures or sequences
morphologies or DNA sequences
When constructing a phylogeny, systematists need to distinguish whether a similarity is the result of ____ or ____
homology or analogy
what causes a homology
shared anacestry
what causes analogy
convergent evolution
what does convergent evolution occur
similar environmental pressures and natural selection produce similar (analogous) adaptations in organisms from different evolutionary lineages
how can homology be distinguished from analogy
-comparing fossil evidence and degree of complexity
-Comparing genes in two organisms that share nucleotide sequence (bioinformatics)
-The more elements that are similar in two complex structures, the more likely it is that they are homologous
what are homoplasies
coincidental similarities
Shared ____ are used to construct phylogenetic trees
characters
Once ____ ____ have been identified, they can be used to infer a phylogeny
homologous characters
what are cladistics
an approach to grouping organisms (classification) by common ancestry
what is a clade
is a group of species that includes an ancestral species and all its descendants
what is a valid clade
if it is monophyletic
what does monophyletic signify consist of
that it consists of the ancestor species and all its descendants
what are the invalid groupings of clades
-paraphyletic
-polyphyletic
what does a paraphyletic grouping consist of
an ancestral species and some, but not all, of the descendants
what does a polyphyletic grouping consist of
distantly related species but does not include their most recent common ancestor
how are polyphyletic groups distinguished from paraphyletic groups
by the fact that they do not include the most recent common ancestor
what is a shared ancestral character
is a character that originated in an ancestor of the taxon
what is a derived character
is an evolutionary novelty unique to a particular clade
can a character be both ancestral and derived
yes
what is an outgroup
is a species or group of species that is closely related to the ingroup
what is an ingroup
the various species being studied
did the outgroup or ingroup diverge first
outgroup
Systematists compare each ingroup species with the outgroup to differentiate between shared ____ and shared ____ characters
derived, ancestral
what does maximum parsimony assume
assumes the most likely tree is one that requires the fewest evolutionary events (appearances of shared derived characters)
what does maximum likelihood use
using probability rules about how DNA changes over time to develop a tree that reflects the most likely sequence of evolutionary events
how do systematists narrow the possibilities of finding the best tree in a large data set
applying the principles of maximum parsimony and maximum likelihood
The best hypothesis for a phylogenetic tree fits the most data: ____, ____, and ____
morphological, molecular, and fossil
what features do birds and crocodiles share
four-chambered hearts, song, nest building, and brooding
The ____ ____ supports nest building and brooding in dinosaurs
fossil record
what did the features shared by birds and crocodiles evolve from
a common ancestor
Comparing ____ ____ or other ____ to infer relatedness is a valuable approach for tracing organisms’ evolutionary history
nucleic acids, molecules
what is useful for investigating branching points that diverged hundreds of millions of years ago
DNA that codes for rRNA
what can be used to explore recent evolutionary events
mtDNA
An organism’s evolutionary history is documented in its ____
genome
____ _____ increases the number of genes in the genome, providing more opportunities for evolutionary changes
Gene duplication
Repeated gene duplications result in ____ ____
gene families
Like homologous genes, duplicated genes can be traced to a ____ _____
common ancestor
where are orthologous genes found
in a single copy of a gene in the genome
are orthologous genes homologous between species
yes
when can orthologous genes diverge
after speciation occurs
what do paralogous genes result from
gene duplication
are paralogous genes found in more than one copy in the genome
yes
Paralogous genes can diverge within the species that carries them and often evolve ____ ____
new functions
____ genes are widespread and extend across many widely varied species
Orthologous
are gene number and the complexity of an organism strongly or not strongly linked
not strongly linked
Genes in complex organisms appear to be very versatile, and each ____ can encode multiple ____ that perform many different functions
gene, proteins
A molecular clock uses constant rates of evolution in some genes to estimate what
the absolute time of evolutionary change
in which genes are nucleotide substitutions are assumed to be proportional to the time since they last shared a common ancestor
orthologous
in which genes are nucleotide substitutions are proportional to the time since the genes became duplicated
paralogous
what are molecular clocks calibrated against
branches whose dates are known from the fossil record
If most of the evolutionary change in genes and proteins has no effect on fitness, then the rate of molecular change should be ____
regular
Differences in clock rate for different genes are a function of what
-the importance of the gene
-how critical the specific amino acid is to protein function
The molecular clock does not run as smoothly as expected if ____ were ____
mutations, neutral
how do irregularities result from natural selection
some DNA changes are favored over others
Dating the Origin of HIV
-Phylogenetic analysis shows that HIV is descended from viruses that infect chimpanzees and other primates
–HIV spread to humans more than once
–Comparison of HIV samples shows that the virus evolved in a very clocklike way
–The earliest sample of HIV (fragments) is a 1959 blood sample from Kinshasa, Democratic Republic of the Congo
-Application of a molecular clock to one strain of HIV suggests that the strain spread to humans during the 1930s
-A more advanced molecular clock approach estimated the first spread to humans around 1910
what are the three domains
bacteria, Archaea, and Eukarya
what did early taxonomists classify all species as
either plants or animals
what are the five kingdoms that are recognized
Monera (prokaryotes), Protista, Plantae, Fungi, and Animalia
what is polytomy
an internal node of a phylogenetic tree linked to three or more child subtrees
which domains are more closely related
eukaryotes and archaea are more closely related to each other than to bacteria
what is the tree of life based largely on
rRNA genes
what is horizontal gene transfer (HGT)
is the movement of genes from one genome to another
how does HGT (horizontal gene transfer) occur
by exchange of: transposable elements, plasmids, viral infection, and possibly fusion of organisms
how can differences between gene trees be explained
by the occurrence of horizontal gene transfer
____ ____ ____ has played a key role in the evolution of both prokaryotes and eukaryotes
Horizontal gene transfer
Eukaryotes can acquire nuclear genes from ____ and ____
bacteria and archaea
