Trophic structure

Question 1

Describe energy transfer in terms of food chains and webs, and trophic (feeding) levels.

Answer 1

trophic structure; energy passed along food chains (too simple) or food webs (more realistic

Question 2

Know examples of a simple food chain to 5 trophic levels for both aquatic and terrestrial ecosystems. Be able to label each trophic level (1y producer, 1y consumer, etc.).

Answer 2

AQUATIC:
1y producer - phytoplankton
1y consumer - zooplankton
2y consumers - carnivores or omnivores
ex: small fish
3y consumers - “top” carnivores
ex: seals
*keystone predators
ex: orcas

TERRESTRIAL:
1y producer - plants
1y consumer - herbivores
ex: grasshopper
2y consumers - carnivores or omnivores
ex: mouse
3y consumers - “top” carnivores
ex: snake
*keystone predators
ex: hawk

Question 3

trophic level top to bottom

Answer 3

keystone predators
tertiary consumers → top “carnivores”
secondary consumers → carnivores, more than likely omnivores
primary consumers → herbivores, heterotroph (grazers/zooplankton)
primary producers → autotroph (plants & phytoplankton)

Question 4

What is a keystone predator (fig. 20.21)? How are they important?

Answer 4

decreases the density of the strongest competitor in communities; helps maintain species diversity
ex: hawk, orca, sea otter

Question 5

Understand concepts of transfer efficiency and production/trophic pyramids. How do they apply to different organisms (fig. 20.28 and 20.29)?

Answer 5

transfer efficiency → amount of energy that transfers from one trophic level to the next (on average only about 10%)

Question 6

How does transfer efficiency apply to different organisms ?

Answer 6

100 pounds of primary producer supports 10 pounds of a herbivore and about 1 pound of carnivores

Question 7

Define detritus. What is the importance of decomposers and detritivores? Give examples (p.433).

Answer 7

detritus → dead organic matter
decomposers → nutrient regeneration (usually small stuff like bacteria and fungi)
detritivores → larger decomposers (scavengers, vultures, rodents, ants, earthworms)
EX: dead plants and animals; feces and urine

Question 8

biogeochemical cycle

Answer 8

all ecosystems depend on the recycling of essential nutrients

Question 9

Biogeochemical cycles for: carbon

Answer 9

-Living organisms: after water, a living cell is mostly made up of carbon based molecules (sugar: C6H12O6)
-Abiotic reservoir: atmosphere in the form of CO2
-Cycled: globally

Question 10

Biogeochemical cycles for: nitrogen

Answer 10

-Living organism: amino groups (are made of nitrogen and hydrogen) → amino acids; and DNA → nitrogenous bases
-Abiotic reservoir: atmosphere in the form of N2 gas
-Cycled: globally

Question 11

Biogeochemical cycles for: phosphorus

Answer 11

-Living organism: found in phosphate group → plasma membrane: phospholipid bilayer; ATP → triphosphate tail; DNA → sugar phosphate backbone
-Abiotic reservoir: from the weathering of rocks (PO4 3-)
-Cycled: locally

Question 12

Biogeochemical cycles for: water

Answer 12

-Living organism: cells 70-95% water
-Abiotic reservoir: oceans
-Cycled: globally