DEFINITION QUESTION BIOLOGY

heterotroph

(Consumer). An organism that requires chemical energy from already formed organic molecules.

detritivore

(Decomposer). Animal that consumes decomposing organic particles, deriving nutrition primarily from microbes on the particles.

autotroph

(Producer). An organism that fixes chemical energy in the form of organic molecules; it "makes its own food" and does not require previously formed organic materials from the environment; e.g. photoautotroph, chemoautotroph.

ecosystem

A community and its abiotic environment.

Organelle

A discrete structure within a cell, with a specific function.

Tissue

A group of cells similar to each other, along with their associated intercellular substances, which perform the same function within a multicellular organism.

clone

A group of genetically identical organisms or a group of cells artificially derived from a single parent cell.

population

A group of organisms of the same species who live in the same area at the same time.

species

A group of organisms which can interbreed and produce fertile offspring.

organ system

A group of organs, vessels, glands, other tissues, and/or pathways which work together to perform a body function within a multicellular organism.

community

A group of populations living and interacting with each other in an area.

organ

A group of tissues which work together as a single unit to perform a particular function within a multicellular organism.

gene

A heritable factor that controls a specific characteristic.

random sample

A method to ensure that every individual in a population has an equal chance of being observed.

action potential

A momentary change in electrical potential on the surface of a nerve cell that occurs upon stimulation, resulting in the transmission of an electrical impulse. (Occurs as sodium ions move into the cell and potassium ions move out).

homologous chromosomes

A pair of chromosomes containing the same linear gene sequences, each derived from one parent

gene mutation

A random change in the base sequence of a section of DNA. This could be by substitution, deletion, or insertion of a base or bases.

active site

A specific region of an enzyme where a substrate binds and catalysis takes place.

denaturation

A structural change in a protein that results in a loss (usually permanent) of its biological properties. Refer only to head and pH as agents.

dominant allele

An allele that has the same effect on the phenotype whether it is present in the homozygous or heterozygous state. Dominant alleles mask the effects of recessive alleles.

recessive allele

An allele that only has an effect on the phenotype when present in the homozygous state.

carrier

An individual that has a recessive allele of a gene that does not have an effect on their phenotype.

pathogen

An organism or virus that causes a disease.

organic

Compounds containing carbon that are found in living organisms.

cell respiration

Controlled release of energy in the form of ATP from organic compounds in cells.

assimilation

Conversion of absorption nutrients into parts of an organism.

universal

Found in all living organisms.

sex linkage

Genes found on sex chromosomes (X and Y chromosomes) are said to be sex linked.

degenerate

Having more than one based triplet to code for one amino acid

heterozygous

Having two different alleles of a gene.

homozygous

Having two identical alleles of a gene.

carrying capacity

Maximum average number or biomass of organisms that can be sustained in a habitat over the long term. Usually refers to a particular species, but can be applied to more than one.

absorption

Movement of fluid/ dissolved substances across a membrane.

allele

One specific form of a gene, differing from other alleles by one or a few bases only and occupying the same gene locus as other alleles of the gene.

saprotroph

Organism that feeds by secreting digestive enzymes onto its food source and absorbing the products of digestion. Fungi and bacteria are examples.

codominant alleles

Pairs of alleles that both affect the phenotype when present in a heterozygote. (The terms incomplete and partial will no longer be used.)

enzyme

Proteins that act as biological catalysts, speeding the rate at which by chemical reactions proceed but not altering the direction or nature of the reactions.

trophic level

Stage in a food chain or web leading from primary producers (lowest trophic level) through primary consumers (herbivores) to secondary and tertiary consumers (carnivores).

test cross

Testing a suspected heterozygote by crossing it with a known homozygous recessive.

genetic screening

Testing an individual for the presence or absence of a gene.

genotype

The alleles possessed by an organism.

phenotype

The characteristics of an organism.

excretion

The discharge of substances from the body. Release of an absorbed or endogenous substance or of a waste product, in urine, faeces, or other products normally leaving the body. Excretion of most chemical compounds from the body occurs mainly through the kidney and the gut, although volatile compounds may be largely eliminated by exhalation. Excretion by perspiration and through hair and nails may also occur.

habitat

The environment in which a species normally lives or the location of a living organism.

locus

The particular position on homologous chromosomes of a gene.

diffusion

The passive movement of molecules from a region of high concentration to a region of low concentration.

osmosis

The passive movement of water molecules, across a partially permeable membrane, from a region of lower solute concentration to a region of higher solute concentration.

evolution

The process of cumulative change in the heritable characteristics of a population.

ecology

The study of relationships between living organisms and between organisms and their environment.

genome

The whole of the genetic information of an organism.

Clad

This is a system that groups taxa together according to traits that have emerged most recently

resting potential

When the neuron is not firing, the inside of the axon is more negative than its surroundings. (High concentration of intracellular potassium ions relative to the outside, and very low concentration of intracellular sodium ions relative to the inside).