Food Chains
and Food Webs
What is a food chain?
• A food chain is “a sequence of organisms,
each of which uses the next, lower member of
the sequence as a food source1”
Important facts about food chains
• In a food chain each organism obtains energy
from the one at the level below.
• Plants are called producers because they create
their own food through photosynthesis. Always
the first organism in a food chain.
• Animals are consumers because they cannot
create their own food, they must eat plants or
other animals to get the energy that they need.
• Arrows point in the direction of energy flow
Grass  rabbit  hawk
Producers
• Primary producers are “organisms capable of
producing their own food4”
• We can also say that they are photosynthetic, use
light energy.
• Examples of primary producers include algae,
phytoplankton, and large plants.
• Primary producers are eaten by primary consumers
(herbivores)
Primary Producers of NJ Marshes
Marsh Mallow
Cattails
http://www.nicerweb.com/doc/class/pix/PRAIRIE/2005_07_18/Typha_angustifolia.jpg
http://www.ncdot.org/doh/Operations/dp_chief_eng/roadside/wildflowerbook/graphics/images/page14a.jpg
Marsh Fern
Blue Flag Iris
http://www.ontariowildflower.com/images/blueflag2.jpg
http://wisplants.uwsp.edu/scripts/detail.asp?SpCode=THEPALvPUB
Four types of consumer
• Herbivores: animals that eat only plants
• Carnivores: animals that eat only other
animals.
• Omnivores: animals that eat animals and
plants.
• Detritivores: Animals that eat dead materials
and organic wastes
Other Ways to Classify Consumers
1. Primary Consumers: Herbivores.
2. Secondary Consumers: Carnivores that eat
herbivores.
3. Tertiary Consumers: Carnivores that eat
other carnivores.
Primary Consumers in Marshes
Muskrat (eats mostly Cattails)
http://wdfw.wa.gov/wlm/living/graphics/muskrat1.jpg
http://www.advancedwildlifecontrolllc.com/images/muskrat.jpg
Primary Consumers in Marshes
• Wood Duck eats seeds like those of the
Swamp Marsh Mallow and Blue Flag Iris
http://dsf.chesco.org/ccparks/lib/ccparks/wood_duck_pair.jpg
Primary Consumers in Marshes
• Glassy-winged Toothpick Grasshopper – eats
leaves of plants like cattail and pickerelweed
http://bugguide.net/node/view/41662
Secondary Consumers
• Black Rat Snake eats eggs of animals like wood
duck
http://www.bio.davidson.edu/projects/tate/Terms.htm
Secondary Consumers
• Swamp Sparrow eats seeds but also insects
like the toothpick grasshopper
http://www.jeaniron.ca/2007/SwampSparrow6645.jpg
Tertiary Consumers
• Eat other animals in marsh including snake
and sparrow
Osprey
www.montereybay.com
www.audubon.org
Omnivore
• Racoon eats seeds, fruits, insects, worms, fish,
and frogs… and pretty much anything else
they can get their paws on!
http://abouttitusville.com/BobPaty/Animals/images/Racoon.jpg
Detritivore
• Worms are common detritivores in many
ecosystems including marshes
What is a food web?
A food web is “an interlocking pattern of food
chains2”
A few notes over Trophic Pyramid
• A trophic level
is the position
that an
organism on a
food chain
10% Rule
• First Law of Thermodynamics- Energy cannot
be created or destroyed
–Basically, you can’t get something out
of nothing
• Second Law of Thermodynamics- Every time
you convert energy, you are going to loose
energy
–You can’t break even
• Organisms only convert up to 10% of chemical
energy from food into energy stored as body
tissues (biomass)
Therefore, every time energy moves up a trophic
level, it loses 90% of energy from previous level
• –Need 10 primary producers to support one
herbivore (primary consumer)
• –Need 10 primary consumers to support one
secondary consumer (carnivore)