definitions - set 4

Question 1

heterozygous

Answer 1

having two different alleles of a gene (e.g. Tt or Gg), not pure-breeding

Question 2

hilum

Answer 2

the scar where a seed was attached to a fruit

Question 3

homeostasis

Answer 3

the maintenance of a constant internal environment

Question 4

homologous chromosomes

Answer 4

the two chromosomes of a pair in a diploid cell; they have genes for the same features at the same positions

Question 5

homozygous

Answer 5

having two identical alleles of a particular gene (e.g. TT or gg). Two identical homozygous individuals that breed together will be pure-breeding

Question 6

hormone

Answer 6

a chemical substance produced by a gland, carried by the blood, which alters the activity of one or more specific target organs and is then destroyed by the liver

Question 7

hydrophyte

Answer 7

a plant adapted to live in wet conditions

Question 8

hyperglycaemia

Answer 8

having too much glucose in the blood

Question 9

hypertension

Answer 9

high blood pressure

Question 10

hypoglycaemia

Answer 10

having too little glucose in the blood

Question 11

hypothalamus

Answer 11

a part of the brain that helps to regulate body temperature

Question 12

immune

Answer 12

able to fight off a particular type of pathogen before it causes any symptoms in the body

Question 13

implantation

Answer 13

the movement of a young embryo into the lining of the uterus, and its attachment there

Question 14

ingestion

Answer 14

taking substances (e.g. food, drink) into the body through the mouth

Question 15

inheritance

Answer 15

the transmission of genetic information from generation to generation

Question 16

inorganic

Answer 16

substances that are not made by living organisms

Question 17

insulin

Answer 17

a hormone secreted by the pancreas, which reduces blood glucose level

Question 18

intercostal muscles

Answer 18

muscles between the ribs, which help to produce breathing movements

Question 19

involuntary action

Answer 19

an action taken automatically, without conscious thought

Question 20

iris

Answer 20

the coloured part of the eye, which controls the amount of light allowed through to the lens and the retina

Question 21

islets of Langerhans

Answer 21

groups of cells in the pancreas which secrete insulin and glucagon

Question 22

key

Answer 22

a series of questions whose answers lead you to the identification of an organism

Question 23

kingdom

Answer 23

one of the five large groups into which all living organisms are classified

Question 24

kwashiorkor

Answer 24

a deficiency disease caused by lack of protein in the diet

Question 25

lactation

Answer 25

production of milk by mammary glands

Question 26

lag phase

Answer 26

the early stage of population growth, when numbers scarcely change

Question 27

lamina

Answer 27

the main part of a leaf

Question 28

LH

Answer 28

luteinising hormone; a hormone secreted by the pituitary gland which causes an egg to be released from an ovary

Question 29

light microscope

Answer 29

a microscope that uses light to produce images

Question 30

lignin

Answer 30

a tough, waterproof material that makes up the walls of xylem vessels; wood is mostly lignin

Question 31

limiting factor

Answer 31

something present in the environment in such short supply that it restricts life processes

Question 32

lipase

Answer 32

an enzyme that digests fats (lipids) to fatty acids and glycerol

Question 33

lipids

Answer 33

fats, oils and waxes

Question 34

log phase (exponential phase)

Answer 34

the stage in population growth when numbers increase exponentially

Question 35

lymph

Answer 35

the fluid found inside lymph vessels, formed from tissue fluid

Question 36

lymph nodes

Answer 36

organs in which large numbers of white blood cells (which can destroy bacteria or toxins) collect

Question 37

maltase

Answer 37

an enzyme that breaks down maltose to glucose

Question 38

marasumus

Answer 38

a disease resulting from a severe lack of energy in the diet

Question 39

maltose

Answer 39

a disaccharide produced by the digestion of starch

Question 40

mechanical digestion

Answer 40

the breakdown of large pieces of food to smaller ones, incresasing their surface area; it is done by teeth in the mouth and by the contraction of muscles in the stomach wall

Question 41

medulla (in kidney)

Answer 41

the central area in a kidney

Question 42

meiosis

Answer 42

reduction division in which the chromosome number is halved from diploid to haploid

Question 43

memory cells

Answer 43

cells produced by activated lymphocytes, that remain in the body and are able to respond quickly to a pathogen

Question 44

menstruation

Answer 44

the loss of the uterus lining through the vagina

Question 45

mesophyll

Answer 45

the tissues in the centre of a leaf, where photosynthesis takes place

Question 46

metabolic reactions

Answer 46

the chemical reactions that take place inside a living organism

Question 47

micrometre

Answer 47

1 x 10 -6 metres

Question 48

micropyle

Answer 48

a tiny hole in the testa of a seed

Question 49

mineral

Answer 49

an inorganic ion required in small quantities by living organisms

Question 50

mitochondria

Answer 50

organelles in which aerobic respiration takes place, releasing energy for use by the cell