OSAT - Biological Science

Ionic bonds

occurs when one atom transfers electrons to another

Translocation

a genetic abnormality where a chromosome breaks and its segment attaches to a different, non-homologous chromosome

Nondisjunction

the failure of homologous chromosomes or sister chromatids to separate properly during cell division

Genetic therpy

technique that modifies, replaces, or inactivates genes within a patient’s cells to treat or cure diseases, often by using vectors (like modified viruses) to deliver genetic material.

Hardy-Weinberg equilibrium

a principle stating that allele and genotype frequencies in a population remain constant—non-evolving—across generations in the absence of evolutionary influences.

Behavioral isolation

a prezygotic reproductive barrier where unique mating rituals, signals, or behaviors prevent closely related species from interbreeding

Point mutation

a genetic mutation where a single nucleotide base pair in DNA is replaced, inserted, or deleted

Nuclear DNA

inherited from both parents

Incomplete dominance

a form of inheritance where one allele for a specific trait is not completely expressed over its paired allele, resulting in a third, intermediate phenotype (a blend) rather than the typical dominant-recessive outcome

Complete dominance

occurs when one allele, or gene version, completely masks the effect of another allele in a heterozygous genotype

Polymerase Chain Reaction

a rapid laboratory technique used to amplify specific DNA segments, creating millions to billions of copies from a tiny sample. It works by cycling through three main steps—denaturation (separating DNA), annealing (primer binding), and extension (DNA synthesis)—using Taq polymerase to build new DNA

DNA restriction analysis

a technique that uses restriction enzymes to cut DNA at specific palindromic sequences, creating fragments of varying sizes. These fragments are separated via gel electrophoresis to determine the structure, sequence, or identity of a DNA molecule, often used to confirm plasmid inserts or map unknown sequences

Prokaryotes

single-celled organisms, comprising bacteria and archaea, that lack a membrane-bound nucleus and specialized organelles

Eukaryotes

organisms—including animals, plants, fungi, and protists—characterized by cells with a distinct, membrane-bound nucleus and specialized organelles

Archea

a domain of single-celled, prokaryotic microorganisms that are genetically and biochemically distinct from bacteria and eukaryotes. While prokaryotic, their genetic processing (transcription/translation) is more similar to eukaryotes than bacteria

5 domain classification system

categorizes life into Monera, Protista, Fungi, Plantae, and Animalia. Organisms are classified based on cell structure (prokaryotic vs. eukaryotic), cellular organization (unicellular vs. multicellular), and nutrition mode.

3 domain classification system

divides cellular life into three primary domains based on 16S ribosomal RNA (rRNA) sequences and genetic relationships. This system recognizes that Archaea are distinct from bacteria and more closely related to Eukarya.

Disruptive selection

a type of natural selection that favors extreme phenotypes over intermediate ones, driving divergence within a population

Directional selection

a mode of natural selection where a single, extreme phenotype is favored over other phenotypes, causing the allele frequency to shift continuously in one direction

Genetic Drift

a mechanism of evolution causing random fluctuations in allele frequencies within a population due to chance sampling events, rather than natural selection

Founder effect

a type of genetic drift occurring when a new, isolated population is established by a very small number of individuals from a larger population

An example of a commensal relationship between organisms is

Bird building a nest on a tree limb

Commensal relationship

a type of symbiotic relationship where one organism (the commensal) benefits, usually by obtaining food, shelter, or transportation, while the other organism (the host) is neither helped nor harmed

Sympatric speciation

Evolution of a new species from a surviving species while both inhabit the same geographic region. Occurs without physical barriers

A black Andalusian chicken mates with a white chicken of the same species. They offspring are all an even Grey color. The phenotypic affect shown is most often caused by which of the following patterns of inheritance?

Incomplete dominace

Immediately following the 1980 eruption of Mount St. Helens in Washington, ash deposition on the leaves of Veratrum plants caused widespride breakage of the plants’ stems. This severely reduced the plants population in the area. This type of population fluctuation is typical of that associated with

Density-independent factors

Stored fat molecules can be used to produce more ATP per gram than glucose molecules because fat molecules are what?

they are highly reduced with only C-C and C-H bonds

The process by which water is moved from a plant's roots to its leaves depends on the

attraction between a hydrogen atom of one water molecule and the oxygen atom of another

The high specific heat capacity of water best explains how water

insulates aquatic organisms in the winter under a layer of ice

During an enzyme mediated reaction, a regulatory molecule binds to a secondary site on the enzyme and changes the conformation of the enzyme's active site. Which of the following processes best describes this interaction

allosteric regulation

Feedback inhibition

Is a cellular control mechanism in which an enzyme's activity is inhibited by the enzyme's end product. This mechanism allows cells to regulate how much of an enzyme's end product is produced.

