Title: Population Growth and Regulation
1Population Growth and Regulation
2Characteristics of Populations
- Demographics are characteristics of populations
- Populations can be characterized by their
- Population Size
- Population Density
- Population Distribution
- Age structure
- Reproductive base
- Reproductive and younger
3Age Structure Diagram
Green - Pre-reproductive years Dark Blue-
Reproductive years Light blue - Post-
reproductive years
4Age Structure Diagram U.S.
Zero growth births deaths and immigrate
emigrate
5Regarding Population Density
- The same area may be home to many species but
they may vary by density - Density refers to the number of individuals in an
area but not how they are dispersed - Population density variations are largely due to
ecological relationships and organism
interactions in an area
6Population Size and Exponential Growth
- How population size changes
- Size depends on births, immigration, deaths,
emigration and migrations - Zero population growth is a near balance between
all the positive and negative factors
7Ground Zero to Exponential Growth
Increase in population of field mice
J Shaped Growth Curve
8Effects of Deaths on Populations
The effects of deaths on the rate of increases in
2 bacterial populations
9Regarding the Biotic Potential
- The biotic potential of a population is its
maximum rate of increase under ideal conditions - Biotic potentials vary from species to species
based on - What age reproduction begins
- How frequent reproduction is
- How many offspring are born at a time
10Limits on the Growth of Populations
- The actual rate of growth depends on the
environmental conditions - Limiting factors are collectively called
environmental resistance and include - Nutrient supply
- Predation
- Competition for space
- Pollution
- Metabolic wastes
11Limiting Factors on Growth
- The sustainable supply of resources defines the
carrying capacity for a population in an
environment - The capacity can vary over time
- Note the S shaped logistic growth
12Carrying Capacity
13Density - Dependent Controls
- The main controls are
- Competition for resources
- Predation
- Parasitism
- Disease
- They exert their effects in proportion to the
number of individuals present - Density - dependent factors
- Events resulting in more deaths
- Fewer births
14Paramecium caudatum
Paramecium aurelia
Fig. 48.4, p. 856
15PREY POPULATION
PREDATOR POPULATION
Fig. 48.7, p. 858
16Fig. 48.8, p. 859
17Density Independent Factors
- Some events such as weather tend to increase the
death rate without respect to the number of
individuals present - Lightning, floods, snowstorms affect both large
and small populations!
18Life History Patterns
- Life Tables
- Demography is the study of the age-specific
patterns of particular populations - Life tables follow the fate of a group (cohort)
and calculate survivorship schedules
19A note on Human Population
Growth
- Increase in growth rate
- Expansion of habitat
- Increased capacity in existing habitats
- Population has sidestepped limiting factors
- Technology
- Medicine
20Population Growth Rate in Different Regions
21Population Growth Rate in Different Regions
1996 - Orange 2025 - Blue