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BIO_SC 3400: EXAM 1
What were the roles of a) Charles Lyell and b) Thomas Malthus in shaping Darwin's understanding of evolutionary mechanisms?
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a) Lyell said that evolution must be looked at over long periods of time to see evidence.
b) Malthus lead to the idea that the worlds population size would outweigh the production of food. |
From where did Darwin derive the term 'natural selection?'
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Natural selection was derived from the idea that it was NOT the survival of an individual, but rather the success in creating offspring in which live long enough to also reproduce.
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Why is it incorrect to attribute the 'discovery' of evolution to Darwin? If he didn't discover evolution, what was Darwin's contribution?
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Darwin did not discover evolution by himself. He linked his ideas with scientists before himself. He created new ideas, branching off others, which allowed others to continue the same. Darwin's contribution to Evolution was seen so largely, as he was a well-known man of high standing.
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What is the distinction between 'the origin of species' and 'the origin of life?' Which issue did Darwin seek to explain?
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The 'origin of species' comes not from multiple unique events, as if creating 'new' life, but instead species come from modified descendants of earlier forms. Life is no longer created, species evolve.
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Why are some fish evolving a smaller body size than in the past?
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Individuals catch fish commercially, for big body size. Fish are smaller than they were in the past, because the smaller fish are always thrown back, rather than being kept like the big fish. The big fish are caught and if they had not yet reproduced, they were unable to pass their "Big-Fish" genes to the next generation. When big-bodied fish continued to be caught, fish evolved to have smaller body sizes.
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Poikilotherms typically grow faster in warm water than in cold water. Why did the fish David was studying exhibit the opposite trend? What is the difference between my example and the example described on page 2 of the reading?
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In colder climates, fish are only able to grow during the summer when its warm--so these fish had adapted to fit all their growth into a few short months. But the fish in the warm climates did not have to adapt that, because it was always warm, so they had the time to grown as a slower pace.
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In order to preserve large fish in the population, David recommends that fishermen selectively harvest medium-size fish. Why does he think this is the best strategy? What’s wrong with selectively harvesting small fish instead?
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Large fish have genetic information that makes them big. Small fish have genetic information that makes them small. Medium fish have either the small or the big, or maybe even both. By catching the medium-sized fish, the alleles for fish size would remain in the population of fish, rather than completely removing the large fish allele.
If the small fish was harvested the genetic information for small body size would be removed.
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This article provides one example of a practical application of evolutionary theory. Think of other ways we can apply evolutionary processes in agriculture and medicine to achieve desired changes in organisms.
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Spraying fertilizers on crops so the animals, in which feed on the crops, will decrease in numbers. Then the crops would grow successfully without being destroyed and the animal population is maintained. Medicine is rapidly evolving and because of this we are able to cure and treat diseases in which once would have resulted in death. Over time genetic information may adapt, immunize, pass on to further generations, creating an immunity to certain diseases.
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What does the author mean by this statement? “Genotypes or genotypic values are not passed on from parents to progeny; rather, it is the alleles at the loci that influence the traits that are passed on.”
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Genotypes are not passed on strictly from parents to progeny because parents only pass one out of two of alleles at each loci. The alleles the parents carry represent different genotypes. Offspring genotypes are made up from the random passing of two alleles, one from the mother and one from the father, in which influences a given trait. Genotypes vary from parent to progeny, depending on the alleles that are passed.
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“The value of heritability always lies between 0 and 1.” Why is this the case? Think about the definition of heritability.
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Heritability is the proportion of phenotypic variation that is due to variation in genetic values. The value of heritability is between 0 and 1 because it captures only that proportion of genetic variation that is due to additive genetic values.
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The most common method for estimating heritability is shown in Figure 1. If you wanted to estimate the heritability of pulse rate in frog calls using this method, how would you do it? What would be the labels on the axes of a graph of your results? How would the graph look if there is high heritability of this trait? And low heritability?
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Test two different frogs, 1 with high a pulse (X axis on one graph), and one with a low pulse (X axis on the 2nd graph). The frogs would reproduce. Test the offsprings (once matured) pulses (offspring= y axis on both graphs. Data is taken on the pulses. Offspring with heritability of 1 (the best), would be plotted directly on the slope line. Those with lower pulses than parents would be plotted below the slope line, and higher pulse would be above.
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In what way is a measure of heritability a snapshot of a population in time? Why is heritability not constant?
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Heritability can change over time, due to the variance of genetic values changing. Environmental factors change. The correlation between genes and environment change. Genetic variance change if allele frequencies change. When one thing changes in a population, everything else shifts, resulting in a change in heritability. The same trait measured over an individuals life may have different genetic and environmental effects influencing it.
