Recommended Study Books
Exam Preparation and Practice Tests
Helpful Websites
- Living in the Environment Textbook Companion Website
- Environmental Science: Earth as a Living Planet Textbook Companion Website
- Environmental Science Textbook Companion Website
- Environment: The Science Behind the Stories Textbook Companion Website
- Environmental Science: Towards a Sustainable Future Textbook Companion Website
Important Formulas
- Lincoln Index
- The Lincoln Index is a statistical measure used to estimate population sizes. The Lincoln Index is often used in conjunction with the catch and release survey method for calculating populating sizes. The formula is given as (E1)(E2)/S where E1 and E2 represent the number of observed individuals captured and tallied in two different occurrences and S represents the number of overlaps. This is why the Lincoln Index works well with catch and release, after organisms are captured, they are tagged prior to release so that if the organism is captured again, observers know that they represent an overlap.
- (Number of individuals collected first time)(Number of individuals collected second time)/(number of individuals common to both samples)
- The Lincoln Index assumes three things:
- Tagged organisms are not more likely to be captured again (they are not maimed or hindered)
- Ample time is allowed for captured/tagged organisms to reintegrate into population again randomly
- Organisms are mobile (not plants, sponges, etc.)
- Rule of 70
- The rule of 70 is used to calculate the time it would take for a population to double in size. Doubling time = 70/(the population's growth rate).
- The Rule of 70 is frequently tested on the APES exam and you will be expected to know the formula. Sometimes the population' growth rate will be provided to you, other times you will need to calculate the growth rate on your own.
- Population Growth Rate
- A population's growth rate refers to how quickly a population is expanding or contracting. This is calculated by subtracting the number of deaths from the number of births in a year and dividing by the population size.
- PGR = (Number of Births - Number of Deaths)/(Total Population Size)
- Energy
- 1000 Joules = 1 kJ
- 1000 calories = 1 kcal
- 1 calorie = 4.184 joules
- 1 BTU = 1.05 kJ
- 1 therm = 100,000 BTU
- Power
- Power = Energy/Time
- 1 watt = 1 j/s
- 1 kwh