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 ___________________________________