competitive inhibition

phenomenon in which a substrate molecule is prevented from binding to the active site of an enzyme by a molecule

allosteric regulation

a form of noncompetitive inhibition that slows down enzymatic activity by binding to an allosteric site

students creating ball-and-stick models of biologically important molecules use white balls to represent hydrogen atoms, red balls for oxygen atoms, and black balls for carbon atoms. Short, flexible pieces of plastic are used for bonds between the atoms. What type of biomolecules could be represented most easily using these materials?

carbohydrates

A cross section of an object under an electron microscope is found to contain a single loop of chromosomal DNA, ribosomes, and a cell membrane. This object is most likely a

bacterium

Which of the following structures is most important with regard to increasing the surface area of the chloroplast for the absorption of light energy

thylakoid stacks

Absorption of nutrients in the human small intestine is facilitated by cells that would most likely exhibit which of the following specialized characteristics?

brush border of microvilli

the inside of a cell has high concentrations of sodium (NA+) ions and low concentrations of chloride (Cl-) and potassium (K+) ions. The solution in which the cell sits has a high concentration of chloride and potassium ions and low concentrations of sodium ions. The outside of the cell has a positive charge relative to the inside of the cell. If the membrane is equally permeable to all of the ions, both the concentration gradient and the force of the electric charge will tend to move

potassium into the cell

Communication between cells in the nervous system differs from cell communication involving the endocrine system because communication between cells in the nervous system:

relies on ligands that are quickly degraded

The phase of the cell cycle where DNA replication takes place.

S phase

This is the first gap phase where the cell grows and prepares itself for DNA replication

G1 phase

This is the phase where the cell divides its duplicated chromosomes. By the end of this phase, the DNA content returns to normal

M phase

This is the second gap, where the cell grows further and prepares for mitosis.

G2 Phase

In humans, the unregulated cell division that may result in cancer is the result of problems with the checkpoint at the end of the following phases of the cell cycle

G2

Compared to that of other heterotrophs, the manner in which multicellular fungi obtain and utilize energy is unique because fungi

digest matter externally before ingesting it.

Which of the following substances is the initial source of energy for most of the microorganisms inhabiting a deep-sea ecosystem?

hydrogen sulfide

which of the following substances is primarily responsible for an increase in mass associated with the growth of a seed into a tree

carbon dioxide taken in by leaves

What is the difference between aerobic and anaerobic respiration

aerobic respiration is more efficient and yields more energy of ATP than anaerobic respiration

A characteristic of chloroplasts and mitochondria related to their function in living organisms is that both of these cell organelle types

have double membranes that facilitate in oxidative phosphorylation

A researcher studying algae growing in fish tank increases the light intensity available to the algae for a period of 5 days. What is the likely outcome?

increased production of carbohydrates

When chlorophyll molecule absorbs the energy from a photon of light, there is an effect of an increase in the potential energy of which of the following particles?

electrons

When desert lizards bask in the sun, they demonstrate that ectothermic organisms need to

maintain a stable internal environment

Spider crabs conform to the minor changes in salinity in their environment by gaining losing water. This contrasts with the strategy of pacific salmon, which actively regulate the solutes in their blood. Compared with the spider crab strategy, the pacific salmon's strategy is most likely associated with which of the following parameters.

greater expenditures of energy

In green plants, the exchange of water and gases with the surrounding environment is directly facilitates by which structure

stoma

The narrow structure of the human cervical canal allows for the cervix to perform which of the following functions

directing sperm into the uterus

Models of optimal foraging behavior predict that individual members of a species will increase the distance traveled and the amount of time spent foraging when the

population density of the foraging species is high

In seeded vascular plants, the sporophyte phase of the repro cycle is dominant and the gametophyte is greatly reduced. What best describes the evolutionary advantage of this arrangement compared to that of seedless vascular plants?

The gametophyte can be protected from the environment and nourished within the sporophyte

As part of an engineering design unit focusing on the human body, students use easily obtained materials to create a protype of a filter that removes objects from water. This prototype models what function in which organ?

kidneys

commensal relationship

a relationship between individuals of two species in which one species obtains food or other benefits from the other without either harming or benefiting the other species

what condition distinguishes a tropical rainforest from a hardwood forest

Most nutrients are held in vegetation and forest litter

density-independent factors

refer to any influences on a population's birth or death rates, regardless of the population density. They are typically a physical factor of the environment, unrelated to the size of the population in question(common density independent factors, such as temperature, natural disasters, and the level of oxygen in the atmosphere.)

K-selected species

species whose populations fluctuate at or near the carrying capacity (K) of the environment in which they reside.

Type I survivorship curves

a curve displayed on a semilogarithmic scale that tracks organisms that tend to live long lives

Boom-and-bust populations

These are dramatic flucuation in population. occur when the population growth of one species is closely tied to a limiting factor that may be expended. (fluctuation of predators and prey affecting the population of other species)

Density-dependent factors

any force that affects the size of a population of living things in response to the density of the population (Some of the common examples are the availability of food, parasitism, predation, disease, and migration)

quadret method

important method by which organisms in a certain proportion (sample) of the habitat are counted directly. It is used to estimate population abundance (number), density, frequency and distributions. The quadrat method has been widely used in plant studies.

