BIOLOGY FINALS REVIEW
What is the likelihood that a child of two carriers of an autosomal recessive disorder will inherit the disorder? 25% 50% 100% 0%
25%
Mass extinctions: Can be responsible for an adaptive radiation where new species develop to occupy newly opened niche environments Permanently and irreversibly reduces the total number of species on Earth Are caused by human activity and did not occur prior to the expansion of the Earth's human population Mainly serves to "weed out" poorly adapted organisms and make room for more advanced species
Can be responsible for an adaptive radiation where new species develop to occupy newly opened niche environments
Transcription factors bind to mRNA plasma membrane receptors tRNA DNA
DNA
Which of the following is a key component of the Sanger sequencing method? RNA polymerase Restriction enzymes Reverse transcriptase DNA polymerase
DNA polymerase
How does the Earth BioGenome Project differ from other large-scale genomics projects? It only targets species that are important for human health and well-being. It does not differ significantly from other large-scale genomics projects. It focuses on the study of ancient DNA. It aims to sequence the genomes of all organisms on Earth, not just a select few.
It aims to sequence the genomes of all organisms on Earth, not just a select few.
What does the ENCODE project aim to do? Map all functional elements in the human genome Identify all structural variations in the human genome Sequence all non-functional elements in the human genome Study the evolutionary history of the human genome
Map all functional elements in the human genome
Which of the following is a term used to describe the collection of microorganisms that live in and on the human body? Proteome Epigenome Metabolome Microbiome
Microbiome
What is the process of genetic drift? The evolutionary adaptation of different species The survival of the fittest The evolutionary arms race between species The random fluctuation of genetic traits in a population
The random fluctuation of genetic traits in a population
Which of the following allows for a single gene to encode for more than one polypeptide? mRNA degradation. DNA packing. CRISPR. alternative mRNA splicing.
alternative mRNA splicing.
The endosymbiotic theory explains all of the choices are correct the origin of all organelles in eukaryotic cells how mitochondria and chloroplasts originated from free-living cells how bacterial cells can invade eukaryotic cells and cause disease
how mitochondria and chloroplasts originated from free-living cells
What are some conditions that can result from chromosome nondisjunction? All of the above Turner syndrome Down syndrome XXY syndrome
All of the above
Which of the following traits do humans share with all other species in the order Primates? Parental care & sociality All of these choices Grasping hand Larger brain Binocular vision
All of these choices
The 3-D structure of RNA is very different from DNA because the base pairing prevents formation of an anti-parallel double helix. the nitrogenous base uracil. All of these choices are true. the 2'-hydroxyl (-OH) makes RNA more chemically reactive.
All of these choices are true.
There is the need for differential gene expression in humans because of one of the following. Identify the one CORRECT answer. Almost all cells contain the same genotype. Gene expression is very straight forward because the genes lie in tandem, and all are turned on at thesame time. There is one master homeotic gene that turns on all genes at one time in all cells. Cells differentiate by the action of enzymes.
Almost all cells contain the same genotype.
