Section 3 – Ecological Communities

1. Section 3 – Ecological Communities

2. Producers and Consumers • Energy: the ability to do work • Energy cannot be created or destroyed, only changed from one form to another • Solar Energy – Thermal Energy – Absorbed by a Beach or a Dark T-Shirt • All 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

4. Energy from the Sun • Photosynthesis: the process by which primary producers use sunlight to convert carbon dioxide and water into sugars, releasing oxygen • Primary Producers • Green Plants • Algae • Cyanobacteria • 6CO2+6H2O+light energy ->C6H12O6(sugar)+6O2

6. Energy From Chemicals • Chemosynthesis: 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 organisms • No Sunlight • Primary Producers use energy stored in Hydrogen Sulfide H2S, to make Carbon Dioxide and Water • 6CO2+6H2O+3H2S -> C6H12O6(sugar)+3H2SO4

7. Consumers • Consumer: 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+energy • Opposite of Photosynthesis

8. Herbivores, Carnivores, and Omnivores • Primary Consumers: organisms that consume producers, most are herbivores • Herbivore: an organism that eats plants • Secondary Consumers consume Primary Consumers, and so on. Most are carnivores • Carnivore: an animal that kills and eats other animals • Omnivore: an animal that eats both plants and animals

12. Detritivores and Decomposers • Detritivore: an organism (e.g., a millipede or soil insect) that scavenges the waste products or dead bodies of other community members • Scavengers: 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

15. Energy and Biomass • Trophic Level: a rank in a feeding hierarchy • Primary Producers • Primary Consumers • Secondary Consumers • Tertiary Consumers • No process of energy conversion is 100% efficient • Gasoline 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.

17. Energy Transfer in Communities • 10% Rule: each trophic level contains just 10% of the energy of the trophic level below it • Primary Producers = 100 calories • 10 calories available to level 2 • 1 calorie to level 3 • 0.1 calories to level 4 • Eating lower trophic level food (fruits and veggies) rather than consumers (meat) decreases a person’s ecological footprint.

19. Numbers and Biomass • Biomass: the total amount of living tissue in a trophic level • Generally, 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.

21. 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

23. Food Webs • Food Web: a visual map of feeding relationships and energy flow • Ecological systems far more complex than linear chains

30. Keystone Species • Keystone Species: a species that has a strong or wide-ranging impact on a community • The 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)