Download Population Ecology

Population Ecology
Ecology - Study of interactions
among organisms and their
environment
Conservation biology,
environmentalism:
preservation of natural world
•
•
•
•
•
Biosphere
Ecosystems
Community
Population
Organism
ECOSYSTEM LEVEL
Eucalyptus forest
COMMUNITY LEVEL
All organisms in
eucalyptus forest
POPULATION LEVEL
Group of flying foxes
ORGANISM LEVEL
Flying fox
Brain
ORGAN SYSTEM LEVEL
Nervous system
ORGAN LEVEL
Brain
Spinal cord
Nerve
TISSUE LEVEL
Nervous
tissue
CELLULAR LEVEL
Nerve cell
MOLECULAR LEVEL
Molecule of DNA
Figure 1.1
Population Ecology
•
•
•
•
Population- how to measure?
Growth rates: J shaped, S shaped
K, r, and reproductive strategies
Human population
How are populations measured?
• Population density = number of individuals
in a given area or volume
• count all the individuals in a population
• estimate by sampling
• mark-recapture method depends on likelihood of
recapturing the same individual
• The dispersion pattern of a population refers
to the way individuals are spaced within their
area
– Clumped – Uniform:
– Random: no pattern
Figure 35.2C
How do populations grow?
• Idealized models describe two kinds of
population growth
1. exponential growth
2. logistic growth
• A J-shaped growth curve, described by the
equation G = rN, is typical of exponential
growth
– G = the population growth rate
– r = the intrinsic rate of increase, or an organism's
maximum capacity to reproduce
– N = the population size
Figure 35.3A
high intrinsic
rate of increase
1500
Population size
1000
low intrinsic
rate of increase
500
r=0
zero population
growth
negative intrinsic
rate of increase
r = -0.05
0
0
5
10
Time (years)
15
20
2. Logistic growth is slowed by populationlimiting factors
K = Carrying capacity is the
maximum
population size
that an environment
can support
Figure 35.3B
• logistic growth curve
– K = carrying capacity
– The term
(K - N)/K
accounts
for the
leveling
off of the
curve
Figure 35.3C
Multiple factors may limit
population growth
declining birth rate or increasing death rate
• The regulation of growth in a natural
population is determined by several factors
–
–
–
–
limited food supply
the buildup of toxic wastes
increased disease
predation
Density Dependent Factors
•
•
•
•
Competition
Predation
Parasitism
disease
Density Independent Factors
•
•
•
•
Natural disasters
Weather
Seasonal cycles
Human activities
– About every 10 years, both hare and lynx populations
have a rapid increase (a "boom") followed by a sharp
decline (a "bust")
Figure 35.5
• Survivorship curves plot the proportion of
individuals alive at each age
• Three types of survivorship curves reflect
important species differences in life history
Figure 35.6
Evolution shapes life histories
• An organism's life history is the series of events
from birth through reproduction to death
• Life history traits include
– the age at which reproduction first occurs
– the frequency of reproduction
– the number of offspring
– the amount of parental care given
– the energy cost of reproduction
• Principles of population ecology may be used
to
– manage wildlife, fisheries, and forests for
sustainable yield
– reverse the decline of threatened or endangered
species
– reduce pest populations
The Spread of Shakespeare's
Starlings
• In 1890, a group of Shakespeare enthusiasts
released about 120 starlings in New York's
Central Park
• Today: over 100 million starlings, spread over N.
Amer.
Current
1955
Current
1955
1945
1935
1925
1945
1905
1915
1935
1925
1925
1935
• The starling population in North America has
some features in common with the global human
population
– Both are expanding and are virtually uncontrolled
– Both are harming other species
Why We Live in Interesting Times…
Pre 2000 A.D.
1. More youth than elderly
2. More rural than urban
Post 2010 A.D.
1. More elderly than youth
2. More urban than rural
People alive 1950-2050 A.D. have seen:
1. Highest growth rate (2.1%/year)
2. Population double during their lifetime
More people have lived in the last 100 years,
than in all of human history before 1900!
Thomas Malthus
(1798)
“An Essay on the
Principle of
Population”
•
•
Populations grow geometrically while supporting resources
grow arithmetically
Population, if not purposefully checked (“preventative
checks”), would outpace resources and lead to unplanned
“positive checks” that would return population to
sustainable levels
HUMAN POPULATION GROWTH
Earth's population: 6 billion (Oct 12, 1999)
Every second, five people are born and two people die,
a net gain of three people.
Every day,
+250,000 = 2 x Champaign-Urbana
This year,
+87,000,000 = Mexico
This decade
+1,000,000,000 = China
THE HUMAN POPULATION
• doubled three times in the last three
centuries
• about 6.1 billion and may reach 9.3 billion
by the year 2050
• improved health and technology have
lowered death rates
• The history of human population growth
Figure 35.8A
• The age structure of a population is the proportion of
individuals in different age-groups
RAPID GROWTH
SLOW GROWTH
ZERO GROWTH/DECREASE
Kenya
United States
Italy
Male
Female
Male
Female
Ages 45+
Ages 45+
Ages 15–44
Ages 15–44
Under
15
Percent of population
Male
Female
Under
15
Percent of population
Percent of population
Also reveals social conditions, status of women
Figure 35.9B
• The ecological footprint represents the amount
of productive land needed to support a nation’s
resource needs
• The ecological capacity of the world may
already be smaller than its ecological footprint
• Ecological footprint in relation to ecological
capacity
Figure 35.8B
Per capita CO2 emissions
(metric tons of carbon)
0
1
2
3
U.S.
China
5
6
5.48
2.65
Japan
2.51
0.29
0
0.5
1
U.S.
Russia
Japan
India
1.5
1.49
China
0.75
Russia
India
4
Total CO2 emissions
(billion metric tons of carbon)
0.91
0.39
0.32
0.28
• What next?
Figure 2.10x