APES
POPULATIONS
POPULATION ECOLOGY
• Studies populations and how these populations interact with the
environment
• Used to develop conservation
• Used to predict the long-term probability of a species
* By understanding the way populations grow and what their
needs are, scientists and policy makers can better plan for
sustainability of resources needed by a population
POPULATIONS
• A group of organisms of the same species that inhabits
a specific geographic area at the same time
• Individuals in a population compete for space, light, air,
water, food
• Living in groups (flocks , schools) has advantages:
• 1. increased protection from predators
• 2. increased chances for mating
• 3. division of labor
POPULATION DENSITY
Refers to the number of individual of a population that inhabit a
specific unit of land or water in the area
*(EX) number of squirrels that inhabit a specific forest
BIRTHS and DEATHS
IMMIGRATION= the # of individuals that enter the population
EMIGRATION= the # of individuals that leave the population
DENSITY IS A RESULT OF A DYNAMIC INTERPLAY BETWEEN PROCESSES
THAT ADD AND REMOVE INDIVIDUALS IN A POPULATION
Births and immigration add individuals to a population
Deaths and emigration remove individuals from a population
LIMITING FACTORS
(cause a population to decrease)
DENSITY-DEPENDENT
*predation
*competition for food / space
*disease
*shelter
*build up of toxic materials
DENSITY-INDEPENDENT
(CATASTROPHIC EVENTS)
*FIRE
*STORMS
*EARTHQUAKES
*DROUGHT
*VOLCANIC ERUPTION
POPULATION DISPERSION
*refers to how individual of a population are spaced within a region
*3 ways of dispersion
CARRYING CAPACITY (K)
• Refers to the number of organisms that can be supported in a given area
• It is the maximum population size that can sustainably be supported by the
available resources in the region
• If a population goes over the carrying capacity– death rates become higher
than birth rates
REGULATING FACTORS OF CARRYING
CAPACITY
*food/nutrient availability
*space
*oxygen
*sunlight
*predation
FACTORS THAT AFFECT POPULATION
GROWTH
INCREASE POPULATION GROWTH
DECREASE POPULATION GROWTH
*high birth rate
*generalized niche
*few competitors
*good predatory defense
*able to migrate
*FAVORABLE
ENVIRONMENT
*low birth rate
*specialized niche
*many competitors
*unsuitable predatory defense
*unable to migrate
*UNFAVORABLE
ENVIRONMENT
BIOTIC POTENTIAL
*is the amount that a population would grow if there were unlimited
resources
FACTORS THAT INFLUENCE BIOTIC POTENTIAL
1. age at reproduction
2. frequency of reproduction
3. number of offspring produced
4. life span
EXPONENTIAL GROWTH (J- shape curve)
• Occurs when resources are unlimited/unrestricted (not realistic)
• Forms a J-shaped curve graph
• rN = ΔN/Δt
(r) = rate of growth
(N) = number of individuals
(ΔN)= change in number of individuals
(Δt) = change in time
LOGISTIC GROWTH (S CURVE)
*when a population grows rapidly, reaches carrying capacity and
stabilizes (realistic model)
*the growth rate changes to match the environmental conditions
*growth rate stabilizes when the birth rate equals the death rate
*growth rate may show fluctuations around the carrying capacity
POPULATION CHANGE and GROWTH RATE
POPULATION CHANGE =
(crude birth rate + immigration) minus (crude death rate + emigration)
EX. A population is 20,000 in 1950.
(500 + 600) - (140 + 200) = 760
In 1951, the population grew from 20,000 to 20,760
__________________________________________________________________
RATE OF POPULATION CHANGE FORMULA:
GROWTH RATE (%) = BIRTH RATE - DEATH RATE
---------------------------------10
EX.
