How do microorganisms maintain the health of ecosystems?

2. How do microorganisms maintain the health of ecosystems? • Some microorganisms are decomposers that break down organic matter into smaller pieces, eventually releasing raw nutrients back to the ecosystem. • Some bacteria convert nitrogen and other nutrients to forms that can be used by primary producers (plants and other photosynthetic organisms). • Specialized “oil-eating” bacteria help restore ecosystems following oil spills. • Mycorrhizal fungi seem to help ecosystems recover following disturbances. 4. Use Analogies How are microorganisms similar to recycling plants?

3. How do microorganisms disrupt the health of ecosystems? • Introduced fungi devastated populations of the American Chestnut in the early 1900s. The death of the chestnut trees affected forest ecosystems throughout the eastern United States. • The nuts of the chestnut tree were consumed by both humans and animals. • Chestnut leaves provided much nutrient content to the forest ecosystem. • Chestnut trees were replaced by oak, hickory, red maple, and sugar maple trees throughout their range. 5. Infer The Chestnut blight fungus was accidentally introduced to the United States around 1900. Why might microorganisms be most disruptive when introduced to an ecosystem where they are not usually found? (contd.)

4. How do microorganisms disrupt the health of ecosystems? Populations of some usually harmless aquatic microorganisms, including dinoflagellates and the photosynthetic protist Euglena (seen here), can grow exponentially following an influx of nutrients. Such responses to added nutrients are called algal blooms, andthey can be very harmful to ecosystems. Algal blooms can block sunlight and disrupt photosynthesis. Blooms of dinoflagellates, called red tides,release toxins into the ecosystem. Increased rates of decomposition following very large blooms can result in dead zones, areas devoid of oxygen that are inhospitable to multicellular life.

5. Why couldn’t you survive a day • without bacteria? • They process our wastes and make them usable again. Without them – nothing would rot. • They purify our water. • Keep our soils productive • Synthesize vitamins in our intestines • Convert our food into useful sugars and polysaccharides • Wage war on alien microbes that enter our digestive system • Pluck nitrogen from the air and convert it into useful nucleotides and amino acids for us.