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Ecology is the study of interactions between organisms (biotic part) and their nonliving environment (abiotic factors)

Biotic factors includes plants, animals, fungi, & microorganisms. They may be producers, consumers, or decomposers.

Abiotic factors include climate, soil, temperature, water, air, sunlight, humidity, pH, and atmospheric gases.

Habitat is the place a plant or animal lives, while its niche is its total way of life.

Life is organized into levels:

Organism (any single living thing)


            Population (members of the same species living in one place)


                    Community (all the populations living in an area)


        Ecosystem (community living in a similar habitat such as a forest)


Biomes (ecosystems covering wide areas & with similar climates & organisms)


Biosphere ( all the living & nonliving things on earth)


Make their own food through photosynthesis or chemosynthesis
Includes plants, algal protists, & some bacteria


Can’t make their own food
May be herbivores (feed only on plants), carnivores (feed only on animals), or omnivores (feed on plants & animals)


Break down dead plants & animals (detritus)
Recycle nutrients
Called detritivores
Include fungi & bacteria

Sunlight is the ultimate energy for all life on earth, but only producers can get their energy directly from the sun.


Trophic levels are feeding levels of producers & consumers in an ecosystem:

1st Trophic Level is producers that use sunlight directly
2nd Trophic Level includes herbivores that feed directly on plants
Higher Trophic Levels are carnivores feeding on each other


Food chains & food webs:

Chains show who eats whom in an ecosystem.
Webs are made up of several food chains.
Always begin with producers absorbing sunlight.
Producers store energy in the chemical bonds of the food they make.
Stored energy is passed to consumers when they eat producers or other consumers.
Some energy is lost at each trophic level as heat when consumers “burn” food during cellular respiration.
Both energy & nutrients must move through an ecosystem.

Three main elements that must move through an ecosystem:


Water or Hydrologic Cycle:

Cells are 70 – 90% water
Water is needed for metabolic processes
Water is most important for terrestrial organisms because of desiccation (drying out)

Steps in the water Cycle:

Evaporation                                         Transpiration
(water loss from lakes, rivers, oceans…)          (water loss from plant leaves)

     ¯                                ¯

(water vapor forms clouds)


(water returns to earth as sleet, rain, snow…)


Surface Runoff
(returns water to bodies of water or to groundwater)

Carbon Cycle:

Consists of photosynthesis, cellular respiration, & decomposition
Begins with producers taking carbon dioxide from the air during photosynthesis
Carbon dioxide used in cellular respiration
Decomposing plants and animals return Carbon to the soil

Carbon Cycle Steps:

Plant leaves take carbon dioxide from air


Plants store carbon in carbohydrates or starches


Plants & animals release carbon dioxide back into the air
(cellular respiration)


Decomposers return carbon to environment


Needed by all organisms
Used to make proteins & nucleic acids (DNA & RNA)
Air made up of 80% nitrogen
Only Cyanobacteria & Rhizobium bacteria can use nitrogen directly from the air (nitrogen fixation)
Bacteria found in the soil & on the roots of legumes (beans, peas …)

Steps in the Nitrogen Cycle:

Cyanobacteria & Rhizobium take nitrogen from air
(nitrogen fixation)


Convert nitrogen gas into ammonia


Nitrifying bacteria in soil change ammonia into nitrates


Plants can absorb & use nitrates to make proteins


Consumers eat plants & get proteins containing nitrogen


Decomposers break down dead organisms & return nitrogen to air
(called ammonification)


Anaerobic bacteria in soil release nitrogen from nitrates into air
(called denitrification)

Three main types of ecosystems:

Terrestrial (land)
Freshwater (rivers, ponds, lakes …)
Marine (oceans & seas)

Terrestrial ecosystems are divided into 7 biomes with similar climates & organisms

Seven Terrestrial Biomes:

Tropical Rain Forest (jungle)
Savanna (tropical grasslands)
Deciduous Forest
Taiga (coniferous forest)


Cold & dark most of the year
Includes the arctic
Permafrost is the top layer of soil that thaws & in which plants grow
No trees, but sedges & grass, mosses, & lichens
Many migratory animals
Lemmings & ptarmigans are year round residents
Approximately 20 cm annual rainfall



  • Coniferous forest
  • Extends across northern Eurasia & North America
  • Contains conifers or evergreens (spruce, cedar, fir, pine …)
  • Needle like leaves withstand weight of snow
  • Bear, deer, moose, wolves, mountain lions …
  • Sequoia or redwood (largest conifer) grows here
  • Bristle cone pine oldest living conifer found here

Coniferous Forest

Temperate Deciduous Forest:

  • South of taiga in North America, eastern Asia, & Europe
  • High annual rainfall (75-150 cm)
  • Moderate temperatures
  • Well-defined seasons of about equal length
  • Trees loose leaves in winter (deciduous)
  • Show stratification (plant layers):
    1. Canopy – broad leaf deciduous trees forming uppermost layer
    2. Under story – shrubs
    3. Forest Floor – herbaceous plants
  • Songbirds, deer, rabbits, foxes, squirrels, frogs 7 toads, lizards …

Temperate Deciduous Forest

Tropical Rain forest:

  • Near equator
  • Warm climate (20 -25 degrees C)
  • Plentiful rainfall (190 cm/year)
  • Contains the greatest diversity of plants & animals
  • Insects, monkeys & apes, snakes, tropical birds, leopards…
  • Animals & plants brightly colored
  • Poor soil for agriculture



  • Mostly grasses with a few trees due to less rainfall
  • Moderate climates
  • Good for agricultural crops
  • Grazing & burrowing animals dominate
  • Also called prairies



  • Tropical grasslands
  • Warm climate & rainy season
  • Antelope, zebra, lions, wildebeests, hyenas, elephants…
  • Suffer from floods & drought



  • Low annual rainfall
  • Subject to strong winds
  • Days usually hot & nights cold
  • Sahara desert is without vegetation
  • Succulents such as cacti & other water storing plants
  • Most animals nocturnal
  • Lizards, snakes, roadrunners, insects, tarantula, hawks, rodents, coyotes…


Aquatic Biomes:

  • May be freshwater or saltwater
  • Wetlands near oceans have brackish water (mixture of fresh & salt waters)
  • Part of the part water or hydrologic cycle
  • Often polluted by man’s activities

Lakes & Rivers:

  • Freshwater
  • Oligotrophic lakes are nutrient poor (catfish, carp…)
  • Eutrophic lake are nutrient rich (trout, bass…)
  • Deep lakes have layers or strata where different plants & animals live
  • Phototropic organisms in upper layers for light
  • Estuary at mouth of river contains brackish water

Ocean Zones:

  • Intertidal zone
    1. Along shoreline
    2. Wave action
    3. Lots of light so many producers
    4. Starfish, sand dollars…
  • Neritic Zone
    1. Ocean water above continental shelf
    2. Coral reef found here
    3. Surrounds continents & receives light in upper layers
  • Oceanic Zone
    1. Beyond continental shelf
    2. Deepest area (up to 7 miles)
    3. Bottom doesn’t receive light so animals adapted to darkness (many produce their own light, feed on other animals…)
    4. Deepest area called abyss
    5. Upper area gets light & called the photic zone (lots of seaweed here)
    6. Floaters called plankton (microscopic organisms)
    7. Swimmers such as fish called nekton
    8. Bottom dwellers called benthos