What is the process by which new blood vessels are formed from existing blood vessels called? Hematopoiesis Angiogenesis Vasculogenesis Atherosclerosis
Angiogenesis
Which of the following genes are known to increase the risk of breast and ovarian cancer when mutated? BRCA1 and BRCA2 genes EGFR genes Oncogenes Tumor suppressor genes
BRCA1 and BRCA2 genes
How does CRISPR work? By inducing apoptosis in cancer cells By inhibiting the signaling pathways within cells By cutting DNA at specific locations and allowing for precise editing of the genetic sequence By inserting foreign DNA into the genome of a cell
By cutting DNA at specific locations and allowing for precise editing of the genetic sequence
Which of the following is associated with the origin of life on Earth? Locomotion to spread to other locations Complex biomolecules capable of replication Oxygen for aerobic growth A nucleus to contain genetic material
Complex biomolecules capable of replication
What is chromosome nondisjunction? Failure of a chromosome to separate during cell division Failure of a chromosome to replicate Failure of a chromosome to synapse with its homologous pair Failure of a chromosome to attach to the spindle fibers
Failure of a chromosome to separate during cell division
A Transiting Exoplanet Survey Satellite locates planets by shooting a laser at a suspected location and observing the reflection. True False
False
Archaea have the simplest known genomes because they are the most ancient microorganisms. True False
False
Protocell fossils were found in Australia. True False
False
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 the group's gene pool is quite different from the population on Earth that they left behind. Which of the following phenomena has left its mark on this population? High rates of mutation Stabilizing selection Directional selection Bottleneck effect Founder effect
Founder effect
What is the reason for phenotypic consequences of natural selection? Struggle for existence Differential survival & reproduction Heredity / genetic variation Overproduction of offspring
Heredity / genetic variation
The K-T boundary is geologically identifiable because scientists found evidence of a massive asteroid impact in the form of depositions of: Iodine Carbon Zircons Iridium
Iridium
Which of the following is not a quality of binocular vision? Excellent focus Advantageous when navigating in trees Large field of view Depth perception
Large field of view
What concept did the video on the Christmas Island crabs emphasize? How organisms can become invasive species How speciation of one species to two species occurs The emergence of the first tetrapod The importance of paleontology More offspring will be produced than can possibly survive
More offspring will be produced than can possibly survive
What is the relationship between beak size and survival during drought in the G. fortis population? Directly correlated Positively correlated Inversely correlated No relationship
Positively correlated
The forelimbs of humans, cats, and bats have a number of detailed similarities in their construction. What best explains these similarities? The forelimbs are similar because there is only one workable way to construct a useful arm, leg, or wing. The forelimbs are similar because all of these organisms inherited the basic forelimb design from a common ancestor. The forelimbs are similar because of adaptation through the process of natural selection. The similarities are coincidental.
The forelimbs are similar because all of these organisms inherited the basic forelimb design from a common ancestor.
Why are so many emerging infectious diseases linked to RNA viruses? They mutate less than DNA viruses. A vaccine cannot be generated to prevent RNA-based diseases. The only viruses that cause disease are RNA viruses. They lack the DNA proofreading mechanisms.
They lack the DNA proofreading mechanisms.
The North American Pronghorn far outraces any predators remaining on the North American continent. If maintaining this speed means bearing fewer offspring, which of the following is the most likely to happen given enough time? This species will go extinct This species will slow down None of the choices are likely to happen This species will become even faster This species will split into two new species
This species will slow down
What is the purpose of adding dideoxynucleotides (ddNTPs) to the Sanger sequencing reaction? To prevent the DNA from denaturing during the reaction To amplify the amount of DNA in the reaction To terminate DNA chain extension at specific bases To label the DNA with a fluorescent dye
To terminate DNA chain extension at specific bases
If the sequence of the DNA template strand for mRNA synthesis is ACC AAA CCG, the mRNA sequence is UGG UUU GGC TGG TTT GGC CTT CCC CCG TCC TTT CCG UGG TTT GGC
UGG UUU GGC
What are single nucleotide polymorphisms (SNPs)? Proteins that regulate gene expression by binding to DNA Genetic markers used to identify specific disease states Variations in the DNA sequence that occur when a one base pair is changed Mutations in DNA that alter stretches of nucleotides
Variations in the DNA sequence that occur when a one base pair is changed
Autosomal disorders cannot be caused by recessive allele disorders X-linked disorders dominant allele disorders None of these choices are true.
X-linked disorders
The following figure shows the lac operon in its active and inactive state. What molecule activates the lac operon to produce the 3 enzymes for lactose utilization? tryptophan lactose transcription factor TATA protein
lactose
In coevolution with moths and bats: bats developed better eye-sight to again be successful at preying on moths moths developed ears or ability to detect sonar and avoid predation by bats moths developed larger wings to better escape from bats all of the answers are correct
moths developed ears or ability to detect sonar and avoid predation by bat
During DNA replication, one DNA strand is copied to make a new DNA molecule composed of two DNA strands. This new DNA contains one strand is the original DNA strand and the other the new DNA strand. none of the original DNA. one DNA molecule with two new strands and the other with two original strands. both strands are the original DNA.
one strand is the original DNA strand and the other the new DNA strand.
