19.1UNDERSTANDING POPULATIONS

1. POPULATION PROPERTIESSize (often hard to measure)Density– amount of population per unit of area (population crowding)

# of individuals = population density area (units2)

Dispersion – spatial organization of the population

1. POPULATION PROPERTIESDispersion – spatial organization of the population

1. POPULATION PROPERTIESDispersion – spatial organization of the population

•Clumped – population is clustered together, usually around resources or from social behavior

ex/ school of fish

clumped

1. POPULATION PROPERTIESDispersion – spatial organization of the population

•Uniform – the population is evenly dispersed from each other usually from social interactions

ex/ bird nesting sites or solitary predators

uniform

1. POPULATION PROPERTIESDispersion – spatial organization of the population

•Random – the population is randomly scattered throughout the area

ex/ trees in a forest with seeds dispersed by wind or animals

random

2. SURVIVORSHIP CURVESSurvivorship Curve

• probability of individuals surviving to a certain age

2. SURVIVORSHIP CURVESSurvivorship Curve

• probability of individuals surviving to a certain age

I – Low birth rate, low infant mortality, survives to old age (Humans & large mammals)

2. SURVIVORSHIP CURVES

II – Survivorship rate equal at all ages

(Birds & reptiles)

2. SURVIVORSHIP CURVES

III – High birth rate, high infant mortality rate (Fish, Insects, Plants)

3. MODELS OF GROWTHExponential

• birth and death rates are constant

(b > d)

3. MODELS OF GROWTHExponential

• birth and death rates are constant

(b > d)• the rate increases as the

population gets larger• limited by density-

independent factors• Ex: Bacteria

3. MODELS OF GROWTHLogistic

• (K): the number of individuals the environment can support over time.

• This is when b rates equal d rates (zero population growth)

• limited by density-dependent factors

Most organisms such as seals, and whales follow

this model

4. REGULATING POPULATION GROWTHLimiting factors: restrains population growth

4. REGULATING POPULATION GROWTHLimiting factors: restrains population growth (2 types)

•Density-independent factors: no regard for population density

EX. Weather, seasons, natural disasters

4. REGULATING POPULATION GROWTH

• Density-dependent factors: increase or become more prominent when the population density increases

EX. predation, pollution, food shortage