Unit 1: What is Biology?
Unit 2: Ecology
Unit 3: The Life of a Cell
Unit 4: Genetics
Unit 5: Change Through Time
Unit 6: Viruses, Bacteria, Protists, and Fungi
Unit 7: Plants
Unit 8: Invertebrates
Unit 9: Vertebrates
Unit 10: The Human Body
Unit 1: What is Biology?
Chapter 1: Biology: The Study of Life
Unit 2: Ecology
Chapter 2: Principles of Ecology
Chapter 3: Communities and Biomes
Chapter 4: Population Biology
Chapter 5: Biological Diversity and Conservation
Unit 3: The Life of a Cell
Chapter 6: The Chemistry of Life
Chapter 7: A View of the Cell
Chapter 8: Cellular Transport and the Cell Cycle
Chapter 9: Energy in a Cell
Unit 4: Genetics
Chapter 10: Mendel and Meiosis
Chapter 11: DNA and Genes
Chapter 12: Patterns of Heredity and Human Genetics
Chapter 13: Genetic Technology
Unit 5: Change Through Time
Chapter 14: The History of Life
Chapter 15: The Theory of Evolution
Chapter 16: Primate Evolution
Chapter 17: Organizing Life’s Diversity
Unit 6: Viruses, Bacteria, Protists, and Fungi
Chapter 18: Viruses and Bacteria
Chapter 19: Protists
Chapter 20: Fungi
Unit 7: Plants
Chapter 21:
Chapter 22:
Chapter 23:
Chapter 24:
What Is a Plant?
The Diversity of Plants
Plant Structure and Function
Reproduction in Plants
Unit 8: Invertebrates
Chapter 25: What Is an Animal?
Chapter 26: Sponges, Cnidarians, Flatworms, and
Roundworms
Chapter 27: Mollusks and Segmented Worms
Chapter 28: Arthropods
Chapter 29: Echinoderms and Invertebrate
Chordates
Unit 9: Vertebrates
Chapter 30: Fishes and Amphibians
Chapter 31: Reptiles and Birds
Chapter 32: Mammals
Chapter 33: Animal Behavior
Unit 10: The Human Body
Chapter 34: Protection, Support, and Locomotion
Chapter 35: The Digestive and Endocrine Systems
Chapter 36: The Nervous System
Chapter 37: Respiration, Circulation, and Excretion
Chapter 38: Reproduction and Development
Chapter 39: Immunity from Disease
Ecology
Principles of Ecology
Communities and Biomes
Population Biology
Biological Diversity and Conservation
Chapter 3 Communities and Biomes
3.1: Communities
3.1: Section Check
3.2: Biomes
3.2: Section Check
Chapter 3 Summary
Chapter 3 Assessment
What You’ll Learn
You will identify factors that limit the
existence of species to certain areas.
You will describe how and why
different communities form.
You will compare and contrast
biomes of Earth.
Section Objectives:
• Identify some common limiting factors.
• Explain how limiting factors and ranges of
tolerance affect distribution of organisms.
• Sequence the stages of ecological
succession.
• Describe the conditions under which
primary and secondary succession take
place.
Life in a Community
• Various
combinations
of abiotic and
biotic factors
interact in
different places
around the
world.
Life in a Community
• The result is
that conditions
in one part of
the world are
suitable for
supporting
certain forms
of life, but not
others.
Limiting factors
• Factors that affect an organism’s ability to
survive in its environment, such as the
availability of water and food, predators, and
temperature, are called limiting factors.
Limiting factors
• A limiting factor
is any biotic or
abiotic factor
that restricts the
existence,
numbers,
reproduction, or
distribution of
organisms.
Common Limiting
Factors
Sunlight
Climate
Atmospheric gases
Temperature
Water
Nutrients/Food
Fire
Soil chemistry
Space
Other organisms
Limiting factors
• Factors that
limit one
population in a
community
may also have
an indirect
effect on
another
population.
Ranges of tolerance
• The ability of an organism to withstand
fluctuations in biotic and abiotic
environmental factors is known as tolerance.
Limits of Tolerance
Organisms
absent
Organisms
infrequent
Organisms
infrequent
Organisms
absent
Population
Greatest number
of organisms
Zone of
Zone of
Physiological
intolerance
stress
Lower limit
Optimum range
Range of tolerance
Zone of
Zone of
Physiological intolerance
stress
Upper limit
Succession: Changes over Time
• Ecologists refer to the orderly, natural
changes and species replacements that take
place in the communities of an ecosystem as
succession.
• Succession occurs in stages. At each stage,
different species of plants and animals may
be present.
