Biology 100 Unit 13 Flashcards
________________’s influential book entitled On the Origin of Species by Means of Natural Selection was published on November 24,1859.
Charles Darwin
Over generations, individuals with the best functioning traits are consistently selected, _____________ ____________ are produced.
evolutionary adaptations
Darwin’s research was nontraditional because he suggested that ___________________________
the Earth was relatively old and populated by all species being related to each other.
In his theory, he predicted _____________________to have existed between species
numerous intermediates
Darwin’s views were
embraced by some, and rejected by others
In December 1831, Darwin (age 22) left Great Britain as the on board naturalist of the ____________
HMS Beagle.
Darwin realized that the distribution of species in the _________________ was unusual.
galapagos islands
It was apparent to him that many Galápagos species resembled those found in South America, but showed some____________________
variation
Darwin was strongly influenced by the writings of geologist ____________, who promoted the idea of an ancient Earth.
Charles Lyell
What two things was Darwin convinces of
– the Earth was very old, had been shaped by slow processes and continues to change even today.
– just as earth changed, or evolved, so could the organisms that lived upon it, because they responded to their environment
– the Earth was very old, had been shaped by _____
___________, and continues to change even today.
slow processes
just as earth changed, or evolved, so could the organisms that lived upon it, because they
responded to their environment
In The Origin of Species, Darwin emphasized two main points.
– All organisms inhabiting Earth today are derived from ancestral species that may have looked differently (descent with modification).
– The mechanism by which this was accomplished is natural selection
– As organisms reproduce, they can have a variety of offspring. Those offspring best fit for their environment are most fit to survive and reprorduce
What are the 4 evidences used to support evolution
fossils, biogeography, comparative anatomy, and molecular biology
are remnants of organisms that lived in the
past that have been turned to stone.
fossils
fossils can include
plants, animals, impressions, bones, & soft tissues.
______________ is where fossilization is most likely.
sedementary rock
Fossils are often used to
compare anatomy with extinct organisms with extant ones
interpreted as chronology of fossils embedded in rock layers of different ages.
fossil record
Fossil records are used to
show that organisms appeared in a historical sequence.
Older more primitive organisms at the_______
bottum of fossils
________more advanced organisms at the top of the fossil
newer
is the study of the geographic distribution of species.
biogeography
Darwin observed Galápagos birds that resembled those in South America. The resemblance infers that
they shared a common ancestor.
Natural selection then explains that organisms
must have specific characteristics to live in a particular environment
is the comparison of body structure between different species.
comparative anatomy
is the similarity of structures due to common ancestry
homology
Ancestral structures became
modified to undergo a new function
__is the similarity of structures based on function, but does not share common ancestry.
analogy
Forelimbs of mammals are constructed from the same skeletal elements, because they are interpreted as sharing a common ancestor they are considered _____________
homologous structures
is the comparison of structures that appear similar during the development of different organisms
Comparative embryology
During early embryology, some vertebrates look similar, implying they have very similar features, which may indicate ______________________.
common ancestry
is also used to show evolutionary relationships among species.
Molecular biology of organisms
can be used to determine how distantly (or closely) organisms are related.
DNA sequence
The more similar one’s DNA is to an organism,
the more likely that they are closely related
The less similar one’s DNA is to an organism,
they are more likely distantly related.
The similarity between human and chimpanzee DNA is __________.
98%
This is the most similar genetic match of humans with any species.
The similarity between human and chimpanzee DNA
Evolutionary biologists indicate that the genetic match of humans with any species. is due to
a close evolutionary relationship.
Darwin’s Galápagos ————re an example of adaptive evolution as a result of natural selection.
s finches a
how many finches are there
14
the __________ shape of a finches favors certain ___________
beak shape, certain enviroments
All the individuals in a population have
slightly different characteristics
Much of this individual variation is______________, and passed down from generation to generation
heritable
Individuals with less reproductive success die,
therefore they do _______________.
not reproduce
Only those individuals with traits best suited for their environment,_________________ _leaving a greater number of offspring.
are more likely to survive, and reproduce,
The genes of individuals with traits suited for their enviroment that are favored by this process (“selected for”) _______________in the population than genes of individuals not favored (“selected against”).
will occur in greater frequency
Examples of natural selection we are observing right now include
– Pesticide resistance in insects
Insects with a resistance to pesticides, will be the ones more likely to survive and reproduce.
Consistent use of antibiotics can select for __________ strains of bacteria that are difficult to treat. (__________
antibiotic resistant MRSA
is a group of individuals of the same species living in the same area at the same time.
A population
Because variance amongst individuals must be present to select from, ______________are the smallest biological unit that can evolve.
populations
___________________ investigate the fate of populations as evolutionary units.
population gentisits
Tracking the genetic makeup of populations over time allows us to determine whether
a population is evolving and how fast it is changing.
In genetic variation studies, Although there is a lot of variation among individuals of a population differences in ___________________ are what is looked at.
genetic (heritable) components
Mutations are random ________________of an organism.
changes in DNA
Most mutations are ______________, but sometimes they are
considered to be beneficial.
deleterious
shuffles and distributes genetic material during meiotic divisions.
