What are the four factors that regulate biotic potential?
- Max # of offspring per birth
- Chance that offspring will reach reproductive age
- # of times per year organism reproduces
- Age at which reproduction begins
What is carrying capacity?
The ability for an environment to support a population
What is density-dependent factors?
Biotic; limit reproduction as pop’n increases (e.g. disease, predation)
What are density-independent factors?
Abiotic; work regardless of pop’n size (e.g. floods, drought)
What is environmental resistance?
Environmental conditions limit a species from growing out of control – influenced by abiotic and biotic factors
What is a J-curve?
- Demonstrate exponential growth – increase in population size at an increasing growth rate
- Usually occur in closed systems (e.g. aquarium containing bacteria, algae, yeast, etc.)
- Often microorganisms with short life spans
- Exception: humans!
What is an S-curve?
- Most natural populations demonstrate an S-shaped curve
- Population increases until limiting factors cause it to reach carrying capacity - as long as resources maintained, population size stabilized
- Density dependent/independent factors may initiate death phase
What does K-selected mean?
K-selected strategies – generally slow reproduction, long life span, longer offspring
rearing, later reproductive maturity
* E.g. Elephants, moose, humans
What does r-selected strategies mean?
r-selected strategies – rapid reproduction, short life span, little/no rearing, early reproductive age
* E.g. Bacteria, yeast, mice
What is a type I survivorship curve?
Large mammals, few offspring, low infant mortality, extended life span (e.g. humans)
What is a type II survivorship curve?
Chances of survival or death are about the same at any age (e.g. squirrels)
What is a type III survivorship cure?
Low survivorship or high mortality rates early in life (e.g. oysters)
What is a histogram?
Useful for studying human populations to see trends and make predictions
- Often take shape of pyramid
What does a double histogram include?
Age and sex of a population