Succession: Changes over Time
• As succession progresses, new organisms
move in.
• Others may die out or move out.
• There are two types of succession—primary
and secondary.
Primary succession
• The colonization of barren land by
communities of organisms is called primary
succession.
• Primary succession takes place on land
where there are no living organisms.
Primary succession
• The first species to take hold in an area like
this are called pioneer species.
• An example of pioneer species is a lichen,
which is a combination of small organisms.
Primary succession
• Decaying lichens, along with bits of
sediment in cracks and crevices of rock,
make up the first stage of soil development.
• New soil makes it possible for small weedy
plants, small ferns, fungi, and insects to
become established.
Primary succession
• As these organisms die, more soil builds.
Moss
Lichen
Exposed rock
Pioneer
species
Primary succession
Primary succession
• After some time, primary succession slows
down and the community becomes fairly
stable, or reaches equilibrium.
Primary succession
• A stable, mature community that undergoes
little or no change in species is a climax
community.
Secondary succession
Climax community
Secondary succession
• Secondary succession is the sequence of
changes that takes place after an existing
community is severely disrupted in some
way.
• Secondary succession, however, occurs in
areas that previously contained life, and on
land that still contains soil.
Secondary succession
• Because soil
already exists,
secondary
succession may
take less time
than primary
succession to
reach a climax
community.
Question 1
A(n) _____ is something that restricts the
existence, numbers, reproduction or distribution
of organisms. (TX Obj 3, 12E)
A. abiotic factor
B. biotic factor
C. tolerance factor
D. limiting factor
The answer is D. A
limiting factor may
be a abiotic factor.
Tolerance refers to
an organism’s
ability to withstand
fluctuations of
environmental
factors.
Common Limiting
Factors
Sunlight
Climate
Atmospheric gases
Temperature
Water
Nutrients/Food
Fire
Soil chemistry
Space
Other organisms
Question 2
Which of the following best illustrates primary
succession? (TX Obj 3; 9D, 13A)
A. lichen growing on a lava bed
B. wildflowers growing where forest fires had
burned
C. pine seedlings sprouting
D. mature trees growing
The answer is A. Primary succession is the
colonization of barren land by pioneer species,
such as moss or lichens.
Question 3
What is required in order for secondary
succession to occur? (TX Obj 3; 9D, 13A)
Secondary
succession occurs in
areas that previously
contained life. Soil
must be present on
this land, and the
species that grow
will differ from
pioneer species.
Question 4
A stable, mature community that undergoes little
or no change in species is a(n) _____. (TX Obj
3; 12E)
A. photic zone
B. primary community
C. climax community
D. estuary
The answer is C. Even though a climax
community is stable, balanced change
continues.
Secondary succession
Climax community
Section Objectives:
• Compare and contrast the photic and aphotic
zones of marine biomes.
• Identify the major limiting factors affecting
distribution of terrestrial biomes.
• Distinguish among biomes.
What is a biome?
• A biome is a large group of ecosystems that
share the same type of climax community.
• There are terrestrial
biomes and aquatic
biomes, each with
organisms adapted
to the conditions
characteristic of the
biome.
What is a biome?
• Biomes located on land are called terrestrial
biomes.
• Oceans, lakes,
streams,
ponds, or
other bodies
of water are
aquatic
biomes.
Aquatic Biomes
• Approximately 75 percent of Earth’s surface
is covered with water.
• Most of that water is salty.
• Freshwater is confined to rivers, streams,
ponds, and most lakes.
• As a result, aquatic biomes are separated into
marine biomes and freshwater biomes.
Marine biomes
• Different parts of the ocean differ in biotic
and abiotic factors (salinity, depth,
availability of light, and temperature) found
there.
• One of the ways ecologists study marine
biomes is to make separate observations in
shallow, sunlit zones and deeper, unlighted
zones.
Marine biomes
• The portion of the marine biome that is
shallow enough for sunlight to penetrate is
called the photic zone.
Marine biomes
• Deeper
water that
never
receives
sunlight
makes up
the aphotic
zone.
Estuaries—Mixed waters
• An estuary is a coastal body of water,
partially surrounded by land, in which
freshwater and salt water mix.
• The salinity, or amount of salt, in an estuary
ranges between that of seawater and that of
freshwater, and depends on how much
freshwater the river brings into the estuary.
Estuaries—Mixed waters
• Estuaries, may
contain salt marsh
ecosystems, which
are dominated by
salt-tolerant smooth
cordgrass, salt
marsh hay, or
eelgrasses.
The effects of tides
• Daily, the gravitational pull of the sun and
moon causes the rise and fall of ocean tides.
