Energy in organisms is either produced or
consumed:
Producers (aka autotrophs) –
Organisms that can convert
chemical or light energy to food
Consumers (aka heterotrophs) –
Organisms that cannot make
their own food
Eats plant material
Eats anything
Eats other animal material
Eats dead stuff
Food and Energy
Food - potential energy that organisms can
convert into kinetic energy to do work
Potential energy in foods is chemical energy.
Chemical energy
• arises from the arrangement of atoms
• can be released by a chemical reaction
Molecules store varying amounts of potential energy in the
arrangement of their atoms.
Organic compounds are relatively rich in such chemical
energy.
Calories and calories
Chemical energy, especially in food, is measured using
calories
A calorie is the amount of energy that can raise the
temperature of one gram of water by 1 degree Celsius.
Food Calories are kilocalories, equal to 1,000 calories.
Not all of that energy is used by or even available to the
organism
The energy of calories in food is burned off by many activities
Calculating Calories
Mountain Dew = 170 Calories = 170 Kcal = 170,000 calories
Hershey Bar = 210 Calories = 210 Kcal = 210,000 calories
1 T Mayonnaise = 110 Calories = 110 Kcal = 110,000 calories
1 Gallon Gasoline = 31,000 Calories = 31,000 Kcal = 31,000,000
calories
Jogging 1 mile burns 100 Calories = 100 Kcal = 100,000 calories
Energy Production
Ecosystem’s energy budget is based on the
potential photosynthetic activity
Aquatic Ecosystems
Production is limited by:
•Light Intensity
•Water Temperature
•Inorganic Nutrients
Terrestrial Ecosystems
Production is limited by:
•Precipitation
•Temperature
•Light Intensity
•Inorganic Nutrients
Aquatic ecosystems are the major producers on
Earth
Production
in the Bay
1. Predict where light
intensity is the greatest.
Explain.
2. Predict where water
temperatures are the
highest? Explain.
3. Predict where inorganic
nutrients are highest in
the bay. Explain.
4. Suggest why production
in the bay is highest in
the middle reaches of the
bay
Food Chains
Represent transfer of energy between organisms
Each link in a food chain is a trophic level
Detritus food chains are most important
More organisms trace themselves back to
detritus than to plants
Food chains have limited use to scientists
because most organisms are not specialists (they
eat more than one type of food)
Food Chains
Biological Magnification
Biological magnification occurs
by increasing the toxicity of
poisonous substances as those
substances move up the food
chain.
Food Webs
Represent
interaction
between
numerous
food chains
Pyramids
Number
How many organisms in
an ecosystem
Biomass
Number + Size
Total mass of organisms in
ecosystem
Energy
Number + Size +
Reproductive Rate
10% Rule
Compares trophic levels
Difficult to make
Biomass
Biomass = The total mass of all organisms in an
ecosystem
The further removed a trophic level is from its
source, the less biomass it will contain
Herbivores make more efficient use of food
than carnivores
Average American eats more grain than people
in Third World countries