 Basic definitions  Food chains and webs  Photosynthesis and respiration  Cycle of energy flow  Ecological pyramids

Man did not weave the web of life. He is merely a strand in it. Whatever he does to the web, he does to himself. Chief Sealth a.k.a. Chief Seattle

The study of the interrelationships between living organisms and their biotic and abiotic environment.

 Both are important parts of an environment….  Biotic = living parts of the environment  Abiotic = nonliving parts of the environment ◦ E.g. The atmosphere, climate, soil, water, pollution

 Species: particular type of organism, which can interbreed and produce fertile offspring.  Population: group of individuals of the same species living in the same area at the same time.  Habitat: the environment where a species normally lives. The habitat includes both abiotic and biotic factors.  Ecological Niche: the role the organism plays in its habitat/environment.

 Community: group of populations living and interacting with each other in a common habitat.  Ecosystem: community of interdependent organisms and the physical environment which they inhabit.  Biome: a collection of ecosystems sharing climatic conditions.  Biosphere: part of the Earth inhabited by organisms.

 Food Chain ◦ The pathway along which food is transferred from trophic level to trophic level, beginning with producers.

Grass  Grasshopper  Frog  Snake  Hawk Producer  primary consumer  secondary consumer  tertiary consumer  quaternary consumer

 Watch the direction of your arrows! They always point in the direction of energy flow!  ALSO, it is easy to find the producers – all arrows point AWAY FROM the producers.  NO arrows point away from the top predators (except toward the decomposers…)

 A complex of interconnected food chains within an ecosystems  Tends to be a more realistic model of the flow of energy and materials…

 Producers…also called “autotrophs”  Consumers…also called “heterotrophs” ◦ Primary, secondary, tertiary, quaternary.  Herbivores, carnivores, omnivores ◦ Can you think of examples?  These are the ones everyone thinks of…who do we tend to forget?

 Decomposers (or saprotrophs) – heterotrophs (often microscopic) that break down dead organic matter ◦ Bacteria, fungi … they don’t really “eat” the material…  Detritivores -- consume detritus (dead remains of animals, leaf litter, feces) ◦ Snails, crabs, clams, worms, beetles, snails, termites, millipedes

 An organism – any living thing  Species – a group of similar organisms that are able to freely interbreed with one another and produce fertile offspring

 Population ◦ A group of organisms of the same species who live in the same habitat (the environment in which a species lives) at the same time.  Community ◦ An association of organisms of different species living together with some degree of interdependence

 Ecosystem ◦ A particular community and its physical (abiotic) environment.  Biosphere (ecosphere) ◦ All ecosystems linked together by biological, physical and chemical processes.

 Two basic concepts: ◦ Energy flows ◦ Nutrients cycle ◦ Today we’re focusing on energy flows…

 Ultimate source of energy for most of the Earth’s ecosystems is the sun.

 30% is reflected back into space  20% is absorbed by the atmosphere (1-3% by ozone)  50% reaches the surface ◦ 30% absorbed by water and earth and reradiated as infrared radiation which is held in as heat. ◦ 20% absorbed by plants but only 1- 2% used in photosynthesis; most re- radiated as heat or released during transpiration.

 Energy flows through food chains and food webs from one trophic level to another.  Trophic levels group organisms based upon their main nutritional source. ◦ Autotroph or producer ◦ Heterotroph or consumer ◦ Detritivore or saprotroph (decomposer)

 Where it all begins…  Plants, algae, and some bacteria  PHOTOSYNTHESIS – radiant energy trapped by plants (or other photosynthetic organisms), and is used to make organic molecules (glucose…a type of SUGAR).

6CO H 2 O + radiant energy  C 6 H 12 O 6 + 6H 2 O + 6O 2 OR 6CO 2 + 6H 2 O + radiant energy  C 6 H 12 O 6 + 6O 2 (the water is just cancelled out…)

 Don’t forget that this process cannot take place without the green light-trapping pigment called CHLOROPHYLL.  ONLY organisms with this pigment can harness the sun’s energy to complete the process of photosynthesis.

 Inputs ◦ Carbon dioxide (6 molecules) ◦ Water (12 molecules) ◦ Radiant energy (from the sun)  Chlorophyll –can be considered already within the system

 Outputs ◦ Glucose (1 molecule…this is organic matter) ◦ Oxygen (6 molecules) ◦ Water (6 molecules)  So what is happening with energy transformation?

 Energy transformation … ◦ From light energy to chemical energy (in the bonds of the organic molecules of glucose)  Storage (or Stock) = organic molecules create starch with stored chemical energy…to be used later…

 The breakdown of organic molecules (like glucose) to release ENERGY ◦ Who does it? Plants, animals, fungi, bacteria….ALL LIVING THINGS!!!

C 6 H 12 O 6 + 6H 2 O + 6O 2  6CO H 2 O + energy (available to do work) OR C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + energy (available to do work)

 Inputs ◦ Glucose (1 molecule…this is organic matter) ◦ Oxygen (6 molecules) ◦ Water (6 molecules)

 Outputs ◦ Carbon dioxide (6 molecules) ◦ Water (12 molecules) ◦ Energy (available to do work)  So what is happening with energy transformation?

 You probably noticed the correlation between photosynthesis and respiration….  In general, the inputs of one are the outputs of the other!  USE THIS TO HELP YOU REMEMBER THEIR FORMULAS!!!!

 It will be used by the organism to DO WORK ◦ Growing, metabolizing, reproducing, moving, etc.  Ultimately, most of it will be “LOST” AS HEAT

 First Law: Energy can neither be created nor destroyed.  Second Law: Every energy transformation involves some loss of usable energy in the form of heat (entropy).

 Only about 10% of the available energy at one trophic level can be used at the next trophic level.  Where does the energy go?

 So if only 10% can be transferred up each level, the 90% loss (or reduction) will be seen…  LOSS AS HEAT!!!

 Due to this loss of energy, and pyramid of energy or a pyramid of PRODUCTIVITY (flow of energy) will ALWAYS SHOW A DECREASE along the food chain  So the shape will always be wider at the bottom, and become narrower as one ascends the pyramid.

 Pyramid of NUMBERS ◦ Shows the # of organisms at each trophic level

 USUALLY, a pyramid of numbers will have a wider base (considering the energy that must be passed along the food chain and how MANY individuals are needed to support a population of organisms)  EXCEPTIONS…

 One tree (or dead log) can provide food for THOUSANDS of insects and leaf eating invertebrates  MUCH less useful than pyramids of energy, productivity, or biomass

 Display the total biomass at each trophic level AT A GIVEN TIME ◦ What does biomass mean? ◦ Can be represented in units as total volume, DRY WEIGHT, or live weight (g m -2 )

 Biomass: “The mass of organic material in organisms or ecosystems, usually per unit area. Sometimes the term dry weight biomass is used where mass is measured after the removal of water. Water is not organic material, and inorganic material is usually relatively insignificant in terms of mass.”

 Since they only represent biomass present at a given time, marked seasonal variations can cause a pyramid of biomass to have an INVERTED shape. ◦ In winter, when most insects die, or when birds migrate…

 Pyramids of biomass and pyramids of numbers simply represent MOMENTARY stock, while pyramids of energy or productivity show the rate at which that stock is being generated…

 Total amount of solar energy converted to organic compounds is called Gross Primary Productivity  The amount of Gross Primary Productivity less the cost of metabolic activities of the plant is called Net Primary Productivity. ◦ Only that sugar which is used in biomass (dry weight) can be passed to the next trophic level.

 To be expanded upon NEXT TIME…