DNA – October 5, What do we mean when we talk about the trophic structure of a community? 2.What’s the difference between an autotroph and a heterotroph? 3.What is ALWAYS going to be at the top of the food chain/food web? Why? 4.Why is there a limit to the # of links in a food chain?

Influential Species in Communities Ms. Klinkhachorn October 5, 2010 AP Biology

Dominant Species Most abundant species in a community – Community: 50A, 10B, 5C, 5D, 15, E, 15F Have a lot of control over the distribution of other species – Example: If a maple tree is your dominant species, it affects abiotic factors like shade and soil nutrients. This shade and soil composition affect the other species that can grow there

Why do species become dominant? Have a competitive advantage Good at avoiding predation or disease – Example: invasive species (not native) Think about what happens when you remove a dominant species from a community

Keystone Species Don’t have to have a high abundance, but have a strong control because of their niches – Removal of a keystone species would affect the species richness of an area

Foundation Species (Engineers) These species physically change the environment – Example: Beaver Also called facilitators because they have positive effects on other species – Example: Black-needle rush (a plant) Prairie Dog