Scientists hypothesize that a major factor promoting the adaptive radiation of mammals was probably: internal fertilization none of these choices are consistent with the hypothesis the origin and diversification of flowering plants the mass extinction of the dinosaurs
the mass extinction of the dinosaurs
Which of the following is the first distinctively hominid trait to appear in the fossil record? upright walking (bipedalism) sophisticated stone tools increased brain size small teeth and relatively delicate jaws
upright walking (bipedalism)
What compounds and conditions did Stanley Miller need to perform his 1953 experiment to simulate an early atmosphere? water vapor, H2, CH4, NH3 and Lightning water vapor, CO2, CH4, NH3 and Lightning water vapor, CO2, H2, NH3 and Heat water vapor, CO2, O2, NH3 and Lightning
water vapor, H2, CH4, NH3 and Lightning
Infectious diseases that can be specifically transmitted from other vertebrate animals to humans are called vector borne diseases. pandemic diseases. bacteriophages. zoonotic diseases.
zoonotic diseases.
What is MRSA? A type of cancer therapy A bacteria that is resistant to certain antibiotics A virus that causes respiratory illness A type of antibiotic
A bacteria that is resistant to certain antibiotics
Epigenetics refers to A change in gene expression without a change in DNA base sequence. A change in gene expression that cannot be inherited. A change in gene expression that does not affect transcription. A change in gene expression through changes in DNA base sequence.
A change in gene expression without a change in DNA base sequence.
What is EGFR? A gene that is associated with the development of cancer A type of stem cell that can differentiate into any type of cell in the body A protein that is involved in signal transduction pathways in cells A biomarker used to detect the progression of a disease
A gene that is associated with the development of cancer
According to the fossil record, the genus Homo first arose in: Europe Africa Asia North America
Africa
Technological advances to manipulate gene expression include which one of the following. DNA packing RNA splicing RNA interference gene silencing (RNAi) Dicer
RNA interference gene silencing (RNAi)
A "ring species" is an example of parapatric speciation. True False
True
Based on mitochondrial DNA analyses the "Out of Africa" hypothesis about where modern humans came from is currently favored. True False
True
A rabbit population consists of animals that are either very dark or very light on top. The color pattern is not related to sex. No rabbit shows intermediate coloration (medium darkness). This pattern might result from: directional selection sexual selection stabilizing selection disruptive selection
disruptive selection
This person independently converged on the idea of evolution by natural selection: Lamarck Colbert Wallace Malthus
Wallace
Birds with average-sized wings survived a severe storm more successfully than other birds in the same population with longer or shorter wings. This illustrates: stabilizing selection disruptive selection artificial selection directional selection
stabilizing selection
Australopithecus afarensis (Lucy's species) is important in the human lineage because this species is the earliest known biped of the human lineage the first to commonly use complex stone tools the first to migrate out of Africa known to have interbred with early Homo sapiens
the earliest known biped of the human lineage
Technological advances to manipulate gene expression include which one of the following? Epigenetic modification CRISPR-Cas9 Shotgun sequencing RNA splicing
CRISPR-Cas9
Species, Family, Genus, Order, Phylum, Class: Lists the taxonomic categories in the order from most specific to most general. True False
False
Stromatolites are deposits of plant material found near the primordial ocean. True False
False
Archaea: all of the answers are correct are one of the three domains of life are found primarily in oceans gave rise to protocells
are one of the three domains of life
Identify the following image. genome graph pancreatic cancer cell at metaphase a male with XYY karyotype
karyotype
These small, single-stranded RNA molecules, 22 nucleotides long, can block the translation of mRNA and are involved in the expression of ~1/3 of all human genes. Choose the CORRECT answer. small epigenetic factors microRNAs (miRNAs) ribosomal RNA (rRNA) histone regulating RNAs
microRNAs (miRNAs)
In eukaryotes, DNA replication occurs in 5' -> 3' direction 3' -> 5' direction both 3' -> 5' direction and 5' -> 3' direction in the ribosome
5' -> 3' direction
Which of the following is a type of immunotherapy that involves modifying T-cells to target cancer cells? Tumor-infiltrating lymphocytes Antibody-drug conjugates Checkpoint inhibitors CAR-T therapy
CAR-T therapy
The same criteria are currently used to define both animal and bacterial species. True False
False
What is correct order of stages of Mitosis? Telophase, Prophase, Metaphase, Cytokinesis, Anaphase G0, G1, S, G2, Prophase Prophase, Metaphase, Telophase, Anaphase, Cytokinesis Prophase, Metaphase, Anaphase, Telophase, Cytokinesis Metaphase, Prophase, Anaphase, Telophase, Cytokinesis
Prophase, Metaphase, Anaphase, Telophase, Cytokinesis
BRCA1 and BRCA2 are genes that are normally expressed only in breast cells. essential for repairing damaged DNA. normally expressed only in women. essential to control cell division. All of these choices are true.
essential for repairing damaged DNA.
Which of the following are main categories of evidence that scientists use to study evolution? fossils and molecular/biochemical fossils and anatomical and molecular/biochemical fossils molecular/biochemical anatomical
fossils and anatomical and molecular/biochemical
A small population of tortoises has been isolated on a small, remote island in the Galapagos for over 10,000 generations. While the population's characteristics are still similar to the ancestral mainland species, male sperm exhibit a variety of abnormalities and female fertility is much lower than on the mainland. What process may have been acting on this island's population? genetic drift stabilizing selection disruptive selection sexual selection
genetic drift
When there seems to be no contemporary selective forces that can explain the traits of recent organisms, such as the New Zealand Moa, evolutionary biologists often invoke the idea of: natural selection ghost of predation past parapatric speciation allopatric speciation convergence
ghost of predation past
Coevolution: occurs between a population and the physical environment in which the population lives. is the evolution of individuals within a population in response to selection pressure from other individuals in the population. is a special type of evolution that differs from Darwinian evolution. is the evolution of two populations of different species in response to selection pressures that individuals from the two populations place on each other.
is the evolution of two populations of different species in response to selection pressures that individuals from the two populations place on each other.
What type of RNA is considered coding RNA? rRNA cRNA tRNA mRNA
mRNA
X-linked conditions are more common in men than in women because women simply do not develop the disease regardless of their genetic composition. men need to inherit only one copy of the recessive allele for the condition to be fully expressed. the genes associated with the sex-linked conditions are linked to the Y-chromosome, which determines maleness. men acquire two copies of the defective gene during fertilization.
men need to inherit only one copy of the recessive allele for the condition to be fully expressed.
During which stage of meiosis does crossing over and formation of tetrads occur? prophase II prophase I metaphase I interphase I
prophase I
A current leading hypothesis about the first system of inheritance in the earliest life forms involved: proteins that served as templates for RNA molecules, leading to the formation of DNA self-replicating DNA molecules self-replicating RNA molecules aided by ribozymes self-replicating polypeptides aided by ribosomes
self-replicating RNA molecules aided by ribozymes
During anaphase, sister chromatids separate into individual chromosomes and are pulled apart. chromosomes become visible for the first time of the cell cycle. chromosomes gather at the opposite ends of the cell and lose their distinct rod-like shapes. Two new nuclear envelopes then form around each of the two regions. Chromosomes line up at the center of the cell and become attached to the kinetochore microtubules.
sister chromatids separate into individual chromosomes and are pulled apart.
Emergence is a property: of only living systems that is not seen in simple systems, such as protocells of only chemical & physical systems that is purportedly responsible for the formation of life
that is purportedly responsible for the formation of life
The reason that pea hens mate with peacocks with large tails and many eye spots is that: peacocks that survive predation are more physically fit and make better mates. the male will draw predators to it and this indirectly protects the pea hen and offspring from predation. flashy displays by males are used to trick females into mating with them. the size and spot density are indicative of peacock fitness shown as an increased survival rate of chicks.
the size and spot density are indicative of peacock fitness shown as an increased survival rate of chicks.
What is the likelihood that a child of an affected parent with an autosomal dominant disorder will inherit the disorder? 25% 100% 50% 0%
50%
Epidemiology is the study of the origin of diseases, how they spread, and how to prevent their spread. Why was Covid-19 considered a pandemic, yet the H5N1 bird flu was not? Covid-19 like Ebola was restricted to Africa. The U.S. Congress designated Covid-19 a pandemic. A disease is named a pandemic when new incidences of the disease increase, spread rapidly, and with a very wide global distribution. The H5N1 bird flu only infects birds not mammals.
A disease is named a pandemic when new incidences of the disease increase, spread rapidly, and with a very wide global distribution.
