1. ENERGY FLOW IN ECOSYSTEMS

2. Producers Producers: Also called Autotrophs.
Organisms that make their own food through photosynthesis or chemosynthesis.
Photosynthesis: use sun’s energy to make food.
Chemosynthesis: use energy stored in chemical to make food.

3. Consumers Consumers: Primary consumers : Eat producers!
Also called heterotrophs.
Organisms that can’t make their own food so they have to consume organic molecules made by other organisms.
Include: Herbivores, carnivores, omnivores, detritivores
Primary consumers : Eat producers!
Herbivores
Teeth designed for grinding

4. Carnivores: eat consumers. Secondary consumers
Feed on primary consumers (herbivores)
Ex. Lions eats a zebra that eats grass
Tertiary consumer
Ex. Shark eats a fish that ate another fish that ate plankton.

5. Omnivores: eat both producers and consumers.
Ex. Grizzly bear: eats both salmon and berries.

6. Detritivores: feed on parts of dead organisms in an ecosystem.
Scavengers – feed on dead organism they did not kill, but found dead
Ex. Vultures, hyenas
Decomposers: bacteria and fungi that break down dead tissue or waste into simpler molecules.
Biodegradable means can be broken down by decomposers

7. Trophic level – feeding level 1st trophic level – Producers
Autotrophs (photosynthetic usually plants/algae)
Chemosynthetic Orgnaisms
Heterotrophs
2nd trophic level – primary consumers (herbivores)
3rd trophic level – secondary consumers
4th trophic level – tertiary consumers
Only about 10% (2% - up to 40%) of usable energy transfers between trophic levels. Where does the rest go???
Remember heat is lost in every transfer between trophic levels (2nd Law of Thermodynamics)
Each organism must also use some energy for their own cellular processes!

8. Food chains and food webs
Food chain: single pathway of feeding relationships (energy transfers) among organisms in an ecosystem.
Food web: interrelated food chains in an ecosystem.

9. Ecological Pyramids
Definition: A graphical model of the quantitative differences between amounts of living material stored at each trophic level for a given time and place
Allow easy examination of energy transfers and loses
Give an idea of what eats what and what organisms exist at each trophic level
Help demonstrate that these are systems in balance
3 Types
Organism Number
Biomass
Energy

10. Pyramid of Numbers Shows the number of organisms at each trophic level
Units are number per unit area
Advantages
Simple
Comparing population numbers with time or season
Disadvantages
All organisms included regardless of size
Does not allow for juveniles or immature forms
Numbers can be too great to represent accurately
Most are broad at the base and have many individuals at the producer level
But… some may have a large single plant as the producer

11. Pyramid of Biomass
Shows the biomass (mass of each individual x number of individuals)
Biomass: The quantity of (dry) organic material in an organism, a population, a particular trophic level, or an ecosystem.
Units are grams per square meter (metre)
Advantages
Overcomes some of the problems of pyramids of numbers
Disadvantages
Only uses samples so it is impossible to measure exactly
Organisms must be killed to measure dry mass
Time of year affects results (algae)
Not all organisms with equal mass have the same energy content…

12. Pyramid of Productivity
Shows the rate of flow of energy through each trophic level
Biomass and numbers are just a snapshot at one time, while these show energy available over time.
Units are often joules per square meter per year
Always pyramid shaped due to the second law of thermodynamics
Advantages
Most accurate system, shows energy transferred, allows for rate of production
Can compare based on relative energy flows
Pyramids are never inverted
Energy from solar radiation can be added
Disadvantages
Very difficult and complex to collect data
Still the problem of having to assign a
species to a particular level (omnivores)