Growth rates can be linear, exponential, or S-shaped Linear growth: growth is steady If graphed it’s a straight line.

Growth rates can be linear, exponential, or S-shaped

Linear growth: growth is steady If graphed it’s a straight line

Exponential growth: as population gets larger, it grows faster because there are more individuals able to reproduce when graphed results in a J-shaped curve

S-shaped growth: population levels off when certain limiting factors are met

If resources are plentiful, there are more births than deaths and carrying capacity can be temporarily exceeded

Overshooting carrying capacity can lead to mass die-offs as resources run out

Deaths exceed births and population again falls below carrying capacity

● Carrying capacity was overshot and population dropped, then grew again, etc.● Overall the growth pattern is S-shaped

2 types: rapid and slow

Rapid life history: Mature quickly Reproduce early in life Produce lots of offspring Short life span Small size Example: rabbit, mosquitoes

Slow life history: Mature slowly Reproduce later in life Produce few offspring Long life span Large size Example: elephants, sea turtles, pandas

Any biotic or abiotic factor that affects a population and limits its growth.

The factor may be too little in quantity or too much.

Each species has a range of tolerance for each limiting factor

Every population thrives in an optimal range of abitoic factors.

Beyond this range, one finds fewer and fewer numbers of these organisms.

Often, the range is shown for each factor, and this is known as the range of tolerance.

1. Density-dependent factors depend on the population size/density

As the population grows the effect of the limiting factor increases

Examples of Density Dependent

a. Predation: an interaction between species in which one species uses another species as food

follows a predictable cycle of population changes over time

Lynx (predator)

Why is the lynx population always lower than the hare population?

Lynx is higher up on the food chain; energy is lost between the herbivores andthe carnivores

Examples of Density Dependent

b. Competition: fighting for resources if population size is low, resources will

build up as resources are used, population increases increased population =increased competition

and population size drops

c. Crowding: fighting for space as crowding increases, stress increases Stress results in:

Increased aggression Lower fertility Lower parental care Lower resistance to disease

Density-independent: does not depend on population density

the factor affects individuals the same regardless of population density

Usually abiotic factors

TemperatureVolcanic eruptionsFlooding/ Droughtpesticides