Interactions in Communities SB.4.a Interactions in communities can take many forms from predation to mutual “friendships”. Symbiosis – a relationship in which to different organisms live in close association with each other

Predator-Prey Relationships One of the most common interactions in the communities. Predation – an interaction between two organisms in which one organism, the predator, kills and feeds on the other organism, the prey. Example:

Herbivory Relationships Herbivores are animals that eat plants. Plants have adapted and try to defend themselves. Chemicals to make them taste bad Spines that can puncture their mouths Toxins In response herbivores came up with ways to defend themselves against the plants Curious? What are your thoughts on that?

Parasitism! http://www.youtube.com/watch?v=o0LuJ6Fe0bw&feature=related http://www.youtube.com/watch?v=NNq6dKguwNU Parasitism – a relationship between two species in which one species, the parasite, benefits from the other species, the host, which is harmed. The host is almost always bigger than the parasite Parasites live on or in their host We always have some form of parasite living within us What are ways to defend ourselves from parasites?

Mutualism A relationship between two species in which BOTH species benefit. Ex. The Crocodile and the Egyptian Plover Bird What are some other examples?

Commensalism A relationship between two organisms in which one organism benefits and the other is neither harmed nor benefits. Ex. Nemo and his home. Where else do you see commensalism?

Energy Transfer: Food Chains SB.4.b Every living being on this planet requires energy to be able to function and are interdependent of each other.

Producers Autotrophs manufacture their own food by capturing energy and use it to make organic molecules (i.e. glucose). Autotrophs are also called “Producers” Producers can either be photosynthetic (use solar energy) or chemosynthetic (use inorganic molecules to make carbohydrates).

Consumers “Heterotrophs” – obtain energy by consuming organic molecules made by other organisms. + =

Five Categories of Consumers What are they?

Herbivores Herbivores – Ex. Cows, Rabbits – eat producers

Omnivores Omnivores – Ex. Humans, Bears – eat producers and other consumers

Carnivores Carnivores – Ex. Lions, Wolves – eat other consumers

Detrivores Detritivores – Ex. Vultures – feed on the “garbage” of an ecosystem (dead plants and animals)

Decomposers Organisms that break down dead or decaying organisms, and in doing so carry out the natural process of decomposition – Ex. Fungi, Bacteria

Food Chains A single pathway of feeding relationships among organisms in an ecosystem that results in energy transfer.

Food Web The interrelated food chains in an ecosystem.

Energy Flow Whenever one organism eats another, the molecules are metabolized and energy is transferred. Energy goes from producers to consumer A way to keep track of energy flow is to place the organisms in a trophic level pyramid according to how they obtain energy (Who eats who?).

Trophic Levels Indicates an organism’s position in the sequence of energy transfer. Producers are always placed in the 1st trophic level. Most ecosystems only contain 3 to 4 trophic levels –What could possibly explain this? Secondary Consumers Primary Consumers Producers

Apple vs. Burger Which do you think is more satisfying? Which is a better source for a quick source of energy? Why? The 10% “Rule”:

Why Such A Low Amount? Some organisms escape and not eaten (lucky them) Even if they are eaten, certain molecules (i.e. cellulose) can not be broken down by the consumer. The energy used by prey for cellular respiration cannot be used by predators to synthesize new biomass. No transformation or transfer of energy is 100% efficient

Does This Explain Why There Are Only A Few Trophic Levels In An Ecosystem? Yes Because of the 10% Energy Transference from one trophic level to the next. Also, this explains why plants are more abundant in an environment than herbivores, and there are more herbivores than carnivores.