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Ecosystems and the Environment
Unit 10
Ecosystems: What is an Ecosystem?
And Energy Flow in Ecosystems
Chapter 16.1 and 16.2
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Interactions of Organisms and Their
Environments
• We are part of the environment along with all of Earth’s
other organisms.
• Ecology: the study of the interactions of living
organisms with one another and with their physical
environment.
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Ecology
• Habitat: The place where a particular
population of a species lives
– The range of tolerance an organism possesses
determines where it can live.
• Community: the many different species that
live together in a habitat
• Ecosystem: a community and the physical
aspects of its habitat (soil, water, weather)
• Abiotic Factors: the physical aspects of a
habitat
• Biotic Factors: the organisms in a habitat
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Diverse Communities in Ecosystems
• Biodiversity: the variety of organisms, their genetic
differences, and the communities and ecosystems
in which they occur.
• Biodiversity can be impacted by limiting factors,
which can control the number of organisms in an
ecosystem. Examples: nutrients, water, shelter, etc.
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Change of Ecosystems Over Time
• The physical boundaries between ecosystems
are not always obvious.
• Additionally, ecosystems do not remain static
(the same).
• For example a volcano, a receding glacier, or
fire can destroy vegetation and create new
habitat.
– The first organisms to live in these newly formed
habitats are often small, fast-growing plants
called pioneer species.
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Succession
• Once new species start moving into this newly
formed habitat, they go through process called
succession.
• Ecological Succession: a somewhat regular
progression of species replacement
• Primary Succession: succession that occurs where
life has not existed before
– Volcanic island
• Secondary Succession: succession that occurs in
areas where there has been previous growth
– Abandoned field
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Glacier Bay: An Example of
Succession
• An example of primary succession is a
receding glacier because land is
continually being exposed as the face of
the glacier moves back.
• The soil is poor in nitrogen at first.
• Pioneer species (the first species to
colonize a new area) move in.
• Alder seeds blow in, their roots fix
nitrogen (make it usable for plants) and
add nutrients to the soil.
– Nitrogen Fixation: the process by which
gaseous nitrogen is converted into
ammonia, a compound that organisms can
use to make amino acids
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Glacier Bay: An Example of
Succession
• New trees are able to move
in.
• Eventually, the area is filled
with dense thickets of trees.
• The ecosystem has finally
become a climax community:
a community that has
reached a steady state
through ecological succession.
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Primary Energy Source
• Everything that we do requires energy, and this energy
flows from organism to organism.
• Most life on Earth depends on photosynthetic
organisms.
• Primary Productivity: the rate at which organic
material is produced by photosynthetic organisms in an
ecosystem.
– This determines the amount of energy available in an
ecosystem.
• Producers: organisms that capture energy in
photosynthesis including plants, algae, and some
bacteria
• Consumers: organisms that consume plants of other
organisms to obtain the energy necessary to build their
molecules.
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Trophic Levels
• Trophic Level: one of the steps in a food chain or pyramid.
• First Level (lowest level): producers which perform photosynthesis and sometimes
absorb nitrogen gas with the help of nitrogen-fixing bacteria.
• Second Level: Herbivores, which eat primary producers. Use microorganisms to
help digest plant materials in their guts.
• Third Level: Secondary consumers; animals that eat other animals.
• Fourth Level: Tertiary Consumers; carnivores that eat other carnivores
• Detritivores: organisms that obtain their energy from the organic wastes produced
at all trophic levels.
– Decomposers: Bacteria and fungi are decomposers because they cause decay.
– Decay is very important because it allows for the recycling of nutrients.
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Aquatic Food Chains
• Food Chain: the path of energy through
trophic levels.
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Aquatic Food Web
• Food Web: a complicated, interconnected group of food
chains.
– In most ecosystems, energy does not follow simple straight paths
seen in simplified food chains.
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Energy Transfer
• During every transfer of energy within an ecosystem,
energy is lost as heat.
• Thus, the amount of useful energy decreases and
energy passes through an ecosystem.
• This is why there are more producers and primary
consumers than secondary and tertiary consumers.
• Only about 10% of energy is passed up trophic levels.
• Sometimes energy is not the only thing transferred
between trophic levels:
– Biological Magnification: the accumulation of increasingly
large amounts of toxic substances within each successive link
of the food chain.
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The Pyramid of Energy
• Ecologists often illustrate the flow of energy
through an ecosystem using an energy pyramid.
• Energy Pyramid: a diagram in which each Trophic
level is represented by blocks stacked one another.
– The width of the block indicates how much energy is
stored at each trophic level.
– Only about 1/10 of the energy in a trophic level is found
in the next trophic level, so it takes a pyramid shape.
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Limitations of Trophic
Levels
• Most ecosystems only
involve three or four
trophic levels because too
much energy is lost to
support more.
• Biomass may sometimes be
a better indicator of energy
than organism number.
– Biomass: the dry weigh of
tissue an other organic
matter found in a specific
ecosystem. Each higher level
contains only 10% of the
biomass found in the trophic
level below it.
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04/03/13 DOL: For each statement below,
identify the relevant ecological term.
1. The LIVING part of an ecosystem.
2. The type of succession that occurs where life
has not existed before.
3. Organisms that capture energy in
photosynthesis including plants, algae, and
some bacteria.
4. Organisms that cause decay.
5. The amount of energy that passes to the next
trophic level.
Cycling of Materials in
Ecosystems
Chapter 16.3
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Biogeochemical Cycles
• Nature does not throw away raw materials!
• The physical parts of the ecosystems cycle constantly in various
nutrient cycles!
• Carbon atoms are passed from one organism to another.
– Producers are eaten by herbivores, which are eaten by
carnivores, which are eaten by top carnivores, which eventually
die and are decayed by decomposers. Eventually their carbon
atoms become part the soil to feed the producers and start the
process over!
• The four biogeochemical cycles we will talk about are the water,
carbon, phosphorus, and nitrogen cycles.
• Biogeochemical cycle: the circulation of substances through living
organisms from or to the environment.
– Substances cycle between living and non-living reservoirs.
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• Of all nonliving
components of an
ecosystem, water
has the greatest
impact on the
inhabitants:
• Precipitation (rain
and snow)
• Ground water
(water stored
under ground)
• Ultimately the
water cycle is
caused by heating
by the sun leading
to evaporation.
The Water Cycle
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• Living Components:
• Water is taken up by
the roots of plants.
• Water moves back into
the atmosphere by
evaporating from
leaves in transpiration
(which is also
ultimately caused by
the sun).
• Water is very
important to aquatic
ecosystems such as
lakes, rivers, oceans,
estuaries, and
wetlands.
The Water Cycle
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The Carbon Cycle
• Carbon cycles between the
nonliving environment and
living organisms.
• The nutrient cycling of
carbon is very closely
related to the cycling of
Oxygen (O2).
• Carbon dioxide (CO2) in the
air/water is used by plants,
algae, or bacteria in
photosynthesis to make
new organic nutrients
(sugars). Carbon atoms can
return to the pool of CO2 in
the air and water in three
ways:
1.
2.
3.
Respiration
Combustion
Erosion
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The Carbon Cycle
1. Respiration:
Oxygen (O2) is
used to oxidize
organic
molecules in
cellular
respiration and
CO2 is released
as a byproduct.
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2. Combustion: Carbon
returns to the
atmosphere through
burning.
–
–
–
The Carbon Cycle
Carbon in wood can
stay there for many
years, and is released
when the wood is
burned.
In fossil fuels (oil,
natural gas, coal) the
carbon has been stored
underground for
millions of years!
Burning releases CO2
which is necessary for
plant growth but can
potentially cause global
warming if too much
carbon is released!
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The Carbon Cycle
3. Erosion: Marine
organisms use carbon
dioxide dissolved in
the sea water to
make calcium
carbonate shells.
– Shells of dead
organisms eventually
form sediments such
as limestone.
– As limestone is
exposed and erodes,
carbon is again
available to different
organisms.
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The Phosphorus Cycle
• Phosphorus is an essential part of our bodies.
– Essential for ATP and DNA creation.
• Phosphorous is usually stored in soil and rock as
calcium phosphate.
• It dissolves in water to form phosphate ions, PO43-.
• This phosphate is absorbed by the roots of plants and
used to build organic molecules.
• Animals eat the plants and reuse the organic
phosphorus.
• Excessive amounts of nutrients such as phosphorus
entering waterways causes too many algae to grow and
hurts the aquatic system.
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The Nitrogen Cycle
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• The atmosphere is 78 percent nitrogen gas, N2.
• In spite of how much nitrogen is around us, most
organisms cannot use it in that form because of the
strong bonds between the two N atoms.
• Some bacteria can break the bond and make ammonia, NH3 in a
process called Nitrogen Fixation.
•Nitrogen Fixation: the
process by which
gaseous nitrogen is
converted into
ammonia, a compound
that organisms can use
to make amino acids.
•Nitrogen fixation is
performed by bacteria
that live in the soil and
root nodules (swellings)
of plants like alder trees.
The Four Stages of the Nitrogen Cycle
1. Assimilation: the absorption and incorporation of
nitrogen into organic compounds by plants.
2. Ammonification: the production of ammonia (NH3) by
bacteria during the decay of organic matter.
3. Nitrification: the production of nitrate from ammonia.
4. Denitrification: the conversion of nitrate to nitrogen
gas.
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2013
04/05/13 DOL: For each statement below,
identify the relevant biogeochemical cycle.
1. Includes the process of combustion
2. Includes the processes of transpiration.
3. The main reservoir (storage area) for this
nutrient is the atmosphere, but most
organisms cannot utilize it in this form.
4. Usually stored in soil and rocks.
5. Includes the process of assimilation, or
incorporation into our proteins.
The Environment
Chapter 18
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Acid Rain
• Coal-burning power plants make
smoke with lots of sulfur, because
the coal contained lots of sulfur.
• Sulfur introduced into the
atmosphere combines with water
vapor to form sulfuric acid.
• Sulfuric acid carried back to
Earth’s surface in precipitation
(rain or snow) is called Acid Rain.
• Lowering the pH of water (making
it more acidic) can cause death of
organisms such as lake animals,
tree root fungi, and plant death.
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The Ozone Layer
• Remember, we need that protective layer
of Ozone (O3) created by early
photosynthetic cyanobacteria.
• The Ozone layer protects us from
dangerous Ultraviolet (UV) light.
• In 1985, Scientists noticed that there was
an Ozone hole over Antarctica. Every
year, the hole gets worse, allowing more
UV light to get to Earth’s surface.
• Increased exposure to UV light can cause
skin cancer, cataracts, etc.
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Ozone Destruction
• The ozone is being destroyed primarily by a class of
chemicals called Chlorofluorocarbons (CFCs). CFCs are
normally stable.
• CFCs are used as coolants in refrigerators and air
conditions, as propellants in aerosol spray cans, and
foaming agents in plastic-foam creation.
• It turns out, high in the atmosphere where we find the
ozone layer, CFCs are not so stable.
• They lose a chlorine atom, which enters into a series of
reactions that destroy the Ozone (O3) and turn it into
regular Oxygen (O2).
• CFCS are now banned as aerosol can propellants in the
U.S.
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Global Temperature
• Since the 1950s, the global temperatures
have been increasing.
• In Earth’s history, there have been many
periods of Global Warming, which are
often followed by periods of cold.
• Scientists hypothesize that human
activity may be significantly contributing
to the modern global warming we see
today.
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The Greenhouse Effect
• Our planet would be cold except that we have a layer of
Greenhouse Gases containing water vapor, carbon dioxide
(CO2), methane, and nitrous oxide keeping it warm because
the bonds between these atoms absorbs solar energy as heat
radiates from earth. This is called the Greenhouse Effect.
– Greenhouse Effect: heat is trapped within the atmosphere of the
Earth in the same way that glass traps heat in a greenhouse.
• Due to the burning of fossil fuels, we have increased the
carbon dioxide in the atmosphere.
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Global Warming
• The figure below shows the average change in
global temperature since 1960 compared to the
concentration of carbon dioxide in the atmosphere.
• There is a strong correlation between the two,
which has convinced many scientists that
temperature and carbon dioxide levels are related.
• However, correlation is not causation.
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Chemical Pollution
• The environment can not absorb any amount of
pollution. Too much pollution can cause problems
in ecosystems and to humans.
• Chemical pollution is a major environmental
problem.
• Examples of chemical pollution:
– Oil spills
– Toxic materials
– Carcinogenic (cancer-causing) materials
– Agricultural chemicals such as pesticides (which are
often toxic)
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• Modern agriculture often
introduces large amounts
of chemicals, including:
pesticides, herbicides,
and fertilizers.
• Molecules of chlorinated
hydrocarbons including
the pesticides DDT,
chlordane, lindane, and
dieldrin are slow to break
down in the environment.
• These chemicals are also
stored in the fat of
animals.
• As these molecules move
up trophic levels, they
become increasingly
concentrated.
Types of Chemical
Pollution
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• Biological Magnification: the
accumulation of increasingly
large amounts of toxic
substances within each
successive link of the food
chain.
• In birds, DDT causes eggs to
be thin, and fragile—these
eggs often break.
• This was the worst in
predatory birds because they
are high in the food chain
and occupy a high trophic
level.
• As such, the numbers of
predatory birds dwindled.
• In 1972 the use of DDT was
restricted in the U.S.
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Types of Chemical
Pollution
Loss of Resources
• We are damaging ecosystems in many ways,
including consuming or destroying resources that
we cannot replace.
• There are three kinds of nonrenewable resources
being consumed or destroyed far too quickly:
1. Extinction of Species: we have destroyed 50% of the
worlds rainforest in 50 years, taking many species with
them. 10% of well known species are endangered, and
there are likely many more unknown species at risk.
2. Loss of Topsoil: fertile soil for agriculture is being
depleted because of poor land management that
washes away rich topsoil (the fertile part of soil that
allows plants to grow)
3. Groundwater Pollution and Depletion Benagh 2013
3. Ground-Water Pollution and Depletion
• Finally, we cannot replace ground water.
• Much of our water is stored underground in aquifers (rock
reservoirs for water).
• Water seeps into aquifers too slowly to replace, and we are
removing too much of the water.
• In the U.S., most areas are not concerned with conserving
ground water—we waste water on lawns, washing cars, and
flushing toilets.
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Growth of Human Population
• Birth rates are high across the world,
and death rates are decreasing. This
leads to an increase in population size.
• Population growth is fastest in the
developing countries of Asia,
Africa, and Latin America.
• We reached 6 billion in
1999. There are now 7 billion people
on the planet.
• There are concerns that
we may be reaching our
carrying capacity.
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04/09/13 DOL: For each statement below,
identify the environmental problem described.
1. Sulfur in the atmosphere leads to lowered pH of
water.
2. The breakdown of this atmospheric structure is
caused by CFCs and can lead to increased rates of skin
cancer.
3. Human-caused increase of Earth’s average
temperature caused by the excessive release of
greenhouse gases.
4. The accumulation of increasingly large amounts of toxic
substances within each successive link of the food
chain.
5. Size of human population.
04/11/2013 Journal Entry
In the journal section of your binder, address the
following questions in paragraph form. At the
end of 5 minutes, you should have written 4-5
complete sentences.
1. What is symbiosis?
2. What was the relationship described in the
video?
3. How has each species changed to help the
other species?
How Organisms
Interact in
Communities and
how Competition
Shapes
Communities
Chapter 17.1 and 17.2
Evolution in Communities
• Ecosystem’s inhabitants are a web of
interactions between organisms.
• Some interactions among species are the
result of a long evolutionary history where the
organisms adjust to one another.
• Natural selection has often matched
characteristics of flowers to a pollinator.
• Coevolution: back-and-forth
evolutionary adjustments between
interacting members of a
community.
Predators and Prey Coevolve
• Predation: the act of one organism killing another
for food.
– Lions eating zebras
• Parasitism: one organism feeds on and usually lives
on or in another, typically larger organism. Parasites
do not usually kill their prey (known as their host).
– External parasites: feed on the host’s outside
• Lice, fleas on dogs
– Internal parasites: live entirely within the host’ body
• Hookworm
Plant Defenses Against
Herbivores
• Predation is also a problem for
plants, which are rooted to the
ground.
• Plants have thorns, spines,
prickles, and chemical
compounds that discourage
herbivores.
• Secondary Compounds:
defensive chemicals found in
plants; often the primary means
of defense.
• Certain herbivores can feed on
and be protected by the
chemicals.
Symbiotic Species
• Symbiosis: two or more species living
together in a close, long-term association.
• Can be:
– Beneficial to both organisms
– Benefit one organism and leave the other harmed
or unaffected
• Parasitism: one type of symbiotic relationship
that is detrimental to the host organism.
Mutualism and
Commensalism
• Mutualism: a symbiotic relationship in
which both participating species
benefit.
– Ants and Aphids: aphids suck sap from
plants which they alter and secrete—
ants use this as food and “milk” the
aphids. The ants protect the aphids, so
they are both helped by the relationship.
• Commensalism: a symbiotic
relationship in which one species
benefits and the other is neither
harmed nor helped.
– Clown Fish and Sea Anemones:
anemones have stinging tentacles, but
the clown fish can live among the
tentacles for protection. Anemones are
not harmed by the relationship.
Competition
• Competition: the biological interaction when two
species use the same resource.
– Examples: food, nesting sites, living space, light, mineral
nutrients, and water.
– Competition occurs for resources in short supply.
• Niche: the functional role of a particular species in a
ecosystem.
– How and organism lives—the job it performs in the
ecosystem.
– A niche may be describe in terms of space utilization,
food consumption, temperature range, requirements for
moisture or mating, etc.
Size of a Species’ Niche
• Fundamental Niche: the entire range of resource
opportunities an organism is potentially able to occupy
within an ecosystem.
• Example: The Cape May Warbler’s niche includes the
temperature it prefers (northeastern U.S. and Canada),
when it nests (Summer), favorite foods (Small insects),
where in the tree it finds food (tips of tree branches).
Dividing Resources Among Species
• Realized Niche: the part of the fundamental niche
actually occupied by a species.
• So, the realized niche of the Cape May warbler is only a
small portion of its fundamental niche.
• Five species of warblers feed on spruce trees at the
same time, but each one feeds on different parts of the
tree.
Competition and Limitations of Resources
• Shortage is the rule in nature, meaning that species are
almost sure to compete with one another.
• Darwin noted that competition should be greatest between
similar organisms.
• Competitive Exclusion: elimination of a competing species
when two species are competing—the species that uses the
resource more efficiently will eliminate the other.
When Can Competitors
Coexist?
• Competitive exclusion is not
always the outcome when
organisms compete for limited
resources.
• If species avoid competing,
they may coexist.
• Gause forced several species
into competition. In one case,
one species won out
(competitive exclusion) but in
the other, both species found
a way to coexist.
Predation and Competition
• Predation reduces the effects of
competition.
• Pain examined how sea stars
(which eat clams and mussels)
affect the numbers of species in
intertidal communities.
• He found that when sea stars were
not present, there were less
numbers of other species. Star
fish reduce competition and
therefore promote biodiversity.
– Biodiversity: the variety of living
organisms present in a community.
Biodiversity and Productivity
• The greater the number of species a plot of land
has, the more plant material the plot can make.
• The more species are found in an area, the
greater the productivity.
• Additionally, a more diverse ecosystem recovers
more fully from disasters such as droughts.
Growth Patterns in Real Populations
• Exponential Growth Patterns
are best to describe faster
growing organisms such as:
– Many plants
– Insects
Exponential Growth Curve:
Also called a
j-curve
• Logistic Growth Model is best to
describe slower growing
organisms such as:
– Bears
– Elephants
– Humans
• Density-Independent Factors:
environmental conditions
– Weather
– Climate
Logistic Growth Model:
Also
Also
called
called
a
an
j-curve
s-curve
Rapidly Growing Populations
• r-strategists: grow exponentially when
environmental conditions allow them to
reproduce.
– Results in temporarily large populations.
• When environmental conditions are good, the
population grows rapidly. When conditions are poor,
the population size drops quickly.
• Generally r-strategists:
– Have a short life span
– Reproduce early
– Many small offspring
– Offspring mature with little parental care
Slowly Growing Populations
• K-strategists: organisms that grow slowly with small
population sizes and a population density usually
near the carrying capacity (K) of their environment.
• Generally K-strategists:
– Have a long life
– Mature slowly
– Have few young
– Provide extensive care for young
04/11/13 DOL: For each statement below, identify the statement
as true or false. If the statement is false, correct it to make it true.
1. Symbiosis includes only positive
relationships.
2. In amensalism, both species benefit.
3. In commensalism, neither species benefits.
4. A niche is the functional role of a particular
species in a ecosystem.
5. An r-strategist will probably live longer than a
K-strategist.
04/15/13 Journal Entry
• In the journal section of your binder, address the
following questions in paragraph form. At the
end of 5 minutes, you should have written 4-5
complete sentences.
1. What is a biome?
2. What determines the vegetation in a biome?
3. Identify any biomes that you know along with
their defining characteristic?
4. What biome do you think we live in here in
Dallas?
Major Biological Communities
Chapter 17.3
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Climate, Temperature, and Moisture
• Climate: the prevailing weather conditions in any
given area.
• The two most important elements of climate are
temperature and moisture:
– Temperature: most organisms are adapted to living
within a particular range of temperatures and will not
thrive if temperatures are colder or warmer.
– Moisture: All organisms require water. On land, water is
sometimes scarce, so patterns of rainfall often
determine an area’s life-forms. The warmer the air, the
more moisture the air can hold.
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Climate, Temperature, and Moisture
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Major Biological Communities
• Very similar communities occur in places with
similar climates and geographies.
• Biome: a major biological community that occurs
over a large area of land.
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Major Biological Communities
• Temperature and
precipitation are
extremely important to
determining where
biomes occur.
• In general, temperature
and available moisture
decrease as latitude
(distance from the
equator increases).
• Temperature and
moisture also decrease
as elevation (height
above sea level
increases.
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Terrestrial Biomes
• Tropical Rain Forest: As much as 450 cm rain/year, little
seasonal differences (warm all year). Contain the most
biodiversity of all biomes, have a high primary
productivity even though they have infertile soils.
• Savannas: Great dry grasslands in tropical areas with
little precipitation (90-150 cm) with a long dry season
and wider fluctuation in temperature. Contain few
trees and have an open landscape.
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Terrestrial Biomes
• Taiga: Cold, wet climates with coniferous forests. Long, cold
winters, most precipitation in summer. Many large mammals
such as elk, moose, and dear, wolves, bears, lynxes, and
wolverines live here.
• Tundra: Between the Taiga and the permanent ice of the
north pole is the Tundra. Covers 1/5 of the Earth’s surface.
Low annual precipitation (less than 25 cm), with low available
water because it is frozen in permafrost (permanent ice).
Foxes, lemmings, owls, caribou.
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Texas Terrestrial Biomes
• Deserts: Less than 25 cm precipitation,
sparse vegetation, found in interior of
continents.
• Temperate Grasslands: Moderate climates
half-way between equator and poles often
are grasslands. Highly productive with deep,
fertile soil. Bison in U.S. were once found
here.
• Temperate Deciduous Forests: Mild
climates, plentiful rain, with trees that shed
their leaves. Warm summers, cold winters,
75-250 cm precipitation. Cover much of
eastern U.S. Deer, bears, beavers, raccoons.
• Temperate Evergreen Forests: Drier weather
leads to evergreen forests.
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Aquatic Communities
• Freshwater (lakes, ponds, streams, and rivers) are very rare; only about 2% of
the Earth’s surface. Ponds and lakes have three zones:
– Littoral Zone: Shallow zone near the shore; insects, amphibians, fish
– Limnetic Zone: Away from the shore, but close to the surface; algae,
zooplankton, fish
– Profundal Zone: Deep-water zone with less light; bacteria, worms—
decomposers
• Wetlands: swamps, marshes, and bogs, store water, diverse organisms.
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Marine Communities
• ¾ of the Earth’s surface is ocean, with 3
types of marine communities.
• Shallow Ocean Waters: many species
live here, and this includes intertidal
zones, coral reefs, and cool coastal
zones with many nutrients.
• Surface of the Ocean Sea: Plankton
drift here and fishes, whales, and
jellyfish feed on these plankton,
which do 40% of photosynthesis on
Earth.
• Ocean Depths: In the deepest waters,
there is no light, and bizarre
invertebrates and fishes live here,
such as squids and angler fishes.
There is great biodiversity here.
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Diatoms
• Diatoms: photosynthetic, unicellular protists
with unique double shells.
• Their shells are made of silica and have unique
markings.
• Diatoms are abundant in lakes and oceans and
are important producers in the food chains,
and do a lot of photosynthesis.
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04/15/13 DOL: For each of the
statements below, identify the biome.
1. Dry and found in interior of continents.
2. Forests in areas with seasons where the
leaves fall.
3. Cold desert, covered in permafrost.
4. Warm and wet with dense vegetation and
poor soil.
5. Grasslands such as those found in Texas.