Encyclopedic Entry

Tall grasses and Bison bison—must be the tallgrass prairie ecosystem.

Photograph by Lela Bouse-McCracken, MyShot

Bactrian and Dromedary
Different desert ecosystems support different species of camels. The dromedary camel is tall and fast, with long legs. It is native to the hot, dry deserts of North Africa and the Arabian Peninsula. The Bactrian camel has a thicker coat, is shorter, and has more body fat than the dromedary. The Bactrian camel is native to the cold desert steppes of Central Asia.

It is easy to tell the two types of camels apart: Dromedaries have one hump, Bactrians have two.

Coral Triangle
The most diverse ecosystem in the world is the huge Coral Triangle in Southeast Asia. The Coral Triangle stretches from the Philippines in the north to the Solomon Islands in the east to the islands of Indonesia and Papua in the west.

Human Ecosystem
"Human ecosystem" is the term scientists use to study the way people interact with their ecosystems. The study of human ecosystems considers geography, ecology, technology, economics, politics, and history. The study of urban ecosystems focuses on cities and suburbs.

Ecocide
The destruction of entire ecosystems by human beings has been called ecocide, or murder of the environment.

An ecosystem is a geographic area where plants, animals, and other organisms, as well as weather and landscape, work together to form a bubble of life. Ecosystems contain biotic or living, parts, as well as abiotic factors, or nonliving parts. Biotic factors include plants, animals, and other organisms. Abiotic factors include rocks, temperature, and humidity.

Every factor in an ecosystem depends on every other factor, either directly or indirectly. A change in the temperature of an ecosystem will often affect what plants will grow there, for instance. Animals that depend on plants for food and shelter will have to adapt to the changes, move to another ecosystem, or perish.

Ecosystems can be very large or very small. Tide pools, the ponds left by the ocean as the tide goes out, are complete, tiny ecosystems. Tide pools contain seaweed, a kind of algae, which uses photosynthesis to create food. Herbivores such as abalone eat the seaweed. Carnivores such as sea stars eat other animals in the tide pool, such as clams or mussels. Tide pools depend on the changing level of ocean water. Some organisms, such as seaweed, thrive in an aquatic environment, when the tide is in and the pool is full. Other organisms, such as hermit crabs, cannot live underwater and depend on the shallow pools left by low tides. In this way, the biotic parts of the ecosystem depend on abiotic factors.

The whole surface of Earth is a series of connected ecosystems. Ecosystems are often connected in a larger biome. Biomes are large sections of land, sea, or atmosphere. Forests, ponds, reefs, and tundra are all types of biomes, for example. They're organized very generally, based on the types of plants and animals that live in them. Within each forest, each pond, each reef, or each section of tundra, you'll find many different ecosystems.

The biome of the Sahara Desert, for instance, includes a wide variety of ecosystems. The arid climate and hot weather characterize the biome. Within the Sahara are oasis ecosystems, which have date palm trees, freshwater, and animals such as crocodiles. The Sahara also has dune ecosystems, with the changing landscape determined by the wind. Organisms in these ecosystems, such as snakes or scorpions, must be able to survive in sand dunes for long periods of time. The Sahara even includes a marine environment, where the Atlantic Ocean creates cool fogs on the Northwest African coast. Shrubs and animals that feed on small trees, such as goats, live in this Sahara ecosystem.

Even similar-sounding biomes could have completely different ecosystems. The biome of the Sahara Desert, for instance, is very different from the biome of the Gobi Desert in Mongolia and China. The Gobi is a cold desert, with frequent snowfall and freezing temperatures. Unlike the Sahara, the Gobi has ecosystems based not in sand, but kilometers of bare rock. Some grasses are able to grow in the cold, dry climate. As a result, these Gobi ecosystems have grazing animals such as gazelles and even takhi, an endangered species of wild horse.

Even the cold desert ecosystems of the Gobi are distinct from the freezing desert ecosystems of Antarctica. Antarcticas thick ice sheet covers a continent made almost entirely of dry, bare rock. Only a few mosses grow in this desert ecosystem, supporting only a few birds, such as skuas.

Threats to Ecosystems

For thousands of years, people have interacted with ecosystems. Many cultures developed around nearby ecosystems. Many Native American tribes of North Americas Great Plains developed a complex lifestyle based on the native plants and animals of plains ecosystems, for instance. Bison, a large grazing animal native to the Great Plains, became the most important biotic factor in many Plains Indians cultures, such as the Lakota or Kiowa. Bison are sometimes mistakenly called buffalo. These tribes used buffalo hides for shelter and clothing, buffalo meat for food, and buffalo horn for tools. The tallgrass prairie of the Great Plains supported bison herds, which tribes followed throughout the year.


