All bio definitions

• Species


  a group of organisms that can reproduce to produce fertile offspring.
• Binomial system


  an internationally agreed system in which the scientific name of an organism is made up of two parts showing the genus and species.
• Tissue


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


  a structure made up of a group of tissues, working together to perform specific functions.
• Organ system


  a group of organs with related functions, working together to perform body functions.
• Diffusion


  the net movement of particles from a region of their higher concentration to a region of their lower concentration down a concentration gradient, as a result of their random movement.
• Osmosis


  the diffusion of water from a region of higher water potential (dilute solution) to a region of lower water potential (concentrated solution), through a partially permeable membrane
• Active transport


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


  a substance that increases the rate of a chemical reaction and is not changed by the reaction.
• Enzyme


  proteins that function as biological catalysts
• Ingestion


  the taking of substances, e.g. food and drink, into the body through the mouth
• Mechanical digestion


  the breakdown of food into smaller pieces without chemical change to the food molecules.
• Chemical digestion


  the breakdown of large, insoluble molecules into small, soluble molecules.
• Absorption


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


  the movement of digested food molecules into the cells of the body where they are used, becoming part of the cells.
• Egestion


  the passing out of food that has not been digested or absorbed, as faeces, through the anus.
• Photosynthesis


  as the process by which plants manufacture carbohydrates from raw materials using energy from light.
• Limiting factor


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


  loss of water vapour from plant leaves by evaporation of water at the surfaces of the mesophyll cells followed by diffusion of water vapour through the stomata.
• Translocation


  the movement of sucrose and amino acids in phloem:from regions of production (source)to regions of storage OR to regions where they are used in respiration or growth (sink)
• Aerobic respiration


  the chemical reactions in cells that use oxygen to break down nutrient molecules to release energy.
• Anaerobic respiration


  the chemical reactions in cells that break down nutrient molecules to release energy without using oxygen.
• Pathogen


  a disease-causing organism.
• Transmissable disease


  can be passed from one host to another.
• Active immunity


  defence against a pathogen by antibody production in the body.
• Synapse


  a junction between two neurones.
• Sense organs


  groups of receptor cells responding to specific stimuli: light, sound, touch, temperature and chemicals.
• Hormone


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


  a response in which parts of a plant grow towards or away from gravity.
• Phototropism


  a response in which parts of a plant grow towards or away from the direction from which light is coming.
• Homeostasis


  the maintenance of a constant internal environment.
• Drug


  any substance taken into the body that modifies or affects chemical reactions in the body.
• Asexual Reproduction


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


  nuclear division giving rise to genetically identical cells
• Sexual Reproduction


  a process involving the fusion of the nuclei of two haploid gametes (sex cells) to form a diploid zygote and the production of offspring that are genetically different from each other.
• Fertilisation


  the fusion of gamete nuclei.
• Meiosis


  nuclear (reduction) division in which the chromosome number is halved from diploid to haploid resulting in genetically different cells
• Pollination


  the transfer of pollen grains from the anther to the stigma.
• Self-pollination


  the transfer of pollen grains from the anther of a flower to the stigma of the same flower or different flower on the same plant.
• Cross-pollination


  transfer of pollen grains from the anther of a flower to the stigma of a flower on a different plant of the same species.