Download Essentials of Biology Sylvia S. Mader

Essentials of Biology
Sylvia S. Mader
Chapter 30
Lecture Outline
Prepared by: Dr. Stephen Ebbs
Southern Illinois University Carbondale
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
30.1 The Human Population
• The growth of any population, including humans,
is determined by the difference between birth
rates and death rates.
(# births - # deaths)
growth per 1,000 individuals =
1,000
• Until the Industrial Revolution in the 1800s,
human population growth was relatively slow.
• During the Industrial Revolution, a sharp
increase in human population growth began.
Present Population Growth
Future Population Growth Rate
• The number of individuals an environment
can maintain over an indefinite period of
time is called the carrying capacity.
• Because of the rapid increase in the
human population, there are concerns that
the human population may someday reach
its carrying capacity.
More-Developed Versus LessDeveloped Countries
• The growth rate of populations in different
countries differs.
– The more-developed countries (MDCs) have
modest population growth rates due largely to
decreased birthrates.
– The less-developed countries (LDCs) have
higher population growth rates because
birthrates remain high.
More-Developed Versus LessDeveloped Countries (cont.)
Comparing Age Structures
• The rate of population growth in a
population can be determined from the
age structure of a population.
– The age structure of MDCs is stable because
the birthrate of these populations is providing
replacement reproduction.
– The age structure of LDCs has a pyramid
shape with a large dependency group, which
indicates that population growth will continue
to expand.
Comparing Age Structures
(cont.)
Comparing Age Structures
(cont.)
Environmental Impact
• When populations grow, they exert a pressure
on the Earth’s resources.
• This pressure can be measured as an
environmental impact (EI)
E.I. = population size x resource consumption per capita
= pollution per unit of resource used
• Thus there are two causes of overpopulation.
– Population size
– Resource consumption
30.2 Characteristics of
Population
• Populations rely on the living (biotic) and
non-living (abiotic) resources in an
environment.
• These resources can be distributed in
three patterns which affect the population
density or range of a population.
– Clumped
– Random
– Uniform
Demographics and Population
Growth
• Survivorship is also important to an
understanding of population growth.
• The study of survivorship in a population
uses life tables and survivorship curves.
– In Type I curves, there is survival to old age.
– In Type II curves, death is spread across all
age groups.
– In Type III curves, death occurs at an early
age.
Demographics and Population
Growth (cont.)
Demographics and Population
Growth (cont.)
Demographics and Population
Growth (cont.)
• The influence of the biotic potential on
population growth depends upon the
reproductive characteristics of the
population.
– The number of offspring per reproduction
– Chances of survival until reproductive age
– Frequency of reproduction
– Age at which reproduction begins
Exponential Growth
• The pattern of population growth depends
upon two primary factors.
– The biotic potential
– Resource availability
• There are two possible patterns of growth.
– Exponential growth has a J-shape
characteristic of a rapidly growing population.
– Logistic growth has an S-shape showing a
stabilization of the population size.
Exponential Growth (cont.)
Factors That Regulate Population
Growth
• Several factors affect population growth.
– Density-independent factors affect population
growth regardless of population size.
– Examples of density-independent factors
include weather and natural disasters.
Factors That Regulate Population
Growth (cont.)
Density-Dependent Factors
• The effect of density-dependent factors
are highly dependent on population size.
– Competition occurs when more than one
population uses the same resource.
– Predation occurs when one organism preys
upon another organism.
• Predator-prey relationships can create
specific cycles of population growth.
Density-Dependent Factors (cont.)
Density-Dependent Factors (cont.)
30.3 Life History Patterns and
Extinction
• The life history of a population consists of
the variation in population characteristics.
– Opportunistic populations show exponential
growth and have small organisms that show
early maturation, short life span, and limited
parental care of offspring.
– Equilibrium populations show logistic growth,
a population size near carrying capacity, and
large animals with long life span.
Extinction
• Extinction is the disappearance of a
species or higher group.
• The probability that a species will become
extinct depends upon three primary
factors.
– Size of geographic range
– Degree of habitat tolerance
– Size of local populations
30.4 The Scope of Ecology
• Ecology is the study of the interactions between
organisms and with the physical environment.
• Ecology can be studied at different levels of
biological organization.
–
–
–
–
Individual organisms
Populations
A group of several species (community)
A group of several species and the environmental
factors that affect those species (ecosystem)
– The biosphere is a portion of the Earth’s surface
where organisms exist.