In the marine food web with seaweeds, phytoplankton, zooplankton, flat periwinkle, common limpet, shanny, herring gull, acorn barnacle, worm, common dog whelk, edible crab, and common prawn, how do you classify each organism as a producer, herbivore, omnivore, or carnivore?

What you are doing with this food web

A food web shows who eats whom. To classify each organism, decide whether it makes its own food (producer) or gets energy by eating plants/algae (herbivore), both plants and animals (omnivore), or only animals (carnivore).

Producers: organisms that photosynthesize

• Seaweed and phytoplankton are producers because they make sugars from light energy by photosynthesis.

Herbivores: organisms that feed on producers

These organisms get energy by eating algae or microscopic producers:

• Flat periwinkle (grazer on algae/seaweed)
• Common limpet (scrapes algae from rocks)
• Acorn barnacle (filter-feeds, often on phytoplankton)
• Worm (in this web, placed as feeding on plant/algal material)
• Zooplankton (often feeds on phytoplankton)

Omnivores: organisms that eat both plant and animal material

• Edible crab (can scavenge and hunt, and also eat plant material)
• Herring gull (eats a wide range, including marine animals and other food sources)
• Common prawn (often feeds on small animals and plant/algal matter)

Carnivores: predators that eat other animals

• Shanny (a small fish that eats animal prey)
• Common dog whelk (predatory snail that feeds on animals like barnacles and other shellfish)

Quick check

If energy can flow from an organism directly from sunlight, it is a producer. If it must eat producers, it is a herbivore; if it eats both producers and consumers, it is an omnivore; and if it eats only consumers, it is a carnivore.