Community Ecology A community is all of the species in one place that interact with one another. Since these organisms live in one place, they share a habitat. These interactions are studied in community ecology. This includes all living things such as bacteria, algae, trees, and animals.

Competition When species are interacting, they often will need the same resources. Interspecific Competition- different species compete for the same LIMITED resource. Competition is not beneficial for any species involved because they may not get what they need to survive.

Avoiding Competition In order to avoid competition, a species can: Find a niche, or a specific job in the ecosystem. This could be only living in a specific place or eating only certain foods. Work together with another species to help both species get what they need.

Interspecific Interactions ( Pages 1194-1200) Explanation/ Definition Effect on Species 1 Species 2 Example Competition + or – or 0 Mutualism Commensalism Predation Herbivory Parasitism Pathogens

Work Time Using your books, work through this table in your groups. For the effects, you are circling +, -, or 0. It does not matter which species is species one or species two. You must have your own examples, they should not be the same for the whole group. These should be turned in before you leave.

Interactions Stations Your group will go to one of the lab stations to start. You will read about the relationship and use your table to determine what kind of relationship it is. You will write the station number, the type of relationship, and an explanation on your paper. Each person should have their own. When the timer goes off, we will all move together to the next station.

Food Chains One type of interaction scientists study to learn about a community is the predator-prey interactions. The flow of energy through these interactions for one part of the habitat is called a food chain. All energy in a community comes from the sun and is converted into chemical energy by primary producers (plants, algae, etc) that complete photosynthesis.

Food Chains When drawing a food chain, the organisms will be connected by arrows. These will be linear, meaning one organism eats one other organism. The arrow always points in the way that the energy is traveling, meaning it will point towards the organism who is the predator.

Types of Organisms in Food Chains Carnivores- Organisms that only eat meat. (predators, tigers, lions) Herbivores- Organisms that only eat plants. (insects, deer, cows) Omnivores- Organisms that eat both plants and animals. (humans, bears) Decomposer- Organism that break down organic material (Bacteria, fungus) Detritivore- Feeds on dead organic matter (vultures)

Trophic Levels Each food chain has trophic levels, or groups of organisms that share the same function in the food chain and have the same relationship to the source of the energy. Trophic levels include Primary Producers Primary Consumers Secondary Consumers Tertiary Consumers Apex Predators Decomposers

10% Rule Not all of the energy that the prey has is passed along to the predator. Only 10% of the energy is passed from one trophic level to the next. Organisms at the top of the food chain must then eat more to get the energy they need.

Cards Activity Using the cards provided, complete the food chain section of the activity. Follow the instructions on the worksheet. Once you get to food webs, stop.

Food Webs Food chains are great for showing one chain of interactions for one part of the community, but they are not the most accurate representation of what really happens. Not all organisms just eat one thing, causing food chains to be interconnected in what we call a food web.

Example Food Chain

Organizing Organisms by Trophic Level Helps In food webs, we still have trophic levels. Organizing the organisms by trophic levels helps us better understand and interpret the food webs. This is especially useful when food webs have many organisms and lots of connections between food chains.

Example Food Chain

Interruptions to the Food Web Interruptions of the “normal” food web can occur when natural disasters, extinctions, and migrations occur. These events cause food sources that were once there to be gone. Since most organisms eat more than one thing, the whole community does not collapse. More competition may be a result of an interruption to the food web.

Cards Activity Complete the rest of the activity using the cards. The instructions for each step are in your packet.