definitions

• Diffusion

  The net movement of particles from a region where they are of higher concentration to a region where they are of lower concentration, that is, down a concentration gradient
• Osmosis

  The net movement of water molecules from a region of higher water potential to region of lower water potential, through a partially permeable membrane
• Active transport

  The process in which energy is used to move the particles of substance across a membrane against its concentration gradient, that it, from a region where the particles are of lower concentration to a region where they are of higher concentration
• Aerobic respiration

  The release of energy by the breakdown of glucose in the presence of oxygen. Carbon dioxide and water are released as waste products. Aerobic respiration releases a large amount of energy
• Anaerobic respiration

  The release of energy by the breakdown of glucose in the absence of oxygen. Anaerobic respiration releases a relatively small amount of energy
• Excretion

  The removal of metabolic waste products, toxic substances and substances in excess of the body's requirements
• Homeostasis

  The maintenance of constant internal environment
• Hormone

  A chemical substance, produced by a gland, carried by the blood, which alters the activity of one or more specific target organs
• Vaccines

  A substance that contains a weakened or killed version of the pathogen, or may contain the DNA of it. It stimulates lymphocytes of the white blood cells to quickly recognise the pathogen to swiftly produce enough antibodies to eradicate the pathogen before it can infect the body
• Transpiration

  The loss of water vapour from the aerial parts of a plant, mainly through the stomata of the leaves
• Translocation

  The transport of manufactured food substances, such as sugars and amino acids, in the phloem tissue in plants
• DNA

  A double helix comprising 2 strands of nucleotides, each nucleotide formed of a sugar, a phosphate group and one of 4 different bases
• Asexual reproduction

  The process resulting in the production of genetically identical offspring from one parent
• Mitosis

  A type of cell division giving rise to genetically identical cells in which the chromosome number is maintained
• Sexual reproduction

  The process involving the fusion of nuclei of male and female gametes to form a zygote and the production of genetically dissimilar offspring
• Haploid

  A cell with one set of chromosomes
• Diploid

  A cell with 2 sets of chromosomes
• Homologous pairs of chromosome

  Pairs of chromosomes that have the same genes at the same loci but may have different alleles. They are inherited from each parent and are crucial for genetic variation and meiosis.
• Meiosis

  A type of cell division that gives rise to genetically dissimilar cells in which the chromosome number is halved due to the separation of homologous chromosome
• Gene

  A sequence of DNA nucleotides that controls the formation of a single polypeptide. It is also a unit of inheritance
• Alleles

  The different forms of the same genes which occupy the same relative position on a pair of homologous chromosome