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Chemistry
LECTURE NOTES ON CHAPTER 6
I. Biomes – a large region characterized by a specific type of climate and certain types of
plants and animal communities
A. Made of many individual ecosystems
B. Include ecosystems on land and in water
C. Terrestrial biomes – groups of land ecosystems
1. Described by vegetation
a. Because plants determine other organisms that can live there
b. Because plants do no migrate
c. Plants are adapted to survive in specific biomes; adaptations include:
1) size
2) shape
3) color
2. Vegetation is determined by climate – weather conditions such as temperature,
precipitation, humidity, and winds in an area over a long period of time
a. Two most important factors determine climate:
1) Temperature
2) Precipitation
a) the larger an organism is, the more water it needs
b) lack of rainfall results in no plants regardless of temperature
3) The higher the temperature and precipitation are, the taller and denser the
vegetation is
D. Biomes, climate, & vegetation vary with latitude and altitude
1. Latitude – the distance north or south of the equator measured in degrees
2 .Altitude – height of an object above sea level
3. As latitude & altitude increase, biomes & vegetation change
a. tropical rain forest close to equator
b. tundras nearer to poles
c. temperate regions
1) Land regions between 30° & 60° north latitude and 30° and 60° south
latitude
2) Most of the food in the world is grown here
3) Has biomes like grasslands and temperate forests
II. Forest Biomes
A. Most wide-spread and divers of all biomes
B. Have large trees that need a lot of water
C. Temperatures mild to hot
D. Rainfall is plentiful
E. Three main types:
1. Tropical rain forests
a. located in a belt around the Earth near the equator
b. help regulate world climate
c. play vital roles in nitrogen, oxygen, & carbon cycles
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d. humid and warm
e. 200-450 cm rainfall annually
f. get strong sunlight year-round
g. temperatures relatively constant year-round
h. nourish more species of plants than any other biome
i. soil is thin and nutrient poor
1) nutrients are within plants, not soil
2) rapid decomposition return nutrients to soil
a) Multitude of plants quickly absorb nutrients
3) many trees support fungi that feed on dead organic matter on rain forest
floor
a) fungi transfer nutrients directly to trees
4) rapid recycle of nutrients makes run-off water very pure
5) cleared tropical rain forests make poor farmland because of lack of
nutrients
6) buttresses or braces – above-ground roots that grow sideways from trees
to provide extra support in thin soil
j. Layers of rain forests – different types of plants grow in four different layers
1) emergent layer – top layer
a) Consists of tallest trees reaching heights of 60-70 meters
b) have very large trunks (up to 5 meters)
c) emerge into direct sunlight
d) eagles, bats, monkeys, & snakes live in layer
2) upper & lower canopy – primary layer; beneath emergent layer
a) trees grow more than 30 m. tall
b) form a dense layer that absorbs 95% of sunlight
c) epiphytes use entire surface of trees as place to live
d) most of the animals of the rain forest live in canopy
3) understory – below canopies
a) receives very little light
b) trees & shrubs adapted to shade
c) plants are small ( 3.5 m)
d) plants usually have broad, flat leaves to catch little sunlight
k. animals of rain forest are diverse and uniquely adapted
l. threats to rain forests
1) habitat destruction – when habitat is destroyed, organisms that depend
on it risk destruction
a) once covered about 20% of Earth’s surface
b) today cover only 7% of Earth’s surface
c) 100 acres per minute per day are cleared
d) 50 million native peoples live in rain forest
2) Trading plants and animals is also a threat
2. Temperate Rain Forests
a. In North America, Australia, and New Zealand
b. have large amounts of precipitation, high humidity, & moderate
temperatures
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c. large trees draped with mosses & tree trunks covered with lichens
3. Temperate Deciduous Forests
a. trees lose broad, flat leaves each fall
b. located 30° and 50° north latitude
c. temperature ranges can be extreme
1) summer temperatures can exceed 35° C.
