Download Food Chains

Food Web Worksheet
Part A: Use the marine food chain below to answer questions 1 to 5
1. Identify the organism (s) that are producers.
Phytoplankton (underwater microorganism which produces glucose by photosynthesis…so a
plant more or less!)
2. Identify the organism (s) that are consumers.
Zooplankton, Small Fish, Big Fish, Mammal
3. Identify the primary consumer (s) or 1st order consumer (s).
Zooplankton → it eats the phytoplankton
4. Identify the secondary consumer (s) 2nd order consumer (s).
Small Fish → it eats the zooplankton
5. Identify the tertiary consumer (s) 3rd order consumer (s).
Big Fish → it eats the small fish
Part B: Use the following food web to answer question 6 to 9.
Make 4 different food chains according to the criteria below:
6. The owl is a second order consumer:
Plant → squirrel → owl
Plant → rabbit → owl
Plant → mice→ owl
Plant → seed eating birds → owl
7. The owl is a third order consumer:
Plant → herbivorous insect → insectivores birds → owl
(only possibility)
8. The owl is a fourth order consumer:
Plant → herbivorous insect → predaceous insect → insectivorous bird → owl
Plant → herbivorous insect → spider → insectivorous bird → owl
9. The owl is a fifth order consumer:
Plant → herbivorous insect → spider → predaceous insect → insectivorous bird → owl
Plant → herbivorous insect → predaceous insect → spider → insectivorous bird → owl
Part C: Use the food web below to answer questions 10 to 13.
10. Explain the consequences to the food web if mice were removed from the ecosystem.
↓ in Golden-crowred kinglet population (increased predation pressure by Hawk)
↓ in Salamander population (increased predation pressure by Snake)
↑ in Oak tree population (released from predation pressure by mice; only mice ate the tree)
11. Explain the consequences to the food web if hawk was removed from the ecosystem.
↑ in Snake population (released from competitive pressure by Hawk as Snake and Hawk had
two food sources in common, the mice and the kinglet)
12. All the organisms in the food web above have arrows pointing to the decomposer. Why
does this happen?
All organisms die; decomposers break down organisms into their elemental components
which then gets recycled and reintegrated into the plant life (chemical recycling)
13. Name the organisms which are part of the biomass.
All of the organisms in the ecosystem; biomass refers to the biological mass of all living
entities in the ecosystem
Oak tree, pine tree, mouse, snake, kinglet, hawk, salamander, pine bore
Part D: Use the food web below to answer questions 14 to.
14. What species is the top consumer? Why?
Sea otter; there are no arrows point from the sea otter to another species, meaning that
nothing eats the sea otter
15. Explain the consequences if the abalones were removed from the food web.
↓ in population of Sea urchins and smaller herbivores fishes/invertebrates (sea stars increased
predation pressure on these species due to the removal of one food source)
↓ in population of sea stars, larger crabs and larger fish/octopi (sea otter increased predation
pressure on these species due to the removal of one food source)
16. What is a keystone species? Explain.
A keystone species is a species that has a disproportionally large effect on an ecosystem. They
are particularly rare in food webs, but they are responsible for maintaining the structure of
the community.
17. Does the otter qualify as a keystone species? Explain.
Yes, without the sea otter, the population of sea urchins would have no natural predator.
Released from predation pressure, they would multiply exponentially, consuming lots of kelp.
The destruction of the kelp would cause the entire ecosystem to collapse