Male bower birds build large, elaborate structures up to six feet high that they decorate with flowers, colored pebbles, and shiny objects. During the breeding season they use these structures as stages to display and court females. What process could drive the evolution of these remarkable bowers? Stabilizing selection Sexual selection All of the choices are false Fluctuating directional selection Disruptive selection
Sexual selection
In the North Pacific Ocean, two groups of the same species of killer whales (Orcinus orca) appear to be forming two different species based on what they eat. One group eats fish while the other eats mammals such as seals. Scientists can tell what they eat based on their teeth because whales that feed on fish have significantly different wear patterns. Which of the following best describes the type of speciation event that is occurring in the whales? None of these choices Punctuated speciation Sympatric speciation Geographic speciation Allopatric speciation
Sympatric speciation
A population of grasshoppers in the Kansas prairie has two color phenotypes, green and brown. Typically, the prairie receives enough water to maintain healthy, green grass. Assume a bird that eats grasshoppers moves into the prairie. How will this affect natural selection of the grasshoppers? The green phenotype should be more easily seen by the predator and decrease in frequency. Both green and brown grasshoppers should be eaten and their relative numbers should remain constant. Predation will cause the brown grasshoppers to mutate into green grasshoppers. The brown phenotype should be more easily seen by the predator and decrease in frequency.
The brown phenotype should be more easily seen by the predator and decrease in frequency.
What is epigenomics? The study of the genetic basis of diseases such as cancer The study of genetic variation within a population The study of how environmental factors can affect gene expression The study of how stem cells differentiate into specialized cell types
The study of how environmental factors can affect gene expression
Two populations of organisms belong to the same biological species when they can't mate with each other, because mating occurs at different times. use different types of behaviors or physical features to attract mates. encounter each other, mate, and produce viable, fertile offspring under natural conditions. have anatomical features that make it difficult for organisms from the different populations to mate.
encounter each other, mate, and produce viable, fertile offspring under natural conditions.
What did Darwin observe during his voyage on the Beagle? The survival of Homo habilis Iridium layer at the K-T boundary A group of drab finches in Galapagos The multiregional hypothesis of human origins
A group of drab finches in Galapagos
Predators have learned to associate desirable prey with bright colors. True False
False
Neil Shubin & colleagues made one of the greatest paleontological discoveries of all time. Why was the discovery of Tiktaalik so important? Tiktaalik fossils revealed a forearm bone structure that was more similar to trilobites It was the missing ancestral link between fish and birds Tiktaalik fossils showed that feeding changed from algae to plants It explained the transition from fish in the water to vertebrates that could walk on land
It explained the transition from fish in the water to vertebrates that could walk on land
The ENCODE Project revealed new insights about the human genome. Identify the one correctanswer. ~80% of the genome encodes proteins. Recognition that evolutionary change occurs through sequences that alter gene regulation. >80% of the human genome could not be explained; it had no biochemical function. The organization of the human genome is similar to the bacterial genome.
Recognition that evolutionary change occurs through sequences that alter gene regulation.
Beta hemoglobin is a conserved protein that is useful for comparing the lineage of species. True False
True
Reduced allele variation results in an increased chance of extinction. True False
True
What are the four mechanisms of natural selection? Overproduction of offspring, struggle for existence, differential survival & reproduction, and heredity/genetic variatio Stabilizing selection, directional selection, disruptive selection, and genetic drift Coevolution, sexual selection, genetic drift, and species Primate adaptations, human origins hypothesis, Homo habilis, and Homo erectus
Overproduction of offspring, struggle for existence, differential survival & reproduction, and heredity/genetic variatio
We have learned the following from Cancer Genomics Project except for the following one statement that is FALSE. All cancer patients do not respond to the same chemotherapy or treatment plan. All breast cancer patients have the same oncogenic signature. Most cancers are caused by 2-8 sequential alterations over 20-30 years. Breast cancer can not be inherited.
All breast cancer patients have the same oncogenic signature.
The major events in the history of life on Earth, from earliest to most recent is: prokaryotes, eukaryotes, photosynthesis, and then colonization of land by plants and fungi. True False
False
Genetic changes that underlie oncogenesis alter fundamental properties of cells including all ofthe following except one choice. Which one is FALSE? Allow cells to evade normal growth controls. Malignant cells are more highly oxygenated and do not migrate toward a blood supply. Cells can acquire the ability to metastasize. Metastasized cells can use the cell's cytoskeleton to promote tumor cell streaming. Cells acquire the ability to proliferate that does not require an external inducing signal.
