Trophic positions

Question 1

sea urchins + starfish

Answer 1

clear away barrens of kelp.

allows starfish to feast on brittle stars and sand dollars

Question 2

Lake Victoria and Nile Perch

Answer 2

• super huge lake in Africa
• 500 species of fish, most of which were endemic
• 90% were cichlids from haplochromis genus
• Nile perch introduced as sport fish bc British ppl killed a bunch of local fish
• extinction (or near) of a ton of endemic fish including half of the 400 tilapia
• loss of phytoplankton
• algae bloom
• algae die –> anoxia
• killed more fish cuz no oxygen
• tons of snails bc fish weren’t eating them
• snail born diseases (Schistomiasis)
• fires needed to dry nile perch
• cut down forests, causing erosion
• pollution and sedimentation of lake killed more fish
• Now nile perch is being overfished

Question 3

Trophic cascade hypothesis

Answer 3

effects of predators can alter multiple trophic levels

Question 4

Autotroph vs heterotroph

Answer 4

autotroph makes own food thru photo- or chemo- synthesis

heterotrophs need to eat other organisms

Question 5

Winemiller’s food web

Answer 5

• way too complicated

- had to simplify by only including most common species and leaving out weakest trophic links

Question 6

How to simplify food webs

Answer 6

• group species with similar trophic relations into one group
• isolate one part of community that doesn’t interact much with the rest

Question 7

energetic hypothesis

Answer 7

• length of food web is limited by energy transfer

- 10% of stored organic matter can be used one trophic level up

Question 8

energetic hypothesis test

Answer 8

limit leaves available to consumers in tree hole communities and then measured levels of trophic cascade

Question 9

Trophic pyramid levels

Answer 9

• primary producers = autotrophs
• primary consumers = herbivores
• secondary consumers = carnivores
• tertiary consumers = carnivores that eat other carnivores

Question 10

Why does energy degradation happen

Answer 10

• limited assimilation
• consumer respiration
• heat production

Question 11

ecological efficiency

Answer 11

percent energy transfer between trophic levels

Question 12

assimilation efficiency

Answer 12

percent of energy stored in food that’s not lost through egestion (feces)

Question 13

net production and growth efficiency

Answer 13

• what remains after respiration

- percent of net production energy out of assimilation energy

Question 14

two things that affect assimilation efficiency

Answer 14

• type of organism (heterotherm vs homeotherm)

- type of food

Question 15

who has better assimilation efficiency>?

Answer 15

homeotherms (birds and mammals), not heterotherms

Question 16

Easily assimilated foods vs not

Answer 16

• flesh of arthropods and vertebrates
• plant sap, nectar, seeds

-anything will cellulose, lignin, fiber

Question 17

growth efficiency in different organisms

Answer 17

• low in mammals + birds (1-3%)
• higher in fish (10%)
• much higher in insects (40%)

Question 18

consumption efficiency

Answer 18

percent of plant material eaten by animals vs what is left in environment

low to high: forests –> grasslands –> ocean

-stream doesn’t really count

Question 19

photosynthetic efficiency

Answer 19

• how well plants can convert sunlight into growth
• NP/ PAR
• PAR = photosynthetically active radiation

Question 20

top-down control

Answer 20

• trophic cascade
• removal of predator or predators increases population of prey
• e.g. foxes and hares/grouse (not vole?)
• mice + rodents required removal of all predators to stop prey cycling

Question 21

bottom-up control

Answer 21

lemmings controlled by amount of moss available

-slow recovery time