22.2 - 6.4
------------------- = 1 .6
10
RULE OF 70
*used to predict long term population growth rates
*used to estimate population doubling
*by dividing 70 by current annual % growth rate of population
*(EX) if the growth rate is 5 %, then population will double in 14 years
70/5% = 14 years
REPRODUCTIVE STRATEGISTS
(2 groups of species based on reproductive strategies)
r – strategists
*reproduce early in life
*mature rapidly/short lived
*tend to be prey
*low in food web
*produce many offspring
*low parental care
*niche generalists
*density-independent regulated
*generally small
*EXAMPLES: insects, algae, bacteria,
rodents, protozoa, weeds
K – strategists____________
*reproduce later in life
*mature slowly/long lived
*both predator and prey
*high on food web
*produce few offspring
*high parental care
*niche specialists
*density-dependent regulated
*generally large
*EXAMPLES: elephants, cacti,
sharks, lions, humans
SURVIVORSHIP CURVES
(show age distributions, reproduction, and life history)
(is measured by how many organisms are able to mature and reproduce
TYPE 1: (LATE LOSS) =reproduction early in life, low
mortality rate, high advance age, death during old age
(EX) humans, sheep, elephants, annual plants
TYPE 2: (CONSTANT LOSS)= all ages uniform death,
predation is primary means of death, reach adult stage
quickly (EX) birds, rodents, perennial plants
TYPE 3: (EARLY LOSS) = have large number of offspring,
death in younger members (EX) trees, sea turtles, fish,
oysters
POPULATION CYCLES
1. BOOM-AND-BUST CYCLE
*common with r –strategist
*rapid increase in population
and then rapid drop off
2. PREDATOR – PREY CYCLE
*rainfall low-> less grass
for rabbit -> less food for coyote ->
Less coyotes
*coyote population does
not change at exactly the same
time as rabbit population
HUMAN POPULATION
• WORLD POPOULATION AS OF March 2014
estimated at 7,152,717,500
BIRTH RATE (CRUDE BIRTH RATE)=
is equal to the # of live births per
1000 members of the population
per year
DEATH RATE (CRUDE DEATH
RATE)= is equal to the # of deaths
per 1000 members of the
population per year
HOW POPULATION CHANGE?
*populations can change because of immigration and emigration
*most significant addition to population is Births
*Total Fertility Rate (TFR) =describes the number of children a woman will bear
in her lifetime
*Replacement Birth Rate (RBR) = describes the number of children a couple must
have in order to replace themselves (must compensate for deaths of children
and non-child bearing females) ( can be 2.1 – 2.5)
*Fertility is influenced by culture, birth control availability, women’s education
REASONS THE WORLD POPULATION HAS
INCREASED: (less deaths)
*INDUSTRIAL REVOLUTION IMPROVED STANDARD OF LIVING
*DEVELOPMENT OF WATER SOURCES
*BETTER SANITATION
*DEPENDABLE FOOD SUPPLIES
*BETTER HEALTH CARE
*TECHNOLOGY
AGE STRUCTURE DIAGRAMS
*graphs that determine birthrate, generation time, death rate,
sex ratios
*they are indicators of future trends in population growth
ZERO POPULATION GROWTH
RESULTS FROM :
HIGH BIRTH & HIGH DEATH RATES
OR
LOW BIRTH & LOW DEATH RATES
DEMOGRAPHIC TRANSITION MODEL
*predicts population trends based on birth rates and death rates
*a country’s population will shift from one growth rate type to another
*4 DEMOGRAPHIC TRANSITION TYPES
1. PRE-INDUSTRIAL- slow growth, (high birth and high death)
difficult living, EX. AFRICA
2. TRANSITIONAL- Fast growth, High birth and less death, better
living conditions, EX. MEXICO
3. INDUSTRIAL- slow growth, (low birth and low death),
developing country, EX. CHINA
4. POST- INDUSTRIAL- population near or at ZERO POPULATION
GROWTH, EX. RUSSIA & UNITED STATES
DEMOGRAPHIC TRANSITION TYPES/PHASES
IMPACTS OF INCREASED POPULATION
GROWTH
1. LAND OVERUSE (for food production)
2. POVERTY
3. HUNGER (insufficient food production and distribution)
4. INCREASE DISEASES
5. POLITICAL INSTABILITY (wars, unemployment, )
6. PESTILENCE (accumulation of waste)
7. INCREASE POLLUTION
8. GLOBAL WARMING (impact of gases and ozone layer)
9. NATURAL RESOURCE DEPLETION
10. INCREASE ENERGY CONSUMPTION
11. ENVIRONMENTAL DEGRADATION
12. ANIMAL AND PLANT EXTINCTION (due to habitat loss)