Malignant cells are more highly oxygenated and do not migrate toward a blood supply.
After fertilization of an egg, the resulting zygote has a diploid chromosome number - one from each parent a haploid chromosome number - two from each parent a diploid chromosome number - two from each parent a tetraploid number - two from each parent
a diploid chromosome number - one from each parent
A codon is the binding site of repressor proteins. a protein that aids in the recruitment of RNA polymerase to DNA. a set of metabolically related genes whose expression is controlled by a single promoter. a triplet-nucleotide sequence that codes for a specific amino acid or termination of translation.
a triplet-nucleotide sequence that codes for a specific amino acid or termination of translation.
What was "Darwin's Dilemma" with evolution? there was a lack of fossil evidence of ancestors to the Cambrian explosion necessary evidence was lost in a fire at the University of Edinburgh there was not any quantitative evidence of evolution it was not likely that the birds in the Cambrian explosion had any previous ancestors
there was a lack of fossil evidence of ancestors to the Cambrian explosion
How did scientists change the behavior of the male polygamous Montane Vole to become monogamous? transferred to the male polygamous vole a gene for a hormone that caused monogamy put a male polygamous vole with a single female vole in isolation until they mated none of the answers are correct gave the male polygamous vole vitamins that changed its behavior put two male polygamous voles together with one female monogamous vole for them to compete for sexual selection
transferred to the male polygamous vole a gene for a hormone that caused monogamy
What is personalized medicine? A type of medicine that focuses on treating the whole person, not just their disease A type of medicine that uses genetic information to tailor treatments to individual patients A type of medicine that uses non-invasive techniques to diagnose and treat diseases A type of medicine that emphasizes the use of natural remedies over pharmaceutical drugs
A type of medicine that uses genetic information to tailor treatments to individual patients
What is CRISPR/Cas9? An exciting technology that offers promise for curing human diseases, advancing agriculture, altering pests that carry disease. All these choices are correct. A defense system that bacteria use to protect against invading viruses. A technology that can cleave target DNA with exceptional precision and edit it.
All these choices are correct.
The Central Dogma in molecular biology refers to RNA is transcribed into DNA and DNA is translated to protein. RNA is translated to DNA and DNA is transcribed to proteins. DNA is translated into RNA and RNA is transcribed to protein. DNA is transcribed into RNA and RNA is translated to protein.
DNA is transcribed into RNA and RNA is translated to protein.
Which of the following is NOT a possible cause of epigenetic changes? DNA mutations addition of methyl and/or acetyl groups nicotine and alcohol environmental factors
DNA mutations
What is the definition of sympatric speciation? Speciation that occurs when a population is isolated by a physical barrier Speciation that occurs within a single geographic location Speciation that occurs gradually over a large geographic area Speciation that occurs rapidly in a single generation
Speciation that occurs within a single geographic location
The figures are histograms of the distribution of Geospirzafortis beak widths observed by Rosemary & Peter Grant in 1976 and in 1978 on Daphne Major Island. Which of the following statements either can be inferred or is supported by the data presented? In comparison to 1976, the beak width of the average G. fortis tends to be smaller in 1978. The total population of G. fortis on the island increased between 1976 and 1978. The G. fortis on this island is evolving towards having larger beak sizes. The population underwent a stabilizing selection.
The G. fortis on this island is evolving towards having larger beak sizes.
The currently available fossil record documents gradual evolutionary changes that can link one group of organisms to another. True False
True
The earliest primates were arboreal and small in size. True False
True
During the Cambrian explosion approximately 535 to 525 million years ago: animals rapidly diversified in the oceans a massive volcanic eruption nearly wiped out life on Earth all modern species of animals suddenly appeared great forests produced peat layers that were later transformed into coal
animals rapidly diversified in the oceans
In eukaryotes, DNA packing seems to affect gene expression primarily by controlling access to DNA. protecting DNA from mutations. enhancing the recombination of genes. positioning related genes next to each other.
controlling access to DNA.
Roses native to India are grown at a plant-breeding center in Arizona, where those with the thickest leaves survive and reproduce best in the drier climate. This evolutionary adaptation of roses to their new environment is due to _____. genetic drift directional selection stabilizing selection disruptive selection
directional selection
