Transcript E-5 Notes
Science 8: Unit E: Fresh and Saltwater Systems Topic 5 – Living in Water Biodiversity in Aquatic Ecosystems Biodiversity – variety of different kinds of species in an ecosystem. Large bodies of water have different layers or zones with each having its own biodiversity. Some organisms live in only one zone, while others live in all three. Zones in Lakes and Ponds Upper Zone – area of a lake from the shore down to where the aquatic plants stop growing. Species you will find here include water lilieis, small fish, clams, insects, frogs. Middle Zone – open water area that still has light reaching the bottom. Species you will find here include phytoplankton, fish. Deep Zone – No light reaches the bottom, so no plant growth here. Food for organisms living here comes from dead organisms/waste from higher zones. Species you will find here include deep water fish (larger fish). Zones in Rivers and Streams Streams usually alternate between areas where water is calm (pools) and areas where water is moving rapidly (riffles). Organisms often attach themselves to rocks as their habitat. Zones in Oceans I. Estuary – Where freshwater washes into the saltwater (at river mouths) forming brackish water. Makes for very diverse ecosystems. II. Inter-tidal Zone – shoreline of ocean. Animals here must be able to withstand pounding of waves. III. Continental Shelf – Warmer water in area with full light penetration. Contains phytoplankton and many fish and plants. IV. Oceanic Zone – little light penetrates here so no plant growth. Aquatic Adaptations Adaptation – physical or behavioral characteristic of a species that increases the species’ chances of survival in their ecosystem. Many aquatic organisms have adapted to being able to filter their food from the water. Aquatic Adaptations Cont’d There are five key ecosystem factors that aquatic species must adapt to, or die out. I. Temperature – Species must be adapted to the temperature of the surrounding water. Certain species actually have a form of antifreeze in their blood to keep it from freezing in cold waters. II. Lights Levels – Most species need light. Some animals in the ocean floor can produce their own light (bioluminescence). Aquatic Adaptations Cont’d III. Pressure – Skeletal and muscular tissues are adapted for pressures/forces a species must deal with in their habitat zone. They will die if moved. IV. Salinity – Because of osmosis animals have been adapted to specific concentrations of salt in the water. V. Water Movement – Animals are adapted to deal with water movement and for moving through water. (streamlined shape of shark) Aquatic Plants Two types: those that float freely: phytoplankton, and those that attach themselves to ocean/lake floor. Stomata are specialized cells in plants that open and close to allow in carbon dioxide for photosynthesis (making sugar) or oxygen (consuming their sugar) Plants need phosphate and nitrate nutrients. They get these in the oceans from detritus. Temperature Mixing When temperatures cool in the fall, the surface water becomes denser, sinking to the bottom, allowing nutrients to resurface. This increases the phytoplankton growth. Cold water holds dissolved gases better than warm water – meaning higher oxygen levels in the surface waters in the fall. The level of nutrients and salts in oceans is in a steady balance. Not only does it get added to the water as described earlier, but it is also taken out of the water. Nutrient Pollution Too many nutrients can cause problems in aquatic environments. An increase in algae growth (algal bloom) covers the surface of the water, blocking out the light. As the algae dies, they are decomposed by bacteria, which use up all the oxygen. This cycle continues until a balance is achieved again. Population Changes Population – a group of organisms of the same species living in the same ecosystem. There are three types of population changes: I. Seasonal Change: Populations swell in the summer and disappear in winter. The disappearance of a population may mean survivors are dormant, or hibernating in the winter months. Breeding cycles can also cause seasonal changes in populations. Population Changes Cont’d II. Short-Term Changes: take place over a relatively short period of time and don't last very long. They happen irregularly and may be part of a natural event, or caused by human activities. III. Long-Term Changes: result from natural events or human activities. A landslide can change the course of a river or stream. Addition of a new species (zebra mussels introduced by accident) to an area (the Great Lakes) may result in overpopulation of that species because there are no natural enemies. Humans and Aquatic Species Over-fishing, dumping of toxic chemicals and fertilizers into aquatic ecosystems, as well as the use of pesticides have all negatively affected populations of aquatic species. Biomagnification – Residues from human produced chemicals can find their way into ground water and bodies of water. As the chemicals move up the food chain, they become more and more concentrated in the tissues of the organisms.