Key Area 2.1 Cells Tissues and Organs

Glossary – Unit 2

Key area 2.1 Cells tissues and organs.

Word / Definition
Multicellular Organisms / A living thing made of more than one cell
Cell Specialisation / When cells become differentiated to carry out a particular function
Tissue / A group of similar cells which carry out the same function
Histology / The study of cells and tissues of plants and animals
Histopathology / The study of cells and tissues to diagnose and monitor diseases
Organ / A group of differentiated tissues that work together to carry out a particular function e.g. heart and lungs
Organ System / A group of organs that work together to carry out a particular function e.g. circulatory, respiratory and digestive

Key area 2.2 – Stem Cells and meristems

Word / Definition
Stem cell / Unspecialised cell capable of dividing into cells that can develop into different cell types
Embryonic Stem Cells / Found in embryos and have the potential to divide and become nearly any cell type in the body
Adult Stem Cells / Found in tissues and organs and can divide and differentiate into different cell types
Meristem / Localised region of actively dividing cells in plants
Ethical issue / A moral dilemma

Key area 2.3a – Control and communication: Nervous system

Word / Definition
Cerebrum / Large folded part of the brain that controls conscious responses, memory, thought, intelligence and emotions
Cerebellum / Part of the brain that controls balance and coordination of movement
Medulla / Part of the brain which controls breathing, heart rate and peristalsis
Stimuli / Changes in the environment detected by receptor cells that trigger a response in an organism
Sensory Strip / Area of the cerebrum that deals with all incoming information from the senses
Motor Strip / Area of the cerebrum that sends information to muscles of the body that we control by conscious thought
Central Nervous System (CNS) / Part of the nervous system made up of the brain and spinal cord
Neurone / Nerve cell that is specialised to transmit electrical impulses
Sensory Neurone / Nerve cell that transmits electrical impulses from a sense organ to the CNS
Relay Neurone / Nerve cell that transmits electrical impulses from sensory neurones to motor neurones
Motor Neurone / Nerve cell that carries electrical impulses from the CNS to effectors such as muscles or glands
Effectors / The muscles or glands that make the appropriate response
Nerve impulse / Electrical signals which travel along nerve cells
Reflex arc / Pathway of information from a sensory neuron through a relay neuron directly to a motor neurone
Synapse / The gap between two neurones
Neurotransmitters / Chemicals which are released to effect a change
Synaptic cleft / The area a neurotransmitter has to cross to continue to the next neurone
Receptor cell / Cell that can detect stimuli inside or outside of the body
Brain / Organ of the central nervous system of mammals where vital functions are coordinated
Spinal cord / Part of the CNS of a mammal that runs within its backbone

Key area 2.3b – Control and communication: Endocrine system

Word / Definition
Endocrine system / Gland that produces and releases a hormone directly into the blood
Hormones / A protein released by an endocrine gland into the blood to act as a chemical messenger
Insulin / A hormone produced by the pancreas, responsible for triggering the conversion of glucose into glycogen in the liver
Glucagon / A hormone produced by the pancreas, responsible for triggering the conversion of glycogen into glucose in the liver
Diabetes / A condition where the sufferer cannot control glucose levels in their body
Glands / A group of cells that produce and secrete chemicals into the body
Pancreas / The organ responsible for the production of digestive enzymes and the hormones insulin and glucagon
Glycogen / Animal storage carbohydrate located in the liver and muscle tissues
Liver / A large organ with many important functions including a role in blood glucose control
Target organ / An organ with receptor molecules on its cell surface that recognise a specific hormone

Key area 2.4 – Reproduction

Word / Definition
Reproduction / The production of new members of a species
Sexual reproduction / Reproduction which requires the use of sex cells
Asexual reproduction / Reproduction which does not require sex cells
Zygote / A fertilised egg cell
Gametes / Sex cells containing haploid chromosome number
Haploid / A cell which only contains half the normal amount of chromosomes (23 in humans)
Diploid / A cell which contains the full chromosome complement (46 in humans)
Testes / Male sex organs in animals responsible for the production of sperm
Sperm cell / A gamete produced in the testes of male animals
Ova (singular Ovum) / Female gametes produced by ovaries in animals
Ovaries / Female sex organs in animals responsible for the production of ova
Ovulation / When ova are released at regular intervals from the female ovaries
Fertilisation / The fusion of gametes
Oviduct / The site of fertilisation of an ova by a sperm cell
Pollination / The transfer of pollen grain from anther to stigma, usually by wind or an animal pollinator
Stamen / The male reproductive organs of a flower
Pollen grain / The structure produced in the anthers of a flower that contains the male gamete
Stigma / Where pollen lands during fertilisation
Ovules / The female gamete of plants

