The Biosphere Chapter 3 Dr. Donna Howell Biology I Blacksburg High School
Ecology • Ecology is the study of interactions among organisms and between organisms and their environment. • The biosphere contains the combined portions of the planet in which all life exists, and includes land, water and air.
Levels of Organization • Organisms in the biosphere range in complexity from a single individual to an entire biosphere.
Energy Flow • Sunlight is the main energy source for all life on Earth. • There are two types of organisms with regards to how they get their energy: • Autotrophs – can produce their own food from the Sun • Heterotrophs – cannot produce their own food from the Sun
Autotrophs • Some autotrophs get their energy through the process of photosynthesis, getting their energy from the Sun. • Other autotrophs get their energy through the process of chemosynthesis, getting their energy from chemical bonds of inorganic molecules.
Consumers • Another name for heterotrophs is consumers. • There are different types of consumers: • Herbivores – obtain energy by eating plants • Carnivores – obtain energy by eating animals • Omnivores – obtain energy from both plants and animals • Detritivores – obtain energy from dead plant and animal matter
Consumers • Another important group of heterotrophs, or consumers, are the decomposers. • These organisms break down organic matter, and contribute to the “circle of life.” • Examples are bacteria and fungi.
Feeding Relationships • Energy flows through an ecosystem in one directions, beginning with the Sun. • Then goes to producers, and then to consumers.
Food Chains • A food chain is a series of steps showing energy flow among organisms.
Food Webs • A food web shows all of the food chains in an ecosystem, and links them together into a series of feeding relationships.
Trophic Levels • Each step in a food chain or food web is called a trophic level. • Producers make up the first trophic level. • Primary, secondary, and tertiary consumers make up all other levels. • Each consumer depends on the trophic level below it for its energy.
Ecological Pyramids • The amount of energy or matter in an ecosystem can be represented by an ecological pyramid. • An ecological pyramid is a diagram that shows the relative amounts of energy or matter within each tropic level.
Ecological Pyramids • Three types of ecological pyramids: • Energy pyramids • Biomass pyramids • Pyramid of numbers
Energy Pyramid • This pyramid shows that only about 10 percent of the energy available within one trophic level is transferred to organisms at the next trophic level.
Biomass Pyramid • This pyramid shows the total amount of living tissue within a given trophic level. • Expressed in terms of grams of organic matter per unit area. • Represents the amount of potential food available for each trophic level in an ecosystem.
Pyramid of Numbers • This pyramid is based on the n umbers of individual organisms at each trophic level.
Cycles of Matter • Unlike the one-way flow of energy in an ecosystem, matter is recycled within and between ecosystems. • These cycles are biogeochemical cycles.