Download Section 2.2 Summary – pages 46

Chapter 4
The Energy of Life
Part 1
How Matter and Energy
Enter Living Systems
• The ultimate source for most of the
energy for life is the sun.
• Photosynthesis:
The process in
which an
organism uses
the sun’s energy
to manufacture
food.
Photosynthesis
Chemosynthesis
• Chemosynthesis: the process of using
chemicals to create food
• Similar to photosynthesis, because it produces
carbohydrates, but uses chemical energy instead of light
energy.
Cellular Respiration
• Respiration: The process of releasing energy
from carbohydrates to perform the functions of
life.
• Used by all living things
Photosynthesis and
Respiration
The producers: Autotrophs
• Autotroph: An organism that uses light energy
(photosynthesis) or energy stored in chemical
compounds (chemosynthesis) to make food
The consumers: Heterotrophs
• Heterotroph: An organism that cannot make its
own food and feeds on other organisms
The consumers: Heterotrophs
• Heterotrophs
display a variety
of feeding
relationships.
• Herbivore: A
heterotroph that
feeds only on
autotrophs
The consumers: Heterotrophs
• Carnivores:
heterotrophs
that eat other
heterotrophs.
• This great white
shark is an
example.
The consumers: Heterotrophs
• Scavengers: eat organisms that have already
died.
• This hardhead catfish is a good example of a scavenger
that is native to the Alabama Gulf Coast.
The consumers: Heterotrophs
• Decomposer: An organism that feeds on and
breaks down dead plant or animal matter, thus
recycling nutrients in the ecosystem.
Part 2
The Ocean’s Primary
Productivity
Primary Production
• Primary production: the creation of energy-rich
compounds (carbohydrates) by autotrophs
• Carbohydrate: the primary energy storage
molecule for living organisms.
• Primary production is measured in terms of the
amount of carbon that is fixed into organic
material per square meter of surface area per
year. (gC/m2/yr)
Marine Biomass
• Biomass is the total
mass of living matter at
each trophic level.
• A pyramid of biomass
represents the total
weight of living material
available at each trophic
level.
• Standing Crop: the
biomass of producers at
a given time.
Pyramid of Biomass
1 kilogram of
human tissue
10 kilograms
of beef
100 kilograms
of grain
Marine Primary Productivity
• Compared to terrestrial primary productivity
– Overall marine productivity is only slightly less
– Marine standing crop is significantly less
– Marine ecosystem cycles energy and nutrients
much more rapidly
• Marine primary producers are phytoplankton
Plankton
• Plankton: Organisms that exist adrift in the
ocean, unable to swim against currents and
waves, most, but not all are very small or
microscopic
– Not a single species
– Both autotrophs and heterotrophs
• Phytoplankton: autotrophic plankton
• Zooplankton: heterotrophic plankton
– Feed on phytoplankton and other zooplankton
Plankton
• Meroplankton: organisms that only live part of
their lives as plankton
– Ex: fish larvae
• Holoplankton: organisms that live their entire
lives as plankton
– Ex: diatoms
Phytoplankton
• The most important primary producers in the
marine environment.
– Account for between 92% and 96%
– Marine plants, kelp, and other multicellular
photosynthesizing organisms account for 2%-5%
– Deep ocean chemosynthesis accounts for the
remainder.
Phytoplankton: four primary kinds
1. Diatoms
–
Most efficient photosynthesizers known
•
–
Convert more than half the light energy they absorb into
carbs
Cell wall made of silica
•
Silica: a transparent, glass-like material
•
Admits light
•
Can be subject to photoinhibition
–
Photoinhibition: The condition in which excess light
overwhelms an autotroph’s ability to photosynthesize
Phytoplankton: four primary kinds
2. Dinoflagellates
–
Characterized by 1 or 2 flagella
•
Flagella: a whip-like tail used for locomotion
–
Most are autotrophic, but a few are heterotrophic
–
Reproduce extremely rapidly
•
Responsible for most plankton blooms
–
Ie: red tide
Phytoplankton: four primary kinds
3. Coccolithophores
–
Shell made of calcium carbonate
•
Calcium carbonate: translucent, milky-white material
•
Screens out some light
•
Live in brightly lit, shallow water
–
All Autotrophic
–
Reproduce extremely rapidly
•
Responsible for most plankton blooms
–
ie: red tide
Phytoplankton: four primary kinds
4. Silicoflagellates
–
Internal supporting structures made of silica
–
Both autotrophic and heterotrophic
–
Have one long flagellum
Limits on Marine Productivity
•
Limiting Factors: physiological or biological
necessities that restrict survival
–
•
Too much or too little will affect survival
Light
–
Too little stops photosynthesis
–
Too much results in photoinhibition
Limits on Marine Productivity
•
Nutrients
– Too little limits population growth
– Eutrophication: can result in harmful
plankton blooms
•
•
Eutrophication: over abundance of nutrients in
an ecosystem
Plankton Bloom: overpopulation of
photosynthysizers that depletes nutrient supply
in an area
– In extreme cases, can deplete oxygen supply in
water
Part 3
Energy Flow Through the
Biosphere
Food chains: Pathways for matter
and energy
• A food chain is a simple model that scientists
use to show how matter and energy move
through an ecosystem.
• In a food chain, nutrients and energy move
from autotrophs to heterotrophs and,
eventually, to decomposers.
Food chains: Pathways for matter
and energy
• A food chain is drawn using arrows to indicate
the direction in which energy is transferred
from one organism to the next.
berries → mice → black bear
Trophic Relationships
• Each organism in a food chain represents a
feeding step, or trophic level, in the passage of
energy and materials.
• Primary Consumer: first trophic level; an
organism that feeds on primary producers
Trophic Relationships
• Secondary Consumer: organism that feeds on
a primary consumer.
• Tertiary Consumer: an organism that feeds on
a seconary consumer
• A food chain represents only one possible
route for the transfer of matter and energy
through an ecosystem.
Food webs
• Ecologists interested in energy flow in an
ecosystem may set up experiments with as
many organisms in the community as they
can.
• The model they create, called a food web,
shows all the possible feeding relationships at
each trophic level in a community.
Food webs
Food chains: Pathways for matter
and energy
• Most food chains consist of two, three, or four
transfers.
• The amount of energy remaining in the final
transfer is only a portion of what was available
at the first transfer.
• A portion of the energy is given off as heat at
each transfer.
Energy and trophic levels: Ecological
Pyramid of Energy
pyramids
• The pyramid of
energy illustrates
that the amount
of available
energy
decreases at
each succeeding
trophic level.
Heat
Heat
0.1% Consumers
1% Consumers
10% Consumers
Heat
Heat
100%
Producers
Energy and trophic levels: Ecological
pyramids
• The total energy transfer from one trophic
level to the next is only about ten percent
because organisms fail to capture and eat all
the food energy available at the trophic level
below them.
Energy and trophic levels: Ecological
pyramids
• Some of the energy transferred at each
successive trophic level enters the
environment as heat, but the total amount of
energy remains the same.