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Glossary of Terms

This section contains brief explanations of some of the terms used elsewhere on Science on the Farm.

a | b | c | d | e | f | g | h | i | j | k | l | m | n | o | p | q | r | s | t | u | v | w | x | y | z

 
   
 

a

active transport
An energy-requiring process that moves substances across a cell membrane often against the concentration gradient.

alkaline
Describes a substance with a pH greater than 7.0. Alkaline (or basic) soils can affect crop growth.

amino acids
Molecules that contain both amine (-NH2) and carboxyl (-COOH) functional groups. Amino acids are the building blocks of proteins. Twenty different amino acids are commonly used in protein synthesis.

anaerobic

Occurring in the absence of oxygen e.g. anaerobic respiration.

anthropogenic
Due to human activity.

Archaea
A group of  prokaryotes that live in extreme environments e.g. very high temperatures (thermophiles), very salty conditions (halophiles).

ATP
Short for Adenosine Triphosphate. ATP is an organic (carbon-based) compound made up of the base adenosine and three phosphate groups. It acts as an energy carrier, releasing energy when it is broken down into ADP plus a phosphate group. All cells generate ATP through cellular respiration; it is also produced during the light reactions of photosynthesis.

 
   
 

b

bacteria
A diverse group of organisms belonging to the kingdom Prokaryote. Common features: no membrane-bound organelles; DNA not enclosed by a nuclear membrane; single circular chromosome.


bicarbonate
An anion (a negatively charged ion) with the formula HCO3-. Bicarbonate is an alkaline substance, and a vital component of the body's pH buffering system.

blue-green algae
Also called cyanobacteria: a group of photosynthetic bacteria. Their photosynthetic pathway is like that of green plants and uses chlorophyll a (found in green plants).
Some species of cyanobacteria are involved in algal blooms.

bolus
A soft rounded mass of chewed food, within the mouth or alimentary canal.

 Bryophytes
Bryophytes are non-vascular plants i.e. they have tissues and reproductive organs, but lack vascular tissue (xylem & phloem) e.g. mosses (Bryophyta), liverworts (Marchantiophyta) & hornworts (Anthocerophyta).
Click on the links for downloadable images of a moss (Splanchnum), a leafy liverwort, and a hornwort (the green needle-like plants). Images courtesy of Allan Green.

 
   
 

c

caldera
 
A large volcanic depression that forms when a volcano collapses, during/after an eruption. Calderas may be up to 50km from rim to rim. (There's more information - volcanoes, earthquakes, tsunami & more, at Te Ara.)

capillaries
The smallest of the blood vessels in the body, measuring 5-10µm in diameter, and with walls made of a single layer of epithelial cells. Capillaries enable the interchange of water, oxygen, carbon dioxide, and many other nutrients and waste products, between cells and blood.

carbohydrates
Also known as saccharides; includes the simple and complex sugars.

cecocolic orifice
The opening through which the caecum connects with the colon.

cellulase
The enzyme that catalyses the  digestion of cellulose. Most animals don't produce cellulase, but it's found in fungi and bacteria.

cellulose
A glucose polysaccharide that it makes up a large proportion of plant cell walls.

chlorophyll
The green photosynthetic pigment found in cyanobacteria, algae and almost all higher plants. (Exceptions include parasitic plants such as dodder.)


circadian rhythm
The 24-hour cycle in the physiological processes of living things, including plants, animals, & fungi.

cisterna
A flattened membranous disc-shaped structure; part of a cell's Golgi body.

collagen
A fibrous protein and a major component of connective tissue.

cortex
The region of tissue in a root or stem lying between the epidermis and the vascular tissue.

covalent
A type of chemical bond where electrons are shared between the two atoms involved.

cytoplasm
The cell substance between the cell membrane and the nucleus, containing the cytosol, organelles, cytoskeleton, and various particles.

cytoskeleton
A network of microtubules and protein microfilaments that  give a eukaryote cell much of its shape and is also involved in movement.

 
   
 

d

disaccharide
A carbohydrate made up of two monosaccharides e.g. sucrose is a disaccharide, formed from one molecule of glucose and one molecule of sucrose.

duct
An enclosed channel leading from one organ to another.


