Chapter 4, Lesson 1
Water, carbon, nitrogen, and oxygen must be recycled because they are necessary for all living things.
If they were not recycled, we would run out.
Water cycle: continuous movement of water between Earth’s surface and the air
Evaporation: liquid to gas
Condensation: gas to liquid
Precipitation: any water that falls from the atmosphere and reaches the ground
(rain, snow, sleet)
Groundwater: water collected in soil and rocks
Watershed: an area from which water is drained
Transpiration: process of plants taking in water and returning it to the air through leaves
Runoff: precipitation that flows across the land and is not absorbed so it flows into rivers, lakes,
and streams
Carbon cycle: the continuous exchange of carbon among living things
Plants take in carbon dioxide  Consumers eat plants and get carbon
They release carbon during cellular respiration
When fossil fuels are burned they release carbon as well
Nitrogen cycle: continual trapping of nitrogen gas into compounds in the soil and its return to the air
Air is 78% nitrogen, but few living things can use the nitrogen gas without it being “fixed”
Volcanic activity and lightning can “fix” nitrogen
Nitrogenn-fixing bacteria: on root nodules; turn gas into ammonia.
The ammonia is changed to a form of nitrogen that can be used by plants
Plants absorb the nitrates and make proteins
Animals take in the nitrogen when they eat the plants.
Animals then excrete the nitrogen.
Bacteria change it into usable nitrogen again.
Denitrification: bacteria in the soil changing some nitrogen back into nitrogen gas
Renewable Resources: resources that can be replaced (trees)
Non-renewable Resources: resources that cannot be replaced (oil, metals)
Compost: mixture of dead organic material that can be used as fertilizer
Chapter 4, lesson 2
Ecosystems can be changed by natural events (earthquakes, floods, storms, volcanoes, droughts) or by
organisms (beavers, elephants, algae, coral, humans)
Some changes are permanent!
Organisms must respond in order to survive. (migrate to different area or adapt by changing)
If the organism does not respond it can become extinct.
Extinct species: last member of species has died
Endangered species: species in danger of becoming extinct (sometimes only a few hundred exist)
Threatened species: low numbers; could become endangered
*biggest threat is destruction or loss of habitats
Succession: 1 group of species is replace by a different group of species in an ecosystem
Primary Succession: begins in an community with few living things
Pioneer Species: the first to live in a lifeless area
Pioneer Community: combination of pioneer species and microorganisms
Climax community: the final stage of succession
Secondary Succession: beginning of a new community where one already existed; faster than
primary succession. This could be after a disaster.
Chapter 4, lesson 3
Biome: one of Earth’s major land ecosystems with its own characteristic animals, plants, soil, and
climate
Six Major Biomes
Desert: sandy or rocky with little precipitation or plant life; can be cold or hot
Tundra: large, treeless biome where ground is frozen all year; permafrost layer
Taiga: world’s largest biome; cool forest biome of conifers; animals with thick coats of fur and
layers of fat
Rain Forest
Tropical Rain Forest: hot, humid, near the equator; heavy rain and variety of life; more
organisms than any other biome; 4 layers
Temperate Rain Forest: a lot of rain, fog, and cool climate; large evergreens, mosses,
ferns
Deciduous Forest: forest biome with four distinct season and deciduous trees; trees change
Color and lose leaves; animals migrate or hibernate in winter
Grasslands: grasses are main plant life; cool winters and hot summers; prairies
Wetter than a desert, but not enough rain for many trees
Chapter 4, lesson 4
97% of water on Earth is saltwater.
3 Categories of Water Organisms
Plankton: organisms that drift freely in water
Nekton: active swimmers (fish, turtles, and whales)
Benthos: live at bottom of body of water (oysters, lobsters)
Freshwater Ecosystems
Running Water Ecosystem: brooks and rivers
Fast moving have more oxygen than slow moving
Standing Water Ecosystem: lakes and ponds; 3 zones
Freshwater Wetlands: marshes, swamps, bogs
Ocean Ecosystems: divided into zones
Intertidal zone: shallowest part; moon’s gravity has impact
Neritic zone: key resource is sunlight; lots of organisms
Oceanic zone: divided into 2 zones
Bathyal: many consumers but few producers
Abyssal: darker and colder; no sun; decomposers and scavengers
Estuary: place where freshwater and saltwater meet; moon has an impact and the amount of salt vs.
fresh water changes with the tide