Roles of Living Things and Ecosystem Structure

Objective Identify the roles of producers, consumers, and decomposers. Explain the concept of trophic level. Infer why the number of organisms at a given trophic level is smaller that in the preceding level. Describe food chains and the food web. Examine how ecosystems structure is related to populations changes and the transfer of pollutants. Predict how introducing a new organisms into an ecosystem may alter the food chain and affect existing populations.

A few reminders: organisms Organisms are divided in trophic categories : –Producers –Consumers –Decomposers Among these organisms, which ones are : –Autotrophs –Heterotrophs

Energy Roles Producers/Autotrophs : An organism that can make its own food. Photosynthesis Photosynthesis Equation: 6CO 2 + 6H 2 O + sunlight > 6O 2 + C 6 H 12 O 6

Consumer/Heterotrophs:An organism that obtains energy by feeding on other organisms is a consumer. Cellular Respiration Equation: 6O 2 + C 6 H 12 O > 6CO 2 + 6H 2 O + 38ATP’s

The Trophic Levels A trophic level is a layer in the structure of feeding relationships in an ecosystem. Producers make the first trophic level. Consumers make up the second, third, fourth, and fifth level of the trophic levels.

This energy pyramid demonstrates three trophic levels and shows many trees & shrubs providing food and energy to giraffes. Note that as we go up, there are fewer giraffes than trees & shrubs and even fewer lions than giraffes. As we go further along a food chain, there are fewer and fewer consumers. In other words, a large mass of living things at the base is required to support a few at the top. Many herbivores are needed to support a few carnivores.

Ecosystems Structure A food chain is a series of events in which one organism eats another and obtains energy. The bottom of a food chain consists of plants and ends with the highest consumer. A food web consists of the many overlapping food chains in an ecosystem. Increasing and decreasing of organisms in a food chain or food web can alter an ecosystem. Example: If plants were to die off, then the consumers above it will then die off. Cause and Effect

Food webs provide a more stable ecosystem because it provides more food options. If an organisms were to be removed for whatever reason. The organism that feeds on it will not starve if it can feed on something else. Biological magnification is when increasing concentration of a pollutant is transferred from one trophic level to the next. Example: Mercury

4-3 Energy in the Ecosystem Objective: Investigate the movement of energy through an ecosystem. Define ecological pyramid, and explain its relationship to energy in an ecosystem. Notes: Sunlight provides the energy necessary for an ecosystem to exist. Plants convert sunlight energy into chemical energy. The transfer of this energy from producers to higher level consumers is called an ecological pyramid. An ecological pyramid is a diagram that shows the relative amount of energy in different tropic levels in an ecosystem.

Each level of ecological pyramid is called a trophic level An ecological pyramid shows three things: 1. Energy 2. biomass 3. # of organisms in a food web is what moves up an ecological pyramid, but food is made of matter. There are four essential elements that is found in food. 1. Carbon 2. Hydrogen 3. Nitrogen 4. Oxygen

4-4 Cycles of Matter Objectives: Describe the chemical composition of human body. Explain the water cycle, the carbon cycle, and the nitrogen cycle. Compare and contrast evaporation and transpiration. Infer the effects that carbon dioxide produced by the burning of fossil fuels with have on the carbon cycle. Notes: Energy from the sun or gasoline can not be recycled. Matter is recycled in the form of atoms over and over again in the ecosystem. Matter is recycled from producer to consumer to decomposer.

Recycling of matter happens in three ways: 1. The Water Cycle 2. The Carbon and Oxygen Cycle 3. Nitrogen Cycle Water Cycle The water cycle is the continuous process by which water moves from the Earth’s surface to the atmosphere and back. The processes of evaporation, condensation, and precipitation make up the water cycle. 1. The process by which molecules of liquid water absorb energy and change to the gas state is called evaporation. 2. The process by which a gas changes to a liquid is called condensation. 3. Precipitation is when water droplets gather together to form clouds and eventually rain, snow, and sleet.

The Carbon and Oxygen CycleWater, carbon, and oxygen are necessary for life. Carbon is the building blocks of all living things.Producers or plants take in CO 2 from the atmosphere during photosynthesis. Plants use the carbon from the carbon dioxide to produce sugars and starches. These sugars and starches are eaten by the first level consumers. The oxygen from carbon dioxide is separated during photosynthesis and released from the plant. Other organisms take in oxygen and release CO