Chapter 47: The Biosphere
Section 4: Energy and Nutrients: Building the Web of Life
Energy and Nutrients: Building the Web of Life
One of the most important factors in any ecosystems is the _______________
______________________ through the ecosystem
Approximately __________ of the energy plants absorb from the sun is used
immediately
The rest is stored in plant tissues in the form of ________________________
Animals that ______________________________ obtain this energy
Energy cannot be ____________________, or _______________________
Thus energy in an ecosystem is referred to as a _____________ rather than a
cycle
______________________ are generally recycled through an ecosystem
When an animal dies, its matter does not _____________________
Rather, it ______________________ and eventually gets used by another
organism
The Flow of Energy
The _____________ is the ultimate source of energy for all living things
Because photosynthetic organisms are able to make their own food from
inorganic substances, they are called __________________________
Animals, on the other hand, are _________________________
Consumers get their energy either _________________________________
from producers
Consumers that feed directly on producers are called ___________________
_____________________________
o __________________________
Consumers that feed on primary consumers are called ___________________
__________________________
o _________________________
Energy flows through an ecosystem from the sun to producers and then to
consumers
When plants and animals in an ecosystem die, their remains do not build up
because of the presence of ____________________________
Decomposers are organisms that obtain their energy from ________________
_________________________________
Each step in this series of organisms eating other organisms is called a
__________________, or ____________________ level
At each higher trophic level, less and less of the energy originally captured by the
producers is available
Approximately ___________ of the energy at one trophic level can be used by
animals at the next trophic level
At each successive trophic level, _________________________ is available to
an organism
Ecological Pyramids
Ecologists use ___________________________________ to represent the
energy relationships among trophic levels
There are three types of ecological pyramids
o _______________________________
o _______________________________
o _______________________________
Pyramid of Energy
A pyramid of energy shows the total amount of ________________________
_________________ at each successive level
Pyramid of Biomass
The trophic levels of an ecosystem can also be represented by a pyramid of
biomass, which shows the ________________________________________
at each level
Pyramid of Numbers
Relationships among trophic levels may also be represented by a pyramid of
numbers
A pyramid of numbers illustrates the ________________________________
________________________ at each level
Biogeochemical Cycles
Although energy moves in a one-way direction through an ecosystem, nutrients
are recycled
All organisms require certain essential nutrients in order to _____________
As members of each trophic level eat members of the level beneath them, they
acquire the complex organic molecules and elements they need in addition to
energy
Nutrients move through the biosphere in a series of physical and biological
processes called ________________________________, or nutrient,
________________
The Water Cycle
The movement of water from the atmosphere to the Earth and back to the
atmosphere is called the ______________________________
The water cycle consists of an alternation of __________________________
and ________________________
Water molecules enter the air by evaporation from the ocean and other bodies
of water
In the air, water molecules condense and then return to the Earth in the form of
_________________________
On land, most of the rainwater runs along the surface of the ground until it
enters a river or stream that carries it to a larger body of water
Some water sinks into the ground and is called ________________________
The upper surface of groundwater is known as the ______________________
The Nitrogen Cycle
All organisms require nitrogen to __________________________________
The movement of nitrogen through the biosphere is called the
_____________________________________
However, most of the nitrogen cannot be directly used by living things
It must be _______________________ into other forms
Certain bacteria that live on roots of plants change free nitrogen in the
atmosphere into nitrogen compounds that can be used by living things
o ______________________________________
Once the nitrogen compounds are available, plants use them to make plant
proteins
Animals then eat the plants and use the proteins to make animal proteins
When the plants and animals die, the nitrogen compounds ________________
________________________________
Eventually other bacteria in the soil break down these nitrogen compounds into
free nitrogen in a process called _________________________________
These bacteria are called denitrifying bacteria
Through the process of denitrification, free nitrogen is returned to the
atmosphere
The Carbon and Oxygen Cycles
The process by which carbon is moved through the environment is called the
______________________________
During photosynthesis, green plants and algae use carbon dioxide from the
atmosphere to form __________________
Consumers and decomposers use glucose is respiration, during which they
produce carbon dioxide
Carbon dioxide is then released into the atmosphere, completing the carbon
cycle
The movement of oxygen through the environment is called the
________________________________
During photosynthesis, water molecules are split, releasing oxygen into the
atmosphere
The oxygen is used by most organisms for respiration
During respiration, ___________________________________
The water is absorbed by plants, and the cycle begins again
Nutrient Limitation
The rate at which producers can capture energy and use it to produce living
tissue is controlled be several factors, one of which is the amount of
___________________________________
If a nutrient is in short supply – thus limiting an organism’s growth – it is called a
_________________________________
Feeding Relationships
The simplest feeding relationship is a _______________________________
In one food chain, a big fish eats little fish that eat tiny fish that eat plankton
Nature is almost never that simple
Instead of using a food chain, which only shows one feeding level, ecologists use
___________________________
Food webs have many ___________________________________
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