19.1 understanding populations
DESCRIPTION
19.1 Understanding Populations. 1. Population Properties. Size (often hard to measure). 1. Population Properties. Size (often hard to measure) Density – amount of population per unit of area (population crowding) # of individuals = population density area (units 2 ). - PowerPoint PPT PresentationTRANSCRIPT
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