Quarter 4 Bio Vocab

evolution

Descent with modification; the idea that living species are descendants of ancestral species that were different from the present-day ones; also defined more narrowly as the change in the genetic composition of a population from generation to generation.

Population

A group of individuals that belong to the same species and live in the same area

natural selection

A process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits.

homologous structures

Structures in different species that are similar because of common ancestry.

vestigial structure

structure that is inherited from ancestors but has lost much or all of its original function

adaptation

inherited characteristic that increases an organism's chance of survival

gene pool

The aggregate of all copies of every type of allele at all loci in every individual in a population. The term is also used in a more restricted sense as the aggregate of alleles for just one or a few loci in a population.

Hardy-Weinberg equilibrium

The state of a population in which frequencies of alleles and genotypes remain constant from generation to generation, provided that only Mendelian segregation and recombination of alleles are at work.

artificial selection

selective breeding of plants and animals to promote the occurrence of desirable traits in offspring

analogous (structures)

Having characteristics that are similar because of convergent evolution, not homology.

genetic drift

random change in allele frequencies that occurs in small populations

gene flow

movement of alleles from one population to another

sexual selection

A form of natural selection in which individuals with certain inherited characteristics are more likely than other individuals to obtain mates.

speciation

the formation of new and distinct species in the course of evolution.

reproductive isolation

Separation of species or populations so that they cannot interbreed and produce fertile offspring

allopatric speciation

The formation of a new species as a result of an ancestral population's becoming isolated by a geographic barrier.

sympatric speciation

The formation of new species in populations that live in the same geographic area

adaptive radiation

Period of evolutionary change in which groups of organisms form many new species whose adaptations allow them to fill different ecological roles in their communities.

phylogeny

The evolutionary history of a species or group of related species

cladogram

Diagram that shows the evolutionary relationships among a group of organisms

hormone

In multicellular organisms, one of many types of secreted chemicals that are formed in specialized cells, travel in body fluids, and act on specific target cells in other parts of the body, changing the target cells' functioning. Hormones are thus important in long-distance signaling.

regulator

An animal that uses internal control mechanisms to moderate internal change in the face of external fluctuation.

conformer

An animal that allows its internal condition to vary with certain external changes.

homeostasis

relatively constant internal physical and chemical conditions that organisms maintain

set point

the point at which an individual's "weight thermostat" is supposedly set. When the body falls below this weight, an increase in hunger and a lowered metabolic rate may act to restore the lost weight.

stimulus

A change in an organism's surroundings that causes the organism to react

sensor

in homeostasis, a receptor that detects a stimulus

response

In cellular communication, the change in a specific cellular activity brought about by a transduced signal from outside the cell.

negative feedback

A form of regulation in which accumulation of an end product of a process slows the process; in physiology, a primary mechanism of homeostasis, whereby a change in a variable triggers a response that counteracts the initial change.

positive feedback

A type of regulation that responds to a change in conditions by initiating responses that will amplify the change. Takes organism away from a steady state.

circadian rhythm

A physiological cycle of about 24 hours that is present in all eukaryotic organisms and that persists even in the absence of external cues.

thermoregulation

the maintenance of body temperature within a range that enables cells to function efficiently.

endothermic

(of a chemical reaction or compound) occurring or formed with absorption of heat

ectothermic

referring to organisms for which external sources provide most of the heat for temperature regulation

countercurrent exchange

the exchange of a substance or heat between two fluids flowing in opposite directions

torpor

a physiological state of decreased activity and metabolism

hibernation

Long-term torpor that is an adaptation to winter cold and food scarcity.

innate immunity

Immunity that is present before exposure and effective from birth. Responds to a broad range of pathogens.

adaptive immunity

immunity or resistance to a specific pathogen; slower to respond, has memory component

B cell

A lymphocyte that produces proteins that help destroy pathogens.

T cell

a lymphocyte that identifies pathogens and distinguishes one pathogen from another

antigen

A protein that, when introduced in the blood, triggers the production of an antibody

antibody

a substance produced by the body that destroys or inactivates an antigen that has entered the body

cell-mediated immune response

The branch of acquired immunity that involves the activation of cytotoxic T cells, which defend against infected cells.

humoral immune response

The branch of acquired immunity that involves the activation of B cells and that leads to the production of antibodies, which defend against bacteria and viruses in body fluids.

memory cell

A long-lived lymphocyte that carries the antibody or receptor for a specific antigen after a first exposure to the antigen and that remains in a less than mature state until stimulated by a second exposure to the antigen at which time it mounts a more effective immune response than a cell which has not been exposed previously.

community

assemblage of different populations that live together in a defined area

niche

Full range of physical and biological conditions in which an organism lives and the way in which the organism uses those conditions

carrying capacity

Largest number of individuals of a population that a environment can support

exponential population growth

Growth of a population in an ideal, unlimited environment, represented by a J-shaped curve when population size is plotted over time.

logistic population growth

population growth that levels off as population size approaches carrying capacity

r-selection

Selection for life history traits that maximize reproductive success in uncrowded environments; also called density-independent selection.

