Dept of Biology, Lewis and Clark College		Dr Kenneth Clifton
	Biology 141 Lecture Outline

Terrestrial ecosystems

Environmental aspects that are generally more "important" above water than below

Temperature - changes in temperature are more extreme and more rapid

Moisture - life above water is no place for an unprotected cell!!

How does dessication influence the life of terrestrial organisms?

Viscosity - Air is a less supportive medium.... what does this mean?

 

In contrast, light levels above water are generally less important as an environmental variable, though shading, cloud cover, latitude, etc, can all be influential.

Nutrient availability can be locally important and "patchiness" may be extreme... i.e., no diffusion as in water.

 

Dispersal may be constrained, leading to closed populations (but seed dispersal may "open" plant populations).

Consider the biology of both juveniles and adults to think about the potential for exchange between populations

 

Compared to marine systems, a larger proportion of terrestrial animals are endotherms.

Why might this be the case?

Surface area to volume considerations as a function of temperature.

Insulation via air pockets vs fat

Water vs air as a heat sink

What does this mean for food webs?

 

Consider an example: the tropical savanna of East Africa

What is it noted for?

How do abiotic and biotic process shape these patterns of biodiversity?

The physiology of primary producers

Mostly green vascular plants (as opposed to algae and phytoplankton within marine and aquatic ecosystems).

The physiology of primary consumers

For herbivores, strategies for digesting plant material is a function of size.

Getting to the cell contents of plants vs cells in algae (differing amounts of cell wall material and cellulose)

Terrestrial herbivores must rely on microbes for cellulose digestion.

The physiology of secondary consumers

For carnivores, getting sufficient energy often limits density (think of trophic constraints and energetic efficiency of consumption)

 

How these factors influence how populations align to resources

Females align with resources

Males align with females

 

Think about patterns of food availability and body size: The African herbivore guild (see slide show on Moodle page)

The players: from oribi to elands... plus a few outliers (dik-diks and duikers up to giraffe, rhinos, and elephants).

Once again, surface area to volume ratios are important

 

What about carnivores?

Social organization, as well as prey type, plays an important role.