definitions - set 7

Question 1

sex-linked gene

Answer 1

a gene found on the X chromosome but not on the Y chromosome

Question 2

sexually-transmitted infection

Answer 2

an infection that is transmitted via bodily fluids through sexual contact

Question 3

sexual reproduction

Answer 3

the process involving the fusion of haploid nuclei to form a diploid zygote and the production of genetically dissimilar offspring

Question 4

sickle cell anaemia

Answer 4

a condition caused by a codominant allele of the gene that codes for haemoglobin, in which a person has two copies of the gene and suffers serious health problems

Question 5

simple sugar

Answer 5

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

Question 6

sink

Answer 6

a place to which substrates are transported in phloem

Question 7

solvent

Answer 7

a liquid in which another substance is dissolved

Question 8

source

Answer 8

a place from which substances are transported in phloem

Question 9

species

Answer 9

a group of organisms with similar characteristics, which can interbreed with each other to produce fertile offspring

Question 10

species diversity

Answer 10

the number of different species living in a habitat

Question 11

sperm

Answer 11

a male gamete

Question 12

sphincter muscle

Answer 12

a muscle surrounding a tube, which can contract to close the tube

Question 13

spongy layer

Answer 13

the tissue beneath the palisade layer in a leaf; it is made up of cells that contain chloroplasts and can photosynthesize, with many air spaces between them

Question 14

stamen

Answer 14

the male parts of a flower

Question 15

starch

Answer 15

the polysaccharide that is used as an energy store in plant cells

Question 16

stationary phase

Answer 16

a stage when the numbers in a population remain approximately constant

Question 17

stem tuber

Answer 17

a swollen part of a stem, which stores food

Question 18

stigma

Answer 18

the part of a flower that receives pollen

Question 19

stimulant

Answer 19

a drug that makes the nervous system work faster

Question 20

stimulus

Answer 20

a change in an organism’s surroundings that can be detected by its sense organs

Question 21

stoma (plural: stomata)

Answer 21

a gap between two guard cells, usually in the epidermis on the lower surface of a leaf

Question 22

style

Answer 22

the connection between the stigma and ovary of a flower

Question 23

substrate

Answer 23

the substance on which an enzyme acts

Question 24

sucrase

Answer 24

a carbohydrase found in the small intestine, which breaks down sucrose to glucose and fructose

Question 25

sucrose

Answer 25

a disaccharide, non-reducing sugar, made of a glucose molecule and a fructose molecule linked together; the form in which carbohydrates are transported in the phloem of plants

Question 26

suspensory ligaments

Answer 26

a ring of ligaments linking the ciliary muscles to the lens

Question 27

sustainable resource

Answer 27

one which can be removed form the environment without it running out

Question 28

sustainable development

Answer 28

providing for the needs of an increasing human population without harming the environment

Question 29

synapse

Answer 29

a point at which an impulse can be passed from one neurone to another

Question 30

synaptic cleft

Answer 30

a tiny gap between two neurones

Question 31

systole

Answer 31

the stage of a heart beat in which the muscles in the walls of the heart chambers contract

Question 32

target organ

Answer 32

an organ that is affected by a hormone

Question 33

tendons

Answer 33

strong, inelastic cords of tissue, which attach muscles to bones; they are also found in the heart, where they attach the atrioventricular valves to the wall of the ventricle

Question 34

test cross

Answer 34

breeding an offspring with the dominant phenotype with an organism with the recessive phenotype; the offspring of the cross can help to determine the genotype of the parent with the dominant phenotype

Question 35

testis (plural: testes)

Answer 35

an organ in which sperm is made

Question 36

testosterone

Answer 36

a hormone secreted by the testes, which causes male characteristics

Question 37

tissue

Answer 37

a group of cells with similar structures, working together to perform a shared function

Question 38

tissue fluid

Answer 38

the fluid that surrounds all the cells in the body, formed from blood plasma that leaks out of capillaries

Question 39

toxin

Answer 39

a poisonous substance

Question 40

trachea

Answer 40

the tube that carries air from the nose and mouth down to the lungs

Question 41

translocation

Answer 41

the movement of sucrose and amino acids in phloem, from regions of production to regions of storage, or to regions of utilisation in respiration or growth

Question 42

transmissible disease

Answer 42

a disease caused by a pathogen that can be passed from one person to another

Question 43

transmitter substance

Answer 43

a chemical that carries a nerve impulse across a synapse

Question 44

transpiration

Answer 44

evaporation of water at the surfaces of the mesophyll cells followed by loss of water vapour from plant leaves, though the stomata

Question 45

transpiration stream

Answer 45

the pathway of water from the root hair of a plant, up the root and stem and out of the leaves into the atmosphere

Question 46

trophic level

Answer 46

the position of an organism in a food chain, food-web or pyramid of biomass, numbers or energy

Question 47

tropism

Answer 47

a plant growth response to a stimulus, in which the direction of growth is related to the direction of the stimulus

Question 48

trypsin

Answer 48

a protease enzyme found in pancreatic juice

Question 49

turgid

Answer 49

a term used to describe a plant cell that has absorbed water ad ha cytoplasm that is pressing outwards on the cell wall

Question 50

type 1 diabetes

Answer 50

a condition in which the pancreas is unable to make insulin