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..)

In random dispersion, the position of each individual is independent of the others.

Overall, dispersion depends on resource distribution.

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

Fig. 52.2c

By contrast, uniform dispersion is when individuals are evenly spaced.

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

Fig. 52.2b

Clumped dispersion is when individuals aggregate in patches.

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

Fig. 52.2a

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 Considerations:

◦Natality: Birth rate. ◦Immigration: Moving in. ◦Mortality: Death rate. ◦Emigration: Moving out.

Populations increase when: Natality + Immigration > Mortality + Emigration

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

Fig. 52.22

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?

2. Estimating Earth’s carrying capacity for humans is a complex problem

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

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.

Affects ALL populations regardless of size. 1. Unusual weather

2. Natural disasters 3. Seasonal cycles 4. Certain human activities

Density-Independent 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

Density-Dependent Factors

Predator/Prey Graph (saw tooth curve)

** Predator always follows the prey!