Understanding Food Chains and Ecological Relationships
What is a Food Chain?
A food chain is a series of feeding relationships between organisms, indicating who eats whom.
Producers
Plants are called autotrophs because they can make their own food.
Herbivores
Herbivores are organisms that eat plant tissue, thus obtaining energy-rich molecules, which they then degrade and release the energy they need to live.
Heterotrophs
Heterotrophs are organisms that feed on other organisms.
Carnivores
Carnivores are organisms that eat other animals. These are also heterotrophs.
Decomposers
Decomposers are in charge of decomposing organic matter (waste, etc.). They are called saprophytes, as their function within the ecosystem is returning to nature the elements needed to complete the cycle.
What is a Trophic Level?
A trophic level is the position of an organism in the food chain.
Food Web
In an ecosystem, to establish who eats whom, we establish not a single food chain but multiple intertwined food chains, known as a food web.
Food Pyramid
A food pyramid shows the extent to which consumers find products. As it ascends, the energy and number of consumers decrease.
Food Cycle
A food cycle is a food chain (or web) that has a closed loop, forming a cycle.
Predation
Predation is the interaction between individuals of different species in which the predator kills its prey before or during consumption.
Competition
Competition is the result of the need of living organisms to survive in environmental conditions where resources are not sufficient for all.
Parasitism
Parasitism (ecto- = on, endo- = inside) is a type of interaction between organisms in which one, called the parasite, lives in or on another organism, from which it feeds.
Symbiosis
Symbiosis is the relationship between two species in which one or both benefit, and neither is harmed.
Commensalism
Commensalism occurs if one of the organisms benefits without harming the other.
Mutualism
Mutualism occurs if both organisms benefit without harming either.
Predator
A predator is an animal that kills another for the purpose of feeding.
Ghoul
Ghouls are consumers that normally eat dead organisms not killed by them.
Prey
Prey is the victim of a predator.
Examples
Predation
- A lion kills a deer to eat it.
- A tiger kills a gazelle.
Competition
Competition between two trees that do not have much space between them.
Mutualism
- The relationship between ants and aphids or scale insects.
- Remora and shark.
Parasitism
- Tick
- Scale
Commensalism
Cattle egrets eat insects that livestock stir up when eating or walking.
Ectoparasites
- Flea
- Tick
- Lice
Endoparasites
- Bacteria
- Intestinal parasites
- Worms
Animal Roles
Lion: Predator, Tiger: Predator, Hyena: Ghoul, Gazelle: Prey, Rabbit: Prey, Eagle: Predator, Panther: Predator, Deer: Prey, Vulture: Ghoul, Leopard: Predator.
Energy Flow and Material Cycle in Trophic Levels
Energy is absorbed by organisms of a higher trophic level through its components.
Circulation of Materials and Energy Flow
Materials circulate and energy flows in food chains and webs through the action of eating between organisms of different trophic levels.
Example of a Simple Food Chain
Source of Energy: Sun, Producer: Plant, Primary Consumer: Insects, Secondary Consumer: Insectivorous Birds, Tertiary Consumer: Hawk, Inorganic Compounds: Carbon Dioxide, Decomposers: Bacteria and Fungi.