ENERGY FLOW IN ECOSYSTEMS

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.

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

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.

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

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

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!

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.

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

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

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…

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)