Ecology
Levels of Organization in
Living Things

A Look at Ecology as a science

•  Ecology - study of interactions
between biotic and abiotic factors
of organisms in environmental
systems
– Biotic factors -living things (plants,
animals, and decomposers)
– Abiotic factors - nonliving things
(air, water, sunlight, and land)

Levels of Organization

The Biosphere

•  Living things are part of a whole. The
parts in levels of organization are:

• Biosphere - the living world
and all Biotic and Abiotic
Factors that affect life within
it.

–  9.
–  8.
–  7.
–  6.

–  5.
–  4.
–  3.
–  2.

The Biosphere
Ecosystems = Biomes
Communities
Populations
Organism
Organ Systems
Organs
Tissues

–  1. Cells

Ecosystems = Biomes

Ecosystems in Biomes

•  Ecosystem – several types of living things
live in environment and interact between
themselves and nonliving surroundings
•  Biome - global ecosystem located in a
specific portion of the world.

•  A deer, rabbit, and all the plant
populations that live in a grasslands
area and the lake, air, and rocks are
part of an ecosystem.


–  Deserts, oceans, and forests are examples of
ecosystems and Biomes.
–  Biomes are characterized by the quantity of
rainfall per year.

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Communities

Populations

•  Community - made up of
populations that interact with each
other

• Population - a group of
organisms that mate with one
another and live in the same
place at the same time.

– Rabbits and hawks may be part of a
community.
– There are many communities in a
Biome.
– Communities may be separated by
living or non-living matter (mountain
or other boundaries are common).


– A deer or several deer may
belong to a population as long as
it can interact with other deer in
the same area.

Organisms

Smaller Than Organisms

• Organism - a specific species
of plant, animal, bacteria,
fungus or other living thing
that lives in a specific area

•  There are two types of organisms

– You and I are both organisms.
So too can be said for my pet
cat.

–  single cellular or multi-cellular organisms
–  multi-cellular organisms have may be broken
down into the following components:

– Organ systems - a set of organs inside
an organism that carry out a specific
function (digestion, circulation,
respiration, etc.)
– Organ - a set of tissues connected tthat
carry out a specific function for a living

thing (an example of an organ may
include the heart, the lung, the brain,
etc.)

Smaller Components Yet

Organisms in Ecosystems

•  Tissues - 2 or more cells carry out a
specific function for an organism.
•  Cell - the smallest unit of life that has
all the characteristics of living things.

•  Habitat - the place where an
organism lives.
•  Niche - the role a species has in
its environment.
•  Cooperation and competition for
biotic and abiotic parts of the
environment is what ecology is
about
–  Habitat and niche are a
function of both.

–  In multi-cellular organisms there are
several types of cells located in different
parts of the living organism that carry out
specific functions.

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Relationships

Symbiosis

• Symbiosis - a relationship
where two or more
organisms depend on each
other for resources.

•  A relationship between two organisms
where one organism benefits while the
other is harmed - parasitism.
•  A relationship between two or more
organisms in which both organisms
benefit - mutualism.
•  A relationship in which one organism
benefits but the other is neither
harmed nor helped - commensalism .

– Resources serve an organism
(such as food, shelter, etc.).

Food and the Trophic Levels

More About Feeding

•  Trophic level - steps in the passage of
energy and matter through an biotic

and abiotic aspects of an ecosystem.
•  Matter and energy are passed from
pieces of the living system through the
feeder levels.

•  Levels of heterotrophs –

–  Autotroph - uses energy from the sun or
energy stored in chemical compounds to
make its food (carbohydrates).
–  Hetertroph - an organism feeds on other
organisms.

– Primary consumers (herbivores)
– Secondary consumers (eat
herbivores)
– Tertiary consumers (eat the
organisms that eat herbivores)
– Scavanger - a heterotroph that eats
dead organisms.
– Decomposer - a heterotroph that
breaks down and absorbs nutrients
from dead organisms.

Primary, Secondary, Tertiary
•  Carnivores eat meat and include
secondary and tertiary consumers.
•  Herbivores eat plants and include
primary consumers.
•  Omnivores eat everything and

anything and include primary,
secondary and tertiary consumers.

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Energy Flow

Energy Flows, Matter Cycles

•  Food chain - linear flow of
matter through an ecosystem.
•  Food web – non-linear flow of
matter and food through an
ecosystem.

•  Why does energy flow and
matter cycle?
•  Matter Cycles are part of the
abiotic materials flow in an
ecosystems:

– Expresses all possible feeding
relationships in each trophic level
– Expressed at the community level
within an ecosystem.

Water Cycle

– Matter moves through ecosystems.

– How matter moves will determine
how life can be supported within the
system.

The Water Cycle
•  Water cycles between the atmosphere,
ocean and land.
•  All living things require water to maintain
homeostasis
•  The Cycle –
–  Evaporation - vapors rise
•  Transpiration – plants evaporate water through their
leaves

–  Condense – particles come together into
clouds
–  Precipitation – water particles drop out, and
–  Percolation – water drains into and through
the dirt

The Water Cycle Continued

The Water Cycle Continued

•  Water's state (solid, liquid or gas) is
determined mostly by temperature.

•  Surface Runoff

–  The water cycle is determined then by the kinetic energy of

the particles and thus is also determined by temperature

•  The amount of water on Earth
remains constant.

–  Much of the water that returns to Earth as
precipitation runs off the surface of the
land, and flows down hill into streams,
rivers, ponds and lakes.
–  Small streams flow into larger streams,
then into rivers, and eventually the water
flows into the ocean.
–  Surface runoff is an important part of the
water cycle because, through surface
runoff, much of the water returns again to
the oceans, where a great deal of
evaporation occurs.

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The Carbon Cycle

The Carbon Cycle

•  Carbon exists in the nonliving
environment as:

•  Carbon enters the biotic world through
the action of autotrophs:

– photoautotrophs

– carbon dioxide in the atmosphere
and dissolved in water
– in rocks like limestone an coral
– deposits of coal, petroleum, and
natural gas derived from onceliving things
– dead organic matter, e.g., humus
in the soil

•  plants, bacteria and algae
•  Use energy of light to convert carbon
dioxide to organic matter

– photoautotrophs
•  Bacteria
•  Use chemical energy to convert substances
into organic matter

The Carbon Cycle

The Carbon Cycle

•  The Carbon cycle takes in carbon dioxide
and water and produces oxygen and
carbohydrates (sugar)

• Carbon returns to the
atmosphere and water by
respiration


•  This process is called primary productivity

•  Since there is so much water on the earth,
organisms in the ocean produce more
oxygen and that ANY OTHER organism in
the world.

– All living things respire

–  Carbon dioxide, burning, decay
all produce carbon dioxide (if
oxygen is present)
• Complete versus incomplete
combustion

The Nitrogen Cycle
•  All life requires nitrogen-compounds for protein
and nucleic acid production.
•  Air is made of 78% nitrogen (N2).
–  Most organisms can’t use nitrogen in this form.

•  Plants get nitrogen by taking it and
incorporating it into compounds such as:
–  nitrate ions (NO3)ammonia (NH3), urea (NH2)2CO.

•  Animals get nitrogen compounds from plants (or
animals that have fed on plants).
•  Four processes participate in the cycling of
nitrogen through the biosphere:

–  nitrogen fixation, decay, nitrification, denitrification

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