Biology 21ST CENTURY SCIENCE key terms

1abiotic

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

2abiotic 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).

3abundance

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

4accuracy

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

5active site

The part of an enzyme where the chemical reaction takes place. The reacting molecules (substrates) fit into the active site.

6active transport

Molecules are moved in or out of a cell using energy. This process is used when transport needs to be faster than diffusion, and when molecules are being moved from a region where they are at low concentration to where they are at high concentration.

7adaptation

A feature that helps an organism survive in its environment.

8ADH

Antidiuretic hormone, which is secreted by the pituitary gland. It controls the reabsorption of water in the kidneys to control the water balance of the body.

9adrenal gland

Gland that secretes the hormones adrenaline and cortisol.

10adrenaline

Hormone secreted by the adrenal gland at times of stress. It prepares the body for action.

11adult stem cell

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

12advantage

An individual organism has an advantage if it has a feature that enables it to survive and reproduce more successfully than other individuals.

13aerobic respiration

A type of cellular respiration that uses oxygen.

14agricultural input

A resource needed by a particular farming method. Intensive farming methods need agricultural inputs such as fertiliser and pesticide.

15AIDS

Acquired immune deficiency syndrome, an STI caused by the HIV virus. The body’s immune system is attacked by the virus and gradually becomes weakened.

16allele

The two copies of a gene in a pair of chromosomes are called alleles. They can be the same or different.

17alveolus (plural alveoli)

Human lungs are divided up into millions of tiny sacs called alveoli. They form an exchange surface with a very large surface area for gaseous exchange.

18amino acid

Amino acids are joined in long chains to make proteins. All the proteins in living organisms are made from 20 different amino acids joined in different orders.

19anaerobic respiration

A type of cellular respiration that does not use oxygen.

20antagonistic

Actions or effectors that have opposite effects.

21antibiotic resistance

The ability of bacteria to survive exposure to antibiotics. The ability is caused by mutations in the bacteria’s genes.

22antibiotics

Substances that kill or stop the growth of bacteria, but which do not work against fungi or viruses.

23antibodies

Protein molecules made by white blood cells to fight pathogens; each antibody only recognises one specific antigen.

24antigens

Molecules on the surface of cells and pathogens.

25antimicrobial

A substance (e.g., an antibiotic) that kills microorganisms (or inhibits their growth).

26archaea

One of the domains used in modern classification systems, containing prokaryotic organisms.

27artery

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

28aseptic techniques

Ways of working that avoid contamination of samples by microorganisms. These include sterilising equipment and growth medium in an autoclave, sterilising surfaces using alcohol, wearing personal protective equipment, working next to a Bunsen burner to create an updraft, and flaming metal tools.

29asexual reproduction

Reproduction by simple division of a cell. The offspring are genetically identical to one another and to the parent cell.

30ATP

Adenosine triphosphate, a substance made by cellular respiration. Cells need a constant supply of ATP for life processes. ATP is a chemical store of energy.

31atrium (plural atria)

The human heart is made of four muscular chambers. The atria are the upper chambers. They receive blood and pump it into the lower chambers (ventricles).

32autotroph

An organism that can make its own food.

33auxins

A group of plant hormones that affect plant growth and development.

34average

The average of a set of data is the single number that best represents the data. Commonly used averages include the mean, median, and mode.

35axon

A long, thin extension of the cytoplasm of a neuron. The axon carries nerve impulses very quickly.

36bacteria (singular bacterium)

Large group of single-celled, prokaryotic microorganisms. Some bacteria cause disease.

37base

Part of a nucleotide. Four bases (A, C, G, and T) are found in DNA. The base U replaces T in mRNA.

38base pairing

The bases in two strands of DNA always pair up in the same way. A always pairs with T, and C always pairs with G.

39biconcave

The shape of a red blood cell, like a disc that has been squeezed from both sides in the middle.

40bioaccumulation

An increase in the concentration of a substance in organisms in the higher trophic levels of a food chain.

41biodegradable

Substances that can be broken down by microorganisms, such as bacteria and fungi. Most paper and wood items are biodegradable, but most synthetic polymers, such as plastics, are not.

42biodiversity

The biodiversity of the Earth, or of a particular area, is the combination of the diversity of living organisms, the diversity of genetic material the organisms have, and the diversity of ecosystems in which the organisms live.

43biofuel

A fuel produced from plants (such as bioethanol from sugar cane, and wood) or other recently living material (such as agricultural waste).

44bioinformatics

Using computers to process and analyse biological data, including genome sequences.

45biological control

The introduction of new species into an ecosystem to kill pests that carry plant pathogens and damage plants.

46biomass

All the tissues that make up an organism. Some of an organism’s biomass is transferred to another organism when it is eaten.

47biotic

The living parts of an ecosystem, i.e., all the living organisms.

48biotic factor

A living factor that can affect the distribution and abundance of living organisms (e.g., a predator, a competitor, or pathogens).

49bladder

Organ that collects urine from the kidneys for excretion by urination.

50blind trial

A clinical trial in which the patient does not know whether they are taking the new medicine, but their doctor does.

51body mass index (BMI)

A calculated value that indicates whether a person’s body mass is healthy for a person of their height.

52brain stem

Part of the brain that controls heart rate and breathing rate.

53capillary

Type of tiny blood vessel that carries blood through tissues (from arteries to veins).

