Chapter 3: The Biosphere
The Study of Ecology
What is Ecology?
• Ecology is the scientific study of
interactions among organisms and
between organisms and their
environment
Why do we study ecology?
• We live in the natural world and use its
resources (water, space,food, etc)
• The natural world effects our lives
(weather, fire, economy)
• To protect biodiversity
Levels of Organization
• Ecologists recognize there is a
hierarchy of organization in the
environment: biosphere, biome
ecosystem, community, population, and
organisms
Levels of Organization
What is a Biosphere?
• Part of Earth in which life exists
including land, water, and air or
atmosphere
What is a Biome?
Temperate Forest
Tundra
• A group of ecosystems that have the same
climate and similar dominant communities
What is an Ecosystem?
• A collection of all
organisms that live
in a particular place,
which includes the
nonliving, or
physical,
environment
What is a Community and a
Population?
• A community is
assemblage of
different populations
that live together in
a defined area
• A population is a
group individuals
that belong to the
same species and
live in the same
area
How Do We Study Ecology?
• Observing
• Experimenting
• Modeling
(Ecological
phenomena that
occur over long
periods of time)
How Do Organisms Obtain
Energy in an Ecosystem?
• Sunlight is the main energy source for life on
Earth
• Autotrophs will then use the energy from the
sun (or chemicals) to make their own food
• Autotrophs are also known as producers
• Examples of autotrophs: plants, algae,
cyanobacteria
How Do Organisms Obtain
Energy in an Ecosystem?
• Autotrophs use photosynthesis to
convert sunlight, carbon dioxide, and
water into oxygen and carbohydrates
How Do Organisms Obtain
Energy in an Ecosystem?
• What if there is no light in the
ecosystem?
• The autotrophs will use
chemosynthesis, which is a process that
uses chemical energy to produce
carbohydrates (ex: bacteria living in
volcanic vents)
How Do Organisms Obtain
Energy in an Ecosystem?
• Organisms that rely on other organisms
for energy are known as consumers or
heterotrophs
Types of Heterotrophs
• Herbivores- consume only plants
• Carnivores- consume only meat
• Omnivores- consume both plants and
animals
• Detritivores- consume plant and animal
remains (earthworms, mites, crabs)
• Decomposer= breaks down organic matter to
obtain energy (bacteria & fungi)
Feeding Relationships
• Energy in an ecosystem flows in one
direction (from sun to the heterotrophs)
• Food chain- a series of steps in which
organisms transfer energy by eating
and being eaten
Food Chain
Food Web
Transfer of Energy
• Each step in a food chain or food web is
called a trophic level
• Autotrophs make up the first trophic
level, consumers make up 2nd, 3rd, 4th
or higher levels
• Only about 10% of energy is transferred
to organisms at the next trophic level
Transfer of Energy
• If 10% of solar energy is captured by
plants then animals who eat the grass
gain only 10% of that energy (1%),
animals who those animals gain 10%
from that (.1%)
• 10% --> 1% --> .1%
What is Biomass?
• Biomass is the total amount of living
tissue within a given trophic level
• A biomass pyramid can show you much
food is available to each trophic level
Recycling Matter in the
Biosphere
• Elements, chemical compounds, and
other forms of matter are passed from
one organism and from one part of the
biosphere to another in
biogeochemical cycles
Important Biogeochemical
Cycles
•
•
•
•
Water cycle
Carbon Cycle
Nitrogen Cycle
Phosphorus Cycle
The Water Cycle
The Water Cycle
• Water moves between the ocean,
atmosphere, and land
• Water evaporates from bodies of water into
the atmosphere
• Water can also enter the atmosphere through
transpiration (process by which water is lost
through the leaves of plants)
Nutrient Cycles
• A nutrient is a chemical substance that
an organism needs to sustain life
• Important nutrient cycles
– Carbon Cycle
– Nitrogen Cycle
– Phosphorus Cycle
The Carbon Cycle
• Carbon’s Roles
– Ingredient in living tissue
– Important component of animal skeletons (CaCO3)
– Important component of the atmosphere (CO2)
The Carbon Cycle
• Carbon enters the atmosphere by:
– Respiration
– Geochemical processes
– Human activities
• Carbon is taken up by:
– Photosynthesis
– Burial and decomposition of dead organisms
(formation of fossil fuels)
The Carbon Cycle
CO2 in
Atmosphere
CO2 in Ocean
The Nitrogen Cycle
• The roles of nitrogen:
– Important component of amino acids
– Major component of fertilizer (NO3-)
– Major component of atmosphere (N2)
The Nitrogen Cycle
• Nitrogen gas (N2) cannot be used by plants
so it must be converted into a usable form
• Soil bacteria convert nitrogen gas into
ammonia (NH3) in the process of nitrogen
fixation
• More soil bacteria convert ammonia into
nitrates (NO3-) and nitrites (NO2-) a usable
form
• Other soil bacteria then convert nitrates and
nitrites back into nitrogen gas, which is known
as denitrification
The Nitrogen Cycle
The Phosphorus Cycle
• Roles of Phosphorus
– Important component of DNA and RNA
• Does not enter atmosphere (gas)
• Steps
– Phosphorus is found in rocks and sediment which
gets moved by water
– Plants absorb phosphorus in the form of
phosphate from soil and water
– Heterotrophs consume plants
What is a Limiting Nutrient?
• A nutrient that is scarce of cycles very
slowly
• When an aquatic ecosystem receives a
large amount of a limiting nutrient it
immediately increases the amount of
algae, which is known as algal bloom
Algal Bloom
• What is the result of
algal bloom?