Download Ecology Summary - Austin Community College

Introduction to Ecology
Ecology = the study of organisms’ interactions with their environment & with each other
Biosphere = the total living world and all parts of the environment with which life directly interacts.
on earth, life is contained within a thin veneer of air, land and water near the earth’s surface
an Ecosystem is a recognizable portion of the biosphere with similar environmental conditions
supporting a characteristic and distinctive group of species
A. Ecosystem Structure: the structure of an ecosystem consists of both biotic and abiotic parts
1. Biotic Components = the living organisms; can study at several levels
a. Individual Organisms: directly affected by environmental factors such as climate, food, etc
individuals vary in their ability to survive and adapt to changing conditions (due to genes)
b. Populations: self contained group of interacting individuals of the same species
each population consists of dozens to thousands of individual organisms of a species
c. Communities: self contained group of all interacting species within an ecosystem; made up of
many populations
2. Abiotic Components = nonliving portions of biosphere
a. Lithosphere: solid: rocks, soil particles, sediments,etc
b. Hydrosphere: liquid: water in every form; oceans, groundwater, rivers, lakes, rainfall, ice
c. Atmosphere - gas: primarily N2 , O2 and CO2 gas
B. Ecosystem Functions: the function of an ecosystem involves all the interactions between abiotic
and biotic components
1. Biogeochemical Cycles: The continuous cycling of elements and molecules through the
ecosystem; all these interactions involve the cycling of matter through the ecosystem
 this matter cycling is powered by the flow of energy through the system
eg. the water cycle; eg. the nitrogen cycle; eg. the carbon cycle
the main source of energy for living organisms is organic molecules
2. Food Chains: within the Biotic part of an ecosystem, these organic molecules pass from 1 life
form to another creating Food Chains
a food chain always begins with producers, then to herbivores, then to carnivores
a. Producers: at the base of every food chain are the Producers
 organisms that use some form of outside energy to make the organic molecules they
need for food = Autotrophs
most producers use energy from sunlight to convert elements and simple molecules into
sugars, starches, etc =Photosynthesis
b. Consumers some members of a food chain cannot make their own food, they must eat
organic food to provide their energy = Heterotrophs
consumers that eat mostly plant material = herbivores
consumers that eat mostly animals=carnivores
consumers that eat dead organic matter=scavengers
consumers that are less selective eaters=omnivores
c. Decomposers: they eat dead organic material from all levels of the food chain; decomposers
play a critical role in the cycling of nutrients
3. Trophic Levels: food webs emphasize how ecosystems cycle specific nutrients through an
ecosystem. Trophic Levels emphasize how energy moves through an ecosystem and up the
food chain
every time energy food passes from one link in the food chain to another much of the stored
energy is lost; most food chains are fairly short
4. Productivity = the maximum amount of the sun’s energy that producers can extract is the
Productivity of that ecosystem
productivity depends on things like climate; the amount of sunlight, annual temperatures, etc.
productivity is also related to the amount of nutrients available
5. Diversity: is most often measured as the number of different species of organisms that are found
there; Diversity is an indication of how complex a particular ecosystem is
6. Symbioses = when two organism are found together and are interdependent; not the same as
predator/prey or food chain relationships; is a closer kind of dependence; ALL living
organisms form symbioses
a. Mutualism = both organisms benefit from the relationship
b. Commensalism = one organism benefits, the other neither benefits nor is harmed
c. Parasitism = one organism benefits at the other’s expense; ie. the other is harmed
Kinds of Ecosystems: the world’s ecosystems can be grouped into four broad categories:
A. Marine Ecosystems (~71% earth’s surface) eg. oceans, seas, intertidal, bays, estuaries, etc
*oceans dominate the biosphere: 71% of area of earth, 99% of volume of biosphere
*most stable overall (most of ocean is 2º C)
*much of the ocean gets NO light from the sun
*buoyancy of water reduces need for support
*less oxygen in water than in airneed more efficient extraction; eg. gills
B. Freshwater Ecosystems (<2% earth’s surface) eg. streams, rivers, lakes, ponds
*more variable than marine, not as much as land based
C. Terrestrial Ecosystems (~27% earth’s surface) land based, exposed to air
*harshest, most variable environment; eg temperature extremes, water availability
*need support to counteract gravity
*must reduce water loss or restricted to moist areas
*reproduction more elaborate, eggs must be kept moist:
D. Parasitic Habitats:
ectoparasites: live on the outside of host, often temporary
endoparasites: live inside host, usually permanent