Density Regulation:

Density Dependence

Intraspecific Competition

Seeking a common limiting resource

Nicholson’s Blowfly Experiments Fig. 12.1

Time lag in adding egg laying adults: overshoot/undershoot

competition was between larvae

Exploitive Competition: organisms not reacting to each other

Utilizing and reacting to resource availabliltiy by all members

: Favors exploitation

Interference Competition: A fraction obtains all it needs, rest are excluded

Density directly affects growth rate and fecundity

Tadpoles Fig. 12.2

Harp Seals Fig 12.3 (whelping age), Fig 12.4 % whelping females

Quail Fig. 12.5

Elk Fig. 12.7

Some may be non-linear: Bison, Fig. 12.6

Self Thinning in Plants: Fig. 12.8

Density effects on habitat quality Fig. 12.15

Density Independence

Organisms controled not by their density but by extrinsic factors:

Abiotic processes, crash and burn

Insects

Deer Fig. 12.21b

Top-down: predation

Bottom up: resource limitation

Quail vs Owls