Evolution: Evidence and Mechanisms Flashcards
What is the general definition of evolution?
change over time
What is the definition of biological evolution?
change in organisms over time beyond the lifetime of an indovidual
Is physiological adaptation biological evolution?
no - it happens during one’s lifetime and is not passed on to offspring
What is microevolution?
change on the time scale of generations - changes in allele frequencies across generations
What is macroevolution?
changes at the species level or above, over long periods of time (geological time)
What three topics in biology does evolution explain?
diversity of species, adaptations, common ancestry
Is evolution a scientific fact?
yes
What regarding evolution is debated by scientists?
the relative importance of different mechanisms and how fast evolution occurs (NOT the fact that organisms evolve)
What does the theory of evolution by natural selection explain?
how organisms change over time, becoming more adapted
What evidence (7) is there for evolution?
fossil record transitional forms vestigial structures homologous structures embryology convergence evolved resistance
How does the fossil record provide evidence for evolution?
documents the pattern of evolution, showing that past organims differ from present organisms, showing evolutionary changes that have occured in various groups of organisms
According to the fossil record, what species is the closest living relative to the whale?
hippopotamus
What are transitional forms?
“missing link” - fossils/organisms that show the intermediate states between an ancient organism (reptiles) and a modern one (birds)
Why are transitional forms convincing evidence for evolution?
they show how one form turns into another
What are vestigial structures?
“leftover structures” - remnants of features that served a function in an organism’s ancestors
What are some examples of vestigial structures?
non-functional hind limbs in an ancient whale; pelvic bones in modern whales…
What are homologous structures?
structures in different species that are similar because of common ancestry
What are homologous structures evidence for?
common ancestry
What does embryology show?
shared anatomical features of vertebrate embryos
What is convergence?
process by which non-closely-related organisms independently undergo similar adaptations as a result of having to adapt to similar niches
What are analogous structures?
structures in different species that are similar due to convergent evolution
What two species show convergence?
marsupial mammals of Australia and placental mammals of North America
If one wanted to determine close relations between species, what structures should be examined and which should be ignored?
focus on homologous structures; ignore analagous ons
What are some examples of evolved resistance?
pathogens (viruses, bacteria) become resistant to drugs; insects become resistance to pesticides?
What type of evolution is evolved resistance?
microevolution
How does evolved resistance occur?
natural selection “edits out” individals without the resistance gene, leaving behind solely resistant individuals to pass on their genes
What were the prevailing ideas regarding time before Darwin’s time?
Earth was very young (so no time for change)
What were the prevailing ideas on stasis before Darwin’s time?
things don’t change
What were the prevailing ideas regarding types of organisms before Darwin’s time?
different types of organisms were created; these species did not change (variation was due to accidents/errors; each species had its own place in the scale of nature)
Which contemporaries influenced Darwin?
Hutton, Lyell, Lamarck
What theory did Hutton propose?
graduallism - Earth changes very gradually
What theory did Lyell propose?
uniformitarianism
What does the theory of uniformitarianism state?
some processes at work today have happened for a long time and are responsible for the Earth as it is now
What did Lamarck propose?
that organisms evolve
What were some of Lamarck’s ideas that were wrong?
organisms changed on purpose (they don’t choose to change)
change that occurred during a lifetime were passed on to offspring (inheritance of acquired characteristics - no)
over time, organisms strived to progress up the “evolutionary ladder”
What does selective breeding accomplish?
plants and animals can be changed by allowing those with the desired characteristic to breed
Where did Darwin make a lot of his important observations?
the Galapagos Archipelago, which was created relatively recently
What are some of Darwin’s observations that convinced him of evolution?
succession of species in the fossil record
island species were more similar to nearest mainland than to those on other islands
Which of Darwin’s observations did not support the prediction that species were created to be adapted to their environment?
island species were more similar to nearest mainland than to species on other islands
What was Darwin’s proposed mechanism for evolution?
struggle for existence - competition between individuals
Where did Darwin’s idea about the mechanism for evoluiton come from?
a book by Malthus (political economist): An Essay on the Principle of Population - said that population multiplies geometrically and food arithmetically; society can’t be improved - if we help the poor, more will survive and procreate, and eat all our food
Compare natural and artifical selection in canines/dogs.
- natural selection took thousands to millions of years to convert the ancestral canine to the African wild dog, the coyote, the fox, the wolf, the jackal, etc.
- artifical selection (selective breeding) took hundreds to thousands of years to convert the ancestral dog to the German sheperd, the Yorkshire terrier, the English springer spaniel, the mini-dachsund, the Golden retriever, etc.
On what two observations was Darwin’s argument for natural selection based?
members of a population vary in their inherited traits;
all species can produce more offspring than the envirionment can support, and many failt ot survive and reproduce
On what two inferences was Darwin’s argument for natural selection based?
individuals whose inherited traits give them a higher probability of survivng and reproducing in a given environment will leave more offspring to breed in future;
this unequal ability to survive and reproduce will lead to the accumulation of favourable traits in the population over generations
What were Darwin’s main contributions to evolutionary theory?
common descent, gradualism, branching evolution, natural selection
Who came up with the same ideas as Darwin?
