1. define adaptation a characteristic of an organism which allows it to survive in its environment natural selection results in evolutionary adaptations name the three types of adaptation structural – change in physical form physiological – change in how body functions behavioural – change in response to stimuli

2. define osmoregulation the mechanisms used by organisms to maintain a water balance state the importance of osmoregulation cells can only survive in a narrow range of water concentrations osmoregulation keeps the water concentration of the cells constant it allows organisms to survive in a range of different habitats freshwater saltwater desert

3. discuss osmoregulation in freshwater fishosmoregulation in freshwater fish fish hypertonic compared to freshwater gains water by osmosis (across mouth and gills) must excrete water and absorb salt ions chloride secretory cells in gills actively absorb salt ions from water does not drink many large glomeruli in kidney high filtration rate of water from blood large volume of dilute urine kidneys efficient at reabsorbing salt ions

4. discuss osmoregulation in saltwater bony fishosmoregulation in saltwater bony fish fish hypotonic compared to saltwater loses water by osmosis (across gills) must absorb water and excrete salt ions chloride secretory cells in gills actively secrete salt ions drinks seawater few, small glomeruli in kidney low filtration rate of water from blood small volume of concentrated urine test