• The portion of the shoreline that lies between
the high and low tide lines is called the
intertidal zone.
• Intertidal ecosystems have high levels of
sunlight, nutrients, and oxygen.
The effects of tides
• Intertidal zones differ in rockiness and wave
action.
• If the shore is
rocky, waves
constantly
threaten to
wash
organisms into
deeper water.
The effects of tides
• If the
shore is
sandy,
wave
action
keeps the
bottom in
constant
motion.
In the light
• The photic zone of the marine biome
includes the vast expanse of open ocean that
covers most of Earth’s surface.
• Most of the organisms that live in the marine
biome are plankton.
In the light
• Plankton are
small
organisms
that drift and
float in the
waters of the
photic zone.
In the light
• Plankton are important because they form
the base of all aquatic food chains.
• Baleen whales and whale sharks, some of the
largest organisms that have ever lived,
consume vast amounts of plankton.
Freshwater biomes
• Although the summer sun heats the surface
of a lake the water a few feet below the
surface remains cold.
• These temperature variations within a lake
are an abiotic factor that limits the kinds of
organisms that can survive in deep lakes.
Freshwater biomes
• Another abiotic factor that limits life in deep
lakes is light.
Warmer layer
Colder layer
Oxygen and
light penetration
Greatest
Least
Greatest
species
diversity
Other aquatic biomes
• Other places where land and water meet are
called wetlands, but there are several
different kinds of wetlands. Swamps have
trees.
• Marshes do not, but both usually have water
flowing through them.
• Other wetland areas, called bogs, get their
water supply from rain. Water does not
flow through bogs.
Terrestrial Biomes: Latitude and climate
• Latitude
describes
your
position in
degrees
north and
south of
the
equator.
North pole
Sun’s rays
Sun’s rays
Sun’s rays
66.5o
23.5o
0Oo
Equator
23.5o
66.5o
South pole
Terrestrial Biomes: Latitude and climate
• At different
latitudes,
the sun
strikes
Earth
differently.
North pole
Sun’s rays
Sun’s rays
Sun’s rays
66.5o
23.5o
0Oo
Equator
23.5o
66.5o
South pole
Terrestrial Biomes: Latitude and climate
• As a result, the climate—wind, cloud cover,
temperature, humidity and precipitation in
that area—are different.
Terrestrial Biomes: Latitude and climate
Annual precipitation (cm)
• Latitude and
climate are
abiotic
factors that
affect what
plants and
animals will
survive in a
given area.
Annual Precipitation vs. Temperature for Various Biomes
400
300
Temperate
rain forest
200
Temperate
forest
100
Tropical
rain
forest
Tropical
seasonal
forest
Woodland Savanna
Grassland
Shrubland
Desert
0
10
20
30
Taiga
Tundra
-10
Average temperature (oC)
Life on the tundra
• The tundra is
a treeless land
with long
summer days
and short
periods of
winter
sunlight.
Life on the tundra
• Because of its latitude, temperatures in the
tundra never rise above freezing for long,
and only the topmost layer of soil thaws
during the summer.
• Underneath this top layer is a layer of
permanently frozen ground called
permafrost.
• The soil is lacking in nutrients.
Life on the tundra
• Lack of nutrients
limits the types of
organisms the
tundra can support.
• The short growing
season limits the
type of plants found in this biome to
grasses, dwarf shrubs, and cushion plants.
Life on the tundra
• Hordes of mosquitoes and black-flies are
some of the most common tundra insects
during the short summer.
• The tundra also is home to a variety of small
mammals, including ratlike lemmings,
weasels, arctic foxes, snowshoe hares, and
even birds such as snowy owls and hawks.
Life on the tundra
• Musk oxen, caribou and reindeer are among
the few large animals that migrate into the
area and graze during the summer months.
Life on the taiga
• Just south of the tundra lies another biome
that circles the north pole.
• The taiga (TI guh) also is called the boreal or
northern coniferous forest.
Life on the taiga
• Common
trees are
larch, fir,
hemlock,
and
spruce
trees.
Life on the taiga
• Because of their
latitude, taiga
communities
usually are
somewhat
warmer and
wetter than
tundra.
Life on the taiga
• However, the prevailing climatic conditions
are still harsh, with long, severe winters and
short, mild summers.
• The topsoil, which develops slowly from
decaying coniferous needles, is acidic and
poor in minerals.
Life on the taiga
• More large
species of
animals are
found in the
taiga as
compared
with the
tundra.
Life in the desert
• The driest biome
is the desert
biome. A desert
is an arid region
with sparse to
almost
nonexistent plant
life.
