Chapter 4. Ecosystems: How They Change. Introduction . Section 4.1. Dynamics of Natural Populations . Dynamics of Natural Populations . In any population, births and deaths will cause the population to grow or shrink
Ecosystems: How They Change
Dynamics of Natural Populations
The J-Curve (blue) demonstrates population growth under optimal conditions, with no restraints. The S-curve (green) shows a population at equilibrium. The horizontal line (red) shows the carrying capacity of the environment for that population. Notice how the J-curve spikes well above and then crashes below the carrying capacity, whereas the S-curve rises up to the carrying capacity and then oscillates between slightly above and slightly below it
An introduced species that has often caused massive defoliation of oak trees, now seems to been brought under natural control in forests
Mechanisms of Population Equilibrium
In 1944, a population of 29 reindeer (5 males, and 24 females) was introduced onto St. Matthew Island, where they increased exponentially to about 6,000 and then died due to overgrazing
In the first photo, the island is largely devoid of vegetation and heavily eroded. Following the eradication of the rabbits in 1988,the island vegetation recovered spectacturaly
Evolution as a Force for Change
Modifications of body shape and color that allow species to blend into the background and thus protect their populations from predation are among the most amazing adaptations. First picture = spanworm, second picture = leaf katydid
Vulnerability of different organisms to environmental changes. A summary of factors supporting the survival and adaptation of species, as opposed to their extinction.
Ecosystem Responses to Disturbance
In this photograph, taken in Banff National Park in the Canadian Rockies, you can visualize the lake that used to exist in the low-level area. It is now filled it with sediment and covered by scrub willow. Spruce and fir forest is gradually encroaching.