Biology Chapter 13 &14
Evolution by natural selection
1) INDIVIDUALS DO NOT EVOLVE (evolution is generation to generation changes in populations) 2) natural selection can amplify or diminish only HERITABLE traits. unless the characteristic is coded for in the genes of an organism's GAMETES, such acquired characteristics cannot be passed on to offspring. 3) evolution is not goal directed; it does not lead to perfectly adapted organisms.
four reasons
1) selection can act only on existing variations. Natural selection favors only the fittest variations from the phenotypes that are available. 2) evolution is limited by historical constraints. Evolution does not scarp ancestral anatomy and build each new complex structure from scratch. 3) adaptations are often compromises. 4) Chance, natural selection, and the environment interact. Natural selection operates on a "better than" basis.
Which of the following terms represents the frequency of heterozygotes in a population that is in Hardy-Weinberg equilibrium?
2pq
Natural Selection
A process in which organisms with certain inherited characteristics are more likely to survive and reproduce than are organisms with other characteristics. -unequal reproduction -ex. individuals whose traits enable them to better obtain food or escape predators or tolerate physical conditions will survive and reproduce more successfully than individuals without those traits. -natural selection is an editing process -natural selection favors those characteristics in a varying population that fit the current, local environment
Which of the following statements regarding natural selection is false?
A) Natural selection is more of an editing process than a creative mechanism. B) Natural selection depends on the local environment at the current time. C) Natural selection starts with the creation of new alleles that are directed toward improving an organism's fitness. D) Natural selection and evolutionary change can occur in a short period of time (a few generations). E) Natural selection can be observed working in organisms alive today. Answer is C
comparative Anatomy
Anatomical similarties between many species give signs of common descent. -same skeletal elements that make up the forelimbs of humans, cats, whales, and bats. Although each function of these forelimbs differ.
evolution
Descent with modification; the idea that living species are descendants of ancestral species that were different from present-day ones; also the genetic changes in a population over generations
bottleneck effect
Earthquakes, floods, or fires may kill large numbers of individuals, leaving a small surviving population that is unlikely to have the same genetic makeup as the orginal population. A drastic reduction in population size and change in allele frequencies. -human actions may also create bottleneck effects for other species such as the Greater prairie chicken.
Jean Baptiste Lamarck
First person to propose that life evolves. -believed that by using or not using its body parts, an individual may change its traits and then pass those changes on to its offspring = Inheritance of acquired characteristics. Although this belief of how life evolves was wrong, it spurred many ideas.
Thirty people are selected for a long-term mission to colonize a planet many light years away from Earth. The mission is successful and the population rapidly grows to several hundred individuals. However, certain genetic diseases are unusually common in this group, and their gene pool is quite different from that of the Earth population they have left behind. Which of the following phenomena has left its mark on this population?
Founder effect
Charles Darwin
His father wanted him to go into medicine, but Darwin got bored of it and didn't like how surgeries were performed at the time. He decided to be a clergyman. (ironic because science and religion don't mix). Darwin then went on a sea voyage with a captain of the HMS Beagle and collected different species. -Darwin then published his book "On the Origin of Species by Means of Natural Selection" - evolutionary history of life - "descent with modification" = as the descendants of a remote ancestor spread into various habitats over millions and millions of years, they accumulated diverse modifications, or adaptations, that fit them to specific ways of life.
Artificial Selection
Humans can modify other species by selecting and breeding individuals that possess desired traits.
Speciation, or the formation of new species, is
Is the bridge between microevolution and macroevolution
Two bird species overlap in a hybrid zone. They are isolated by a slight difference in the male songs and by the females' tendency to select males with the "correct" song. Hybrid offspring tend to have reduced fertility compared to either of the parent species. What effect should natural selection have in this situation?
Natural selection will favor males with more distinctive calls and/or females that are more "choosy." As a result, the reproductive barrier between the two species will be reinforced.
During the 1950s, a scientist named Lysenko tried to solve the food shortages in the Soviet Union by breeding wheat that could grow in Siberia. He theorized that if individual wheat plants were exposed to cold, they would develop additional cold tolerance and pass it to their offspring. Based on the ideas of artificial and natural selection, do you think this project worked as planned?
No, because there was no process of selection based on inherited traits. Lysenko assumed that exposure could induce a plant to develop additional cold tolerance and that this tolerance would be passed to the plant's offspring.