 
   
 

e

endocytosis
A process of cellular ingestion by which the plasma membrane folds inward to bring substances into cell.

endophyte
A fungus that completes its lifecycle within the tissues of a host plant. Endophytes are parasitic on grasses and produce compounds (mycotoxins) that are toxic to animals eating the grass.

endosperm
The nutritive tissue found within the seeds of flowering plants, surrounding the embryo..

endosymbiont
An organism living inside another, in a symbiotic (mutually beneficial) relationship.

enzyme
A biological molecule that increases the rate of a chemical reaction.

eukaryote
In these organisms the DNA in each cell is enclosed in a nuclear membrane (the name 'eukaryote' means 'true nucleus'). They also have membrane-bound organelles.

eutrophication
A rapid (usually) increase in nutrient levels in a waterway, due to natural causes &/or human activity. May trigger very rapid growth of algal species (blooms) and subsequent decline in available oxygen.

 
   
 

f

fatty acids
A hydrocarbon chain with a methyl (-CH3) group on one end and a carboxyl group (COOH) on the other. May be saturated (all carbon-carbon bonds are single bonds) or unsaturated (at least one carbon-carbon bond is a double bond.)

fermentation
An anaerobic reaction (happens in the absence of oxygen) that follows glycolysis. Fermentation converts pyruvate to lactate (in homolactic fermentation) or ethanlol (in yeast fermentation). The reaction generates two NAD+ molecules.

flagella (sing. flagellum)
A long, thin, hairlike structure, protruding from the cell membrane & used for motility. Found in both eukaryote and prokaryote cells, although the internal structure differs between the two cell types.

 
   
 

g

genetic drift
Change in gene frequencies due to chance/random events. The effect of genetic drift tends to be greater in small populations.

glucose 
 
A 6-carbon sugar with the formula C6H12O6. Glucose is a building block for larger molecules such as sucrose (a disaccharide) and cellulose, starch and glycogen (polysaccharides). Plants produce glucose during photosynthesis.

 
   
 

h

heterotrophic
Describes an organism that obtains its energy through consuming other organisms.

heterozygous
Describes an individual that has two different alleles for a particular gene e.g. A1A2.

homozygous
Describes an individual with two identical alleles for a particular gene e.g. A1A1.

hydrocarbons
Molecules composed of carbon and hydrogen.


hydrolysis
A chemical reaction or process in which a chemical compound is broken down by addition of a water molecule.

hydrophilic
Having an affinity for water; readily absorbing or dissoving in water.

hydrophobic
Repelling, tending not to combine with, or incapable of dissolving in water.

hydrosphere
The water on or surrounding the surface of the Earth, including the water content of the atmosphere as well as that in the oceans, lakes and rivers.

 
   
 

i

invertebrate
The term used to describe any animal that lacks a spinal column (a backbone) - any animal that is not a vertebrate.

 
   
 

j


 
   
 

k

 

 
   
 

l

lacteals
Lymphatic capillaries within the villi of the small intestine; lipid molecules are absorbed into the lacteals.

legumes
Plants belonging to the legume family (Fabaceae, or Leguminosae). Well-known legumes include alfalfa, clover, peas, beans, lentils, lupins and peanuts.

lithosphere
The solid part of the Earth, consisting of the crust and outer mantle.

 
   
 

m

mastication
Mastication, or chewing, is the process by which food is mashed and crushed by teeth.

mesophyll
The tissues of a leaf that are found between the upper & lower epidermis; mesophyll cells carry out photosynthesis.


metamorphosis
The change in form and structure that occurs between larval and adult stages in some animals e.g. insects, amphibians

monoglyceride
A glycerol molecule with a single fatty acid attached.

mutualism
Two organisms in a relationship where both benefit from that relationship.

mycotoxin
Any of the compounds produced by endophytic fungi that are harmful to animals ingesting them e.g lolitrem B, ergovaline.


 
   
 

n

NADH
Nicotinamide adenine dinucleotide. Carries H+ ions during metabolic reations.

neurotransmitter
Any of a number of compounds (e.g acetylcholine) that transmits a nerve impulse across the gap (synapse) between two nerve cells or between a nerve and a muscle.

non-vascular
A term used to describe plants that do not have transport tissues i.e. they lack xylem and phloem. Examples: mosses, liverworts.

nucleotide
A compound formed of a nitrogenous base (adenine, guanine, cytosine, guanine, uracil), a sugar (ribose or deoxyribose) and a phosphate group. Nucleotides are the building blocks of nucleic acids.

 
   
 

o

omnivore
An animal that eats both plants and animals.