As human populations have grown, however, people have overtaken many ecosystems. The tallgrass prairie of the Great Plains, for instance, became farmland. As the ecosystem shrunk, fewer bison could survive. Today, a few herds survive in protected ecosystems such as Yellowstone National Park.

In the tropical rain forest ecosystems surrounding the Amazon River in South America, a similar situation is taking place. The Amazon rain forest includes hundreds of ecosystems, including canopies, understories, and forest floors. These ecosystems support vast food webs.

Canopies are ecosystems at the top of the rainforest, where tall, thin trees such as figs grow in search of sunlight. Canopy ecosystems also include other plants, called epiphytes, which grow directly on branches. Understory ecosystems exist under the canopy. They are darker and more humid than canopies. Animals such as monkeys live in understory ecosystems, eating fruits from trees as well as smaller animals like beetles. Forest floor ecosystems support a wide variety of flowers, which are fed on by insects like butterflies. Butterflies, in turn, provide food for animals such as spiders in forest floor ecosystems.

Human activity threatens all these rain forest ecosystems in the Amazon. Thousands of acres of land are cleared for farmland, housing, and industry. Countries of the Amazon rain forest, such as Brazil, Venezuela, and Ecuador, are underdeveloped. Cutting down trees to make room for crops such as soy and corn benefits many poor farmers. These resources give them a reliable source of income and food. Children may be able to attend school, and families are able to afford better health care.

However, the destruction of rain forest ecosystems has its costs. Many modern medicines have been developed from rain forest plants. Curare, a muscle relaxant, and quinine, used to treat malaria, are just two of these medicines. Many scientists worry that destroying the rain forest ecosystem may prevent more medicines from being developed.

The rain forest ecosystems also make poor farmland. Unlike the rich soils of the Great Plains, where people destroyed the tallgrass prairie ecosystem, Amazon rain forest soil is thin and has few nutrients. Only a few seasons of crops may grow before all the nutrients are absorbed. The farmer or agribusiness must move on to the next patch of land, leaving an empty ecosystem behind.

Rebounding Ecosystems

Ecosystems can recover from destruction, however. The delicate coral reef ecosystems in the South Pacific are at risk due to rising ocean temperatures and decreased salinity. Corals bleach, or lose their bright colors, in water that is too warm. They die in water that isnt salty enough. Without the reef structure, the ecosystem collapses. Organisms such as algae, plants such as seagrass, and animals such as fish, snakes, and shrimp disappear.

Most coral reef ecosystems will bounce back from collapse. As ocean temperature cools and retains more salt, the brightly colored corals return. Slowly, they build reefs. Algae, plants, and animals also return.

Individual people, cultures, and governments are working to preserve ecosystems that are important to them. The government of Ecuador, for instance, recognizes ecosystem rights in the countrys constitution. The so-called Rights of Nature says Nature or Pachamama [Earth], where life is reproduced and exists, has the right to exist, persist, maintain and regenerate its vital cycles, structure, functions and its processes in evolution. Every person, people, community or nationality, will be able to demand the recognitions of rights for nature before the public bodies. Ecuador is home not only to rain forest ecosystems, but also river ecosystems and the remarkable ecosystems on the Galapagos Islands.

Vocabulary

Term Part of Speech Definition Encyclopedic Entry

abiotic

Adjective

lacking or absent of life.

adapt

Verb

to adjust to new surroundings or a new situation.

agribusiness

Noun

the strategy of applying profit-making practices to the operation of farms and ranches.

algae

Plural Noun

(singular: alga) diverse group of aquatic organisms, the largest of which are seaweeds.

animal

Noun

organisms that have a well-defined shape and limited growth, can move voluntarily, acquire food and digest it internally, and can respond rapidly to stimuli.

aquatic

Adjective

having to do with water.

arid

Adjective

dry.

biome

Noun

area of the planet which can be classified according to the plant and animal life in it.

Encyclopedic Entry: biome

biotic factor

Noun

effect or impact of an organism on its environment.

bison

Noun

large mammal native to North America. Also called American buffalo.

butterfly

Noun

type of flying insect with large, colorful wings.

canopy

noun, verb

the top layer of a forest formed by the thick leaves of very tall trees.

carnivore

Noun

organism that eats meat.

Encyclopedic Entry: carnivore

characterize

Verb

to describe the characteristics of something.

climate

Noun

all weather conditions for a given location over a period of time.

Encyclopedic Entry: climate

complex

Adjective

complicated.

constitution

Noun

system of ideas and general laws that guide a nation, state, or other organization.

continent

Noun

one of the seven main land masses on Earth.

