Notes: Ecology Print Friendly and PDF

Question: What determines how many species live in a given place?


What determines how large each population can grow?


What is the relationship between sea otters, sea urchins and kelp forests?


ECOLOGY - the study of interactions among organisms with each other and with environment

BIOSPHERE - portion of planet where life exists


Species - individuals that can breed with one another

Population - all the individuals of the same species (ducks) in an area

Community - all the different species in an area (ducks + maple trees + dragonflies)

Ecosystem - the community plus the physical factors in an area (ducks + maple trees + dragonflies + temperature + soil + rainfall)

Biome - large area that has a particular climate, and particular species of plants and animals that live there (tundra)

Biosphere - the part of the earth that supports life

Ecological methods - how do we study it?


3-2 Energy Flow

Autotrophs (producers) - capture energy from environment and convert it into "food"

Heterotrophs (consumers) - must eat things

Detritivores / Decomposers

*SUNLIGHT is the main source of energy*

Photosynthesis - uses light energy to make "food"

Chemosynthesis - makes food from chemicals (some bacteria synthesize food in this way)



FOOD CHAINS AND FOOD WEBS - illustrate the flow of energy in an ecosystem

*Note the direction of the arrows, they indicate where the energy is going when one organism consumes another.
*Each step in a chain or web is called a TROPHIC LEVEL

Identify the primary, secondary and tertiary consumers on the food web.

food web

Ecological Pyramids

Energy Pyramid

Pyramid of Numbers and Pyramid of Biomass

productivity biomass

Consider the kelp forest ecosystem to answer these questions.

What determines how many species live in a given place?

And, what determines how large each population can grow?

3.3 Biogeochemical Cycles

(biology + geology + chemical)

matter is not used up, it is transformed, the same molecules are passed around (see images in your book)

Water Cycle

ground water
transpiration (from plants)
evaporation (from bodies of water)
precipitation (from clouds)

water cycle

Nutrient Cycles

nutrients = all the chemical substances needed to maintain life
body's chemical building blocks
carbon, nitrogen phosphorous

Carbon Cycle

Respiration (breathing of animals)
Combustion (burning)
Photosynthesis (uses CO2 and converts to oxygen)

Nitrogen Cycle

Nitrogen is a fertilizer for plants
78% of the air is made of nitrogen

Nitrogen Fixation - Bacteria take nitrogen from the air and convert to a form used by plants

Phosphorous Cycle

Part of DNA
Stays mostly in land and rock (not the atmosphere)


Primary Productivity - rate at which matter is created by producers

Lots of plants = high productivity

Limiting Nutrient - what limits the amount of productivity (water, light, nitrogen)

Fertilizer adds nitrogen to increase growth
Nitrogen enters water systems --> causes algal blooms