 
   
 

p

passive transport
The movement of atoms or molecules across a cell membrane without the use of energy. Diffusion and osmosis are both examples of passive transport.

photosynthesis
The use of light energy to make carbohydrates, using CO2 as the carbon source and hydrogen from water (with O2 as a waste product). The light energy is trapped by the green pigment, chlorophyll.

photon
A 'packet', or quantum, of electromagnetic radiation. Photons travel at the speed of light  (300,000km.s-1). The concept of a photon is used to explain the observation that some phenomena of light  have a particle nature.
The Physics 2000 website has some great material on electromagnetic radiation, plus heaps of other physics content.

pith
The soft, spongelike, central cylinder of tissue in the stem of a young flowering plant.

podzol
A group of acid, extremely infertile soils where strong leaching under acid conditions has removed iron, silicon, aluminium and humus material from an upper, bleached layer or horizon (the E horizon), and moved them down where they have accumulated in dark-coloured lower horizons. These lower layers are a black, humus-rish horizon (Bh) and a reddish horizon rich in metal oxides (Bs). The Bs horizon can sometimes become cemented into a hard pan.
The acid conditions are aided by some vegetation types, which include kauri, rimu, kamahi and silver beech in New Zealand, and coniferous forests and heaths in the Northeren hemisphere.
The word podzol is Russian and means 'ashes underneath', which is a reference to the ash-grey colour of the E horizon (it looks a bit like burnt ashes when exposed by ploughing.
An equivalent and widely-used term for podzol is 'spodosol'.


polymer
A substance composed of large molecules with repeating structural units, or monomers, connectec by chemical bonds e.g proteins are amino acid polymers; cellulose is a glucose polymer.

polysaccharide
A long chain-like carbohydrate made up of many sugar molecules (i.e. a polymer). Polysaccharides are often storage (e.g. starch) or structural (e.g. cellulose) elements in plants.

precipitation
Formation of a precipitate - an insoluble compound produced as the result of a chemical reaction.

prokaryote (or procaryote)
Includes the domains Bacteria and Archaea. Prokaryotes have a plasma membrane, but lack extensive internal membrane systems and membrane-bound organelles. Their DNA is free in the cytoplasm, rather than enclosed within a nuclear membrane.

protein
A polymer formed from a chain of amino acids joined together with peptide bonds.

protozoa
These eukaryotes are single-celled (sometimes colonial) 'animal-like' organisms and belong to the phylum Protista. Protozoa are heterotrophs. Most are motile and use cilia, flagella, or amoeboid movement to get around.

pyruvate
A salt or an ester of pyruvic acid. Produced by glycolysis (anaerobic respiration).


 
   
 

q


 
   
 

r

reticulo-omasal orifice
This is the technical term for the opening between two stomach chambers, the reticulorumen and the omasum.

rhyolitic

riboflavin
Also known as vitamin B2, a member of the B vitamin family. It is an easily absorbed micronutrient.

ribosome
A spherical structure found in the cytoplasm and formed ofgRNA and .protein. The site of protein synthesis.


 
   
 

s

scanning electron micrograph
This is an image taken with a scanning electron microscope. This type of microscope uses magnets to focus a beam of electrons on a specimen, which then emits electrons of its own, creating a 3-D image.

symbiosis
Two organisms living together or in close association. The two organisms are referred to as symbionts.

 
   
 

t

terpenes
Any of various unsaturated hydrocarbons found in the essential oils and oleoresins of plants such as conifers, and used to manufacture more complex molecules.

thiamine
Also known as vitamin B1, a member of the B vitamin family, and an easily-absorbed micronutrient.

trace element

transcription
The process by which messenger RNA (mRNA) is synthesised from a DNA template, resulting in the transfer of genetic information from the DNA molecule to the mRNA.


tRNA
Transfer RNA: the RNA molecules that transport amino acids to ribosomes to be added to a growing polypeptide chain, during the process of protein synthesis.

 
   
 

u

unsaturated
Describes a fat or oil molecule that contains at least one double bond between adjacent carbon molecules.

 
   
 

v


vascular plants
These are also known as tracheophytes or 'higher' plants. They contain vascular tissue that transport water, minerals, and photosynthetic products throught the plant. Vascular plants include the ferns, clubmosses, conifers and other gymnosperms, and flowering plants.

vascular tissue
Vascular tissue is a complex tissue (made up of more than one type of cell)  found in vascular plants. The main components of vascular tissue are the xylem and phloem, for transport of water and photosynthates respectively.

vermiform
Resembling a worm: long, thin, & cylindrical.

vertebrate animals
Animals with an internal skeleton made of bone, including a  vertebral column (spine). Mammals, birds, reptiles, amphibians and fish are all vertebrates.

vesicle
A membrane-bound sac, found in eukaryote cells, that stores or transports the cell's metabolic products and is sometimes also used for the breakdown of metabolic wastes..

volatile fatty acids
These are fatty acids based on a carbon chain of 6 or less carbon atoms. They can be formed by fermentation in the rumen.



 
   
 

w


 
   
 

x

xenograft

 
   
 

y


 
   
 

z


 
   
 
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