Biology Key terms OCR 21ST CENTURY SCIENCE

abiotic

The non-living parts of an ecosystem (e.g., the atmosphere, water, soil, and rocks).

abiotic factor

A non-living factor that can affect the distribution and abundance of living organisms (e.g., temperature, light intensity, soil pH, and the availability of water).

abundance

How many organisms are found in each part of an ecosystem.

accuracy

How close a quantitative result is to the true or actual value.

active site

The part of an enzyme where the chemical reaction takes place.

active transport

Molecules are moved in or out of a cell using energy, especially when moved against a concentration gradient.

adaptation

A feature that helps an organism survive in its environment.

ADH

Antidiuretic hormone, which controls the reabsorption of water in the kidneys.

adrenal gland

Gland that secretes the hormones adrenaline and cortisol.

adrenaline

Hormone secreted by the adrenal gland at times of stress.

adult stem cell

A stem cell that can only differentiate to make one or a small number of cell types.

advantage

An individual organism's feature that enables it to survive and reproduce more successfully.

aerobic respiration

A type of cellular respiration that uses oxygen.

agricultural input

A resource needed by a particular farming method.

AIDS

Acquired immune deficiency syndrome, an STI caused by the HIV virus.

allele

The two copies of a gene in a pair of chromosomes.

alveolus (plural alveoli)

Tiny sacs in human lungs where gaseous exchange occurs.

amino acid

Monomers that join together to make proteins.

anaerobic respiration

A type of cellular respiration that does not use oxygen.

antagonistic

Actions or effectors that have opposite effects.

antibiotic resistance

The ability of bacteria to survive exposure to antibiotics.

antibiotics

Substances that kill or stop the growth of bacteria.

antibodies

Proteins made by white blood cells to fight pathogens.

antigens

Molecules on the surface of cells and pathogens.

antimicrobial

A substance that kills microorganisms.

archaea

Domain containing prokaryotic organisms.

artery

Type of blood vessel carrying blood from the heart to cells and tissues.

aseptic techniques

Ways of working that avoid contamination of samples by microorganisms.

asexual reproduction

Reproduction by simple division of a cell.

ATP

Adenosine triphosphate, a substance made by cellular respiration.

atrium (plural atria)

Upper chambers of the human heart.

autotroph

An organism that can make its own food.

auxins

Group of plant hormones that affect plant growth and development.

average

A single number that best represents a set of data.

axon

Long, thin extension of a neuron that carries nerve impulses.

bacteria (singular bacterium)

Single-celled, prokaryotic microorganisms.

base

Part of a nucleotide, found in DNA and RNA.

base pairing

The way in which bases pair in DNA strands.

biconcave

Shape of a red blood cell.

bioaccumulation

Increase in concentration of a substance in an organism.

biodegradable

Substances that can be broken down by microorganisms.

biodiversity

The variety of life in an ecosystem.

biofuel

A fuel produced from recently living material.

bioinformatics

Using computers to process biological data.

biological control

Introduction of new species to kill pests.

biomass

All the tissues that make up an organism.

biotic

The living parts of an ecosystem.

biotic factor

Living factors that can affect organisms.

bladder

Organ that collects urine from the kidneys.

blind trial

A clinical trial where the patient does not know if they're receiving treatment.

body mass index (BMI)

A calculated value indicating whether body mass is healthy.

brain stem

Part of the brain that controls heart and breathing rates.

capillary

Type of tiny blood vessel.

capture-mark-recapture

A technique to estimate animal population size.

carbohydrate

Substance made of carbon, hydrogen, and oxygen.

carbon cycle

Processes that recycle carbon in the ecosystem.

carbon neutral

Biofuels that do not increase atmospheric CO2.

carcinogen

A substance that can cause cancer.

cardiovascular diseases

Diseases affecting the heart and blood vessels.

carrier

An individual who carries a recessive trait without showing it.

catalyst

A substance that speeds up a chemical reaction.

cataract

A cloudy patch in the lens of the eye.

cause

A factor producing an outcome.

cell culture

Growing cells under controlled conditions in a lab.

cell cycle

The process cells undergo for growth and division.

cellular respiration

Reactions in cells that produce ATP.

central nervous system (CNS)

The brain and spinal cord.

cerebellum

Part of the brain for movement coordination.

cerebral cortex

Brain region associated with higher functions.

chemical control

Use of substances to reduce pest spread.

chlorophyll

Pigment that absorbs light for photosynthesis.

chloroplast

Organelle where photosynthesis occurs in plants.

chromosome

Threadlike structures made of DNA.

ciliary muscle

Muscle in the eye that adjusts lens shape.

circulatory system

System for transporting substances in the body.

classification

Grouping organisms based on similarities.

clinical testing

Stage of drug development testing on humans.

coding DNA

Regions in the genome encoding protein instructions.

communicable disease

Disease caused by pathogens spread from one host to another.

community

Interacting populations living in the same ecosystem.

competition

Organisms competing for limited resources.

complication

A second disease arising from a primary disease.

computational model

A mathematical model computed by a computer.

control group

A group not receiving a treatment in an experiment.

cornea

Transparent tissue at the front of the eye.

coronary arteries

Blood vessels supplying the heart muscle.

coronary heart disease

Cardiovascular disease caused by artery blockages.

correlation

When two factors have a relationship.

crop rotation

Planting different crops in a field each year.

cuticle

Layer covering plant leaves to prevent pathogen entry.

decomposition

Process of breaking down dead organisms.

deforestation

Clearing forests, damaging ecosystems.

deletion mutation

Removal of nucleotides from DNA.

denatured

When an enzyme's shape has changed.

deoxygenated blood

Blood lacking oxygen.

depth of field

The extent of the imaging plane of a microscope.

descriptive model

A scientific model using words to describe features.

desertification

Transformation of ecosystems into desert.

development

Changes during growth and maturation of an organism.

diagnostic test

Test to help identify a disease.