K-selection

Selection for life history traits that are sensitive to population density; also called density-dependent selection.

competitive exclusion

The concept that when populations of two similar species compete for the same limited resources, one population will use the resources more efficiently and have a reproductive advantage that will eventually lead to the elimination of the other population.

predation

An interaction in which one organism captures and feeds on another organism

autotroph

an organism that is able to form nutritional organic substances from simple inorganic substances such as carbon dioxide.

heterotroph

organism that obtains energy from the foods it consumes; also called a consumer

mutualism

A relationship between two species in which both species benefit

commensalism

A relationship between two organisms in which one organism benefits and the other is unaffected

parasitism

A relationship between two organisms of different species where one benefits and the other is harmed

coevolution

Process by which two species evolve in response to changes in each other

cryptic coloration

camouflage that makes a potential prey difficult to spot against its background

aposematic coloration

The bright coloration of animals with effective physical or chemical defenses that acts as a warning to predators

primary succession

An ecological succession that begins in an area where no biotic community previously existed

secondary succession

type of succession that occurs in an area that was only partially destroyed by disturbances

keystone species

A species that influences the survival of many other species in an ecosystem

net primary productivity

The energy captured by producers in an ecosystem minus the energy producers respire

Gene

A discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA (or RNA, in some viruses).

Asexual Reproduction

The generation of offspring from a single parent that occurs without the fusion of gametes (by budding, division of a single cell, or division of the entire organism into two or more parts). In most cases, the offspring are genetically identical to the parent.

Clone

(1) A lineage of genetically identical individuals or cells. (2) In popular usage, an individual that is genetically identical to another individual. (3) As a verb, to make one or more genetic replicas of an individual or cell.

Sexual Reproduction

A type of reproduction in which two parents give rise to offspring that have unique combinations of genes inherited from both parents via the gametes.

Karyotype

A display of the chromosome pairs of a cell arranged by size and shape.

Homologous Chromosomes

A pair of chromosomes of the same length, centromere position, and staining pattern that possess genes for the same characters at corresponding loci. One homologous chromosome is inherited from the organism's father, the other from the mother. Also called homologs, or a homologous pair.

Sex Chromosomes

A chromosome responsible for determining the sex of an individual.

Autosome

A chromosome that is not directly involved in determining sex; not a sex chromosome.

Haploid Cell

A cell containing only one set of chromosomes (n).

Fertilization

(1) The union of haploid gametes to produce a diploid zygote. (2) The addition of mineral nutrients to the soil.

Gamete

A haploid reproductive cell, such as an egg or sperm. They unite during sexual reproduction to produce a diploid zygote.

Zygote

The diploid product of the union of haploid gametes during fertilization; a fertilized egg.

Diploid Cell

A cell containing two sets of chromosomes (2n), one set inherited from each parent.

Meiosis

A modified type of cell division in sexually reproducing organisms consisting of two rounds of cell division but only one round of DNA replication. It results in cells with half the number of chromosome sets as the original cell.

Crossing Over

The reciprocal exchange of genetic material between nonsister chromatids during prophase I of meiosis.

Trait

One of two or more detectable variants in a genetic character.

True-breeding

Referring to organisms that produce offspring of the same variety over many generations of self-pollination.

P Generation

The true-breeding (homozygous) parent individuals from which F1 hybrid offspring are derived in studies of inheritance; P stands for "parental."

F1 Generation

The first filial, hybrid (heterozygous) offspring arising from a parental (P generation) cross.

F2 Generation

The offspring resulting from interbreeding (or self-pollination) of the hybrid F1 generation.

Allele

Any of the alternative versions of a gene that may produce distinguishable phenotypic effects.

Dominant

An allele that is fully expressed in the phenotype of a heterozygote.

Recessive

An allele whose phenotypic effect is not observed in a heterozygote.

Law of Segregation

Mendel's first law, stating that the two alleles in a pair segregate (separate from each other) into different gametes during gamete formation.

Homozygous

Having two identical alleles for a given gene.

Heterozygous

Having two different alleles for a given gene.

Phenotype

The observable physical and physiological traits of an organism, which are determined by its genetic makeup.

Genotype

The genetic makeup, or set of alleles, of an organism.

Testcross

Breeding an organism of unknown genotype with a homozygous recessive individual to determine the unknown genotype. The ratio of phenotypes in the offspring reveals the unknown genotype.

Monohybrid

An organism that is heterozygous with respect to a single gene of interest. All the offspring from a cross between parents homozygous for different alleles are monohybrids. For example, parents of genotypes AA and aa produce a monohybrid of genotype Aa.

Dihybrid

An organism that is heterozygous with respect to two genes of interest. All the offspring from a cross between parents doubly homozygous for different alleles are dihybrids. For example, parents of genotypes AABB and aabb produce a dihybrid of genotype AaBb.

Law of Independent Assortment

Mendel's second law, stating that each pair of alleles segregates, or assorts, independently of each other pair during gamete formation; applies when genes for two characters are located on different pairs of homologous chromosomes or when they are far enough apart on the same chromosome to behave as though they are on different chromosomes.

Incomplete Dominance

The situation in which the phenotype of heterozygotes is intermediate between the phenotypes of individuals homozygous for either allele.