Population Ecology - Weeblybirdmanscience.weebly.com › uploads › 5 › 6 › 5 › 7 ›...
Transcript of Population Ecology - Weeblybirdmanscience.weebly.com › uploads › 5 › 6 › 5 › 7 ›...
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Population
Ecology
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I. Population Dynamics
• Population:
•All the individuals of a species that live together in an area at the same time.
• Demography/Demographics:
•The statistical study of populations
•allows predictions to be made about how a population will change over time.
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II. Three Key Features of
Populations
1a. Size: number of individuals
in an area (aka: how many?)
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Three Key Features of
Populations
Population growth rate can drastically
change population size:
•Birth Rate (aka natality) - Death Rate
(mortality)
•How many individuals are born vs. how
many die in a given year?
•1b. Birth rate (b) − death rate (d) =
growth rate (r)
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2. Density: measurement of population
per unit area or unit volume
Pop. Density = # of individuals ÷ unit of
area
Three Key Features of
Populations
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a. Immigration: movement of individuals into a population
b. Emigration: movement of individuals out of a population
c. Density-dependent factors: Biotic factors in the environment that have an increasing effect as population size increases (disease, competition, parasites)
d. Density-independent factors: Abiotic factors in the environment that affect populations regardless of their density (temperature, weather)
3. How Do You Affect Density?
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Immigration
Emigration
Natality MortalityPopulation+
+
-
-
Factors That Affect Future Population
Growth
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4. Dispersion: how spread out individuals
in a population are
•Clumped
•Uniform
•Random
Three Key Features of
Populations
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• 5a. count all the individuals in a
population, called a direct count
(actual #)
• 5b. Estimate by:
• Random sampling – stationary species
• Mark-recapture method – mobile species
• Remember % error??? Formula???
5. How Are Populations
Measured?
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6a. R Strategists
a. Short life span
b. Small body size
c. Reproduce
quickly
d. Many young
e. Little parental
care
f. Exponential
growth (J-curve)
Ex: cockroaches,
weeds, bacteria
6. Reproductive Strategies
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6. Reproductive Strategies6b. K Strategists
a. Long life span
b. Large body size
c. Reproduce slowly
d. Have few young
e. Provides
parental care
f. Logistic growth
(S-curve)
Ex: humans,
elephants
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6. Reproductive Strategies
Summary
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7. Carrying Capacity
• Carrying Capacity (k):
• The maximum population size that can be
supported by the available resources in
each environment
• KEY POINT HERE… There can only be as
many organisms as the environment’s
resources can support
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• Declining birth rate or increasing death
rate (negative “r”) are caused by several
factors including:
a. Limited resources (food, H2O, space)
b. The buildup of toxic wastes
c. Increased disease
d. Predation
e. Competition
8. Factors that Limit
Population Growth Rate
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“Boom” and “Bust” Cycles
“Boom” characterized
by rapid growth witch
is followed by “busts”
during which the
population falls back to
a minimal level.
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Age Distribution
• Distribution of males and females in
each age group of a population
• Used to predict future population
growth
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Human Population
Growth
• J curve growth
• Grows at a rate of about 80 million yearly
• r =1.3%
• Why doesn’t environmental resistance take effect?
• Altering their environment
• Technological advances
•The cultural revolution
•The agricultural revolution
•The industrial-medical revolution
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• 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 Human Population
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History of the Human Population