Wallace (while studying species in the Malay Archipelago)
What is the timeline of evolutionary theories? (look at this for test)
1795: Hutton proposes his theory of gradulaism
1798: Malthus publishes “Essay on the Principle of Population”
1809: Lamarch publishes his hypothesis of evolution; Darwin is born
1812: Cuvier publishes his extensive studies of vertebrate fossils
1830: Lyell publishes Principles of Geology
1831-36: Darwin travels around the world on HMS Beagle
1844: Darwin writes his essay on descent with modification
1858: Wallace sends Darwin his hypothesis of natural selection while studying species in the Malay Archipelago
1859: On the Origin of Species is produced
What is “modern synthesis”?
integration of Darwinian Evolution and idea of a gene
How does “modern synthesis” explain how evolution occurs through natural selection?
over time (generation after generation) the trait, and the genes for the trait, are favoured by natural selection, and so increase in frequency in the population
What critera must be met for natural selection to occur?
a trait can evolve through natural selection if it is variable, heritable, and adaptive
What does is a heritable trait?
passed on through genes
What does natural selection lead to over time (generation to generation)?
changes in the measureable characteristics of individuals in the population
What is heritability?
measure of genetic basis of a trait - what proportion of the expression of a trait is due to genetics
At what level is heritability measured?
at the level of the population (parent-offspring pairs)
What are the possible extreme values of correlation between a trait of parent and offpsring, and what do they mean?
~1.0: trait entirely genetically-based
~0: trait entirely due to environment - no genetic basis
What is fitness?
relative measure of individual “success” (compared to other individuals)
What decides if an individual is more fit (has higher fitness) than another?
individual A is more fit than individual B if A leaves more offspring to breed in the next generation than does B (contribution to the gene pool of the next generation)
What is fitness an attribute of?
the individual
What is the only way in which fitness can be measured?
in comparison to other individuals
What evidence is there for bill size in a Galapagos finch to evolve through natural selection (from study)?
bil size is heritable; birds with deeper bills survive droughts better (crack open bigger seeds); their offspring have deeper bills; next generation has larger average bill depth
Does the following example provide evidence for evolution? If not, what additional information is needed?
Sally is studying a possible case of microevolution in an invasive species of crab. She measures the number of spines on the carapace that were collected when the population was first noticed 50 years ago. Sally finds that the crabs today have more spines than they did 50 years ago.
no - need:
- data showing trait is heritable
- data showing more spines provides an advantage to individuals
- data showing trait varies among individuals
What are the ways in which natural selection can alter the frequency distribution of heritable traits (selection pressures)?
stabilizing selection, directional selection, disruptive/divsersifying selection
What does stabilizing selection do to a population?
removes extreme variants from a population and preserves intermediate types
What does directional selection do to a population?
shifts the overall makeup of a population by favouring variants at one extreme of the distribution
What are ecotypes?
populations within a species in different environments that may have different average characteristics that are adaptive - better suited to the specific environments in which they live
What is genetic polymorphism?
more than one genetically-determined phenotype (morph) in the same population at the same time, maintained through natural selection, at >= 1% (not just occasional mutants)
What selection pressure results in genetic polymorphism?
disruptive/diversifying
What is an example of genetic polymorphism?
ABO blood group system in humans, which is deteremined by multiple alleles for one group
What does sexual selection explain?
ornamentation that can be detrimental to survival but is beneficial to obtaining mates
What does distruptive selection do to a population?
favours variants at both ends of the distribution
What is sexual selection?
form of selection in which individuals with certain inherited characteristics are more likely than other individuals to obtain mates
What is intersexual selection?
one sex chooses individual of other sex (ex: male choice)
What is intrasexual selection?
individuals of 1 sex compete for access to individuals of the other sex to mate (other sex doesn’t get to choose)
What are some ways in which individuals may compete in intrasexual selection?
fighting, ritualized display…
What type of sexual selection is the following example? Female red-necked Phalaropes are the more colourful sex and can have >1 mate. Males choose females, incubate eggs, and raise young.
intersexual selection
What is genetic drift?
microevolution occuring without adaptation
How does genetic drift occur?
by chance - only a subset of alleles of original population are represented
In what types of populations is genetic drift more likely to occur?
small sizes
What size of population evolves more quickly?
small populations
What are some results of genetic drift?
some alleles are lost, others are fixed
What is a fixed allele?
everyone is homozygous for that allele
When an allele is fixed, what is the only way in which the population can get new alleles?
mutation or immigration
What is the bottleneck effect?
a population’s size is greatly reduced all at once, resulting in the loss of many alleles by chance
What may cause a bottleneck effect?
any large mortality - because of disease, disaster, etc.
What effect does the bottleneck effect have on a populaiton?
greatly reduces the population
What is the founder effect?
a new population is founded by a few individuals from an old one
In the founder effect, how does the new population differ from the old one?
subset of alleles (and more will be lost over time through genetic drift)
What is an example of a cause of the founder effect?
colonization of an island
LIST AND EXPLAIN THE EVIDENCE FOR EVOLUTION.
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EXPLAIN HOW OUTSIDE INFLUENCES AND HIS OWN OBSERVATIONS LED DARWIN TO DEVELOP HIS THEORY.
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LIST DARWIN’S 4 MAIN CONTRIBUTIONS TO EVOLUTIONARY THEORY.
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EXPLAIN WHAT IS MEANT BY THE MODERN SYNTHESIS.
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EVALUATE EVIDENCE FOR NATURAL SELECTION.
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RECOGNIZE THE SIGNIFICANCE OF VARIABILITY, HERITABILITY, ADAPTATION, AND FITNESS FOR THE PROCESS OF NATURAL SELECTION.
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DISTINGUISH BETWEEN INTERSEXUAL AND INTRASEXUAL SELECTION.
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DISTINGUISH BETWEEN ECOTYPES AND POLYMORPHISMS.
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LIST AND DISTINGUISH THE THREE TYPES OF MODES OF SELECTION.
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EXPLAIN HOW GENETIC DRIFT OCCURS, WHY IT OCCURS, AND WHAT IT LEADS TO.
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