Biology Letter A - Definitions

Question 1

abdomen

Answer 1

central body part. Specialises in digestion, reproduction and excretion

Question 2

absorption

Answer 2

the movement of ions and small food molecules through the wall of the intestine into the blood

Question 3

accomodation

Answer 3

changes in the ciliary muscles, suspensory ligaments and lens that allows the eye to focus on distant and near objects

Question 4

acquired immune deficiency (AIDS)

Answer 4

a sexually transmitted disease caused by the HIV virus. This disease can be fatal and has killed millions of people around the world

Question 5

acrosome

Answer 5

a specialized organelle in the head of a sperm which contains enzymes used to break through the surface of the egg cell during fertilisation

Question 6

activation energy

Answer 6

the minimum amount of energy needed for a reaction to occur

Question 7

active immunity

Answer 7

immunity that develops in response to a pathogen and involves the activation of memory cells

Question 8

active site

Answer 8

a specific region of an enzyme where catalysis happens

Question 9

active transport

Answer 9

the movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration, using energy from respiration

Question 10

Adam’s apple

Answer 10

a lump that appears more prominent on the throat, which is formed by the thyroid cartilage surrounding the larynx or voice box becoming larger during puberty

Question 11

adaptation

Answer 11

the process, resulting from natural selection, by which populations become more suited to their environment over many generations

Question 12

adaptive features

Answer 12

an inherited feature that increase the fitness of an organism, and helps it to survive and reproduce in its environement

Question 13

adrenaline

Answer 13

a hormone secreted by the adrenal gland that cause the ‘fight or flight’ response

Question 14

adventitious roots

Answer 14

plant roots that form from any non-root tissue

Question 15

aerobic

Answer 15

describes conditions in which air or oxygen is present

Question 16

aerobic respiration

Answer 16

chemical reactions in cells in which nutrient molecules are broken down using oxygen to release energy

Question 17

alcohol

Answer 17

a group of chemicals that is a by-product of anaerobic respiration

Question 18

algae

Answer 18

a class of plants that grown water and are formed by small filaments

Question 19

algal bloom

Answer 19

the rapid, uncontrolled growth of algae on the surface of water

Question 20

alginate

Answer 20

a carbohydrate extracted from algae

Question 21

alimentary canal

Answer 21

the tube in which food passes through the body, consisting of the mouth, oesophagus, stomach, small intestine and large intestine

Question 22

alkaline

Answer 22

describes a substance that can neutralise the pH of acidic substances in the body

Question 23

allele

Answer 23

an alternative version of a gene. A section of DNA that codes for a particular protein

Question 24

alveoli

Answer 24

tiny air sacs in the lungs that provide a large surface are to volume ratio for efficient gas exchange

Question 25

amino acids

Answer 25

small molecules that makes up proteins

Question 26

amniotic fluid

Answer 26

the fluid that surrounds and protects the developing fetus within the amniotic sac

Question 27

amniotic sac

Answer 27

a thin sac that protects the developing fetus within the uterus

Question 28

amphibians

Answer 28

animals which are cold blooded vertebrates

Question 29

amylase

Answer 29

enzyme that breaks down starch to maltose

Question 30

anaerobic

Answer 30

describes the conditions in which air or oxygen is absent