Planktonic organisms – drifting organisms

1. Marine environment unique to different habitats Planktonic organisms – drifting organisms

2. Benthic organisms – bottom dwellers

3. Nekton organisms - free swimming organisms

4. Organisms need to maintain a stable internal conditions Salinity of environment has a large impact on organism that must be controlled. A selectively permeable membrane helps control movement of molecules into or out of an organisms cells. H2O diffuses through the membrane from a higher to a lower concentration (osmosis).

5. Regulating water / salt balance in a marine environment Osmoconformers – their internal concentrations mimic water concentrations. Organisms must live in water that stays within livable range. Open oceans provide a suitable living area with little salinity changes Osmoregulators – control their own internal concentrations.

6. One way is to adjust solute concentration of body fluids to match salinity of the water. Sharks do this by increasing or decreasing urea in their blood. Dumaliella use glycerol to control solute level. They can regulate from nearly freshwater to saltwater 9x saltier than seawater Second method is maintaining a body fluid solute levels lower than seawater. Marine fish drink water – produce low amounts of urine that is high in salts – excrete salts through gills

8. Marine birds, plants and reptiles have special glands that rids them of excess salt.

9. Temperature regulation Ectotherms – body temperature rises and falls with water temperature. Most marine animals are ectotherms Lower temperatures slows down metabolic rate, animal becomes sluggish. Exception – some large fishes can maintain body temperature above water temperature due to heat generated by muscles.

10. Endotherms – able to maintain body temperature regardless of water temperature. Marine mammals and birds retain heat as by product of muscle activity, also control rate of respiration producing heat by burning up fats. Results in energy drain – lessened by insulation of hair, feathers, or blubber.

11. Surface to volume ratio Influences how fast salts and heat can flow into and out of organism. The larger an organism grows the smaller the surface to volume ratio becomes. Small organisms have large S/V ratios and can rely on diffusion to exchange heat and molecules with the environment. Large organisms need a system to exchange heat and molecules. Example respiratory and excretory systems.