THE EARTH’S LIFE SUPPORT SYSTEMS The biosphere consists of several physical layers that contain: Air Water Soil Minerals Life

Biosphere (Ecosphere) Atmosphere Membrane of air around the planet. Stratosphere Lower portion contains ozone to filter out most of the sun’s harmful UV radiation. Hydrosphere All the earth’s water: liquid, ice, water vapor Lithosphere The earth’s crust and upper mantle.

What Sustains Life on Earth? Solar energy The cycling of matter (atoms, ions, molecules) Gravity

Life depends on these three interconnected factors.. The one way flow of high-quality Energy from the sun through materials and living things in food webs….then into the environment as low quality energy ( mostly heat) and ….eventuallly back into space as heat. The earth is an OPEN system for energy. The Cycling of matter through parts of the biosphere. The earth is a CLOSED system for matter. Gravity: which allows the planet to hold on to its atmosphere and causes the downward movement of chemicals in the matter cycles.

What Happens to Solar Energy Reaching the Earth? Lights and warms planet. Supports photosynthesis Powers the cycling of matter Drives the climate and weather systems that distributes heat and fresh water over the Earth’s surface.

ECOSYSTEM COMPONENTS Life exists on land systems called biomes and in freshwater and ocean aquatic life zones.

Do Ecosystems have distinct boundaries? Ecotone A region containing a mixture of species from adjacent ecosystems and often species not found in either of the bordering ecosystems. A transitional zone between ecosystems

Nonliving and Living Components of Ecosystems Ecosystems consist of nonliving (abiotic) and living (biotic) components.

Two Secrets of Survival: Energy Flow and Matter Recycle An ecosystem survives by a combination of energy flow and matter recycling.

Aerobic and Anaerobic Respiration: Getting Energy for Survival Organisms break down carbohydrates and other organic compounds in their cells to obtain the energy they need. This is usually done through aerobic respiration. The opposite of photosynthesis

Aerobic and Anaerobic Respiration: Getting Energy for Survival Anaerobic respiration or fermentation: Some decomposers get energy by breaking down glucose (or other organic compounds) in the absence of oxygen. The end products vary based on the chemical reaction: Methane gas Ethyl alcohol Acetic acid Hydrogen sulfide

Producers or Autotrophs Make their own food from compounds obtained from their environment. Examples: green plants on land, algae and plants near shorelines, phytoplankton in open water.

Producers: Most producers capture sunlight to produce carbohydrates by photosynthesis. But…..Some organisms such as deep ocean bacteria draw energy from hydrothermal vents and produce carbohydrates from hydrogen sulfide (H2S) gas . (chemosynthesis)

Photosynthesis: A Closer Look Chlorophyll molecules in the chloroplasts of plant cells absorb solar energy. This initiates a complex series of chemical reactions in which carbon dioxide and water are converted to sugars and oxygen. Figure 3-A

Consumers: Eating and Recycling to Survive Consumers (heterotrophs) get their food by eating or breaking down all or parts of other organisms or their remains. Herbivores Primary consumers that eat producers Carnivores Primary consumers eat primary consumers Third and higher level consumers: carnivores that eat carnivores. Omnivores Feed on both plant and animals.

Decomposers and Detrivores Decomposers: Recycle nutrients in ecosystems. Detrivores: Insects or other scavengers that feed on wastes or dead bodies. Figure 3-13

ENERGY FLOW IN ECOSYSTEMS Food chains and webs show how eaters, the eaten, and the decomposed are connected to one another in an ecosystem. Figure 3-17

Food Webs Trophic levels are interconnected within a more complicated food web. 10% transfer of usable energy from one trophic level to next. “Ecological efficiency” Figure 3-18

Energy Flow in an Ecosystem: Losing Energy in Food Chains and Webs Ecological efficiency: percentage of useable energy transferred as biomass from one trophic level to the next. Figure 3-19

Energy Flow in an Ecosystem: Losing Energy in Food Chains and Webs In accordance with the 2nd law of thermodynamics, there is a decrease in the amount of energy available to each succeeding organism in a food chain or web. The large loss in energy between successive trophic levels explains why food chains rarely have more than 4 or 5 levels and why so few top carnivores. Energy flow pyramids explain why the earth can support more people if they eat at lower trophic levels.

Energy Flow in an Ecosystem: Losing Energy in Food Chains and Webs Ecological efficiency: percentage of useable energy transferred as biomass from one trophic level to the next. Figure 3-19

Productivity of Producers: The Rate Is Crucial Gross primary production (GPP) Rate at which an ecosystem’s producers convert solar energy into chemical energy as biomass. Figure 3-20

Net Primary Production (NPP) NPP = GPP – R Rate at which producers use photosynthesis to store energy minus the rate at which they use some of this energy through respiration (R). Figure 3-21

What are nature’s three most productive and three least productive systems? Figure 3-22

How much of the World’s Net rate of Biomass production do we use? Biomass- the dry weight of all organic matter contained in the organisms at each trophic level in a food chain or web. Estimated humans now use, waste or destroy about 27% of the earth’s total potential NPP and 40% of the NPP of the planet’s terrestrial ecosystems. How does the above affect other species?