A Population is a group of interbreeding individuals living in the same space at the same time.
It's good to stick together. Some of the benefits of herds are:
- Help with finding resources
- Protection from predation
- Hunting in packs is highly effective
Population Dispersion Patterns
Population dispersion patterns are the patterns that appear with the distribution of certain plants or animals in their habitat. The three patterns are Clumped, Uniform, and Random. The most common dispersion pattern is clumped.
Density Dependent Factors
All of these things are effected by how closely a population lives with each other, so they are Density Dependent.
Density Independent Factors
Natural Disasters such as drought, fires, floods, etc. These are all things you have no control over, so they are called Density Independent.
Two types of Population curves: Exponential Vs. Logistic Growth (Malthusian Growth)
Exponential Growth is shown in Red below and has a J-shape due to doubling each unit of time. Logistic Growth has an S-shape due to the addition of Carrying Capacity (K). Carrying Capacity is the maximum size a population can sustainably become.
What happens after a population hits carrying capacity? There are four different major possibilities. Stable curves might occur in an undisturbed section of the Rainforest with a Primate or other high trophic level organism. Cyclic curves are similarly shaped, but go farther above and below K due to a predator/prey relationship. Irruptive curves occur when a predator is removed and the prey eats too many of its resources causing an overshoot of growth and a dieback once the resources are gone. Irregular curves usually are the result of human activity interrupting the natural cycles.
K-Selected Vs r-selected Species
How would you describe the following organisms? What would their strategy for survival be?
The r-selected species are also known as opportunists. The r is a variable for biotic potential which is the maximum size a population could reach if the conditions were ideal. The r-strategists have a lot of babies and then leave them, so if they all by some chance were able to survive they would be at their biotic potential. Traits of r-selected species include:
- High rate of reproduction
- Many small offspring
- Little to no parental care
- High population growth rate
- Early successional species
- Early reproductive age
- Short lives (<1 year)
- Opportunists: insects, weeds
How would you describe these animals? What would their strategy for survival be?