Sexual recombination
DNA containing these mutations can then be passed
from a parent to an offspring
includes all versions (alleles) of all genes in all
individuals making up a population.
the gene pool
What is the gene pool?
is the collective genome of the population.
in a gene pool occur at certain frequencies.
alleles
can be symbolized by p for the relative frequency of the dominant (expressed) allele in the population and q for the frequency of the recessive (hidden) allele in the population.
p+q=1
p=dominant
q=recessive
These symbols are represented in the Hardy Weinburg equilibrium
p^2+2pq+q^2
p^2
homozygous dominant
2pq
heterozygotes
q^2
homozygous recessive
The Hardy-Weinberg equation adds up all of the ____________ in a population and is used to determine expected ______________ of the next generation.
genotypes, phenotypes
If the Hardy-Weinberg equation is in equilibrium, this describes a ____________________ that is in genetic stasis (not changing over time).
non-evolving population
When the Hardy –Weinberg equation is not in equilibrium, the allele frequencies continually change over time, and the population is undergoing small scale evolution called ____________________.
microevolution
Allele frequency
P+Q=1
What is the formulas for p and q?
p number of dominant alleles for a given gene in a population/ sum of totalalleles for a given gene in the population
q number of recessive alleles for a given gene in a population /sum of totalalleles for a given gene in the population
If a locus has two alleles, W and w, there could be three
possible genotypes: WW, Ww, and ww.
Imagine that there are two alleles in a blue-footed booby population, W and w.
– Uppercase W is a dominant allele for a nonwebbed booby foot.
– Lowercase w is a recessive allele for a webbed booby
Consider the gene pool of a population of 500 boobies. – 320 (64%) are homozygous dominant (WW).
– 160 (32%) are heterozygous (Ww).
– 20 (4%) are homozygous recessive (ww).
– p = 80% of alleles in the booby population are W. – q = 20% of alleles in the booby population are w.
The frequency of all three genotypes must be
100% or 1.0.
The Hardy-Weinberg equation that can test if a population is evoloving
p2 + 2pq + q2 = 100% = 1.0
What about the next generation of boobies?
-The probability that a booby sperm or egg carries W = 0.8 or 80%
________.
– The probability that a sperm or egg carries w = 0.2 or 20%
– The genotype frequencies will remain constant generation after generation unless something acts to change the gene pool.
is measured by changes in allele frequency in a population.
Microevolution
Mechanisms of microevolution
– genetic drift
– gene flow
– mutations
_______________is a change in the gene pool of a small population due to chance.
genetic drift
– is an example of genetic drift.
– results from a drastic reduction in population size. and therefore a reduction in genetic variation
because this limits the possible genes to select from
The bottle neck effect
the bottle neck effect – is an example of genetic drift.
– results from ________________________________________
because this limits the possible genes to select from
a drastic reduction in population size. and therefore a reduction in genetic variation
The ______________ is genetic drift in a new colony.
the founder effect
It explains why certain unusual alleles (such as genetic disorders among humans) are expressed more frequently in populations founded by only few individuals than in the original, large population.
– Founding populations of Galapagos organisms carried only a small, random subset of mainland population genomes.
Their allele frequencies therefore were different from that of mainland populations, and this allowed rapid diversification.
Tristan da Cunha is the world’s most remote inhabited island.
– In 1815, fifteen British settlers colonized the island, one of whom carried the recessive allele for an eye disease (retinitis pigmentosa).
Example of the founder effect
– In the 1960s, some decedents still living on the island, still had the eye disease.
When populations regularly or irregularly exchange genetic material, this is called ________________.
gene flow
The influx of genetic material from other populations will reduce
the genetic differences between populations.
______________ are permanent changes in an organism’s genome.
mutations
A single mutation in a single organism ordinarily will not have an impact on a large population since most mutations are
lethal.
A mutation that is beneficial ___________________, however, can make the difference between survival and death.
during periods of environmental stress
n those conditions, the mutation may______________________________ in the population, favoring those organisms in a population which carried that allele.
significantly alter the allele frequencies
_________________is the contribution an individual makes to the gene pool of the next generation relative to contributions of others within that population.
relative fitness
Genes are contributed to the next generation
through offspring.
The number of offspring is a way to determine
zero offspring=
fitness; zero fitness
During ___________________the phenotype of a population is shifted.
directional selection
directional selection type of selection favors a more __________shifting alleles in a population
extreme phenotype,
ex: Mice
during ______________________both extremes of phenotype are favored.
disruptive selection
disruptive selection : _______________ is not advantageous and its frequency becomes reduced.
The intermediate phenotype
During ___________________the variation of a particular trait becomes limited.
stabilizing selection
If the extreme trait values are not beneficial, then the _______________________
itermediate is selected/ mean value is selected for.
– is a form of natural selection
– in which individuals with certain characteristics are more likely than other individuals to obtain mates.
sexual selection
In many animal species, males and females show distinctly different appearances, called ____________ ________________.
sexual selection
Intrasexual selection (within the same sex) involves competition for ___________________
mates, usually by males.