Compared to terrestrial area undergoing primary succession, a terrestrial area that is going through secondary succession following the abandonment of an agricultural field is usually characterized by

existence of nutrient-rich soil

An invasive species, such as the zebra mussel, impacts the biodiversity of an aquatic ecosystem because

lacks natural predators

In a forest ecosystem, the conversion of organic matter to inorganic matter for use by autotrophs would be carried out by which of the following organisms?

bacteria

The relationship between energy and matter in an ecosystem is reflected by which of the following patterns among its inhabitants?

the producer level that has the greatest biomass

the primary reason that generalist predators are more likely to survive an environmental disturbance than are specialist predators dependent on a single prey species is that generalist predators have a

wider range of potential food sources

As a group, chemoautotrophic bacteria share ability to

use inorganic compounds as a source of relatively high-energy electrons

A science teacher builds a compost pile out of dried sheep manure, shredded leaves, grass clippings, kitchen waste, and water. Each component is weighed before it is placed in the pile and the pile's volume record. Students regularly turn and mix the pile and add water. After six weeks, the pile has become compost and is reweighed and its volume calculated. The pile is shown to have decreased significantly in both weight and volume

release of carbon as carbon dioxide during the process of bacterial respiration

release of sulfur dioxide into the atmosphere contributes most directly to which of the following environmental problems

acid precipitation

The rapid growth of algae in a suburban lake has resulted in a die-off of fish and other aquatic organisms. Which of the following factors most likely contributed to this phenomenon

a runoff of fertilizer used on nearby lawns

An environmental advantage associated with the use of genetically modified agricultural crops is that these plants

require less use of pesticides

Wildlife biologists have proposed and developed wildlife corridors b/w different populations of wolves primarily to help prevent what?

inbreeding within isolated populations of wolves

The green revolution was a worldwide confluence of research, development, and transfers of technology that saved hundreds of millions of people from starvation from the 1940s through the 1970s. The primary component of this agricultural revolution was the development of

high-yielding varieties of cereal grains

Bioremediation is a process in which organisms metabolize toxic substances and produce less harmful byproducts. In consideration of laboratory safety, this method of cleaning up environmental contamination would best be modeled by investigation of the

variables that affect respiration in yeast using sugar as a carbon source

An increase in the rate of sea level rise is primarily caused by an increase in

ocean temps

The following sequence is ranking genetic material in order from smallest to largest

nucleotide --> DNA --> gene --> chromosome

deletions and duplications of genetic material in sister chromatids are most likely caused by which of the following types of alteration to chromosomal structure

translocations

inversions

occurs when part of your chromosome breaks off and then reattaches, but sometimes pieces along the edges are lost

nondisjunction

when chromosomes do not separate properly during cell division

What event occurs during translation process in eukaryotic cells?

tRNA molecules bind to both amino acids and mRNA transcripts

In the bacterium Escherichia coli, tryptophan molecules inhibit the synthesis of amino acid tryptophan by blocking gene transcription as a result of

activating a repressor protein that binds to the operator

The development of which of the following components of genetic engineering was key in enabling scientists to successfully insert the human gener for insulin into bacteria

DNA restriction analysis

Which of the following steps of transgenic crop engineering would require the use of polymerase chain reaction (PCR)

producing multiple copies of the gene

Examination of an individuals karyotype pattern provides evidence of errors in which of the following levels of genetic material

chromosome

incomplete dominance

when a dominant allele does not completely mask the effects of a recessive allele, and the organism shows a blending of both alleles

Codominance

a form of inheritance where two alleles of the same gene are expressed roughly equal amounts in an organism

sex-linked trait

an observable characteristic of an organism that is influenced by the genes on the chromosomes that determine the organism's sex

Historically, tall pea plants were crossed with short pea plants and the resulting F1 generation plants were all tall. When these F1 generation plants were crossed, however, 75% of these F2 offspring were tall plants and 25% were short. These experiments provided support for the idea that

certain traits appear to mask other trait

compared to other patterns of inheritance, a characteristic of traits inherited by mitochondrial inheritance is that

only bio mothers can pass the trait to their offspring

Most cases of Down syndrome are caused by

chromosomal nondisjunction's during meiosis

A geneticist would use a testcross in order to determine

given organism is homozygous or heterozygous for a trait

Which phenomenon was discovered well after On the Origin of Species was published and is also vitally important to the process of natural selection

mutation

Which of the following statements best describes speciation as viewed in the punctuated equilibrium model of evolution compared with the gradualism model

speciation is assumed to occur much more rapidly in the punctuated equilibrium model