1. Populations

2. Population – a group of organisms of one species living in a given area at the same time

3. Factors Affecting Population
Geographical Distribution – range inhabited by a species
Density – number of individuals per unit area
Growth Rate – how fast a population is able to increase in number
Birth rate
Death rate
Immigration
Emigration

4. Limiting Factor – something that causes a population to decrease
Carrying Capacity (K) – the maximum number of individuals an environment can sustain without detrimental effects

5. 2 Types of Limiting Factors
Density-dependent – factors that depend on the size of the population
Only become limiting when the population density becomes very high
Effects are intensified as the population density increases
Density-independent – factors that do not depend on the size of the population
Are limiting regardless of the size of the population
Affect all populations in similar ways

6. Density Dependent Factors
Predation
The effect of predation intensifies as the population density of predators increases
Disease
High population densities make the spread of disease easier to transmit
Parasitism
High densities make it easier for parasites to find hosts, and spread diseases
Competition
More members of a population = Less Available resources = More competition
Less members of a population = More available resources = Less competition

7. Density-Independent Factors
Human Activities
Deforestation
Over-hunting/fishing
Natural Disasters
Hurricane, tornado, flood, severe drought
Equally devastating to populations regardless of size
Weather
Extremely hot/cold temperatures; frost
Adversely effects all populations regardless of their size

8. Types of Growth
Logistic Growth – population growth ↑ as resources ↑, and population growth ↓ as resources ↓

9. Types of Growth
Exponential Growth – individuals in a population reproduce at a constant rate

10. Role of microorganisms in maintaining the health of organisms
. Sometimes helpful bacteria are called “natural flora”. Ex. E.coli bacteria found in our large intestine. They help us nutrients out of some foods. They also produce vitamin K that aids in blood clotting. Lactobacilli help us digest milk proteins.

11. Role of microorganisms in disrupting the health of organisms.
Some bacteria and fungi are pathogenic – cause diseases. Ex. Strep throat
–Streptococcus pyogenes.

12. Role of microorganisms in maintaining the health of ecosystems:
Bacteria and fungi are important in nutrient recycling (decomposers). - Nitrogen – fixing bacteria. - “Oil eating” bacteria – restore ecosystem after am oil spill

13. Role of microorganisms in disrupting the health of ecosystems
The Chestnut blight fungus (1900) caused the death of chestnut trees in the eastern US. They were replaced by hickory, oak, and maple trees.
- Algal blooms Ex. Red tides