What is ecology?

Ecology Ecology = scientific study of the interactions among organisms and between organisms and their environment (surroundings) Each organism plays a role in their “household” (the environment) = ‘niche’ Interactions produce a web of interdependence between organisms and the environment The environment and interactions are constantly changing (dynamic)

Levels of Organization-big->small Biosphere = portions of the planet where all life exists (land, water, air, etc) Biome = group of ecosystems that have the same climate and similar dominant communities Ecosystem = collection of all the organisms that live in a particular place together with their nonliving (physical) environment Communities = different populations that live together in a defined area Populations = groups of individuals that belong to the same species and live in the same area Species = group of organisms so similar that they can breed and produce fertile offspring Individual = one member of a specific species

Figure 3-2 Ecological Levels of Organization Section 3-1 Go to Section:

Energy flow Every organism needs energy to power life’s processes Energy is obtained through interactions with the environment The flow of energy through an ecosystem is one of the most important factors that determines the system’s capacity to sustain life

Populations INCREASES– immigration; higher birth rate than death rate DECREASES– emmigration; higher death rate than birth rate

Producers Sunlight is the main energy source of life on Earth Only plants & certain bacteria can capture energy from sunlight or inorganic chemicals and use that energy to produce food = autotrophs Autotrophs are also called producers, Some autotrophs use light energy to convert carbon dioxide & water into oxygen & sugars through the chemical reaction photosynthesis (plants/algae) Some use chemical energy to produce carbohydrates in absence of light through chemosynthesis (bacteria)

Consumers Must acquire energy from other organisms = heterotrophs Heterotrophs are also called consumers Herbivores = eat only plants Carnivores = eat only animals Omnivores = eat both plants and animals Detritivores = eat plant/animal remains and other dead matter called detritus Decomposers = break down organic matter

Feeding Relationships Energy flows through an ecosystem in one direction Energy flows from the sun or inorganic compounds to autotrophs (producers) and then to various heterotrophs (consumers)– FOOD CHAIN Feeding relationships among organisms in an ecosystem usually form a network of complex interactions shown as a food web Each step in a food chain/web = trophic level

Food Chain

Food Web Section 3-2 Go to Section:

Trophic Levels Each step in a food chain or web is a trophic level. The first trophic level is the producers. The second trophic level is the consumers (herbivores). The third and fourth levels are more consumers (omnivores and the carnivores).

Ecological Pyramids The amount of energy or matter in each trophic level of a food chain/web of an ecosystem can be represented by an ecological pyramid Energy pyramid = only about 10% of the energy stored in one trophic level is passed on to the next higher level, because most of the energy is used for life processes and some is released into the environment as heat Biomass pyramid = potential total amount of living tissue within a given trophic level (grams per unit area) for each trophic level in an ecosystem Pyramid of numbers = relative number of individual organisms at each trophic level

Ecological Pyramids Section 3-2 Energy Pyramid Shows the relative amount of energy available at each trophic level. Organisms use about 10 percent of this energy for life processes. The rest is lost as heat. Pyramid of Numbers Shows the relative number of individual organisms at each trophic level. Biomass Pyramid Represents the amount of living organic matter at each trophic level. Typically, the greatest biomass is at the base of the pyramid. Go to Section: