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Chapter 23
Ecosystems and Biomes
23-1: Energy Roles
An organism’s energy role is determined by how it obtains
energy and how it interacts with the other living things in its
ecosystem.
An organism can have one of three energy roles in an
ecosystem:
1-Producer
2-Consumer
3-Decomposer
All ecosystems energy begins with sunlight. Sunlight enters
the ecosystem and autotrophs use it to make their own
“food” (aka: sugars, carbohydrates, glucose) through
performing photosynthesis.
Producers
Producer- an organism that can make its own food.
Therefore producer is a synonym for autotroph.
Producers are the source of all the food in an
ecosystem.
Examples: grass, trees,
plants, algae
Q: What happens when ecosystems are where there
is no sunlight? (example: rocky, deep soil)
A: Certain bacteria in this ecosystem produce their
own food using the energy in a gas, hydrogen sulfide,
instead of energy from sunlight.
Consumers
Consumer- obtains energy by feeding on other organisms
Therefore consumer is a synonym for heterotroph.
Consumers can be a:
1- herbivore
2- carnivore
3- ominivore
4- scavenger
Herbivore
Carnivore
Omnivore
Scavenger
Definition
Consumers that Consumers that Consumers that Carnivores that
eat plants only eat animals
eat both plants eat dead
only
and animals
animals
Examples
Caterpillar,
deer, cattle
Lions, spiders,
snakes
Crows, goats,
humans
Vultures,
catfish
Decomposers
Decomposer- an organism that break down wastes and dead
organisms and return the raw materials to the environment.
Examples of Decomposers:
fungi and bacteria
Q: Why are decomposers essential for an ecosystem?
A: If raw materials were not replaced, new organisms would
not be able to grow.
Also- If wastes and dead organisms were not somehow
removed from the ecosystem, they would pile up until
they overwhelmed the living things.
Food Chains and Food Webs
Order of Energy Transfer
1-Energy enters ecosystems in the form of
sunlight.
2-Producers use that energy to produce “food”sugars.
3-Those sugars are then eaten by consumers.
4-Then other consumers eat the first consumer
and so on.
The movement of energy through an ecosystem
can be shown in diagrams called food chains
and food webs.
Food Chain- a series of events in which one organism eats
another and obtains energy.
The first organism in a food chain is always a producer.
The second organism is called a first-level consumer
because it eats the producer.
The third organism is called a second-level consumer
because it eats the first-level consumer.
There can be one or possibly two more levels in some
ecosystems.
Look at the food chain above. What represents each role?
Producer- _____________________
First-level consumer- __________________
Second-level consumer- ________________
Third-level consumer- _________________
Fourth-level consumer- ________________
In most ecosystems, there must be decomposers that return
nutrients to the soil. What is the decomposer in the
example above? __________________
Food Web- many overlapping food chains in an ecosystem.
A food chain only shows one possible path energy can
take in an ecosystem.
However, that is not realistic because organisms do not
eat the same thing day after day. Most producers and
consumers are a part of many food chains.
Therefore, a food
web is a more
realistic
representation of
energy flow in an
ecosystem.
Look at the food
web above.
Answer these
questions:
1- What is the
only producer
shown?
______________
2- Name the three mammals that are first-level consumers.
_________________________________________________
3- What are the two birds that an owl will consume?
_________________________________________________
4- How many different organisms could the snake possibly
eat? ________
Energy Pyramids
Q: How does an organism in an ecosystem obtain energy?
A: By eating another organism
Q: What happens to that energy?
A: The organism uses some of that energy to move, grow,
reproduce and carry out other life functions.
Q: What happens to the rest of the energy that is not used?
A: The rest of the energy is available for the next organism in
the food web.
Energy Pyramid- a diagram that shows the amount of energy
that moves from one feeding level to another in a food web.
The most energy is available at the producer level.
Q: On the pyramid below, what organism has the
most energy available? _the trees_____
At each level in the pyramid, there is less available
energy than the level below.
Q: On the pyramid below, what organism has the
least amount of energy available? _the lion___
In general, only about 10 % of the
energy at one level of a food web
(or pyramid) is transferred up to the
next level.
Q: If there is 100% energy
available at the producer level, how
much energy will get transferred up
to the giraffe level? ___10%____
Q: What happens to the other 90% that doesn’t get
passed up to the next level?
A: Two things happen to it: It is used for the organism’s
life processes and it is lost to heat.
Because of this, most food webs only have 3-4 feeding
levels. Since 90% is lost at each step, there is not enough
energy to support many feeding levels.
Notice how there are fewer organisms at each level as
you move up (if you actually count organisms)….
That is because as you move up the pyramid, and
only 10% gets transferred up, there is less energy
to support those consumers.
Example: far fewer lions in a grassland than there are giraffes
Label the following energy pyramid with the following words:
Producers, 1st Level Consumers, 2nd Level Consumers, Top Consumers
.1%
Top
Consumers
1%
2nd Level
Consumers
10%
100%
1st Level Consumers
Producers
Now, label the pyramid with the amount of energy available at each
level.
Label the following energy pyramid with organisms that would fit
into a MARINE (OCEAN) ecosystem.
23-2: Cycles of Matter
Recycling Matter
The way matter is recycled in ecosystems is similar to the
way the metal in old cars is recycled. The supply is limited.
If matter could not be recycled, ecosystems would quickly
run out of the raw materials necessary for life.
Energy, on the other hand is not recycled. Ecosystems must
have a constant supply of energy (mostly from the sun).
In general:
Matter CYCLES and Energy FLOWS in One Direction
Examples of Matter: Water, Nitrogen, Carbon, and Oxygen
The Water Cycle
Water Cycle- the continuous process by which water moves
from Earth’s surface to the atmosphere and back.
There are three process that are active in the water cycle:
1- Evaporation
2- Condensation
3- Precipitation
Evaporation- the process by which molecules of liquid water
absorb energy and change to the gas state.
Water on the
surface of lakes
and oceans
Water Vapor in the
atmosphere
Condensation- the process by which a gas changes to a
liquid. (water vapor turning into clouds)
Water Vapor in the
atmosphere
Cools and
rises
Water droplets +
particles of dust=
clouds
Precipitation- the process by which water vapor condenses,
grow heavier, and fall in the form of rain, snow, sleet, or
hail.
Water Droplets
In Clouds
Grow
Heavy
Rain, Snow,
Sleet, Hail
Q: What happens to the rain, snow, sleet, and hail?
A: They eventually end back up in bodies of water.
Label the water cycle below with evaporation,
condensation, and precipitation:
Condensation
Evaporation
Precipitation
The Carbon and Oxygen Cycle
Carbon and Oxygen Cycle- process in which producers use
carbon from carbon dioxide to produce other carboncontaining molecules.
This cycle is the basically the same thing we learned in
Chapter 2: how animal
cells go through the
C6H12O6
process of
O2
respiration and the
products from respiration
are used for
CO2
plants to go through
photosynthesis- and vice
versa!
The Nitrogen Cycle
Just like carbon, nitrogen is a necessary building block of life.
The air around you contains 78% nitrogen gas. It seems like
it would be easy for organisms to obtain it then right???
Actually, most organisms cannot use nitrogen gas (called
“free”- meaning not attached to other elements) directly
from the air. It needs to be converted into a usable form.
Q: How does “free” nitrogen become usable?
A: It has to be “fixed” or combined with other elements to
form nitrogen-containing compounds.
Examples of nitrogen containing compounds- nitrates,
nitrites
Nodules- bumps on
the roots of plants
that bacteria live in to
carry out nitrogen
fixation.
Nitrogen Fixation- the
process of changing
free nitrogen gas into
usable nitrogen
compounds.
Q: What organism carries out the work of nitrogen
fixation?
A: Bacteria
A real life example of the nitrogen cycle and nitrogen fixation is
farmers using bacteria to enrich their fields.
In fields of legumes (clover, beans, peas, alfalfa, and peanuts)
bacteria live in the nodules of plants in a mutualistic relationship.
Remember mutualism is a WIN-WIN.
The bacteria feeds on the plant’s sugars.
The plant gets a usable form of nitrogen from the bacteria.
Ever notice how farmers rotate crops? One year it is corn and
the next year it is soybeans….
This is because the soybean years
make the soil richer in usable nitrogen
for plants because of the bacteria/legume
relationship.
23-3: Biogeography
Biogeography- the study of where an organism lives.
“Bio”- means life
“Geo”- means earth
Continental Drift- the very slow motion of the continents
drifting on a layer of dense hot liquid.
A factor of how certain species ended up where they are
today is continental drift.
An example of how continental drift has effected the
distribution of species on the earth is in Australia.
When Australia drifted and became its own island continent,
the species that ended up there evolved independently.
This is what is
thought to have
happened in
continental
drift:
200 million
years ago:
Pangaea
existed.
Present Day:
There are seven
separate
continents.
Means of Dispersal
Dispersal- movement of organisms from one place to
another.
Dispersal can be caused by 1) wind or water, or 2) living
things- including humans.
Wind and Water
Many animals move into new areas by simply walking,
swimming or flying there. But plants and other small
organisms need assistance getting places.
Wind Helps: seeds, spores, tiny organisms
Water Helps: leaves, fruit and nuts, some insects
Other Living Things-can carry things from one place to
another like a duck’s feet carrying algae to a new pond.
Humans also play a role in dispersal.
As people move around the globe, they bring plants and
animals with them. Sometimes it is intentional and
sometimes it is unintentional.
Native Species- species that have naturally evolved in an
area.
Exotic Species- when an organism is carried to a new
location by humans.
Sometime exotic species seem native, because they fit in,
and sometimes they cause harm to food webs because they
don’t fit in.
Limits to Dispersal
There are three factors that limit dispersal of a species:
1- physical barriers
2- competition
3- climate
Physical Barriers
Barriers such as water, mountains, and deserts are hard to
cross. These features can limit the movement of organisms.
Competition
Competition can become a barrier when an organism enters
a new area and has to compete for resources or find a niche.
Climate
Climate- the typical weather pattern in an area over a long
period of time.
Climate is largely determined by temperature and
precipitation.
Climate differences keep certain
species from moving (or growing)
into new areas if their
adaptations do not suit the
climate.
Example: The different plants
and animals that inhabit
the different elevations of a
mountain.
23-4: The Earth’s Biomes
Biome - a group of ecosystems with similar climates and
organisms.
Classifying ecosystems into biomes helps ecologists describe
the world.
Not all ecologists agree on the exact number and kinds of
biomes.
Q: What determines biomes?
A: climate conditions—temperature and rainfall—in an area
that determine its biome.
This is because climate limits the distribution of plants
in the area. In turn, the types of plants determine the
kinds of animals that live there.
Map of Earth’s Biomes
BOREAL FOREST
Tropical Rainforest
Location
Near the equator
Temperature
Warm year round
Rainfall
Year round rain
Plants
Wide variety of trees: Canopy- tall trees that form a leafy roof
Understory- shorter trees and vines
Forest Floor Plants- thrive in near darkness
Examples: Orchids, Ferns
Animals
Millions of species of insects
Wide variety of birds, amphibians, and reptiles
Also: Jaguars, primates, and bats
Temperate Rainforest
Location
Northwest region of Unites States
Temperature
Four seasons, moderate temperatures, stays cool
Rainfall
Abundant rain year round (> 300 cm)
Plants
Large coniferous trees: cedars, redwoods, douglas firs
Animals
Squirrels, beavers, wolves, bears, variety of birds
Desert
Location
Southwest US, Northern Africa, Middle East, Central Australia
Temperature
Hot days, cold nights
Rainfall
Very little rainfall (< 25 cm a year)
Plants
Cacti
Animals
Lizards, snakes, scorpions, some birds
Grassland: Temperate (Prairie)
Location
Central US, Middle Asia
Temperature
Four seasons, moderate temperatures
Rainfall
Rainy season, more than desert, less than rainforest (25-75 cm)
Plants
Rich Soil supports the growth of many crops, tall grasses
Animals
Large herbivores, prairie dogs, snakes, hawks, sparrows, rabbits
Grassland: Savanna
Location
Mid-Southern Africa (closer to the equator than prairies)
Temperature
