ECOSYSTEM DYNAMICS

Populations SymbiosisSuccession

Populations

• Group of the same type of organism living in the same geographic area at a given time.

• Limiting Factors – Food

• Carrying Capacity - limits size

• Zero Growth (Steady State)

Measuring Populations

• Census – count all of the organisms in a population• Direct count

• Sampling – count a small sample and use it to estimate the total population

Techniques for Sampling

• Quadrat Method• Good for counting sessile things• Construct a grid• Count several random quadrats

http://www.psychology.ex.ac.uk/lundy/images/quad.jpg

Capture-Recapture Method

• Assumes population remains constant

• Capture, mark and release organisms

• Capture again, use formula:

Population Density

• Need: population size and area• Ex. 40 oak trees in 10 acres

Population Distribution

• Clumped• Uniform/Even• Random

Symbiosis Species Interaction

• Predation• Predator – consumes another individual, the

prey

• Plants – adaptations to prevent predation (thorns)

http://www.public.iastate.edu/~bsbowen/ZOOL-EEOB507/images/predprey-cheetahgazelle.jpg; http://www.bigfoto.com/themes/closeup/thorn-photo_if.jpg; http://www.ndpteachers.org/perit/Tapeworm%5B1%5D.JPG

Parasitism

• Parasite – feeds on host, harming but not killing it

• Ectoparasite – external (ticks)• Endoparasite – internal (tapeworm)

http://www.public.iastate.edu/~bsbowen/ZOOL-EEOB507/images/predprey-cheetahgazelle.jpg; http://www.bigfoto.com/themes/closeup/thorn-photo_if.jpg; http://www.ndpteachers.org/perit/Tapeworm%5B1%5D.JPG

Competition – species compete for same limited resource (water)

• Mutualism – both species benefit

(clown fish, sea anemone)

• Commensalism – one species benefits, the other unharmed

(human, apple tree)

http://www.sandyart.com/Clown_Fish_.jpghttp

Succession

• The gradual change in a community over time.

• Primary community – development of a community where none existed before.

(Bare rock succession)

• Secondary community – reclamation of a previously existing community

(Farmer’s field succession)

• Climax community – long-term, generally stablestable( Old forest community)( Old forest community)