bio ch 13 evolution Flashcards
what is evolution
the idea that Earth’s many species are descendants of ancestral species that were different from those living today
what are fossils
the imprints or remains of organisms that lived in the past
what did the study of fossils reveal in the 1700s
a succession of fossil forms in layers of sedimentary rock that differed from current life-forms
what did lamark do/believe
suggested that organism’s evolve using fossil records
believed this happened by inheritance of acquired characteristics (i.e. giraffes got longer necks because their ancestor lengthened their necks and passed this on; didn’t happen/not true)
what happened to darwin that profoundly influenced his thinking
went on a round the world voyage on the HMS Beagle to chart poorly known stretches of the South American coast
what did Darwin notice while on his voyage
patterns of biodiversity; species vary globally, locally, and over time
who was darwin strongly influenced by
Charles Lyell and his book about geology that showed darwin that natural forces are gradually changing earth’s surface
what did darwin come to believe after the voyage and his readings
that the earth was actually very old and constantly changing and that it hadn’t been specially created only a few thousand years ago
what finally motivated Darwin to publish his ideas on his theory of evolution
in 1858, alfred wallace came up with a hypothesis almost identical to his and he didn’t want to lose credit/originality
what is darwin’s book called
“on the origin of species by means of natural selection”
what did dawson’s book do
- presented the world with a logical and well-supported explanation for evolution
- provided evidence that present day species arose from a succession of ancestors
what did darwin call his evolutionary history of life
descent with modification
what are adaptations
diverse modifications that fit a species to specific ways of life in their environment; any heritable characteristic that
increases an organism’s ability to survive and
reproduce in its environment
what did darwin propose was the mechanism of evolution
natural selection
what are the factors that shape a population
overproduction of offspring
limited natural resources
heritable variations
what is artificial selection
selective breeding of plants and animals to produce offspring with desirable traits; produces a great change in a short amount of time
what has artificial selection led to
greater yields of crops, meat, and milk
dogs like chihuahuas, dachshunds, and afghan hounds
what were darwin’s two concepts that led him to evolution
Diverse species have arisen by descent of
modification
The mechanism of modification is natural
selection working over long periods of time
what is fitness
how well an
organism can survive and reproduce in its
environment
what are the 2 observations that led darwin to make two inferences that led him to his idea of natural selection
- members of a population often vary in their observed traits
- all species are capable of producing more offspring than the environment can support
what are the 2 inferences darwin made from his two observations that led him to natural selection
- individuals whose inherited traits give them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than other individuals
- this unequal production of offspring will lead to the accumulation of favorable traits in a population over generations
what is the essence of natural selection
unequal reproduction; individuals whose traits better enable them to obtain food, escape predators, or tolerate physical conditions will survive and reproduce more successfully, passing these adaptive traits to their offspring
is natural selection fast or slow
slow; it can modify species considerably over hundreds or thousands of generations
what are the 3 key points about evolution by natural selection
- individuals do not evolve; it is the population that evolves over time as adaptive traits become more common in the group and other traits change or disappear
- natural selection can amplify or diminish only heritable traits, not acquired traits
- evolution is not goal-directed and does not lead to perfectly adapted organisms; a trait favorable in one situation may be useless or detrimental in another
what is natural selection
favorable traits that allow an organism to
adapt to their environment result in successful
reproduction and survival of a species
what is a fossil record
Ordered array in which fossils appear within layers of sedimentary rock
what is an example of natural selection in action
ground finches in the galapagos and changes in beak size based on whether it was a dry year or wet year due to the type of seed that was in abundance for eating
what is another example of natural selection in action
the evolution of pesticide resistance in hundreds of insect species; the proportion of pesticide resistant ind
what are two important points about evolution
- natural selection is more an editing process than a creative mechanism
- natural selection is contingent on time and place
what are trace fossils
footprints, burrows, and other remnants of an ancient organism’s behavior
how can an entire organism be fossilized
when it is buried in a medium that prevents bacteria and fungi from decomposing the corpse
how can relative ages of fossils be determined
by the layer of strata in which they are found
why is our fossil record of history incomplete
not all organisms live in areas that favor fossilization
many rocks are distorted by geologic processes
not all fossils that have been preserved will be found
what does the fossil record reveal
the historical sequence in which organisms evolved; illustrate the transition of existing groups to new groups
what are the oldest known fossils
prokaryotes; there is evidence that prokaryotes are the ancestors of all life
what are the types of scientific evidence that support evolution
biogeography
comparative anatomy
comparative embryology
molecular biology
what is biogeography
the geographic distribution of species
what is an example of biogeography that supports evolution
the galapagos animals resembled species of the south american mainland more than they resembled animals on islands that were similar but much more distant. the logical explanation was that the galapagos species evolved from animals that migrated from south america.
