FOOD WEBS
The web of life
Within ecosystems, organisms can be identified as being either producers or consumers.
Producers contain special pigments called chlorophyll which help them make their own food from the sun. Consumers eat other organisms for energy.
In a process called photosynthesis seaweeds use carbon dioxide and water to make sugars and oxygen.
Phytoplankton are tiny algae which which also get their energy from the sun.
Like seaweeds and plants, they are also primary producers
Zooplankton are primary consumers as they eat phytoplankton
All consumers get their energy from eating other organisms
Animals that eat only plants are called herbivores
Urchins are one type of herbivore which grazes on algae
Since they only eat primary producers, herbivores are primary consumers
Animals that eat only other animals are called carnivores
Organisms that eat both plants and animals are called omnivores
Detritivores eat decomposed animal and plant material.
Food chains show a single pathway that energy and nutrients may transfer through an ecosystem.
Arrows show the transfer of biomass from one trophic level to another
Interacting food chains are called food webs.
Quick summary
Primary producers use photosynthesis to get energy from the sun.
Herbivores eat exclusively plants and algae
Primary consumers are herbivores and eat mostly plants or algae
Secondary consumers eat herbivores
Tertiary consumers eat carnivores
Detritivores eat decomposing matter
Trophic levels represent the position that an organism occupies in a food chain
Interacting food chains form a food web
Now it’s your turn
to create an Australian kelp forest food web.
Step 1 - Research
Download the worksheet and use the marine life section of this website to research each species to fill in the table.
Start with the first row on the table to work out the diet of each species. Look on the ‘fast facts’ section at the bottom of each species page. Work out the trophic level depending on it’s diet (see tips at bottom of worksheet)
Note that some species can be on multiple trophic levels. (ie. an omnivorous fish that eats seaweed and other fish is both a primary and secondary consumer.)
Step 2 - Draft food web
Create a draft copy of your food web and decide if it will be digital or on paper. Start with primary producers on the bottom and move up. Use pencil as you may need to move things around to make it work. Use arrows to show feeding relationship and direction of energy flow (towards the predator).
Step 3 - Food web
Fill up as much of your page as possible
Consider using colours to represent different trophic levels
Teachers download lesson plan and Australian Curriculum links here
