-
A food web is the network of feeding interactions
-
among species in an ecosystem.
-
When you think about feeding interactions,
-
predators and prey are the first thing
that spring to mind,
-
like a cheetah chasing,
killing and eating an antelope.
-
But in fact, there are lots of ways
that matter and energy
-
get transferred from one
organism to another:
-
a calf consuming milk from its mother,
-
a vulture feeding on a dead fox,
-
a parasatoid wasp larva living inside
and feeding on a caterpillar,
-
a honey bee gathering nectar
and pollen from a sunflower,
-
and a katydid taking
small bites of willow leaves.
-
There are many ways that the existence
of one creature depends on another.
-
A food chain is one way of representing
feeding relationships among several species
-
with predators eating herbivores that eat
plants that draw energy from the sun.
-
An example is a hawk
that eats a rabbit that eats grass.
-
That's a good start, but it doesn't really
let you understand the whole complex ecosystem.
-
To do that we collect data
on the myriad species that co-occur in a habitat
-
and then figure out who they eat and who eats them.
-
Each species is usually in many different food chains
and those chains weave together to form a network.
-
That ecological network is called a food web.
-
Here's an example of an aquatic food web
from Little Rock Lake, Wisconsin,
-
that includes fishes, aquatic insects,
zooplankton, algae, plants, and parasites.
-
The spheres represent different species
and the links show the interactions between the species.
-
There are 92 tacks in this food web
with almost a thousand feeding interactions.
-
This image places species in the food web
based on their trophic level.
-
Trophic is just another word for feeding,Trophic is just another word for feeding,
-
and trophic level is a measure of how many times
energy and matter are transformed
-
as they work their way up
-
from species to species up the food web.
-
Or organisms such as plankton and algae
that generate energy from sunlight
-
have a trophic level of one, and they show up at the bottom of food web.
-
The species that feed on these, like zooplankton
-
and aquatic insects, show up in the middle.
-
Predatory fishes and their parasites
show up on the top.
-
You can use food webs to learn many different things about ecosystems.
-
For example, we can use food webs from different places
-
to understand whether a desert food web,
-
a marine food web
-
and a tropical forest food web
-
are organized in similar or different ways.
-
Our best science suggests that they have
fundamentally similar organization,
-
no matter what the habitat that is examined.
-
Even food webs from hundreds of millions of years ago
-
appear to be structured like modern webs.
-
The species may be very different
but their fundamental relationships are not.
-
We can even use food webs to understand
how humans fit into and impact ecosystems
-
through their roles as hunters,
gatherers, fishers, herders and farmers.
-
We can compare the feeding roles of humans to other species and their food webs
-
and learn lessons that help us to understand
ecological resilience and sustainability.
-
Developing the science of ecological networks such as food webs
-
is some of the research
we do here at the Santa Fe Institute.