4.2 To Eat or What to Eat . . .
3. Identify the energy sources of different groups of organisms.
4. Arrange organisms into a food chain or food web.
5. Predict the consequences of food web perturbation.
Reminders: New Group Assignment (#2) on Food Webs will be due Monday Oct 5th
What is Food?
Ecologically, there are two ways of obtaining energy (aka food).
Autotrophs Self- feeders vs Heterotrophs feeding from others
Photoautotrophs obtain energy Heterotrophs are further categorized by their means of acquiring
from the sun creating chemical energy.
bonds between carbon atoms
forming energy rich sugar Decomposers – chemically break down organic material externally
molecules and absorb the small chemical compounds QUESTION: What domains
(and kingdom) do they come from?(bacteria & fungi)
Organisms (mostly from Domain
Bacteria and Domain Detritivores – consume dead organic material typically by
Archaebacteria) called fragmenting the material and consuming the small pieces.
chemoautotrophs obtain energy Decomposers in their guts completely breakdown the organic matter
by performing particular chemical and detritivores absorb some of the excess not used by the
reactions to make organic carbon decomposers. QUESTION: What type of a relationship is this?
compounds eg. Bacteria near Symbiotic & mutualism
hydrothermal vents obtain energy
from hydrogen sulfide (H2S gas Herbivores – consume plants/algae (producers)
released by the vents).
Omnivores – consume both producers and other animals
Carnivores – consume other animals
These organisms are referred to These organisms are collectively referred to as consumers.
Carpenter ants consuming wood is an example of A) carnivory
The mold on the loaf of bread in your kitchen is an A) carnivory
example of . .
A bird eating berries, seeds and insects is an A) carnivory
example of . .
QUESTION: How you define how a tapeworm obtains energy? They live in our intestinal tract
and absorb nutrients we have ingested.
A food chain represents a linear series of species feeding on each other.
Grasses Field mice Burrowing owl Badger Wolf
Producer Pr1imary consumer Secondary Tertiary consumer Quaternary
1st trophic level 2nd trophic level consumer 4th trophic level consumer
3rd trophic level 5th trophic level
A deep sea hydrothermal vent food chain
H2S reducing Copepod Amphipod Shrimp Octopus
Producer Primary consumer Secondary Tertiary consumer Quaternary
A food chain also represents the transfer of energy among organisms.
Organisms are not able to use Trophic level refers to the
all of what they consume. Why position along a food chain in
not? QUESTION: What can’t relation to the producers.
Much of what is consumed is On average there are 2 to 5
excreted as waste. species linked in a food chain
representing 5 trophic levels.
All organisms die and add to the
layer of dead organic material.
This in turn is ‘food’ for Longer food chains of 5 to 8
detritivores and decomposers. species are found in stable
environments, where the
populations of each species are
less susceptible to elimination.
Most consumers obtain their energy from at least 2 to 3 species of prey. A food web is a visual
representation of these multiple links illustrating the interconnections of feed or energy acquisition.
Building a food web
Consider the producers in your community and arrange them at the base of your web. Then add each
subsequent trophic level in order above the producers.
Draw arrows to indicate the direction of energy flow. Ensure that the arrow heads are distinctive. The
thickness of an arrow can be used to show the most common flow of energy (or food preference).
Be sure to include detritivores and decomposers in your web.
Questions for you to consider:
1. If you reduce the number or abundance of producers in a food web, what impact does this have on the
subsequent trophic levels?
2. Why is the abundance of the top predators (tertiary consumers) considered an indication of the health
or stability of a food web?
3. Why is it important to study an ecosystem thoroughly before introducing a non-native species?
New working groups have been assigned through Vista for your next assignment. These groups will be
displayed in class. Meet your new group members at the numbers taped up in the classroom to work
through an in-class activity that will help prepare you to do Assignment #2.
