Biology 5C~Lecture 11 (Community Characteristics)

What are the factors that influence community assembly?

-Evolutionary history
-dispersal
-abiotic factors
-biotic factors

How do we measure diversity?

By counting the variety of species that make up the community

Species richness:

the number of species in the community

Relative abundance:

the proportion each species represents of all individuals in the community (evenness)

Two communities can have the same species richness (number of species) but...

a different relative abundances (evenness)

Ecologists quantify species diversity using...

indices that combine species richness and relative abundance.

The Simpson's diversity index (D):

D=( N-(N-1) ) / ( total n (n-1) )

N = total number of organisms
n = number of individuals of each species
-Look up examples

What is a food chain?

A series of steps in which organisms transfer energy by eating and being eaten

Terrestrial food chain:

1). Plant (Primary producer)
2). Herbivore (Primary consumers)
3). Carnivore (Secondary consumers)
4). Carnivore (Tertiary consumers)
5). Carnivore (Quaternary consumers)

Marine food chain:

1). phytoplankton
2). zooplankton
3). Carnivore
4). Carnivore
5). Carnivore

Food web:

a branching food chain with complex trophic interactions.

What interactions are represented in food webs but not food chains?

food webs show all the food chains within that ecosystem.