what is homology
similarities in characteristics that results from common ancestry
what is an example of homology
the same skeletal elements make up the forelimbs of humans, cats, whales, and bats
what are homologous structures
features that often have different functions but are structurally similar because of common ancestry
what does comparative anatomy illustrate
that evolution is a remodeling process in which ancestral structures that originally functioned in one capacity become modified as they take on new functions
what are vestigial structures
remnants of features that served important functions in the organism’s ancestors
what are some examples of vestigial structures
the small pelvis and hind-leg bones of ancient whales are vestiges of their walking ancestors
eye remnants that are buried under scales in blind fish species of cave fishes are vestiges of their sighted ancestors
what has molecular biology enabled biologists to do
read a molecular history of evolution in the DNA sequences of organism
what is the relationship between the number of differences in DNA sequences between species and how closely they are related
the more differences, the less related they are
why does molecular biology provide strong evidence for the claim that all life forms are related
all forms of life use the same genetic language of DNA and RNA and the genetic code is essentially universal
what is a population
a group of individuals of the same species that live in the same area and interbreed
what is one example of evolution occurring within populations
the increasing proportion of resistant insects in areas sprayed with pesticide
are members of one population more or less closely related to each other than to members of other populations
more bc they are most likely to choose mates locally
what is a gene pool
the total collection of genes in a population at any one time
what is a microevolution
when the relative frequencies of alleles in a population change over a number of generations
where do new alleles originate from
mutations
what is the ultimate source of genetic variation that serves as raw material for evolution
mutation
what produces the genetic variation that makes evolution possible
mutation and sexual reproduction
are mutation rates higher in prokaryotes or eukaryotes
prokaryotes
what prevents most mutations in animals and plants from significantly affecting genetic variation from one generation to the next
- low mutation rates
- long time spans between generations
- diploid genomes
what are the 3 random components of sexual reproduction that contribute to genetic variation
- crossing over
- independent orientation of homologous chromosomes at metaphase 1 of meiosis
- random fertilization
what is the hardy-weinberg principle
Frequency of alleles in a gene pool are constant over time unless other factors are operating
what 5 conditions must a population meet to satisfy the hardy-weinberg equation
- very large population
- no gene flow between populations
- no mutations
- random mating
- no natural selection
what is the hardy weinberg equation used for
to test whether evolution is occurring in a population
is the hardy-weinberg equilibrium common or rare
rare - does not exist in nature for long
how is the hardy weinberg equation used by public health scientists
to estimate how many people carry alleles for certain inherited diseases
what causes microevolution
natural selection, genetic drift, and gene flow
what is genetic drift
a change in the gene pool due to chance
the (smaller/bigger) the population, the more impact genetic drift is likely to have
smaller
what is the bottleneck effect
a situation in which genetic drift can have a significant impact; drastic reduction in population usually due to a natural disaster
what does the bottleneck effect do
reduces genetic variation because certain alleles will be present in a higher frequency than before, others will be present at lower frequencies, and others will not be present at all
can human actions create severe bottleneck effects for other speicies
yes - florida panther, african cheetah
what is the founder effect
a situation in which genetic drift can have a significant impact; when a few individuals colonize an island or other new habitat; the smaller the group, the less likely the genetic make up of the colonists will represent the gene pool of the larger population they left
what is one thing that the founder effect explains
the relative high frequencies of certain inherited disorders among some human populations
what is gene flow
Transfer of alleles between populations due to
members coming and going in and out of
populations
does gene flow reduce or increase differences in population
reduce
what is the only mechanism that consistently leads to adaptive evolution. why?
natural selection because some alleles are favored over others in a given environment
why are endangered species endangered
Loss of genetic variation
Less able to adapt to new environments
what three things cause gene variations
Mutations
Genetic recombination (meiosis)
Lateral gene transfer-organisms swap genes
what are some examples of organisms where natural selection has led to adaptive evolution
blue footed boobies
cheetahs
how does natural selection improve the match between organisms and their environment
by consistently favoring some alleles over others
what is relative fitness
the contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals
who are the fittest individuals within the context of evolution
those that produce the largest number of viable fertile offspring and thus pass on the most genes to the next generation
what is stabilizing selection
favors intermediate phenotypes
reduces variation and maintains the status quo
what is directional selection
shifts the overall make up of the population by acting against individuals at one of the phenotypic extremes
most common during periods of environmental change/species migrating to a new environment
what is disruptive selection
typically occurs when environmental conditions vary in a way that favors individuals at both ends of the phenotypic range over individuals with intermediate phenotypes
what is sexual selection
a form of natural selection in which individuals with certain traits are more likely to obtain mates
what is sexual dimorphism
the distinction in appearance between males and femailes
what is intrasexual selection
individuals compete directly with members of the same sex for mates
what is intersexual selection
individuals of one sex (usually females) are choosy in selecting their mates
what is the advantage of females being choosy?
females prefer male traits that are correlated with “good genes”
what helps prevent natural selection from making populations genetically uniform
- having two sets of chromosomes; in a heterozygote, a recessive allele is protected from natural selection bc it wont exhibit that trait
- natural selection -> balancing selection
what is balancing selection
occurs when natural selection maintains stable frequencies of two or more phenotypic forms in a population
what is heterozygote advantage
a type of balancing selection in which heterozygous individuals have greater reproductive success than either type of homozygote, with the result that two or more alleles are maintained in the population
what is an example of heterozygote advantage
the protection from malaria conferred by the sickle cell allele
what is frequency dependent selection
a type of balancing selection that maintains two different phenotypic forms in a population - selection acts agains either phenotypic form if it becomes too common in the population
what is an example of frequency dependent selection
the scale eating fish in africa
why cant natural selection fashion perfect organisms
- selection can only act on existing variations
- evolution is limited by historical constraints
- adaptations are often compromises
- chance, natural selection, and the environment interact
what is a species
A species is a population that interbreeds and produces fertile offspring
what is speciation
the formation of a new species; Caused by reproductive isolation
what are the 3 types of reproductive isolation
- behavioral
- geographic
- temporal
what is behavioral isolation
behaviors of the organisms prevent them from mating
what is geographic isolation
a population is separated by geographic barriers, but not
necessarily the whole population.
what is temporal isolation
organisms reproduce at different times
how do we measure speciation
molecular clocks
what do molecular clocks do
measure mutation rates of DNA to estimate when the common ancestor became two separate species.
what are HOX genes
During the embryo stage, hox genes control the development of the organism, decide when to turn genes on and off
mutations in the hox genes caused major evolutionary differences (like fins or legs)
Timing during development is critical
