Chapter 3

1. Chapter 3 The Biosphere

2. Ecology • The scientific study of interactions among organisms and between organisms and their environment, or surroundings. • Biosphere: contains the combined portions of the planet in which all of life exists, including land, water, and air. • Interactions within the biosphere produce a web of interdependence between organisms and the environment in which they live.

3. Species: a group of closely related organisms that can breed and produce healthy, fertile, offspring. Populations: groups of individuals that belong the same species and live in the same area. Communities: different populations that live together in a defined area. Ecosystem: a collection of all of the organisms that live in a particular place, together with their nonliving environment. Biome: a group of ecosystems that have the same climate and similar communities. Biosphere: the largest level of study. Levels of Organization that Ecologists Study

4. Ecological Methods • Scientists conduct ecological research using 3 basic approaches: • Observing: Ask an ecological question • Experimenting: Test the hypothesis which answers the question. • Modeling: Many ecological events occur over long periods of time so ecologists make models to gain insight into complex events such as global warming. Many models consist of mathematical formulas based on data which allow for predictions.

5. Energy Flow • Sunlight is the main energy source for life on Earth. • Less than 1% of all of Sun’s energy that reaches the surface of the Earth is used by living things.

6. Autotrophs (Producers) • Use energy from the environment (usually the sun) to make food (organic compounds, like glucose). • Ex. Plants, some algae, and some bacteria. • Photosynthesis: the process by which autotrophs use sunlight to convert CO2 and H2O into glucose (C6H12O6) and O2. • This process is responsible for adding O2 to- and removing CO2 from-Earth’s atmosphere.

7. Chemosynthesis • Some autotrophs can produce food in the absence of light. • These autotrophs rely on energy within the chemical bonds of inorganic molecules such as hydrogen sulfide H2S. • When organisms use chemical energy to produce carbohydrates, the process is called chemosynthesis. • Ex. Bacteria living in volcanic vents and hot springs in Yellowstone Park and other remote locations.

8. Heterotrophs: (Consumers) • Organisms that rely on other organisms for their energy and food supply are heterotrophs. • Herbivores: Cows • Eat plants • Carnivores: Lions • Eat other animals • Omnivores: Humans • Eat both plants and animals • Detritivores: Earthworms • Eat dead plant and animal matter • Decomposers: Mushrooms • Break down organic matter

9. Food Chains • The energy stored by producers can be passed through an ecosystem along a food chain, a series of steps in which organisms transfer energy by eating and being eaten. • Ex: grass → antelope → coyote

10. Food Webs • The feeding relationships among various organisms in an ecosystem that form complex interactions. • A food web links all of the food chains in an ecosystem together. • Food Web Activity

11. Trophic Levels • Each step in a food chain or food web is a trophic level. • Producers make up the first trophic level. • Consumers make up the second, third, or higher trophic levels. • Each consumer depends on the trophic level below it.

13. Ecological Pyramids • Ecological pyramids show the decreasing amounts of energy, living tissue, or number of organisms at successive feeding levels. • The pyramid is divided into sections that represent trophic levels. • The area of each level represents the amount of energy or matter remaining at that level. • 3 Types: • Energy Pyramid • Biomass Pyramid • Pyramid of Numbers

14. Energy Pyramid • Shows the amount of energy available at each trophic level. • Organisms use about 10% of this energy for life processes. • The rest is lost as heat. • Percentage of light or chemical energy available at each trophic level: • Producers (Plants): 100% • Primary consumers (cows): 10%. • Secondary consumers (humans): 1%. • Tertiary consumers (lions): 0.1% and so on.

15. Biomass Pyramid • Represents the amount of living organic matter at each trophic level • Typically the greatest biomass is at the base of the pyramid. • Biomass is usually measured in grams. • A biomass pyramid represents the amount of potential food available for each trophic level in an ecosystem.

16. Pyramid of Numbers • Shows the relative number of individual organisms at each trophic level.

17. Cycles of Matter • Unlike the one-way flow of energy (non-recyclable), matter is recycled within and between ecosystems. • 3 cycles we will talk about: • The Water Cycle • The Carbon Cycle • The Nitrogen Cycle

18. Water moves between the ocean, atmosphere, and land. Water molecules enter the atmosphere as water vapor when they evaporate from the ocean, or other bodies of water. During the day the sun heats the atmosphere. As the warm, moist air rises, it cools causing it to condense into droplets that form clouds. When the droplets become large enough, the water returns to Earth’s surface in the form of precipitation: rain, snow, sleet, or hail. On land, much of the precipitation runs along the surface of the ground until it enters a river or stream that carries the runoff back to a lake or ocean. The Water Cycle

20. The Carbon Cycle • 4 main processes move carbon through its cycle: • Photosynthesis, respiration, decomposition. • Photosynthesis: Plants (chloroplasts) • 6CO2 + 6H2O + sunlight → C6H12O6 + 6O2 • Respiration: Plants and animals (mitochondria) • C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP energy • Erosion and volcanic activity. • Burial and decomposition of dead organisms and their conversion under pressure into coal and petroleum. • Mining, cutting, and burning forests and burning fossil fuels.

21. The Nitrogen Cycle • Organisms require nitrogen for making amino acids, which are used to make protein. • Many forms of nitrogen exist on Earth: • Nitrogen gas (N2) (78% of Earth’s atmosphere) • Ammonia (NH3) • Nitrate ions (NO3-) • Nitrite ions (NO2-)

22. The Nitrogen Cycle

23. Only certain bacteria can use N2 gas directly. These bacteria are found in the roots of plants called legumes. These bacteria convert N2 gas to ammonia (NH3) in a process called nitrogen fixation. Other bacteria convert ammonia into nitrates (NO3-) and nitrites (NO2-). Once these products are available, producers (plants) can use them to make proteins. Consumers then eat the producers and reuse the nitrogen to make their own proteins. When organisms die decomposers turn nitrogen to the soil as ammonia. Other soil bacteria convert nitrates into nitrogen gas in a process called denitrification, releasing nitrogen into the atmosphere again. The Nitrogen Cycle (continued)