54capture-mark-recapture

A sampling technique used to estimate the size of a population of animals. A sample of individual animals is collected from the population, and each animal given an identifying mark. Later, another sample is collected. A mathematical equation is used to estimate the population size based on the number of marked animals in the second sample.

55carbohydrate

A substance made of carbon, hydrogen, and oxygen. Carbohydrates include sugars (e.g., glucose) and natural polymers (e.g., starch and cellulose).

56carbon cycle

The natural processes that recycle carbon through the living and non-living parts of an ecosystem.

57carbon neutral

Biofuels are carbon neutral because the amount of carbon dioxide used (by photosynthesis plants) to make them is equal to the amount released when the biofuel is burnt.

58carcinogen

A substance that can cause damage to DNA. This can result in a mutation and can cause a cell to become a cancer cell.

59cardiovascular diseases

A group of non-communicable diseases affecting the blood vessels and heart.

60carrier

An individual who has a recessive variant but does not show the feature associated with the variant because they also have a dominant variant (they are heterozygous). They can pass the recessive variant to their offspring.

61catalyst

A catalyst is a substance that increases the rate of a chemical reaction, but which is left unchanged by the reaction.

62cataract

A cloudy patch that forms in the lens of the eye, causing blurred vision.

63cause

When a change in a factor produces a particular outcome, and there is a mechanism to explain this link, then the factor is said to cause the outcome.

64cell culture

Growing cells in carefully controlled conditions in a laboratory. The cells are grown in (or on) a growth medium, usually in warm conditions in an incubator.

65cell cycle

Most cells go through a cycle of phases, including interphase and either one cell division (mitosis) or two cell divisions (meiosis).

66cellular respiration

A series of chemical reactions that happens in all living cells. Glucose is used up and ATP is made for the cell to use.

67central nervous system (CNS)

The brain and spinal cord.

68cerebellum

Part of the brain associated with conscious movement.

69cerebral cortex

Part of the brain associated with consciousness, intelligence, language, and memory.

70chemical control

The use of substances, usually sprayed onto crops, to reduce the spread of plant pathogens and pests that carry them.

71chlorophyll

A pigment that absorbs light and splits water into hydrogen and oxygen in the first stage of photosynthesis.

72chloroplast

An organelle containing chlorophyll, found in some plant cells. The reactions of photosynthesis happen in chloroplasts.

73chromosome

Long, thin, threadlike structure made from molecules of DNA. Chromosomes store genetic information.

74ciliary muscle

Muscle in the eye that changes the shape of the lens to help focus light on the retina.

75circulatory system

An organ system that includes the heart, blood vessels, and blood. The circulatory system transports substances around the body.

76classification

Placing organisms into groups based on their similarities and differences.

77clinical testing

A stage of drug development. A new medicine is tested on humans to find out whether it is safe and whether it works.

78coding DNA

Regions (genes) in the genome that store the genetic code for making proteins.

79communicable disease

A disease caused by an infection with a pathogen, which can be passed from one organism to another in body fluids, contaminated food and water, or by direct contact.

80community

Interacting populations of organisms living in the same ecosystem.

81competition

Organisms that require the same resource (e.g., food, water, space, light, shelter, mates, pollinators, and seed dispersers) must compete for the resource.

82complication

A second disease that results from having a first disease.

83computational model

A type of mathematical model in which the calculations are done by a computer.

84control group

When testing a new treatment, a control group of people does not receive the new treatment. They may receive an existing treatment or a placebo.

85cornea

Transparent tissue that covers the iris of the eye. It helps focus light onto the retina by refraction.

86coronary arteries

Blood vessels that supply blood carrying oxygen and glucose directly to the muscle cells of the heart.

87coronary heart disease

A type of cardiovascular disease in which fatty deposits cause blood clots in the coronary arteries, increasing the chance of a heart attack.

88correlation

When an outcome happens if a specific factor is present but does not happen when it is absent, or if a measured outcome increases (or decreases) as the value of a factor increases, there is a correlation between the two. For example, there is a correlation between pollen count and the number of hay fever cases.

89crop rotation

Crops are grown in different fields each year, so that each field is planted with a different crop each year.

90cuticle

Layer of molecules of fat and wax, covering the outside surface of plant leaves. It helps to stop pathogens entering the leaf tissue.

91decomposition

Process in which dead organisms are broken down (decay) and substances in their bodies are returned to the environment.

92deforestation

Cutting down and clearing forests leaving bare ground. This damages ecosystems and causes biodiversity loss.

93deletion mutation

A change in the DNA of an organism where one or more nucleotides are removed. This changes the way the bases are divided into triplets.

94denatured

When the shape of an enzyme has been changed, usually as a result of high temperature or a pH change. Denatured enzymes no longer work because the shape of the active site has changed.

95deoxygenated blood

Blood in which most or all of the haemoglobin in the red blood cells is not bound to oxygen.

96depth of field

When a microscope is focused on a structure being observed, objects outside the depth of field (above and below the structure) appear blurred.

97descriptive model

A type of scientific model that uses words to identify features of a system and to describe how they interact. One example of a descriptive model is a simple account of the inputs and outputs of photosynthesis.

98desertification

The process in which an ecosystem turns to desert (a place where no crops can grow).

99development

How an organism changes as it grows and matures. Its cells are organised into different tissues and organs, and they take on specific jobs.

100diagnostic test

A test to help diagnose or detect disease. The tests can involve observing symptoms, cell culture, microscopy, staining, testing with antimicrobials, genome analysis, and use of monoclonal antibodies.