lacking or absent of life.

to adjust to new surroundings or a new situation.

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

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

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.

having to do with water.

dry.

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

effect or impact of an organism on its environment.

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

type of flying insect with large, colorful wings.

one of the top layers of a forest, formed by the thick leaves of very tall trees.

organism that eats meat.

to describe the characteristics of something.

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

complicated.

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

one of the seven main land masses on Earth.

rocky ocean features made up of millions of coral skeletons.

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

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

agricultural produce.

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

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

type of fruit tree.

fragile or easily damaged.

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

ruin.

to decide.

unique or identifiable.

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

total destruction of an ecosystem.

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

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

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

organism threatened with extinction.

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

change in heritable traits of a population over time.

area used for agriculture.

fruit and tree native to Asia.

blossom or reproductive organs of a plant.

clouds at ground level.

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

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

ecosystem filled with trees and underbrush.

often.

water that is not salty.

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

small antelope native to Africa and Asia.

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

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

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

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

type of plant with narrow leaves.

animal that feeds on grasses, trees, and shrubs.

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

system for addressing the physical health of a population.

organism that eats mainly plants and other producers.

group of animals.

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

leather skin of an animal.

study of the past.

environment constructed or adapted to by people and culture.

amount of water vapor in the air.

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

wages, salary, or amount of money earned.

activity that produces goods and services.

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

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

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

the geographic features of a region.

to continue, keep up, or support.

infectious disease caused by a parasite carried by mosquitoes.

having to do with the ocean.

substance used for treating illness or disease.

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

tiny plant usually found in moist, shady areas.

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

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

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

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

living or once-living thing.

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

to die or be destroyed.

to endure or continue.

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

flat, smooth area at a low elevation.

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

art and science of public policy.

small body of water surrounded by land.

to maintain and keep safe from damage.

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

drug used to treat malaria.

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

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

dependable or consistent.

unusual and dramatic.

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

large stream of flowing fresh water.

natural substance composed of solid mineral matter.

world's largest desert, in north Africa.

saltiness.

small, loose grains of disintegrated rocks.

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

type of plant that grows in the ocean.

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

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

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

animal that lives near the bottom of oceans and lakes.

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

bird related to the seagull.

reptile with scales and no limbs.

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

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

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

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

to live.

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

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

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

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

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

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

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

cold, treeless region in Arctic and Antarctic climates.

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

ecosystem between the canopy and floor of a forest.

environment of cities, towns, and suburbs.

huge and spread out.

necessary or very important.

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

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