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1 Your web browser (Safari 7) is out of date. For more security, comfort and the best experience on this site: Update your browser Ignore Encyclopedic Entry omnivore secondary consumer For the complete encyclopedic entry with media resources, visit: An omnivore is an organism that regularly consumes a variety of material, including plants, animals, algae, and fungi. They range in size from tiny insects like ants to large creatures like people. Human beings are omnivores. People eat plants, such as vegetables and fruits. We eat animals, cooked as meat or used for products like milk or eggs. We eat fungi such as mushrooms. We also eat algae, in the form of edible seaweeds such as nori, which are used to wrap sushi rolls, and sea lettuce, eaten in salads. Bears are omnivores, too. They eat plants like berries as well as mushroom fungi and animals like salmon or deer. Omnivores are a major part of the food web, a description of which organisms eat which other organisms in the wild. Organisms in the food web are grouped into trophic, or nutritional, levels. There are three trophic levels. Autotrophs, organisms that produce their own food, are the first trophic level. These include plants and algae. Herbivores, organisms that consume plants and other autotrophs, are the second trophic level. Both omnivores and carnivores, meat eaters, are the third trophic level. Autotrophs are called producers, because they produce their own food. Herbivores, carnivores, and omnivores are consumers. Herbivores are primary consumers. Carnivores and omnivores are secondary consumers. Most birds are omnivores. Robins pull worms from the ground. They also feast on berries. Ostriches graze on plants and grasses. They also eat lizards and insects. 1 of 6

2 Many mammals are omnivorous. Skunks eat rodents, lizards, honeybees, leaves, grasses, nuts, fungi, and almost anything else they can find. Some reptiles are also omnivorous. Box turtles feed on fish, frogs, rodents, and many other creatures, but they also eat flowers, berries, and roots. Fish can also be omnivorous. The opaleye, a fish that feeds mostly on seaweeds along the Pacific Coast of North America, also eats small creatures found among the seaweed. Some insects are omnivores. Ants eat seeds, nectar, and, often, other insects. Some omnivores are scavengers, creatures that eat the meat of dead animals. Black bears eat mostly nuts, berries, and other fruit. But if they find a dead animal, they eat it. Many animals that are often thought of as carnivores are in fact omnivores. Red foxes, for example, prey on rabbits, but they also eat fruit. Some animals that are thought of as herbivores also eat animals. Squirrels eat mostly nuts, fruits, and seeds, but they sometimes eat insects, small birds, and other creatures. Omnivore Adaptations Many omnivores have biological adaptations that help them eat a variety of kinds of foods. They have adapted many characteristics of both carnivores and herbivores. Like many carnivores, raccoons have sharp front teeth that help them rip apart mice and other small creatures. And like many herbivores, raccoons also have large molars that help them chew up plants. Raccoons also have quick paws and long fingers that they can use both to grab prey and to reach a variety of fruits and other plant products. Compared to herbivores and carnivores, omnivores often have a greater chance of surviving difficult conditions. They can adjust their diets. If all the salmon or other animals disappear from a river ecosystem, a big cat living in that habitat 2 of 6

3 could not survive. Cats are carnivores that cannot digest or obtain nutrients from plant material. However, a grizzly bear could still survive eating berries, fruit, roots, and insects. Because they have an easier time finding food, omnivores are sometimes better at adapting to new environments than creatures with more specific feeding habits. Omnivores can better adapt to development than herbivores or carnivores. Urban development, the process of clearing land for homes, business, and agriculture, destroys habitats, the places where animals live in the wild. Herbivores such as elephants cannot survive without a lot of trees and grasses to eat. But omnivores such as opossums, seagulls, and many species of monkey easily adapt to life in urban areas and farmland, where they often find meals in garbage cans. Vocabulary Term Part of Speech Definition agriculture the art and science of cultivating the land for growing crops (farming) or raising livestock (ranching). algae plural (singular: alga) diverse group of aquatic organisms, the largest of which are seaweeds. autotroph organism that can produce its own food and nutrients from chemicals in the atmosphere, usually through photosynthesis or chemosynthesis. big cat large predators, including tigers, lions, jaguars, and leopards. biological physical change in an organism that results over time in adaptation reaction to its environment. box turtle small reptile with a tall, domed shell. carnivore organism that eats meat. characteristic physical, cultural, or psychological feature of an organism, place, or object. consumer person who uses a good or service. decline verb to reduce or go down in number. development growth, or changing from one condition to another. 3 of 6

4 Term Part of Speech Definition diet foods eaten by a specific group of people or other organisms. digest verb to convert food into nutrients that can be absorbed. ecosystem community and interactions of living and nonliving things in an area. farmland area used for agriculture. food chain group of organisms linked in order of the food they eat, from producers to consumers, and from prey, predators, scavengers, and decomposers. food web all related food chains in an ecosystem. Also called a food cycle. fruit edible part of a plant that grows from a flower. fungi (singular: fungus) organisms that survive by decomposing plural and absorbing nutrients in organic material such as soil or dead organisms. grizzly bear large mammal native to North America. habitat environment where an organism lives throughout the year or for shorter periods of time. herbivore organism that eats mainly plants. insect type of animal that breathes air and has a body divided into three segments, with six legs and usually wings. mammal animal with hair that gives birth to live offspring. Female mammals produce milk to feed their offspring. meat animal flesh eaten as food. molar large, flat tooth used for chewing and grinding. monkey mammal considered to be highly intelligent, with four limbs and, usually, a tail. mushroom fungus, usually with an umbrella-shaped cap on top of a slender stalk. nectar sweet plant material that attracts pollinators. nori red algae that is often dried and used to wrap sushi. nutrient substance an organism needs for energy, growth, and life. omnivore organism that eats a variety of organisms, including plants, animals, and fungi. 4 of 6

5 Term Part of Speech Definition opaleye medium-sized fish native to the Pacific Ocean. organism living or once-living thing. ostrich very large, flightless bird native to Africa. plant organism that produces its own food through photosynthesis and whose cells have walls. prey animal that is hunted and eaten by other animals. primary consumer organism that eats plants or other autotrophs. producer organism on the food chain that can produce its own energy and nutrients. Also called an autotroph. reptile animal that breathes air and usually has scales. robin small bird native to Europe. rodent order of mammals often characterized by long teeth for gnawing and nibbling. root part of a plant that secures it in the soil, obtains water and nutrients, and often stores food made by leaves. scavenger organism that eats dead or rotting biomass, such as animal flesh or plant material. sea lettuce seaweed with large, flat leaves. seaweed marine algae. Seaweed can be composed of brown, green, or red algae, as well as "blue-green algae," which is actually bacteria. secondary consumer organism that eats meat. specific adjectiveexact or precise. sushi bite-sized rolls or balls of sticky rice topped with seafood or vegetables. tamarin small monkey native to Central and South America. trophic level one of three positions on the food chain: autotrophs (first), herbivores (second), and carnivores and omnivores (third). urban area developed, densely populated area where most inhabitants have nonagricultural jobs. vegetable plant that is grown or harvested for food. Websites 5 of 6

6 National Geographic Ocean: Marine Food Chain National Geographic Society. All rights reserved. 6 of 6