We’ve seen that animals may eat other animals, plants, or a mixture of both. Some animals even eat dead or decaying organisms.

Adaptations for obtaining these foods and nutrients include a variety of feeding mechanisms. Most animals are bulk feeders. They eat relatively large pieces of food. Many vertebrates, including ourselves, are bulk feeders. Both carnivores and herbivores may use the same feeding mechanism. A lion chewing meat from a fresh kill is a bulk feeder, as is a hippopotamus dining on a tasty meal of water plants.

Fluid feeders suck nutrient-rich fluids from a living host. Fluid feeders may also be herbivores or carnivores. Aphids suck the sap from plants. Leeches and mosquitos suck blood from mammals.

Some aquatic animals are suspension feeders. They sift food particles suspended in water through specialized structures, such as the gills of clams, or the baleen plates of some whale species.

Although most vertebrates are bulk feeders, baleen whales like the blue whale are an exception. A whale strains hundreds of pounds of tiny invertebrate animals from millions of gallons of seawater every day.

Baleen whales and clams are both active suspension feeders. A clam generates its own water current to move particles through its filters.

A baleen whale actively searches out an area that is rich in the plankton on which it feeds, swimming with its mouth wide open to filter its food.

Other suspension feeders, like the Gorgonian coral, are passive suspension feeders, waiting for the ocean current to waft food particles past its branches. Coral colonies are oriented at right angles to the prevailing currents. This maximizes their chances of catching food particles.

Imagine spending your life swimming in a huge bowl of porridge.

Substrate feeders live this kind of existence, dwelling in or on their food source. Leaf miners are tiny substrate-feeding insects that tunnel their way through leaves.

Termites are substrate feeders that destroy wooden structures by burrowing through the wood, feeding on the cellulose.

An earthworm is a deposit feeder, a special type of substrate feeder that ingests partially decayed organic material along with its substrate.

As an earthworm eats its way through soil, it excretes the inorganic material and digests the organic matter the soil contains.

The material excreted by the worm as it burrows and eats its way through the soil is called the worm cast.

Whether food is obtained by burrowing through soil or by hunting a gazelle, the end result is the ingestion of nutrients that will be used to obtain energy or build body parts. Next, we’ll look at how energy is obtained from food.

Copyright 2006 The Regents of the University of California and Monterey Institute for Technology and Education