Gene Flow
Population may gain or lose alleles when fertile individuals move into or out of a populatino or when gamets are transferred between population. -gene flow reduces difference between populations
A woman struggling with a bacterial illness is prescribed a month's supply of a potent antibiotic. She takes the antibiotic for about two weeks and feels much better. Should she save the remaining two-week supply, or should she continue taking the drug?
She should continue taking the drug until her immune system can completely eliminate the infection. Otherwise the remaining bacteria in her system may recover, and they will probably be resistant.
A population of 1,000 birds exists on a small Pacific island. Some of the birds are yellow, a characteristic determined by a recessive allele. The others are green, a characteristic determined by a dominant allele. A hurricane on the island kills most of the birds from this population. Only ten remain, and those birds all have yellow feathers. Which of the following statements is true?
The hurricane has caused a population bottleneck.
Certain whale species were hunted to near extinction. With a moratorium on hunting them, their population sizes have expanded. Which of the following is true?
The populations may still be endangered because they may have little remaining genetic variation.
A dog breeder wishes to develop a breed that does not bark. She starts with a diverse mixture of dogs. Generation after generation, she allows only the quietest dogs to breed. After 30 years of work she has a new breed of dog with interesting traits, but on average, the dogs still bark at about the same rate as other dog breeds. Which of the following would be a logical explanation for her failure?
The tendency to bark is not a heritable trait.
Which one of the following represents two structures that are homologous?
The wing of a bat and the flipper of a whale
Tay-Sachs is inherited as an autosomal recessive allele. Homozygous individuals die within the first few years of life. However, there is some evidence that heterozygous individuals are more resistant to tuberculosis. Which of the following statements is true?
This situation is an example of heterozygote advantage.
Who developed a theory of evolution almost identical to Darwin's?
Wallace
founder effect
When few individuals colonize an isolated island or other new habitat. The smaller the group, the less likely the genetic makeup of the colonists will represent the gene pool of the larger population they left. Differences in the gene pool of a small colony compared with the original population is called the founder effect. -explains the relatively high frequency of certain inherited disorders among some human populations.
Which provides the most general and correct description of the idea of a reproductive barrier?
a biological difference between two species that prevents them from successfully interbreeding
Which of the following would a biologist describe as microevolution?
a change in allele frequencies within the gene pool of a population
Genetic drift
a change in the gene pool of a population due to chance. -the smaller the sample, the greater the chance of deviation from an idealized result. -frequencies of alleles in gene pool will be more STABLE from one generation to the next when population is LARGE. -frequencies of alleles in gene pool may VARY unpredictably when population is SMALL -genetic drift tends to reduce genetic variation. -two parts of genetic drift is in the bottleneck effect and the founder effect
Mutation
a change in the nuceotide sequence of DNA -New alleles orginate by mutation. -ultimate source of genetic variation that serves as raw material for evolution. -in multicellular organisms, most mutations occur in body cells and are lost when individual dies. -ONLY mutations in cells that produce gametes can be passed to offspring and affect a population's genetic variability. -chromosomal mutations that delete, disrupt, or rearrange many gene loci at once are almost certain to be harmful. -repeated segment of chromosome can persist through generations, it may provide a bigger genome with extra genes that may eventually take on new functions by further mutation. -mutations in bacteria generate genetic diversity quickly bc bacteria multiply so rapidly. -genetic variation is necessary for a population to evolve.
a population is
a group of individuals of the same species living in the same place at the same time.
population
a group of individuals of the same species living in the same place at the same time. -measure evolution as a change in prevalence of certain heritable traits in a population over a span of generations.
Microevolution, or evolution at its smallest scale, occurs when
a population's allele frequencies change over a span of generations
Antibiotics (Penicillin)
antibiotics select for resistant bacteria. Penicillin works by preventing the formation of bacterial cell walls. - resistant bacteria contain a gene that codes for a protein taht breaks down penicillin. -antibiotics bind to bacterial ribosomes and block protein synthesis. However, existing or new mutations may alter the sites on the ribosomes where the antibiotic binds, making the bacterium and its offspring resistant to that antibiotic.
Broccoli, cabbages, and Brussels sprouts all descend from the same wild mustard and can still interbreed. These varieties were produced by
artificial selection
frequency-dependent selection
balancing selection that maintains two different phenotypic forms in a population. ex. scale eating fish.
