Transcript Environmental Systems Mr. Wells Spring 2006

Environmental Systems
TAKS Review Session
Lecture 1
Energy Flow in
Ecosystems
Movement of Energy
• Almost all of the life
forms on earth get
their energy from
the sun and its light
energy
Primary Productivity
• All photosynthetic (like plants)
organisms take the light from the sun
and convert it to chemical stored
energy. This chemical energy is an
organic compound (organic means
having carbon).
Producers and Consumers
• All creatures and plants that create food
with photosynthesis are called primary
producers
• Creatures that eat the plants are called
consumers
Trophic Levels
• Energy travels
through the
ecosystem and goes
through levels.
• Each level is called a
trophic level
Flow of Energy
• To understand the flow of energy lets say
that when energy leaves the sun it is
worth 100 dollars.
• Next when the plant makes food the
energy is now worth 10 dollars
• When the rabbit eats the plant the energy
is worth 1 dollar
• When the wolf eats the rabbit it is worth
0.1 dollars or 10 cents
Flow…
• So, as the energy moves through the
ecosystem only 1/10th of it makes it to
the next level!
The Trophic Levels
• The lowest level of the food chain is
made up of the producers
• The second level of the chain is the
herbivores (plant eaters)
• The third level is made up of the
omnivores (eats plants and animals) and
the carnivores (eats only meat)
Producer
Herbivore
Omnivore
Carnivore
The Special Case
• The Detritivores-worms, fungus, and
bacteria-all survive by eating the
dead things and returning the
nutrients to the soil and air. If these
creatures cause the decay they are
called decomposers.
• They are on all trophic levels except
the first
Energy
• As the energy moves from the producers to
the herbivores, then to the carnivores, energy
is lost in the form of heat.
• Because energy is lost, each level gets
smaller (fewer # of organisms)
• For instance, there are more blades of grass
than there are zebras and more zebras than
there are lions.
Energy Pyramid
• Producers have the most members, then
the herbivores have less, and the
carnivores even less. This is because
there is less energy available at each
level. Think about it, there are many many
plants (producers), many rabbits
(herbivores), and few wolves (carnivores).
Pyramid of Energy
Biomass
• If we add up all the dry weight of tissue
and other organic material in an
ecosystem it is called Biomass
Pyramid of Biomass
Environmental Systems
TAKS Review Session
Organism Interactions
Interactions among species
• 5 types of close interactions
1.Predation
2.Parasitism
3.Competition
4.Mutualism
5.Commensalism
Predation – Co-evolution of
Predator and Prey
• Tools: Predator – Improve efficiency at
finding, capturing and consuming prey

Sharp Teeth

Keen senses; sight, hearing, smell

Strong, fast legs

Camouflage
Predation – Co-evolution of
Predator and Prey
• Tools: Prey – Improve efficiency at hiding,
evading and avoiding being eaten.

Sharp Teeth

Keen senses; sight, hearing, smell

Strong, fast legs

Camouflage Spines

Bad Taste / Warning Coloration / Mimicry
Parasitism
• One individual benefits (parasite) while
another is harmed (host).
Examples:
Ticks
Fleas
Tape Worms
Malaria
Parasitism – Co-evolution of
Parasite and Host
• Tools: Parasite – Highly specialized
physiologically and anatomically
 Feeding apparatus
 Small size, hard to see
 Strong, attachment apparatus
 Natural pain killers at feeding site
Parasitism – Co-evolution of
Parasite and Host
• Tools: Host – Defense
 Eyes, nose and mouth are
protected by tears, mucous and
saliva
 Grooming behaviors
 Natural body defenses
TAPE –
WORM
DIET!
Competition
• Use of a limited resource by two or more
species
• Resources could be food (prey) or
nesting sites, for example.
• Hyenas and Lions
• Hawks and Eagles
• Ducks and Geese
Commensalism
• When one species benefits and the
other is not affected.
• Example: Bromeliads (Spanish Moss)
grow on trees to obtain sunlight
• Barnacles on a whale
• Birds that follow behind elephants and
eat the insects stirred up by the
elephant