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Why do butterflies have colors? Use the information in the article to provide a) a proximate answer to the question and b) an ultimate answer to the question.
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a) Proximate: The butterfly is made up of chitin structures, in which bend and reflect light, creating colors to occur.
b) Ultimate: The colors attract mates and fend off predators.
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Why is artificial selection typically so much faster than natural selection? Describe a hypothetical scenario in which the same color change could have happend rapidly via natural selection.
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Artificial selection happens so much faster than natural selection because it is controlled. Individuals perform experiments and change things to artificially change things.
Natural selection could have rapidly wiped out butterfly color if a mutation occur in which enabled chitin to form among butterflies. Without chitin the colors wouldn't arise.
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Heritability was estimated from the selection pressure applied and the response to selection. Our artificial selection experiment demonstrated that B. anynana lab populations have significant genetic variation controlling reflectance peak wavelength, allowing the rapid evolution of a novel scale color." a. Summarize this paragraph in one sentence. b. Think about the graph that could have been used to calculate these heritability values. How would you label your axes?
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a.) By using artificial selection, a rapid growth of scale color among butterflies arose.
b.) y= response to selection pressure x=selection pressure
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The reading assignment indicates that the following features are the basics of natural selection: variation, inheritance, selection, time. How do each of these features apply to the evolution of drug resistance in bacteria?
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Many antibiotics are created to fight variations of bacteria. After years (time) of creating the new drugs to fight bacteria, bacteria adapted (inheritance) an immunity and is able to overpower the drug. The leftover bacteria in the system, not killed by the drug, multiply. These bacteria multiply more than others (selection). The basic features of natural selection are identified among the evolution of drug resistance in bacteria.
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What is the difference between the original and new proposals for limiting the evolution of antibiotic resistance in hospitals? Why does Carl Bergstrom think the new proposal is more likely to succeed?
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Their original proposal was to cycle drugs. It say it would reduce levels of antibiotic resistance b/c the bacteria would no to keep up with the changing drugs.
The new proposal say to treat patients with different antibiotics, so its hard for bacteria to succeed when it infects another patient.
The model of the original proposal shows all patients taking the same drug actually makes it easier to adapt to the drug.
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The final page of the assignment makes reference to the importance of 'managing evolution.' What is meant by this phrase?
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By managing evolution, we have the potential to increase our understanding of evolutionary processes to improve the quality of human lives. (through ways like medicine, agriculture, environmental health)
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"increasingly, we are realizing that many of the biological problems we face are fundamentally problems of _______________."
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managing evolution
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Mechanisms of Evolution
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mutation, migration (gene flow), genetic drift, and natural selection
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Who is the most fit in a population?
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the one who produces the most successful offspring
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______ is the # of copies of an individuals genes that get passed on to future generations.
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Fitness |
How do you measure fitness?
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The # of surviving children produced (or even better the # of surviving grandchildren
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If organisms seek to maximize their fitness, why does infanticide occur?
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If an offspring is weak, infanticide saves time and effort, and puts it into healthy offspring
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Why does infanticide occur?
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lack of resources, poor offspring quality, uncertain percentages
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Immediate cause or stimulus (environmental triggers, physiological mechanisms)
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proximate
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adaptive functions (why did it evolve?) (how the trait promotes survival or reproduction?)
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ultimate
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Give proximate and ultimate reasons why cardinals are red.
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proximate: they eat carotenoids, which are red, and the red color deposits to their feathers.
ultimate: males with red feathers are the chosen males
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a segment of DNA with instructions for building a protein molecule
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gene |
A ______ specifies the sequence of Amino Acids that make up a protein
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gene |
different possible forms for the same gene
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allele |
_______ differ in DNA sequence, and therefore in protein structure
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alleles |
there may be many ________ on the same gene
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alleles
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Any 1 person can have a maximum of ____ alleles
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2
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a change in allele frequencies in a population over time
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evolution
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Evolution occurs in populations, NOT _____________
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individuals
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Evolution requires genetic variation to act on, in which genetic variations come from ________ that generate new __________
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mutations, alleles
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Some ______ become more common than others in a population
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alleles
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a group of organisms of the same species that breed with each other
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population
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Things that cause allele frequencies to change
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mechanisms of evolution
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what are 3 mechanisms of evolution
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selection, genetic drift, migration
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Three types of selection
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artificial, natural and sexual
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All 3 forms of selection share what TWO features?
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share heritable variation among individuals, and share differences among individuals in the number of surviving offspring
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the proportion of a populations phenotypic variation controlled by genetics rather than environmental factors?