Which of the following types of reproductive barriers separates a pair of moth species that could interbreed except that the females' mating pheromones are not attractive to the males of the other species?
behavioral isolation
Book of Genesis
believed that species were individually designed by a divine creator
Genetic drift resulting from a disaster that drastically reduces population size is called
bottleneck effect
In their 30-year studies of Darwin's finches, the Grants have discovered that while the medium ground finch and cactus finch occasionally form hybrids, these hybrids
can only survive during wet years when there are plenty of small seeds.
secondary sexual characteristics
characteristics not directly associated with reproduction or survival
gene pool
combined genetic information of of all the members of a population
Which of the following best expresses the concept of natural selection?
differential reproductive success based on inherited characteristics
rabbit population consists of animals that are either very dark on top or very light on top. When examining them closely, biologists were surprised to find no rabbit with a medium darkness, intermediate to the two extremes. This is an example of
disruptive selection
sexual dimorphism
distinction in appearnce is manifested in a size difference. Also evident in the form of male adornment, such as manes on lions, antlers on deer, or colorful plumage on birds.
The biological species concept is
easy to apply to all present sexually reproducing organisms, but harder to apply to asexual organisms and fossils.
Diploid
eukaryotes are diploid. They have two sets of chromosomes to prevent populations from becoming genetically uniform. - in a heterozygote, the recessive allele is hidden or protected from natural selection. The hiding of these recessive alleles allows for a larger number of recessive alleles to remain in a gene pool.
stabilizing selection
favors intermediate phenotypes. -typically occurs in stable environments, where conditions tend to reduce phenotypic variation. - hump of the graph is emphasized in the middle
homologous structures
features that often have different functions but are structurally similar because of common ancestry.
Pesticides resistance
first spray of pesticide kills 99% of insects. The few survivors of the first pesticide wave are insects that are genetically resistant, carrying an allele that somehow enables them to resist the chemical attack. The application of pesticide only leaves the resistant individuals to reproduce and pass on the alleles for pesticide resistance to their offspring. -the pesticide doesn't create alleles that allow insects to resist it. Instead, the presence of the pesticide leads to natural selection for insects already in the population who have those alleles.
trace fossils
footprints, burrows, and other remnants of an ancient organism's behavior.
sexual selection
form of natural selection in which individuals with certain characteristics are more likely tahn other individuals to obtain mates.
In a hybrid zone, ________ can occur if the reproductive barrier between two species is weak, as seen among cichlids in the murky waters of modern Lake Victoria.
fusion
Which of the following types of reproductive barriers separates two species of sea cucumbers, whose sperm and eggs often bump into each other but do not cross-fertilize because of incompatible proteins on their surfaces?
gametic isolation
Genetic differences between populations tend to be reduced by
gene flow
neutral variation
genetic variation that does not appear to provide a selective advantage or disadvantage.
sexual reproduction
genetic variation thru sexual reproduction results from the unique commbination of alleles that each individual inherits. 1) independent orientation of homoogous chromosomes at metaphase I of meiosis 2) random fertilization 3) crossing over.
Biogeography
geographic distribution of species. -ex. marsupials (pouched animals) in Australia such as, kangaroos and koalas, evolved in isolation after geologic activities separated that island continent from the landmasses on which placental mammals diversified.
Which of the following types of reproductive barriers separates a pair of insect species that could interbreed except that one mates on goldenrod flowers and the other on autumn daisies that both blossom at the same time?
habitat isolation
A biological species is defined as a group of organisms that
have the potential to interbreed in nature and produce fertile offspring.
Which of the following promote(s) genetic variation in a population?
heterozygote advantage
heterozygote advantage
heterozygous individuals have greater reproductive success than homozygotes, with the result that two or more alleles for a character are maintained in the population.
allele frequency
how often a form of a gene appears in a gene pool
fossils
imprints or remains of organisms that lived in the past. -dead organisms usually decay rapidly except for their hard parts that are rich in minerls (e.g. bones, teeth, shells) -a whole organism can be preserved if they are engulfed in a medium that prevents bacteria and fungi from decomposing the corpse. -oldest known fossil are prokaryotes. (ancestors of all life)
intersexual selection
individuals of one sex (usually female) are choosy in selecting their mates. Males with the largest or most colorful adornments are often the most attractive to females. - females prefer male traits that are correlated with "good genes". -traits preferred by females are related to overall male health.
