Bio - Ch.40 Part 2: Population Ecology

1. Characteristics of populations

1. Composed of individuals of the same species

2. Occupy the same area

3. Depend on the same resources

4. Are affected by the same environmental conditions

5. Have the opportunity to interact with each other

Density

1. How many individuals there are in the population per area or volume

2. Constantly changing due to immigration (moving in) and births and emigration (moving out) and deaths

Dispersion

1. Refers to how the individuals are distributed within their range

Clumped

1. Usually grouped where food is found

Uniform

1. Evenly space, usually based upon predation and competition

Random

Flowers

Demography

1. Is the study of vital stats for a population (births/deaths)

2. It is shown by a survivorship curve

3. Generation time (lifetime) is directly related to body size in most cases as this graph clearly shows

4. Energetic trade off between high survival rates and increased parental care

Type III Demography

1.  small organisms (oyster) give no parental care tend -> leads to high mortality rates of young -> thus they have tons of offspring

Type II Demography

1.  small rodents, some lizards and plants show a constant death rate over the lifespan

Type I Demography

1. ex. Humans have an increased mortality rate in old age

1. R-strategists

1. Small individuals 

2. Short life span

3. Fast to mature

4. Produce many offspring

5. Little to no cared for offspring

1. K-strategists

1. Large individuals

2. Long life span

3. Slow to mature

4. Produce few offspring

5. Often care for offspring

1. exponential model

1. Possible when resources are plentiful

2. Usually r-selected species

3. Doubles in size

1. Logistic model

1. Growth shows what happens for k-selected species as they near carrying capacity

2. Growth slows as N approaches carrying capacity (K)

1. Carrying capacity (K)

1. Is the maximum population size that can be supported by an ecosystem 

2. It varies over time with fluctuating levels of limiting resources

3. Human max carrying capacity is 10-15 billion

1. Density dependent factors

1. Limit population size by decreasing the birth rate or increasing the death rate

2. Food supply, space, predation,

1. Density independent factors

1. Are unrelated to population size

2. Weather and climate, fires, volcanic eruptions