Encyclopedic Entry: continent

coral reef

Noun

rocky ocean features made up of millions of coral skeletons.

corn

noun, adjective

tall cereal plant with large seeds (kernels) cultivated for food and industry. Also called maize.

crocodile

Noun

reptile native to parts of Africa, Asia, and the Americas.

crop

Noun

agricultural produce.

Encyclopedic Entry: crop

culture

Noun

learned behavior of people, including their languages, belief systems, social structures, institutions, and material goods.

curare

Noun

resin obtained from South American trees, often dried and used as an ingredient in muscle relaxants.

date palm

Noun

type of fruit tree.

delicate

Adjective

fragile or easily damaged.

desert

Noun

area of land that receives no more than 25 centimeters (10 inches) of precipitation a year.

Encyclopedic Entry: desert

destruction

Noun

ruin.

determine

Verb

to decide.

distinct

Adjective

unique or identifiable.

dune

Noun

a mound or ridge of loose sand that has been deposited by wind.

Encyclopedic Entry: dune

ecocide

Noun

total destruction of an ecosystem.

ecology

Noun

branch of biology that studies the relationship between living organisms and their environment.

Encyclopedic Entry: ecology

economics

Noun

study of monetary systems, or the creation, buying, and selling of goods and services.

ecosystem

Noun

community and interactions of living and nonliving things in an area.

Encyclopedic Entry: ecosystem

endangered species

Noun

organism threatened with extinction.

Encyclopedic Entry: endangered species

epiphyte

Noun

plant that grows on the branches or trunk of another plant or object.

evolution

Noun

process of how present types of organisms developed from earlier forms of life.

farmland

Noun

area used for agriculture.

fig

Noun

fruit and tree native to Asia.

flower

Noun

blossom or reproductive organs of a plant.

fog

Noun

clouds at ground level.

Encyclopedic Entry: fog

food

Noun

material, usually of plant or animal origin, that living organisms use to obtain nutrients.

Encyclopedic Entry: food

food web

Noun

all related food chains in an ecosystem. Also called a food cycle.

Encyclopedic Entry: food web

forest

Noun

ecosystem filled with trees and underbrush.

frequent

Adjective

often.

freshwater

Noun

water that is not salty.

Galapagos Islands

Noun

archipelago in the Pacific Ocean, off the coast of Ecuador.

gazelle

Noun

small antelope native to Africa and Asia.

geographic

Adjective

having to do with places and the relationships between people and their environments.

geography

Noun

study of places and the relationships between people and their environments.

Encyclopedic Entry: geography

goat

Noun

hoofed mammal domesticated for its milk, coat, and flesh.

government

Noun

system or order of a nation, state, or other political unit.

grass

Noun

type of plant with narrow leaves.

grazing animal

Noun

animal that feeds on grasses, trees, and shrubs.

Great Plains

Noun

grassland region of North America, between the Rocky Mountains and the Mississippi River.

health care

Noun

system for addressing the physical health of a population.

herbivore

Noun

organism that eats mainly plants.

Encyclopedic Entry: herbivore

herd

Noun

group of animals.

hermit crab

Noun

type of marine animal (crustacean) that uses found materials, such as other creatures' shells, as its shell.

hide

Noun

leather skin of an animal.

history

Noun

study of the past.

human ecosystem

Noun

environment constructed or adapted to by people and culture.

humidity

Noun

amount of water vapor in the air.

Encyclopedic Entry: humidity

ice sheet

Noun

thick layer of glacial ice that covers a large area of land.

Encyclopedic Entry: ice sheet

income

Noun

wages, salary, or amount of money earned.

industry

Noun

activity that produces goods and services.

insect

Noun

type of animal that breathes air and has a body divided into three segments, with six legs and usually wings.

Kiowa

Noun

people and culture native to the Great Plains of North America.

Lakota

Noun

people and culture of seven Sioux tribes native to the Great Plains.

landscape

Noun

the geographic features of a region.

Encyclopedic Entry: landscape

maintain

Verb

to continue.

malaria

Noun

infectious disease caused by a parasite carried by mosquitoes.

marine

Adjective

having to do with the ocean.

medicine

Noun

substance used for treating illness or disease.

monkey

Noun

mammal considered to be highly intelligent, with four limbs and, usually, a tail.

moss

Noun

tiny plant usually found in moist, shady areas.

mussel

Noun

aquatic animal with two shells that can open and close for food or defense.

nutrient

Noun

substance an organism needs for energy, growth, and life.

Encyclopedic Entry: nutrient

oasis

Noun

area made fertile by a source of fresh water in an otherwise arid region.

