Section 3 – Ecological Communities

Producers and ConsumersEnergy: the ability to do work

Energy cannot be created or destroyed, only changed from one form to anotherSolar Energy – Thermal Energy – Absorbed by a

Beach or a Dark T-ShirtAll energy in the world remains constant (like the

amount of matter in the world)Primary Producer: an organism that can

capture energy from the sun or from chemicals and store it; also called autotroph

Energy from the SunPhotosynthesis: the process by which primary

producers use sunlight to convert carbon dioxide and water into sugars, releasing oxygen

Primary ProducersGreen PlantsAlgaeCyanobacteria

6CO2+6H2O+light energy ->C6H12O6(sugar)+6O2

Energy From ChemicalsChemosynthesis: the process by which

bacteria use energy stored in bonds of hydrogen sulfide to convert carbon dioxide and water into sugars

Deep Sea Vents – communities of organismsNo SunlightPrimary Producers use energy stored in Hydrogen

Sulfide H2S, to make Carbon Dioxide and Water

6CO2+6H2O+3H2S -> C6H12O6(sugar)+3H2SO4

ConsumersConsumer: an organism that relies on other

organisms for energy and nutrients; also called heterotroph

Cellular Respiration: the process by which organisms use oxygen to release the chemical energy of sugars, producing carbon dioxide and water

C6H12O6(sugar)+6O2 -> 6CO2+6H2O+energyOpposite of Photosynthesis

Herbivores, Carnivores, and Omnivores

Primary Consumers: organisms that consume producers, most are herbivoresHerbivore: an organism that eats plants

Secondary Consumers consume Primary Consumers, and so on. Most are carnivoresCarnivore: an animal that kills and eats other

animalsOmnivore: an animal that eats both plants

and animals

Detritivores and DecomposersDetritivore: an organism (e.g., a millipede or

soil insect) that scavenges the waste products or dead bodies of other community membersScavengers: large detritivores, like vultures

Decomposer: an organism (e.g., a fungus or bacterium) that breaks down nonliving matter into simple parts that can be taken up and reused by primary producers

Energy and BiomassTrophic Level: a rank in a feeding hierarchyPrimary Producers

Primary ConsumersSecondary Consumers

Tertiary ConsumersNo process of energy conversion is 100%

efficientGasoline burned in an engine, 14% is used

to move the car down the road, the rest is converted to thermal energy and released (“lost”) as heat.

Energy Transfer in Communities

10% Rule: each trophic level contains just 10% of the energy of the trophic level below it

Primary Producers = 100 calories10 calories available to level 21 calorie to level 30.1 calories to level 4

Eating lower trophic level food (fruits and veggies) rather than consumers (meat) decreases a person’s ecological footprint.

Numbers and BiomassBiomass: the total amount of living tissue in a

trophic levelGenerally, there are fewer organisms at higher

trophic levels.A mouse eats many plants in its lifetime.A snake eats many mice.A hawk eats many snakes.

Food Webs and Keystone Species

Food Chain: a linear series of feeding relationships

Energy transferred from species on lower trophic levels to species on higher trophic levels

Food WebsFood Web: a visual map of feeding

relationships and energy flowEcological systems far more complex than linear

chains

Keystone SpeciesKeystone Species: a species that has a strong or

wide-ranging impact on a communityThe wedge at the top of the arched stone structure,

if you take it out the whole thing collapses.Sea otters eat Urchins – Urchins eat Kelp

In the 1990’s, sea otter population declined Urchin population increased Kelp “forest” declined dramatically

Trophic Cascade: predators at high trophic levels (sea otters) indirectly help organisms at low trophic levels (kelp) by limiting populations at intermediate levels (urchins)