Key area 2.5 – Variation and inheritance

Word / Definition
Variation / Differences in characteristics that can be seen between individual members of a species
Discreet (discontinuous) variation / Variation that is clear cut and observable as categories
Continuous variation / Variation where a characteristic can have any value in a range
Ploygenic / Inheritance determined by the interaction of several genes acting together
Gene / A small section of DNA that codes for the production of a particular protein
Alleles / Different versions of the same genetic characteristic
Genetics / The study of variation and inheritance
Phenotype / The visible characteristics of an organism that occur as a result of its genes
Genotype / The alleles that an organism has for a particular characteristic
Dominant alleles / Form of a gene that is expressed in the phenotype, whether it is homozygous or heterozygous
Recessive allele / An allele of a gene that only shows in the phenotype if the genotype is homozygous for that allele
Homozygous / Describes a genotype in which the two alleles for the characteristic are the same
Heterozygous / Describes a genotype in which the two alleles for the characteristic are different

Key area 2.6a – The need for transport in plants

Word / Definition
Transpiration / The evaporation of water through the stomata of leaves
Xylem / Narrow, dead tubes with lignin in their walls for the transport of water and minerals in plants
Phloem / Vessels in plants that transport sugars
Photosynthesis / Process carried out by green plants to make their own food using light energy
Stomata / Tiny pores in the leaf epidermis that allow gas exchange
Guard cells / Found on either side of a stoma; they control gas exchange in leaves by controlling opening and closing of the stoma
Lignin / Carbohydrate material lining the xylem vessels and providing strength and support
Minerals / Nutrient ions essential for healthy growth
Root hair cell / A specialised cell that increases the surface area of the root epidermis to improve the uptake of water and minerals
Spongy mesophyll / Plant leaf tissue with loosely packed cells and air spaces between them to allow gas exchange
Vascular tissue / Plant tissue composing of phloem and xylem that transports minerals in a plant

Key area 2.6b – The need for transport in animals: circulation

Word / Definition
Circulatory system / Consists of the heart, blood vessels and the blood they contain
Heart / Muscular organ that pumps blood around the body
Blood vessels / Structures which allow blood to be transported around the body
Artery / General name for a blood vessel that carries blood away from the heart
Vein / General name for a blood vessel that transports blood to the heart
Capillaries / Tiny blood vessels with walls one-cell thick where exchange of materials occurs
Plasma / The liquid part of blood that carries many substances such as sugars, salts, amino acids, proteins, vitamins, water, carbon dioxide and urea.
Haemoglobin / Pigment in red blood cells that transports oxygen as oxyhaemoglobin
Valves / Structures in veins that prevent backflow of blood
Aorta / The main artery that carries oxygenated blood away from the heart in mammals
Pulmonary artery / Artery carrying deoxygenated blood from the heart to the lungs
Pulmonary vein / Vein carrying oxygenated blood to the heart from the lungs
Vena cava / Vein carrying deoxygenated blood to the heart from the body systems
Ventricle / Lower chambers of the heart that receive blood from the atria and pump it into the arteries
Atria / Upper chambers of the heart which receive blood from veins

Key area 2.6c The need for transport in animals: gas exchange and nutrient absorption

Word / Definition
Alveoli / Tiny sacs in lungs that form the gas exchange surface
Cartilage / Flexible tissue forming C-shaped rings in the trachea to keep the airways open
Cilia / Hair-like structures lining the trachea that move mucus with trapped bacteria away from the lungs
Digestion / The breakdown of large, insoluble food molecules into smaller, soluble ones
Lacteal / Central vessel in the villi responsible for the absorption of fats
Lungs / Organs responsible for gas exchange
Lymph / Liquid that circulates within a mammals body, transporting the products of fat digestion from the lacteals
Mucus / Sticky substance lining the trachea and bronchi, trapping dust and bacteria
Peristalsis / Waves of muscular contraction responsible for the movement of food through the intestines
Villi / Finger-like projections of the small intestine lining providing a large surface area for the digestion of food
Gas exchange / The movement of molecules such as oxygen and carbon dioxide
Carbohydrate / A substance such as sugar, starch or glycogen, containing the elements carbon, hydrogen and oxygen
Fats / A substance which is used as an energy source and for insulation, made from fatty acids and glycerol
Proteins / A substance composed of chains of amino acids containing the elements carbon, hydrogen, oxygen and nitrogen

Key area 2.7 – Effects of lifestyle choices on human transport exchange systems

Word / Definition
Lifestyle choice / Decisions on lifestyle that impact on an individual’s health
Diet / The food and drinks which a person consumes
Obesity / A condition where a person is heavily overweight which often puts strain on their organs
Heart attack / A blockage to the coronary artery
Tobacco / Smoking increases the risk of developing heart disease
Exercise / Healthy activities which improve circulation and blood flow to muscles
Alcohol / Heavy drinking can lead to an increase in blood pressure which increases the risk of having a heart attack or stroke