Encyclopedic Entry: oasis

ocean

Noun

large body of salt water that covers most of the Earth.

Encyclopedic Entry: ocean

organism

Noun

living or once-living thing.

Pachamama

Noun

goddess of the Earth recognized by many cultures of the Andes Mountains.

perish

Verb

to die or be destroyed.

persist

Verb

to endure or continue.

photosynthesis

Noun

process by which plants turn water, sunlight, and carbon dioxide into water, oxygen, and simple sugars.

plain

Noun

flat, smooth area at a low elevation.

Encyclopedic Entry: plain

plant

Noun

organism that produces its own food through photosynthesis and whose cells have walls.

politics

Noun

art and science of public policy.

pond

Noun

small body of water surrounded by land.

preserve

Verb

to maintain and keep safe from damage.

public

Adjective

available to an entire community, not limited to paying members.

quinine

Noun

drug used to treat malaria.

rain forest

Noun

area of tall evergreen trees and a high amount of rainfall.

reef

Noun

a ridge of rocks, coral, or sand rising from the ocean floor all the way to or near the ocean's surface.

reliable

Adjective

dependable or consistent.

remarkable

Adjective

unusual and dramatic.

resource

Noun

available supply of materials, goods, or services. Resources can be natural or human.

river

Noun

large stream of flowing fresh water.

Encyclopedic Entry: river

rock

Noun

natural substance composed of solid mineral matter.

Sahara Desert

Noun

world's largest desert, in north Africa.

salinity

Noun

saltiness.

sand

Noun

small, loose grains of disintegrated rocks.

scorpion

Noun

animal related to a spider with a poisonous sting in its tail.

seagrass

Noun

type of plant that grows in the ocean.

sea star

Noun

marine animal (echinoderm) with many arms radiating from its body. Also called a starfish.

seaweed

Noun

marine algae. Seaweed can be composed of brown, green, or red algae, as well as "blue-green algae," which is actually bacteria.

shelter

Noun

structure that protects people or other organisms from weather and other dangers.

shrimp

Noun

animal that lives near the bottom of oceans and lakes.

shrub

Noun

type of plant, smaller than a tree but having woody branches.

skua

Noun

bird related to the seagull.

snake

Noun

reptile with scales and no limbs.

snowfall

Noun

amount of snow at a specific place over a specific period of time.

soil

Noun

top layer of the Earth's surface where plants can grow.

soy

Noun

beans, or fruit, of the soybean plant, native to Asia.

spider

Noun

eight-legged animal (arachnid) that usually spins webs to catch food.

survive

Verb

to live.

takhi

Noun

endangered species of wild horse native to Central Asia. Also called Przewalski's horse.

tallgrass prairie

Noun

plain where grasses grow up to 2 meters (6 feet) tall.

technology

Noun

the science of using tools and complex machines to make human life easier or more profitable.

temperature

Noun

degree of hotness or coldness measured by a thermometer with a numerical scale.

Encyclopedic Entry: temperature

tide

Noun

rise and fall of the ocean's waters, caused by the gravitational pull of the moon and sun.

Encyclopedic Entry: tide

tide pool

Noun

small pond created by an ebb tide and submerged by a high tide.

tropical

Adjective

existing in the tropics, the latitudes between the Tropic of Cancer in the north and the Tropic of Capricorn in the south.

tundra

Noun

cold, treeless region in Arctic and Antarctic climates.

underdeveloped country

Noun

country that has fallen behind on goals of industrialization, infrastructure, and income.

understory

Noun

ecosystem between the canopy and floor of a forest.

urban ecosystem

Noun

environment of cities, towns, and suburbs.

vast

Adjective

huge and spread out.

vital

Adjective

necessary or very important.

weather

Noun

state of the atmosphere, including temperature, atmospheric pressure, wind, humidity, precipitation, and cloudiness.

Encyclopedic Entry: weather

wind

Noun

movement of air (from a high pressure zone to a low pressure zone) caused by the uneven heating of the Earth by the sun.

Credits

Media Credits

The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit. The Rights Holder for media is the person or group credited.

Writer

Kim Rutledge
Melissa McDaniel
Diane Boudreau
Tara Ramroop
Santani Teng
Erin Sprout
Hilary Costa
Hilary Hall
Jeff Hunt

Illustrator

Tim Gunther
Mary Crooks, National Geographic Society

Editor

Kara West
Jeannie Evers

Educator Reviewer

Nancy Wynne

Producer

Caryl-Sue, National Geographic Society

Sources

Dunn, Margery G. (Editor). (1989, 1993). "Exploring Your World: The Adventure of Geography." Washington, D.C.: National Geographic Society.

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