Life in the desert
• Deserts
usually get
less than 25
cm of
precipitation
annually.
Life in the desert
• With rainfall as the major limiting factor,
vegetation in deserts varies greatly.
• The
driest
deserts
are
drifting
sand
dunes.
Life in the desert
• Many desert plants are annuals that germinate
from seed and grow to maturity quickly after
sporadic rainfall.
• The leaves of some desert plants curl up, or
even drop off altogether, thus reducing water
loss during extremely dry spells.
• Many desert mammals are small herbivores
that remain under cover during the heat of the
day, emerging at night to forage on plants.
Life in the desert
• Coyotes, hawks, owls and roadrunners are
carnivores that feed on the snakes, lizards,
and small mammals of the desert.
Life in the grassland
• Grasslands are
large communities
covered with rich
soil, grasses, and
similar plants.
Life in the grassland
• Grasslands, occur principally in climates that
experience a dry season, where insufficient
water exists to support forests.
• Grasslands contain few trees per hectare.
Life in the grassland
• The soils of grasslands have considerable
humus content because many grasses die off
each winter, leaving byproducts to decay and
build up in the soil.
• At certain times of the year, many grasslands
are populated by herds of grazing animals.
Life in the grassland
• Other
important
prairie animals
include jack
rabbits, deer,
elk, and
prairie dogs.
• Many species of insects, birds, and reptiles,
also make their homes in grasslands.
Life in the temperate forest
• When precipitation
ranges from about
70 to 150 cm
annually in the
temperate zone,
temperate
deciduous forests
develop.
Life in the temperate forest
• Temperate or deciduous forests are dominated
by broad-leaved hardwood trees that lose their
foliage annually.
• The soil of
temperate forests
usually consists of a
top layer that is rich
in humus and a
deeper layer of clay.
Life in the temperate forest
• The animals that live in the temperate
deciduous forest include squirrels, mice,
rabbits, deer, and bears.
Life in the temperate forest
• Many birds,
such as
bluejays, live
in the forest
all year long,
whereas
other birds
migrate
seasonally.
Life in rain forests
• There are two types of rain forests in the
world—the temperate rain forest and the
more widely known tropical rain forest.
• Temperate rain forests are found on the
Olympic peninsula in Washington state and
in other places throughout the world, such as
South America, New Zealand, and Australia.
Life in rain forests
• As their name implies,
tropical rain forests have
warm temperatures, wet
weather, and lush plant
growth.
Life in rain forests
• The average
temperature
is about
250C.
Life in rain forests
• Rain forests receive at least 200 cm of rain
annually; some rain forests receive 600 cm.
• One reason for the large number of niches in
rain forests is vertical layering.
A Tropical Rain Forest: Canopy
• The canopy layer, 25-45 meters high, is a
living roof.
• The tree tops are exposed to rain, sunlight,
and strong winds.
• A few giant trees called emergents pole
through the canopy.
A Tropical Rain Forest: Canopy
• Monkeys
frequently pass
through.
• Birds, such
as scarlet
macaws,
live on the
fruits and
nuts of the
trees.
A Tropical Rain Forest: Understory
• In the understory, the air is still, humid, and
dark. Vines grow from the soil to the
canopy.
• Leaf cutter ants harvest leaves and bring
them to the ground.
• Plants include ferns, broad-leaved shrubs,
and dwarf palms.
A Tropical Rain Forest: Understory
• Insects are common in the understory.
• The limbs of the trees are hung with a thick
layer of epiphytes, plants that get most of
their moisture from the air.
• Birds and bats prey upon the insects.
A Tropical Rain Forest: Understory
• Tree frogs are
common
understory
amphibians.
• Reptiles
include
chameleons
and snakes.
A Tropical Rain Forest: Ground
• The ground layer is a moist forest floor.
• Leaves and other organic materials decay
quickly.
• Roots spread throughout the top 18 inches of
soil
• There is great competition for nutrients.
A Tropical Rain Forest: Ground
• Mammals living on
the ground include
rodents and cats,
such as the jaguar.
• Ants, termites,
earthworms, bacteria,
and fungi live in the
soil and quickly
decompose organic
materials.
Life in rain forests
• Some rain forest plants are important sources
of medicinal products and hardwood trees
and have provided a source of income for
people.
Life in rain forests
• Agricultural land is not common in rain
forests.
Life in rain forests
• Soils in rain forests do not have substantial
amounts of organic matter because leaf
matter, which contains nutrients, disappears
so quickly.
• Without organic matter, once rain forest soil
is exposed and farmed, it becomes hard,
almost brick-like, and nutrient-poor in a
matter of a few years.
