CHAPTER 5: POPULATIONS
How Populations Grow (5-1)
Limits to Population Growth (5-2)
Human Population Growth (5-3)
5-1: How Populations
Grow
POPULATION
A population is a group of organisms
that belong to the same species and live in a given area.
A. 3 Factors That Influence Population Size
1. Birth Rate
2.
3. Migration a. immigration =
b. emigration =
Death Rate
movement of organisms into an area
movement of organisms out of an area
4. Calculation of Population Growth
Population Growth Rate =
Zero population growth is when:
(Birth Rate+Immigration – Death Rate+Emigration)
Birth Rate+Immigration = Death Rate+Emigration
B. Population Dynamics
= Change in population size over time
Biotic Potential
+ Environmental Resistance
= Carrying Capacity
1. Biotic Potential= The at which a species can
increase if unchecked maximum rate
1. Biotic Potential
Considerations Include:
a.
b. frequency of reproduction during life
c.
d. survival rate of offspring to reproductive age
e.
age at which reproduction begins
# of offspring per reproductive event
length of reproductive ability
1. Biotic Potential
(logarithmic, J-shaped curve).
Many species, particularly herbivores, generally have
Creates a growth curve that is exponential
higher birth rates
2. Environmental Resistance= The sum of all the forces that cause death
or lowers reproduction
This includes: ( but is not limited to the following)StarvationClimatic factorsPredationDisease/parasitesNumerous human created elements
3. Carrying Capacity
= The number of organisms that can be supported in a given area at a given time
Carrying Capacity – The Kaibab If humans do not harvest part of the herd by
using licensed hunters, natural forces of disease and starvation will bring about the reduction with starvation and disease.
QUESTION:
Are human populations ultimately controlled by the same equation?
C. Change in Population Size Over Time Population increases for living things are
generally exponential
1. Exponential Growth (J-Shaped)a.
, followed by increasingly faster
rates of growth
b. , the exponential phase of growth may drop off sharply due to environmental constraints
c. Note: Happens to a population
Type of exponential growth that shows slow growth at first
Under natural conditions
only briefly
when encountering a new habitat.
J-Shaped Growth Curve
2. Logistic Growth (S-Shaped)a.
, but eventually the rate of growth slows and stabilizes at a certain level
A growth model that starts off like the J-shaped form
2. Logistic Growth (S-Shaped)
2. Logistic Growth (S-Shaped)b. Environmental resistance ultimately limits
growth in the S-shaped growth model.
c. Real-world populations vary in complex ways, and may show either a J- or an S-shaped growth form at different times in their history.
What factors limit population growth?
Environment
5-2: Limits to Population Growth
Objectives•Identify factors that limit population growth.•Differentiate between density-dependent and density-independent factors.
Density DEPENDENT Controls
Competition
Predation
Parasitism
Disease
POPULATION DENSITY
Remove higher % of individuals as population size increases
1. Density Dependent ControlsAs population size increases, competition for
resources also increases.
Density Dependent Controls:a. INTRASPECIFIC COMPETITION Intraspecific competition =
•Includes mate competition
Chuckwallas
Among same
species
Humans?
Density Dependent Controls:b. INTERSPECIFIC COMPETITION Interspecific Competition –
Does not include mate competition
Big Horn Sheep and Burros
Between species
Density Dependent Controls:c. PREDATION one organism feeding on another
C. PREDATION1. Types
a) Equilibrium –
b)
prey can avoid predator
Boom-Bust cycle – lynx and hare
c. PREDATION2. Plant Defenses
a)
b) Chemical –
Morphological (body forms) – thorns, spines
poisons
c. PREDATION3. Animal Defenses
a) Morphological
1. size –
2. coloration –
3.
hide, frightencamouflage, warning, mimicry
other - sting, bite, run
c. PREDATION3. Animal Defenses
b) Chemical – poison
c. PREDATION3. Animal Defenses
c) Vigilance (intelligence) – watch for
predators, learned behavior
Meerkats
c. PREDATION3. Animal Defenses
d) Parasitism -
Freshwater Leech
Predators feed on prey but
do not kill it immediately
c. PREDATION3. Animal Defenses
e) Crowding and Stress
c. PREDATION3. Animal Defenses
f)
Zebra and Wildebeest Migration
Migration
c. PREDATION3. Animal Defensesg) Broken wing display
2. Density Independent Controlsa) Remove a % of the population
b)
certainregardless of number of individuals in the population
Are typically random or extreme abiotic events (weather, natural disaster)
2. Density Independent Controls
Floods are an example of a density-independent factor. This is the aftermath of Katrina in New Orleans.
