Download Food Chains and Food Webs

Marine
Ecology
Activity 3
Energy
Production
In their daily struggle for survival marine animals perform a variety of
activities e.g. movement - squids and octopuses use jet propulsion, scallops
clap their shells and fish swim. Energy is required to perform all of these
activities, however, unlike plants who can photosynthesis (see activity 2) to produce
energy animals get their energy from food.
Food provides nutrients for animals, i.e. proteins, sugars, starches, fats, vitamins, minerals
and water, which allows them to maintain their energy level to carry out their essential
daily routines. Animals break down and utilize these nutrients through a process known as
metabolism.
Cells of living organisms are composed of proteins, carbohydrates and fats
(lipids) which they obtain from the food which they consume. Proteins are
made up of building blocks called amino acids. When these amino acids join
together within the animal cell the result is growth.
Sugars and Starch provide a quick energy release to organisms - together these nutrients
make up carbohydrates. An example of a simple sugar compound is glucose (C6H12O6 ).
When glucose is not being used in the body it is changed into, and stored as starch.
Starches can be changed back into glucose when the body needs energy through a
chemical process known as hydrolysis. Hydrolysis is a breaking down process and occurs
when food is digested.
Marine plants obtain the minerals they need by absorbing the minerals from the
surrounding water. Marine animals that eat marine plants absorb the plants minerals into
their body tissues.
Water is the most abundant nutrient in most living organisms - with on
average about 80% of an organism’s weight being water. Water contains
and transports many dissolved substances within the body. Water is also
necessary for chemical reactions such as photosynthesis to occur.
Marine Biodiversity and Ecosystem Functioning EU Network of Excellence
Sustainable development, global change and ecosystems
GOCE-CT-2003-505446
Marine
Ecology
Activity 3
Food Chain
All organisms on Earth survive by participating in a Food Chain and a Food Web.
Food chains and food webs show the transfer of energy from the sun to the producers,
(e.g. seaweeds), which in turn transfer their own food to consumers (e.g. marine animals).
Food chains therefore describe the eating relationships between species within an
ecosystem.
A marine food chain is made up of:
1)
Primary producers: make their own food. These organisms are typically
photosynthetic and are also commonly known as autotrophs, where they produce
simple organic substances (essentially "food") from an energy source and inorganic
materials.
Example: phytoplankton, seagrass, zooxanthellae.
2)
Consumers: obtains food by eating other organisms.
Example: Starfish, sponge, shark.
A) Primary consumers: Organisms that get their energy from organic substances by
eating only producers are called heterotrophs. Heterotrophs include herbivores,
which obtain their energy by consuming live plants.
Example: Manatee, limpet.
B) Secondary consumers: these mainly include carnivores, which obtain their energy
from eating primary consumers.
Example: Shark, octopus, sea otter.
C) Tertiary consumers: those animals that feed on secondary consumers including
the omnivores i.e. detritivores, scavengers and decomposers, which all consume
dead biomass (both consumers and producers).
Example: Basking shark, sponge, coral, crab.
Typically, the highest level upon which a consumer feeds determines what it is called,
even though it may feed on more than one level.
Marine Biodiversity and Ecosystem Functioning EU Network of Excellence
Sustainable development, global change and ecosystems
GOCE-CT-2003-505446
Marine
Ecology
Energy
Transfer
Activity 3
Organisms in a food chain are grouped into trophic levels,
based on how many links they are removed from the
primary producers. At the very first level are producers
(plants) and these are the most important part of the
chain. Without producers, the chain would collapse, and all
animals above would starve and perish!
Blue whale
At each level of the food chain, about 90% of the energy
is lost in the form of heat. The total energy passed
from one level to the next is only about one-tenth of the
energy received from the previous organism. Therefore,
as you move up the food chain, there is less energy
available. Animals located at the top of the food chain
need a lot more food to meet their energy needs.
Copyright www.pixel-lab.ie
Krill
Copyright wikipedia
Biomass: The total amount of organisms per unit volume,
of carnivores is much less than that of herbivores they
consume. Similarly the biomass of herbivores will be much
less than the total weight of plants they consume.
For example: a hundred tons of plants would produce only
about 10 tons of herbivores, which would in turn feed and
sustain only one ton of carnivores. “As you move up levels
in the food chain, biomass decreases.”
Plankton
Basic food chain of the baleen whale
(Blue whale)
The transfer of energy is complete when both the producers and consumers die and their
remains are consumed by scavengers.
The end of a food chain or web occurs when decomposers such as bacteria break down
dead plants and animals as well as wastes.
Marine Biodiversity and Ecosystem Functioning EU Network of Excellence
Sustainable development, global change and ecosystems
GOCE-CT-2003-505446
Marine
Ecology
Food Web
Activity 3
A diagram illustrating
showing a Food Chain
within the Food Web
A food chain becomes complicated when other animals get into the picture and create
a food web. A food web is a network of food chains that are linked
together. For example, krill are not only eaten by whales but are also
eaten by other fish, penguins and seals. The baleen whale may also be
eaten by the killer whale. In this case the killer whale would be at the
top of this food web.
A food web follows a natural order i.e. plants or animals at the lower levels are consumed by
animals higher up the chain. If a plant or animal at lower levels begins to die out or disappear,
then animals higher up would also begin to die from lack of nourishment. There are a number of
causes for a break in a food web e.g.
1.
Disease or sudden weather changes can alter the biomass of particular plants, or animals
such as zooplankton. These are both natural phenomena and a food web will usually recover
form such occurrences.
2.
The world’s fishing industry, however, is something that could destroy the ocean’s food
chain if not monitored. If the fishing industry began wiping out lower levels of the food
chain, they would upset the natural balance of marine life.
Marine Biodiversity and Ecosystem Functioning EU Network of Excellence
Sustainable development, global change and ecosystems
GOCE-CT-2003-505446
Marine
Ecology
Quick Test
Activity 3
Match each description with the correct term in each section.
Write the letter on the line provided
___ 1. plant and animal eater
A. Tertiary consumers
___ 2. Eat primary consumers
and sometimes producers
B. Herbivores
___ 3. Plant eaters
C. Secondary consumers
___ 4. Eat only producers
D. Omnivores
___ 5. Animal eaters
E. Primary consumers
___ 6. Eat secondary consumers,
and sometimes primary consumers
and producers
F. Carnivores
Marine Biodiversity and Ecosystem Functioning EU Network of Excellence
Sustainable development, global change and ecosystems
GOCE-CT-2003-505446
Marine
Ecology
Quick
Questions
Activity 3
On a separate page write the answers to these questions and create your
own food web.
1. What are some of the causes for a break in the
ocean’s food chain?
2. How might a break in the ocean’s food chain
affect us?
3. How is a food web different from a food chain?
4. Define 4 of the following terms:
A)
B)
C)
D)
E)
F)
G)
Biomass
Phytoplankton
Omnivores
Hydrolysis
Metabolism
Trophic Levels
Protein
5. Create your own Marine Food Web mural
and show three possible food chains within
your food web.
[For each animal or plant used show what each
depends upon by drawing an arrow from each
animal or plant to what it depends upon].
Marine Biodiversity and Ecosystem Functioning EU Network of Excellence
Sustainable development, global change and ecosystems
GOCE-CT-2003-505446