definitions - set 5

Question 1

mitosis

Answer 1

nuclear division giving rise to genetically identical cells in which the chromosome number is maintained by the exact duplication of chromosomes

Question 2

monoculture

Answer 2

a large area of the same crop plant

Question 3

monosaccharide

Answer 3

a simple sugar; a carbohydrate whose molecules are made of one sugar unit

Question 4

morphology

Answer 4

the overall shape and form of an organism’s body

Question 5

movement

Answer 5

an action by an organism or part of an organism causing a change of position or place

Question 6

mutagen

Answer 6

a substance that causes mutations

Question 7

mutation

Answer 7

a change in a gene or a chromosome

Question 8

myelin

Answer 8

a fatty substance surrounding the axons of many neurones, enabling the nerve impulse to travel faster

Question 9

natural selection

Answer 9

the greater chance of passing on of genes by the best-adapted organisms

Question 10

nectary

Answer 10

a gland producing a sugary fluid, found in many insect- or bird- pollinated flowers

Question 11

negative feedback

Answer 11

a mechanism used in homeostasis, in which a change in a parameter brings about actions that push it back towards normal

Question 12

nephron

Answer 12

one of the thousands of tiny tubules in a kidney, in which urine is produced

Question 13

nerve

Answer 13

a bundle of axons or dendrons belonging to many different neurones

Question 14

nerve impulse

Answer 14

an electrical signal that sweeps along a neurone

Question 15

neurone

Answer 15

a nerve cell; a cell specialised for the rapid transfer of electrical impulses

Question 16

nicotine

Answer 16

an addictive drug found in tobacco smoke

Question 17

nitrifying bacteria

Answer 17

bacteria that obtain their energy by converting ammonia or nitrite ions to nitrate ions

Question 18

nitrogen fixation

Answer 18

changing unreactive nitrogen gas into a more reactive nitrogen compound such as nitrate or ammonia

Question 19

nitrogenous waste

Answer 19

excretory products containing nitrogen - for example, ammonia, urea, uric acid

Question 20

non-biodegradable

Answer 20

not able to be broken down by microorganisms

Question 21

normal distribution

Answer 21

a curve in which the largest number occurs near the midpoint, with approximately equal quantities on either side of this point and a gradual decrease towards the extremes

Question 22

nucleus

Answer 22

a large organelle in which chromosomes are found

Question 23

nutrition

Answer 23

taking in materials that are required for energy, growth and development

Question 24

oesophagus

Answer 24

the part of the alimentary canal along which food travels from the mouth to the stomach

Question 25

oestrogen

Answer 25

a hormone secreted by the ovaries that helps to control the menstrual cycle

Question 26

optimum temperature

Answer 26

the temperature at which something happens most rapidly

Question 27

organ

Answer 27

a structure made up of a group of tissues, working together to perform specific functions

Question 28

organ system

Answer 28

a group of organs with related functions, working together to perform body functions

Question 29

organelle

Answer 29

a structure within a cell

Question 30

organic

Answer 30

a term used to describe substances that have been made by living organisms, or whose molecules contain carbon, hydrogen and oxygen

Question 31

organism

Answer 31

a living thing

Question 32

osmosis

Answer 32

the diffusion of water molecules from a region of high water potential to a region of lower water potential, through a partially permeable membrane

Question 33

ovary

Answer 33

an organ in which female gametes are made

Question 34

oviduct

Answer 34

the tube leading from an ovary to the uterus

Question 35

ovulation

Answer 35

the release of an egg from an ovary

Question 36

ovule

Answer 36

a structure in the ovary of a flower which contains a female gamete

Question 37

oxygen debt

Answer 37

the extra oxygen that must be taken in by the body following strenuous exercise, when anaerobic respiration took place; the oxygen is needed to break down the lactic acid that accumulated as a result of anaerobic respiration

Question 38

oxygenated blood

Answer 38

blood containing a lot of oxygen; in humans, blood becomes oxygenated in the lungs

Question 39

palisade layer

Answer 39

the upper mesophyll layer in a leaf, made up of rectangular cells containing many chloroplasts

Question 40

pancreas

Answer 40

an organ lying close to the stomach, which is both an endocrine gland (producing insulin and glucagon) and an exocrine gland (producing pancreatic juice)

Question 41

pancreatic juice

Answer 41

the liquid secreted into the pancreatic duct by the pancreas; it flows into the duodenum where its enzymes help with digestion of fats, proteins and carbohydrates

Question 42

partially permeable

Answer 42

allowing some molecules to pass through, but not others

Question 43

passive immunity

Answer 43

having antibodies provided from another organism, that temporarily protect against a pathogen

Question 44

pathogen

Answer 44

a disease-causing organism

Question 45

pelvis

Answer 45

(in kidney) the part from which the ureter emerges

Question 46

penicillin

Answer 46

an antibiotic which destroys bacteria by damaging their cell walls

Question 47

pepsin

Answer 47

a protease enzyme found in the stomach

Question 48

peripheral nervous system

Answer 48

all the nerves and receptors in the body, not including the brain or spinal cord

Question 49

peristalsis

Answer 49

rhythmic contractions of muscles that ripple along a tube - for example, peristalsis pushes food through the alimentary canal

Question 50

petiole

Answer 50

a leaf stalk