Question 1
Groups of ecosystems that reach similar
climax communities are ________. (TX
Obj 3; 12E)
A. stable
B. biomes
C. terrestrial
D. populations
The answer is B. There are terrestrial and
aquatic biomes, each with organisms adapted
to the characteristics of the biome.
Question 2
Explain the difference between the photic and
aphotic zones of a marine biome. (TX Obj 3;
12E)
The photic zone is
the part of the marine
biome that is shallow
enough for sunlight
to penetrate.
Deeper water that
never receives
sunlight makes up the
aphotic zone.
Question 3
Compare an estuary to an intertidal zone.
(TX Obj 3; 12E)
Estuaries are coastal bodies of water that form
where rivers meet oceans, and in which
freshwater and salt water mix. Intertidal zones
are the portions of ocean shorelines that lie
between the high and low tide lines.
Question 4
The floating protists, animal eggs and larvae in
the photic zone are known as ________. (TX
Obj 3; 12E)
A. tide pool collections
B. foraminiferans
C. barnacles
D. plankton
The answer is D. Plankton are small
organisms that drift in the photic zone and
form the base of all aquatic food chains.
Question 5
Describe the oxygen levels at different depths
of a freshwater lake. (TX Obj 3; 9D)
Shallower waters are exposed to more sunlight,
are warmer and contain more oxygen. Deeper
layers are colder and contain less oxygen.
Question 6
Which of the following biomes has the lowest
annual precipitation? (TX Obj 3; 12E)
A. tropical rain forest
B. taiga
C. savanna
D. desert
The answer is D. Deserts are the driest
biomes.
Communities
• Communities, populations, and individual
organisms interact in areas where biotic or
abiotic factors fall within their range of
tolerance. Abiotic or biotic factors that define
whether or not an organism can survive are
limiting factors.
Communities
• The sequential development of living
communities from bare rock is an example of
primary succession. Secondary succession
occurs when communities are disrupted. Left
undisturbed, both primary succession and
secondary succession will eventually result in a
climax community which can last for hundreds
of years.
Biomes
• Biomes are large areas that have
characteristic climax communities. Aquatic
biomes may be marine or freshwater.
Estuaries occur at the boundaries of marine
and freshwater biomes. Approximately
three-quarters of Earth’s surface is covered
by aquatic biomes, and the vast majority of
these are marine communities.
Biomes
• Terrestrial biomes include tundra, taiga,
desert, grassland, deciduous forest, and
temperate and tropical rain forests.
Latitude influences the angle at which the
sun reaches Earth and is a strong factor in
determining what a particular biome is like.
Two climatic factors, temperature and
precipitation, are major limiting factors for
the information of terrestrial biomes.
Question 1
Grasslands are another name for which of the
following? (TX Obj 3; 12E)
A. savannas
B. taiga
C. tundra
D. temperate forest
The answer is A. Grasslands are also called
prairies, steppes, pampas, and savannas.
Question 2
Key
TX Obj 3; 12E
Monthly temperature
range (0C)
Monthly precipitation
(cm)
The answer is C.
Because tropical rain
forests are near the
equator, they have
consistently warm
temperatures.
Key
Monthly temperature
range (0C)
Monthly precipitation
(cm)
Question 3
In which layer of a tropical rain forest are
you most likely to find tree frogs? (TX
Obj 3; 12E)
A. canopy
B. understory
C. ground
D. root
The answer is
B. Insects,
amphibians and
reptiles are
commonly
found in the
understory.
Question 4
Describe the importance of bacteria in a
healthy ecosystem. (TX Obj 3; 9D, 12E)
Answer
Bacteria help decay dead organisms and
releases nutrients, recycling them through the
food web.
Question 5
As you travel north from a tropical rain forest,
what are some of the variations you would
observe? (TX Obj 3; 12E)
Answer
As you travel north, you would observe
decreasing average temperatures and drier
weather. Biodiversity would decrease.
Question 6
In which biome would you expect the
greatest biomass? (TX Obj 3; 9D)
A. tropical rain forest
B. temperate deciduous forest
C. desert
D. taiga
The answer is A. In
tropical rain forests,
sunlight, moisture and
nutrients are available in
abundance. These
biomes are the most
species-rich places on
Earth, and the biomass is
high.
Question 7
In which biome would you expect to find
only shallow-rooted grasses and small
plants? (TX Obj 3; 12E)
A. grassland
B. deciduous forest
C. taiga
D. tundra
The answer is D. Tundra has little topsoil and
lacks nutrients.
Photo Credits
• Corbis
• Digital Stock
• PhotoDisc
• Alton Biggs
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