Chapter 7 Fresh Water Ecosystems.docx - CHAPTER 7 Section 1...

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CHAPTER 7 Section 1 Fresh Water Ecosystems - The types of organisms in an aquatic ecosystem are mainly determined by the water’s salinity—the amount of dissolved salts the water contains. - Freshwater ecosystems include sluggish waters of lakes and ponds such as wetlands which is periodically underwater. Characteristics of Aquatic Ecosystems - Factors such as temperature, sunlight, oxygen, and nutrients determine which organisms live in which areas of the water. - Three groups of aquatic organisms include plankton, nekton, and benthos. - Plankton are organisms that cannot swim against currents, so they are called drifters. o Drifting plants, called phytoplankton , are food base for most aquatic ecosystems. o Drifting animals, which may be microscopic or as large as jellyfish, are called zooplankton . - Nekton are free-swimming organisms, such as fish, turtles, and whales. - Benthos are bottom-dwelling organisms, such as muscles, worms, or barnacles. Life in a Lake - Lakes and ponds can be structured into horizontal and vertical zones. - In the nutrient-rich littoral zone near the shores aquatic life is diverse and abundant. - Phytoplankton make their own food by photosynthesis. - Eventually, dead and decaying organisms reach the benthic zone, the bottom of a pond or lake, which is inhabited by decomposer, insect larvae, and clams.

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