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heritability
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a process by which allele frequencies change due to differences among individuals in the number of surviving offspring they produce
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selection
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How do the 3 types of selection differ from one another?
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differ in who determines who will breed the most
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________ is when humans choose which individuals should pass on their alleles. (when something causes evolution to occur.)
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artificial selections
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some alleles become more common than others due to ____________
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selective breeding
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what is an example of artificial selection?
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-dogs (they are bred to produce the most favored dog--i.e: fight dog, herding dog)
-cows (they are bred to produce different things--i.e.: milk cows, meat cows)
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When nature decides which individuals reproduce most
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Natural selection
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Who proposed Natural Selection to be a mechanism of evolution?
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Charles Darwin
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Who were the two people Charles Darwin was influenced by?
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Lyell- geologist, Malthus
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What were Lyell's ideas about evolution?
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earth had been around for a long time, and said we should be looking at natural causes to determine evolution, NOT to super natural causes
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What were Malthus' ideas about evolution?
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pointed out there were limitations on population size and there is competition for resources (there are winners and losers)
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When individuals who are better at obtaining mates reproduce more than others
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sexual selection
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In most animals, what gender is more 'choosier' when finding a mate, and invest more time and energy into the offspring?
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females
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Mating mistakes are more costly for _________ than for _________.
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females, males
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Who are the two components of sexual selection?
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1. female mate choice
2. males competing for females
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what does a female look for in a mate?
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-correct species
-ability to reproduce
-protector
-good territory
-good parental care
-good genes for survival |
How can we quantify the heritability of a trait (for height?)
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average the parents height and correlate it with the average of the offspring height
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What costly traits do males demonstrate their good genes with?
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bright colors
-long tails
-energetic courtship displays |
What do the costly traits males perform show the females?
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-health of male
-energetic condition of male
-good alleles in male
-good immune system
-good metabolism
-food acquisition abilities
-can be a predator
-escape behaviors |
Females who are choosy obtain better ________ for their offspring and therefore leave behind _______ offspring than females who mate randomly.
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genes, more
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Any of the males alleles that attracted the female will _______ in frequency. |
increase
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Preferences don't need to be ________
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conscious
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Males who attract the most females and/or win the most competitions obtain the most ____________.
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matings |
The most competitive males pass on the most ________
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alleles |
_______ that help the male obtain a female are passed on
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traits |
Why do males tend to be the more decorative sex?
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They have to attract the females because the females are 'picky'
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_____________ influences which individuals survive long enough to reproduce, but __________ influences which individuals among the survivors reproduce the most
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natural selection, sexual selection
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What is the 'random' part of evolution?
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the occurrence of changes in DNA
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Over time, changes occur in the appearance of birds in population, b/c some birds pass more copies of their alleles to the next generation. The bird population is evolving as a form of?
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Natural selection, artificial selection, and sexual selection
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___________ is when selection can cause a trait to change or to stay the same
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modes of selection
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__________ is the proportion of a populations phenotypic variation controlled by genetic factors rather than environmental factors.
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heritability
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Vp = ?
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total phenotypic variance
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Vg = ?
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the total genetic variance
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Ve = ?
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the environmental variance
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Heritability formula?
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Vg
Vp |
Heritable mutations, which allow a population to evolve, are produced by _________
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chance
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What did Darwin observe about evolution?
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-variations among individuals is heritable
-more offspring are born than will survive to reproduce
-some individuals are more likely to survive than others
-some individuals carry alleles that make them better survivors
it is NOT arbitrary (random) which individuals will survive long enough to breed
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individuals who possess ___________ will pass the alleles for these traits to their offspring
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good traits
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The frequency of a good allele will _______ in the population
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increase
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selection doesn't create new traits; it simply ________ a trait if a better one exists
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eliminates
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Different _________ will selection for different _______, depending on what the major causes of death are
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environments, traits
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In the years affected by the drought when beak size increase, what describes the beak size of a typical full-grown offspring compared to his/her parent?
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the offsprings beak is roughly the same size as its parents
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Natural selection results in _________.
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Adaptations
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A characteristic of an organism that helps it to survive and reproduce in a particular environment
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adaptation
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Natural selection is _____ goal-directed
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NOT |
natural selection can only act on variations that occur due to _______________
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chance mutations
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Natural selection preserves alleles, but does not _____ them
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create
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Natural selection does not have an internal drive for _________
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perfection |
Natural selection can be a _______ or a ________ process
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rapid, gradual
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individuals may have only a slight advantage over others, meaning:
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many generations may be required to spread the allele
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rapid changes in allele frequencies occur when:
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selection pressure is strong (when few individuals reproduce)
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natural selection reduce ___________
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genetic variation
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