Lecture 3 Diversity and Biological Community

Biological community

an association of interacting species inhabiting some defined area

How is a biological community often perceived through time?

Consistent or stable through some length of time

Give two examples of a biological community

1. Creosote bursage community in the Mojave Desert

2. Saguaro cactus community in Northern Sonoran Desert

What are the attributes to a community structure?

1. Species Richness

2. Species Evenness

3. Species Diversity

What is species richness

the number of species in a community

what is species evenness

the relative abundance of species

What is species diversity

Incorporating both richness and evenness

What is a quantitative index that measures species diversity?

The Simpson Index where diversity value ranges between 0 (none) to 1 (most)

T/F Most species are moderately abundant and few are rare or very abundant

T

What does species abundance show?

Lognormal distribution or a bell shaped curve

Sample size affects the number of species detected.

How does sample size affect the number of species detected?

The larger the sample size, the more likely rare species are detected thus the more bell-shaped or normal the curve is

Environmental complexity affect what?

species diversity

In general how does an environment affect species diversity?

A more heterogeneous environment will have more species diversity due to niches

What is a community defined by?

its different species

Who first defined an ecosystem and when? How would a forest be considered?

British ecologist Arthur Tansley in 1935 considers a forest as a system that absorbs, transforms and stores energy

What does ecosystem ecology focus on

Productivity, energy, and nutrient arrangement

What is primary productivity and what conversion of what to what?

Production of new organic matter (biomass) by autotrophs per area per time

Conversion of inorganic energy/nutrients/ to the organic forms

What is biomass?

a measure of organic matter (per area per time)

What is gross primary productivity?

total biomass produced by autotrophs

What is net primary productivity?

Total biomass - the costs of autotrophs own energetic needs (respiration)

How is net primary productivity measure by?

by the uptake of carbon or production of oxygen by primary producers

What is primary productivity in terrestrial systems controlled by:

1. Temperature

2. Moisture

3. Nutrients

Which two factors have major influence on primary productivity in terrestrial systems?

Temperature and Moisture

what are considered broad global patterns?

Biomes

What is evapotranspiration affected by

Precipitation and temperature

Trophic level

the position in a food web based on the number of energy transfers from the level of primary producers