It will be useful to have the following 2 pages with you for this in-class activity:
Kamloops Bunchgrass Community Food Web
red-bellied clerid beetle badger ponderosa pine burrowing owl
Enoclerus sphegeus Taxidea taxus Pinus ponderosa Athene cunicularia
This beetle preys upon Badgers prey on small (includes seeds, This small owl (20 cm tall)
bark-boring beetles like the mammals such as seedlings, rotting logs) lives in burrows originally
mountain pine beetle squirrels, chipmunks, These trees are a major made by other animals
(Dendroctonus gophers, voles, rats and component of the such as badgers or
ponderosae). It is 8-12 mm mice a well as birds, community but most are gophers. It preys upon
long and is found in pine occasionally large insects infested with mountain small mammals such as
forests. and also rarely on pine beetle and are dying. voles, mice, pocket gophers
rattlesnakes. They live in Seeds from the cones are and bats. It also preys on
burrows in grassland eaten by a number of bird small birds, large insects (>
areas. They have few species as well as 20 mm), salamanders and
predators but have been chipmunks, and squirrels. toads. It is preyed upon by
preyed upon by coyotes Small seedlings of this hawks, coyotes, dogs and
and cougars while their tree may be consumed by other owls. Its young are
young have been preyed voles. Decomposition of preyed on by badgers,
on by eagles and hawks. dead logs adds nutrients skunks, foxes, weasels,
Badgers are 60 090 cm back to the soil of the snakes and raccoons. It is
long and weigh 7-14kg. forest ecosystem. endangered mainly due to
There are only ~250 habitat loss.
badgers in BC and are
cellulolytic bacteria Northern Pacific Rough Fescue chipmunk
(many species) rattlesnake Crotalus Festuca scabrella Eutamias minimus
These microscopic bacteria oreganus This perennial grass These small rodents (16-28
generally live in the guts of This is the only rattlesnake (survives over winters) cm long) eat nuts, seeds,
detritivorous insects and in BC and generally quiet grows in sprawling tufts berries, grasses and
herbivorous animals. Along and non-aggressive. It has with a flowering stem of occasionally fungi or
with cellulolytic fungi and venom sacs associated which can grow to a invertebrates (bugs). It is
cellulolytic protists they with its fangs which it uses height of 1m. The seeds preyed upon by every
possess enzymes to digest to immobilize prey. It feeds are consumed by carnivore with which it
the cellulose found in plant on shrews, moles, voles, rodents, and birds, while shares the habitat. In the
material. pocket gophers, ground the leaves are grazed on spring when nuts and seeds
squirrels, chipmunks, by deer and voles. Rough are scarce it eats green
marmots, the occasional fescue is more tolerant of shoots of plants which have
bird and very rarely other wider range of moisture overwintered and are just
snakes. It is preyed upon conditions it replaces beginning their growth for a
by hawks, bears, badgers bluebunch wheat grass new season.
and skunks. as the dominant species
at higher altitudes.
mountain pine beetle mountain chickadee bluebunch wheat grass red-backed vole
Dendroctonus Poecile gambeli Psuedoroegneria Clethrionomys gapperi
ponderosae These small birds (12-14 spicatum (includes This small vole (14cm long)
The mountain pine beetle cm) eat small insects and grass and seeds) feeds on grasses, shrubs,
(5mm long) bores under insect larvae as well as This relatively small seeds, berries, roots and
the bark of pine trees. seeds. They are important perennial native grass occasionally on
There the adult feeds on to BC pine forests (40 cm tall) is consumed underground fungi. They are
the phloem (a layer of live because, along with by many herbivores such preyed upon by weasels,
tissue which transports woodpeckers, they as deer, elk moose, badgers, hawks, owls and
sugars) and lays eggs consume bark-boring rabbits, chipmunks and snakes.
there. The larvae which insects. Their most voles. Some organisms
hatch from the eggs common predators are consume the seeds
consume the wood of the hawks. Their eggs are including voles,
tree with assistance from consumed by weasels, chipmunks and birds.
microbes in their gut. The snakes, chipmunks and
beetle also spreads a blue- squirrels.
staining fungus which
infects the tree and
contributes to killing the
Pine mushroom or
This highly prized mushroom
also has a significant role in
the community. It is consumed
by rodents such as chipmunks
and voles as well as insects
(adults and larvae). These
mushrooms derive their
nutrition by decomposing dead
organism material (plant as
well as animal).