Adaptations
inherited traits that enhance an organism's ability to survive and reproduce in a particular environment
Mate-attracting features such as the bright plumage of a male peacock result from
intersexual selection
Large antlers in male elk, which are used for battles between males, are a good example of
intrasexual selection
extinction
irrevocable loss of a species
Which of the following conditions would tend to make the Hardy-Weinberg equation more accurate for predicting the gene frequencies of future generations in a population of a sexually reproducing species?
little gene flow with surrounding populations
Which of the following types of reproductive barriers separates two flowering plant species that could interbreed except that one has a deep flower tube and is pollinated by bumblebees, whereas the other has a short, narrow flower tube and is pollinated by honeybees?
mechanical isolation
molecular biology
molecular history of evolution in the DNA sequences of organisms. -siblings have greater similarity in their DNA and proteins than do unrelated individuals of the same species. -the greater the number of sequence differences between species, the more distant is their last common ancestor.
Darwin found that some of the species on the Galápagos islands resembled species of the South American mainland
more than they resembled animals on ecologically similar but distant islands.
The ultimate source of all new alleles is
mutation in parent cells (asexual organisms) or in cells that produce gametes (sexual organisms).
Which of the following will tend to produce adaptive changes in populations?
natural selection
Balancing selection
occurs when natural selection mantains stable frequencies of two or more phenotypic forms in a population.
Natural selection and the ability to generate perfection are limited by all of the following except that
organisms with the greatest fitness often don't reproduce.
Imagine that you are studying a very large population of moths that is isolated from gene flow. A single gene controls wing color. Half of the moths have white-spotted wings (genotype WW or Ww) and half of the moths have plain brown wings (ww). There are no new mutations, individuals mate randomly, and there is no natural selection on wing color. How will p, the frequency of the dominant allele, change over time?
p will neither increase nor decrease; it will remain more or less constant under the conditions described
When plants undergo allopatric speciation, an initial reproductive barrier is often
pollinator choice
Organisms that possess more than two complete sets of chromosomes are said to be
polyploid
Sympatric speciation commonly occurs through ________ in plants, but is more likely to occur through ________ in animals.
polyploidy . . . habitat differentiation and sexual selection
Two species that sometimes mate and produce vigorous but sterile offspring are separated by
reduced hybrid fertility
Which one of the following is false? Natural selection
results from an organism's needs.
intrasexual selection
secondary sex structures are used to compete with members of the same sex for mates. - common in species where the winning individual garners a harem of mates.
Directional selection
shifts overall make up of the population by acting against individuals at ONE of the phenotypic extremes. - most common during periods of environmental change or when members of a species migrate to some new habitat with different environmental conditions.
homology
similarity in characteristics that results from common ancestry.
haploid
single gene for each inherited character.
The likelihood of allopatric speciation increases when a splinter population is ________ and ________ the broader range of the species.
small...isolated from
An elk herd is observed over many generations. Most of the full-grown bull elk have antlers of nearly the same size, although a few have antlers that are significantly larger or smaller than this average size. The average antler size remains constant over the generations. Which of the following effects probably accounts for this situation?
stabilizing selection
vestigial organs
structures that are of marginal or perhaps no importance to the organism now, but served as important functions in organism's ancestors.
homologous structure
structures that have different mature forms in different organisms but develop from the same embryonic tissues
Speciation without geographic isolation is called ________ speciation
sympatric speciation
Which of the following types of reproductive barriers separates a pair of species that could interbreed except that one mates at dusk and the other at dawn?
temporal isolation
The degree of adaptation that can occur in a population is limited by
the amount and kind of genetic variation in a population.
Fitness
the contribution an individual makes to the gene pool of the next generation relative to the contributions of other individuals. -most fit are thoise that produce the largest number of viable, fertile offspring, and thus pass on the most genes to the next generation.
The fossil record shows all of following EXCEPT that
the first life forms were eukaryotes.
fossil record
the sequence in which fossils appear within layers of sedimentary rocks -strongest evidence of evolution -sedimentary rocks = form from layers of sand and mud that settle at the bottom of seas, lakes, and swamps. Over millions of years, deposits pile up and compress the older sediments below the rock. (rock forms in strata, or layers)
gene pool
the total collection of genes in a population at any one time. -consists of all alleles in all the individuals making up the population. For many genes there are two or more alleles.
Hardy-Weinberg equilibrium
there be no natural selection-that all individuals in a population be EQUAL in their ability to reproduce.
Disruptive selection
typically occurs when environmental conditions are varied in a way that favors individuals at BOTH extremems of a phenotypic range. - both extremes are favored. camels hump in the graph.
evolutionary tree
used to represent patterns of descent.
microevolution
when relative frequencies of alleles in a popuation change like this over a number of generations, evolution is occuring on its smallest scale.