2) winter temperatures can fall below freezing
a) leaves little water for plants
3) Vary due to seasons
d. receive 75 – 125 cm of precipitation annually
e. precipitation contributes to decomposition which creates deep, rich soil
f. plants grow in layers
1) Canopy filled with large trees (maples, oak, & birch)
2) small tress & shrubs cover understory
3) forest floor receives sunlight to grow ferns, herbs & mosses
4) plants adapted to seasonal changes
g. animals adapted to use the forest plants for food and shelter
1) hibernation is an adaptation for winter in some animals
2) most birds migrate to avoid harsh winters
4. Taiga
a. northern coniferous forest forming band in Northern Hemisphere below Arctic
Circle
b. winters are 6-10 months long
1) average temperatures are below freezing
a) often fall to -20° below
c. forest floor is dark with little vegetation
d. trees have straight trunks of bark and wood with leaves only at top
e. growing season is as little as 50 days
f. plant growth in summer is abundant because of nearly constant daylight &
larger amount of precipitation
g. conifers – trees that have seeds that develop in cones
1) do not shed leaves
2) leaves are needle-shaped
a) shape and waxy coating help retain water
3) pointed shape helps shed snow to ground
4) acidic needles on ground prevent other plants from growing
h. soil
1) acidic because of conifer needles
2) slow forming because of climate
i. have many lakes and swamps
III. Savannas – grasslands located in tropical and subtropical areas near the equator &
between tropical rain forest & desert biomes
A. Have wet season and dry season
1. grass fires during dry season help restore nutrients to soil
B. Plants
1. adapted to long periods without rain
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a. some have large horizontal root systems
b. enable plant to regrow quickly after fires
c. grasses have vertical leaves for less exposure to sun to conserve water
d. some trees lose leaves during dry season to conserve water
2. often have thorns or sharp leaves to keep away herbivores
C. Animals
1. grazing animals have migratory lifestyles
a. follow rains to new areas of vegetation and water holes
2. predators follow migratory animals
3. many give birth during rainy season when food & water is abundant
4. herbivores have adapted to eat vegetation at different heights to reduce
competition
IV. Temperate Grasslands
A. dominated by grasses with few trees
B. hot summers and cold winters
C. moderate rainfall compared to temperate forests
1. 50-88 cm per year
2. rain is often blocked by mountains
3. grass fires due to high temperatures & little rain in summer
D. have most fertile soil than any other biome
1. most have been replaced with farms and grazing areas
E. located on interiors of continents where too little rain falls for trees to grow
1. prairies North America
2. steppes of Russia and Ukraine
3. pampas of South America
F. Plants
1. perennials – plants that survive from year to year
a. grasses and wildflowers
2. grasses have dense root systems in layers
a. help survive drought and fire
b. hold soil in place
3. few trees
G. Animals
1. grazing animals
a. have large, flat back teeth for chewing coarse grasses
2. some animals live in underground burrows for protection
H. Threats
1. Farming
a. Soil erosion occurs because grains cannot hold soil like grasses
2. Grazing
a. also causes soil erosion
3. Soil erosion can change grasslands to less productive, desertlike areas
V. Chaparral
A. Temperate woodland biome dominated by broad-leafed evergreen shrubs
B. Located in middle latitudes - 30° north and south of equator
1. located primarily in coastal areas with Mediterranean climates
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C. Have warm, dry summers and mild, wet winters
D. Plants
1. mostly low-lying evergreen shrubs & small trees
a. grow in dense patches
b. have leathery leaves that retain water
1) contain oils that promote burning
c. can resprout from small bits of surviving plant tissue
2. have few scattered coniferous trees
E. Animals
1. Camouflage – shape or coloring that allows an animal to blend into its
environment
a. common adaptation in this biome
F. Threats
1. Human development is greatest threat
a. developed because biomes get a lot of sun, is near oceans, and have mild
climate year-round
VI. Deserts
A. driest places on Earth
1. receive less than 25 cm of precipitation per year
2. have little or no vegetation
3. often located near mountain ranges which block passage of rain clouds
B. have extreme temperatures
C. Two kinds of deserts
1. Hot deserts – located closer to the equator
2. Cold deserts – farther away from equator
D. Plants
1. have adaptations for obtaining & conserving water
2. succulents – have thick, fleshy stems & leaves that store water
a. have waxy coating to prevent water loss
b. sharp spines keep animals from eating
3. roots spread out just under the surface of soil
4. some are adapted to survive long periods of time without water
a. seeds stay dormant until next rain fall
b. plants germinate quickly & bloom before soil becomes dry again
c. can survive when water content drops to 30%
1) most plants die when water levels are below 50-70%
E. Animals
1. Many reptiles with thick, scaly skin to prevent water loss
2. Amphibians often estivate – burying into ground & sleeping through dry
season
3. Some nest in cactuses to avoid predators
4. Many insects & spiders are covered with body armor to prevent water loss
5. Most desert animals are nocturnal – active at night
VI. Tundra
A. biome dominated by grasses, lichens, and herbs
B. located primarily north of the Arctic Circle
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C. short summers
D. permafrost – a permanently frozen soil beneath topsoil
1. in summer, only a few centimeters of topsoil thaw
2. thawing creates bogs and swamps
E. Plants
1. many mosses and lichens which can grow without soil
2. plants have wide, shallow roots because of thin soil
3. flowering plants are short
a. growing close to ground keeps plants out of wind & helps absorb heat from
sunlit soil
4. wood plants have adapted to dwarf forms that grow flat or along ground
F. Animals
1. Millions of migratory birds in summer
a. breed on tundra
b. bogs & swamps attract insects for food
2. Caribou, deer, & moose migrate through
3. wolves & other predators follow migratory animals
4. small rodents burrow underground & remain active
5. animals that live on tundra year round have adapted
a. camouflage
b. highly insulated
G. Threats
1. one of the most fragile biomes on planet
a. food chains are simple & easily disrupted
b. because of extreme conditions land is easily damaged & slow to recover
2. Oil exploration, extraction, and transport has disrupted tundra recently
3. Pollution caused by spills or leaks of oil poisons food & water sources
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