Population: All members of 1 species within defined area.

Spacing/ Distribution: Distribution is often determined by needs of the organisms (food, water, mates, shelter, etc..)

Overall, dispersion depends on resource distribution. In random dispersion, the position of each individual is independent of the others. Overall, dispersion depends on resource distribution. Fig. 52.2c Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

By contrast, uniform dispersion is when individuals are evenly spaced. Fig. 52.2b Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Clumped dispersion is when individuals aggregate in patches. Fig. 52.2a Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

We define a change in population size based on the following verbal equation. Change in population = Births during –Deaths during size during time interval time interval time interval Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Graphing Populations Natality: Birth rate. Immigration: Moving in. Considerations: Natality: Birth rate. Immigration: Moving in. Mortality: Death rate. Emigration: Moving out. Populations increase when: Natality + Immigration > Mortality + Emigration

Fig. 52.22 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

2. Estimating Earth’s carrying capacity for humans is a complex problem Predictions of the human population vary from 7.3 to 10.7 billion people by the year 2050. Will the earth be overpopulated by this time? Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings

Factors affecting population increase/decrease : a. male/female ratio b. age distribution / 3 at reproductive age c. species density: effects health, food & H20 supply - territory needs d. climate, availability of shelter, predator numbers, adaptability, means of protection

J-curve Exponential growth phase: Maximum population growth rate. Example: Humans

S - curve Transitional phase: Population increases / decreases. Plateau phase: Steady state. Population in equilibrium. This is the carrying capacity. Carrying capacity: Max. population size a particular environment can support with no net increase or decrease over a long period of time.

k-strategies Reproductive strategy where the population puts more resources into development and long-term survival of each individual. This reproductive strategy is common in stable, unchanging environments Examples: whales, sharks, humans.

Characteristics of this strategy include: a) long life span b) late maturity c) large body size d) reproducing many times over long periods of time. e) one or two offspring per reproductive cycle

Reproductive Strategies: r-strategies Reproductive strategy where the population puts more resources into producing as many offspring as possible in a short period of time. This reproductive strategy is common in unstable or rapidly changing environments. Examples: salmon (those that reproduce only once), protozoa, bacteria.

Characteristics of this strategy include: a) short life span b) early maturity (they are capable of reproducing very quickly) c) small body size d) reproduce only once e) many offspring produced per reproductive cycle.

What limits population growth? *Limiting factors: factors that cause population growth to decrease.

Density-Independent Factors Affects ALL populations regardless of size. 1. Unusual weather 2. Natural disasters 3. Seasonal cycles 4. Certain human activities

Density-Dependent Factors Affects populations when the population reaches a certain size. 1. Competition - more organisms competing for the same resource  driving force behind evolution (those that have adaptations survive). 2. Predation 3. Parasitism/disease

Predator/Prey Graph (saw tooth curve) ** Predator always follows the prey!