2. Density Independent Controls
c. After extreme abiotic events, new habitats are
opened for organisms to create new logistic
growth
POPULATION GROWTH
Density DependentFactors
Density IndependentFactors
Limited by
So let’s review!
The following statements will involve a situation that will affect the growth of a population. Classify each of the statements as:
DD Density Dependent
DI Density Independent
1. Fish A and Fish B attempt to occupy the same area. The more aggressive Fish A survives; Fish B does not.
DDCompetition between species only occurs at
certain densities
2. A severe flood brings a lot of sediment and silt into the lake. Turbidity (cloudiness) increases greatly.
DINatural disasters affect all populations
regardless of density
3. A drought decreases the water level in the lake. The carrying capacity of the lake decreases.
DINatural disasters affect all populations
regardless of density
4. Due to the introduction of Fish Z, the lake becomes crowded and some fish species do not survive.
DDCrowding only occurs at certain densities
5. Since sea otters prey on sea urchins, an increase in sea urchins causes an increase in the sea otter population.
DDPredation only occurs at certain densities.
6. Many fish die due to an increase in water temperature.
DITemperature affects all population densities.
7. Due to over-fishing, the number of Fish T in the lake decreases.
DIHuman activities affect all population densities.
8. A population is growing quickly when parasites cause disease to spread quickly.
DDParasitism only affects certain population
densities.
THE END
5-3: Human Population Growth
5-3 Human Population GrowthA. Human Populations
1. Growth rates were low for much of human history, but rates started
and became in the 1950’s, exhibiting a ever since.
increasing in the 1700’s exponential
J-shaped curve
Time Culture Strategy B D Graph
Pre-Industrial
Transitional
Industrial
Post Industrial
Agriculture
Moving into
cities
Living in cities
Technology
Large Family
Large Family
Smaller Families
and Labor Laws
College degree
to compete
Human Population Growth:Past History and Current ConditionsYEAR POPULATION
1804
1974
2005
End of 21st Century
1 billion
4 billion
6.2 billion
Estimated 8.5 – 11 billion
Human Population Growth:Past History and Current Conditions2. World population growth is fastest in
3. is a key in developing countries:
a) If educated to grade = 8 babies/female
b) Women with higher education/careers = delay childbirth and typically
developing countries
Education
2nd or 3rd
have fewer
children
Human Population Growth:Past History and Current Conditions
COUNTRY ANNUAL GROWTH RATE
Developed
Less-developed:
China, India, parts of Africa, and Latin America
0.4%
1.8 - 3%
B. Effects of Large Human Population 1. Food and agriculture
a) Only three plants provide of our food supply –
b) Crops are - not resistant to disease or weather, lose 70 to 80% of a crop
50%wheat, rice and corngenetically identical
Effects of a Large Human Population
2. Usable land
a)
b) is the fastest growing area of land being destroyed
c) removes circulating water and deserts are getting bigger
high percentage of potentially
usable land is being cultivated
agricultural land
removal of tropical forest
Deforestation in
the Tropics
Effects of a Large Human Population3. Other human impacts
a) Global warming – the increase in
during the last 150 years concerns ecologists because of its potential effect on global temperature
atmospheric CO2 concentrations
through the greenhouse effect.
Effects of a Large Human Populationb) Ozone depletion -
1979
2003
increased UV radiation hits
the earth
Effects of a Large Human Populationc) Acid rain/Water pollution
Statue of Queen Victoria - England
The Parthenon in Greece shows discoloration and
chemical weathering effects from air pollution and acid
rain
Effects of a Large Human Populationd) Habitat destruction/soil destruction
Effects of a Large Human Populatione) Biodiversity loss
Fragmentation of
habitat causes
species to go
extinct.
Effects of a Large Human Populationf) Waste build-up Example: Open Pit Mining
Effects of a Large Human Populationg) Non-native/exotic
species – would not be present without the direct or indirect help of humans
Walking catfish
Starlings