Mr.+Dunbar's+Notes

=2.1 Population and Resources=


 * population** is a group of organisms of one type (e.g. population of humans, of cats, of dandelions).


 * resource** is something that organisms use to live or reproduce.


 * exponential growth** is when populations grow really rapidly (non-linear growth)


 * Populations grow until they hit a limit or they use up available resources.
 * Population size is limited by resource availability, e.g. amount of land, prey, nutrients
 * If resources are not renewable eventually the population must move or evolve

e.g. Fungus grows on a ripe orange. 1) fungus grows very rapidly until all sugars or space are used up 2) fungus makes spores which are sent to new locations
 * Exponential growth happens only under special conditions


 * Question**: Why doesn't exponential growth happen all the time?
 * Response**:


 * Topic. Exponential growth and...**


 * 1. Re-introduction of species**

When a species is absent from an area and is then re-introduced it will grow exponentially, until it hits the limits of its environment. e.g Turkeys in Ontario
 * **Year** || **Number of turkeys** ||
 * 1970s || 0 ||
 * 1980s || 4400 ||
 * 2001 || 30 000 ||
 * 2008 || 70 000 ||


 * 2. Limiting factors**

e.g. one yellow perch (fish in Ontario) female can produce 23 000 eggs per year. In five years her family could grow to 1 trillion (1 000 000 000 000) offspring

There are biotic and abiotic factors that are **limiting factors** that restrict how many perches can exist in a population at any time.

e.g. habitat to hide, food to eat, predators to eat them, etc.


 * Topic. Carrying Capacity**


 * the size of a population that can be supported indefinitely by the resources of an ecosystem
 * population must be in equilibrium (i.e. not too big, not too small)

Read pp. 52 & 53. Define: urban sprawl, intensification and summarize the story of the redside dace.