Warmer than prairie, typically warm year round
Rainfall
More rain than prairie (as much as 120 cm)
Plants
Tall grasses, small trees and shrubs
Animals
Zebras, rhinos, giraffes, lions
Deciduous Forest
Location
Eastern US (where we live), Central S. America, Europe, Eastern
Asia
Temperature
Cool nights, warm days, four seasons
Rainfall
Rainy seasons (at least 50 cm)
Plants
Deciduous trees (oak, maple), ferns, mosses- wide variety due to
damp forest floor with decaying leaves
Animals
Chipmunks, many birds, deer, mice, bear
Boreal Forest (also known as Taiga)
Location
Canada, Northern Asia
Temperature
Cool-Cold Year round
Rainfall
Snowy winters and rainy summers
Plants
Coniferous trees- fir, spruce, hemlock
Must have waxy needles to prevent water loss
Animals
Porcupines, elk, moose, wolves, bears
Tundra
Location
Northern-most Canada and Asia
Temperature
Very cold year-round
Rainfall
Very dry “frozen desert”, the soil stays frozen as permafrost
Plants
Moss, grasses, shrubs, willows, lichens
Animals
Flies, mosquitos, birds, caribou, hares, foxes
Other Biomes
(do not fall into the major land biome categories)
Mountains
As you read in section 3, climate conditions can vary greatly from the
base of a mountain to the summit.
For this reason, mountains can be the home to a wide variety of plants
and animals depending on the particular elevation of the mountain.
Ice
Some areas on earth are covered by ice year round, such as Greenland
and Antarctica.
A few organisms are adapted for icy conditions: penguins, polar bears,
and seals
Freshwater Biomes
Photosynthesis is important in water, just like it is on land.
However, because water absorbs sunlight, there is only
enough light for photosynthesis near the surface or in
shallow water
Algae is the most important producer in water biomes.
Ponds and Lakes- Still Water
Plants- ponds are shallow enough to have plants growing
throughout.
- lakes may only have plant life around the edges.
Animals- fish, frogs, insects, snails
Streams and Rivers- Moving Water
Plants- few plants are adapted to the current,
some can anchor in the bottom to provide
habitats for animals.
Animals- fish like trout and salmon, insects
Marine Biomes
Marine Biomes are divided into five parts:
1- Estuary
2- Intertidal Zone
3- Neritic Zone
4- Surface Zone
5- Deep Zone
Estuary- where freshwater of a river meets the salt water of
the ocean.
Estuaries are rich habitats for organisms. Many plants,
grasses, and algae are producers.
Estuaries are home to crabs, worms, clams, oysters, and fish.
Intertidal Zone- Part of the shore between the highest tide
line and the lowest tide line.
Organisms here must be able to withstand the pounding
waves, changing water temps, and being exposed to both
water and air.
Organisms that live here are barnacles, sea stars, clams and
crabs.
Neritic Zone- Region of shallow water below the low tide
line that extends like a shelf into the ocean.
A wide variety of fish can inhabit this area.
Surface Zone- Area in the open ocean where light only
penetrates a few hundred meters.
Organisms that live here are:
Producers- mainly algae
Consumers- tuna, swordfish, whales
Deep Zone- the open ocean, below the surface zone where
water is completely dark
Most organisms here feed on the remains of things that sink
from the surface zone.
Squid and glow-in-the-dark fish live here.
Label the zones of the ocean below. Estuary is not included.
Intertidal Zone
Neritic Zone
Surface Zone
Deep Zone
Succession
Succession- series of predictable changes in
a community over time.
Examples: gradual physical changes or
sudden natural or human disasters
There are two types of succession:
1) Primary Succession
2) Secondary Succession
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Primary Succession- occurs on surfaces
where no ecosystem or soil existed before.
Examples: after a volcanic eruption, on bare
rock when a glacier melts
Pioneer Species- first species to occupy an
area, often lichens.
Secondary Succession- occurs where soil
is still present after a disturbance.
Examples: abandoned farm land or after a
wildfire
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Primary Succession
Bare Rock------lichens----------weeds and grass---------shrubs and trees
Secondary Succession
Wildfire, soil----weeds and wild flowers----young
trees-----mature trees
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