Unit 5 Fresh and Saltwater Systems Topic 5 Living in Water Read: Pages Remember to name and date your notes!

Lakes and ponds are bodies of fresh water that collect in low areas of land. Remember – a pond is small, shallow, and light can hit the bottom. Plants can grow at the bottom of a pond.

Lake is usually larger than a pond. Plants cannot grow on the bottom of a lake…except along shorline.

Rivers and streams are usually shallow and contain sediments eroded from land. Most animals who live in rivers and streams must attach themselves to rocks or plants (or be good swimmers) as the rivers are always moving.

Oceans are salty, deeper, and move more due to tides, currents, and waves. Most marine organisms are found in the top 180m of water. (average depth to which light can penetrate.)

Most marine organisms live on the continental shelf as this is where plants can grow. 90% of marine life occurs here.

Most aquatic animals use gills to extract oxygen from water.

Marine mammals (whales, sea lions) use lungs. Some marine life tuck themselves under rocks, bury themselves in sand, or suction themselves to avoid being swept away.

Larger marine life, like fish and whales, are shaped to move easily through water. Plankton (zooplankton – animal plankton, and phytoplankton – plant plankton) float on currents. Food for marine life.

Some marine life capture food and eat it. Others filter food out of the water. Great whales filter plankton out of the water using baleen.

Aquatic Plants Two types: those attached to the bottom and those that float. Where is plant life found?

Attached plants: plants in shallow water often have roots – get nutrients from soil. Many plants have long open channels in their stems to carry oxygen to the roots.

Marine plants have stomata on top of their leaves so that floating leaves can get oxygen. Flexible stems allow plants to move with currents and waves. They are supported by water around them.

Seaweed does not have roots, flowers, or leaves. Photosynthesize for food. Use a holdfast to attach to bottom. Get nutrients from water.

Phytoplankton: mm to 2mm in size. Much of marine life depends on them for food. Stay in upper or surface to get sunlight to photosynthesize.

Aquatic plants need nutrients like nitrates and phosphates. Washed into water from land or come from detritus – decaying bodies of dead plants and animals. Nutrients plentiful in spring from runoff and melting.

Human wastes, fertilizers and pollution sometimes cause too many nutrients in water. Causes growth of algae – another aquatic plant. An algae explosion, called an algae bloom can occur.

When algae die they fall to the bottom of water where they are decomposed by bacteria. Decomposition require oxygen – and oxygen from the habitat can be used up, killing plants and animals.

Aquatic Food Chains A sequence of feeding relationships between organisms.

Fishing can affect food chains. Fisheries catch larger and most in demand fish. Their population can fall. Other populations of fish may also decrease, or even increase as a result.