There are three characteristics in which population researchers take into consideration
when study different populations.
1. Crude Density: population density measured in terms of number of organisms of
the same species within the total area of the entire habitat.(D)
2. Ecological Density: population density measured in terms of the number of
individuals of the same species per unit area or volume actually used by the
individuals.(D)
3. Population size: the number of individuals of a specific species occupying a given
area/ volume at a given time.
Three Patterns of Dispersion that Populations Exhibit
1. Clumped Dispersion: ( figure 1)
2. Uniform Dispersion: (figure 2)
3. Random Dispersion: ( figure 3)
Mark- Recapture Method
This technique is used to estimate the size of and density of mobile wildlife
populations.
Three Assumptions made for Mark-Recapture Method
1. Every organism in a population has an equal opportunity of being captured.
2. The proportion of marked to unmarked animals remains constant during the time
period between the initial marking and the subsequent recapture,
3. The population size does not change during the sampling study.
Equation for the Mark-Recapture Problems
Total # marked (M)
Total population (N)
-
# of recaptures (m)
size of second sample (n)
Finding Population Density
D= N/S
D= density
N= Number of Individuals
S= space
Example
There are thirty five mice on 5 acres of land, what is the density of mice
per acre of land?
Solution
D= N/S
= 35 mice/ 5 acres
= 7 mice/acre
Therefore there are 7 mice per acre of land.
Factors that Affect Population Growth

Population dynamics are determined by natality ( number of births), mortality( the
number of deaths), immigration9 the number of individuals moving into an
ecosystem), emigration ( number of individuals moving out of a existing
population)
Survivorship Patterns
These graphs illustrate the length of time organisms in a given species will live.
The first type shown is the one showing high survivorship until fairly late in life and then
showing of high mortality.
The second type shows a fairly constant death rate.
The third type shows a low survivorship early in life.
K Strategist
- Shorter lifespan
- Density dependant factors control their size
independent factors control their size
- Rapid doubling time
time
-Produce large amounts of offspring
amount of offspring
- Take little care of their offspring
care of their offspring
vs.
R- Strategists
- longer lifespan
- density
- slow doubling
- produce small
- take good
Calculating Changes in Population Size
As previously mentioned population dynamics are affected by many factors, so in order
to take these factors into consideration and equation has been established.
Population Change = [(births + immigration)] – [( deaths + emigration)] x100%
Initial population size (n)
 If the numbers of individuals that are born and migrated are higher than the
number of individuals what have died ad emigrated, then the population will have
a positive growth (increasing in size).
 If the number of deaths and emigrations exceeds the number born and migrated
then the population will have a negative growth (decreasing in size).
 If the number of deaths/emigrations and the number born/immigration is equal
then there is a zero growth.
Factors that Effect Growth

Closed Population: population that is only influenced by natnlity and mortality in
determination of decrease or increase in the population. Ex. Land- based
populations that exist in secluded areas.

Open Population: population that is influenced by natality, mortality, emigration
and immigration. Ex. Wild populations.
 Biotic Potential: the maximum rate a population can increase under ideal
conditions.
Different Types of Growth
Exponential Growth

Pattern of population growth where organisms reproduce continuously at a
constant rate.
N= No[e(rt)]
E= constant ( 2…)
N= the final population
No= initial population
R= rate of growth
T= time for growth
Example
There are 2000 people in a population at the year of 2002. If the rate is
constantly increasing at 3% each year, how many people will there be in 10 years?
Solution
No= 2000
T= 10 years
R= .03
N= ?
N= No[e(rt)]
= 2000[ e( 0.03)(10)]
=
Geometric Growth
Pi= N( t+1)/ N(t)
Pi= 3.14..
N= population in the year (t+1)
N (t) = population in given time
T= time
Logistic Growth
dN/dt= rmaxN[(K - N) / K]
dN/dt: the change in population in relation to time
rmaz: the maximum intrinsic growth rate
N: population size
K: carrying capacity
Density Dependant Factors
Density Dependant Factors: factors that influence population regulation, having a greater
impact as population density increase or decrease.

Intraspecific Competition: an ecological interaction in which individuals of the
same species or population compete for resources in their habitat.

Predation: an ecological interaction in which predator( a member of one species)
catches kills and consumes prey ( usually a member of another species).

Allee Effect: occurs when population cannot survive or fails to reproduce enough
to offset mortality once the population density is too low; such populations
usually do not survive.
Density Independent Factors
Density independent Factors: factors that influence population regulation of population
density.
 Limiting Factor: any essential resource that is in short supply or unavailable.

Human introversion

Temperature
Ecological Niches
- Ecological niches are needed to in order to survive in a given ecosystem.
Ecological Niche: an organism’s biological characteristics, including use of and
interaction with abiotic and biotic resources in its environment.
Fundamental Niche: the biological characteristics of the organism and the set of resources
individuals in the population are theoretically capable of using under ideal conditions.
Realized Niche: the biological characteristics of the organism and the resources
individuals in a population actually use under the prevailing environmental conditions.
Symbiosis: various interactions in which two species maintain a close, usually physical,
association; in clue parasitism, mutualism and compensation.
Survival Tactics
Competition
In order for a species to survive, they must receive resources. Since these resources are in
a limited supply, they must compete for their portion.
Interspecific Competition
Competition between individuals of different species when an essential resource is in
limited supply.
Interference competition: competition between individuals that involves violence.
Exploitive Competition: competition between individuals that involves the use of
resources.
Intraspecific Competition
Competition between individuals of different species.
Predation
Predation is a form of population size regulation; it prevents the prey and predator
population from exceeding their limits.
Symbiosis
As mentioned above symbiosis takes place when individuals of two different species live
in close proximity.
There are three types of symbiosis.
1. Commensalisms: one species is not affected by the association, while the other
specie member gains.
2. Mutualism: Both members of each species gains from the relation.
3. Parasitism: One species gains while another looses benefits. There are two types
of Parasitism associations; a- Endoparaisites: Parasites that live within the host’s
body. B- Ectoparaisites: Parasites that live on the host’s body.
History of the Human Population
1,000,000 years ago ancestors began to walk up straight, had large brains and used
tools such as fire.
100,000 years ago ancestors lived in successful hunter-gatherers and rapidly spreading
across globe.
- Able to learn and communicate.
12 00years ago humans reached, and inhabited the worlds greatest landmasses with the
exception of Antarctica.
Human demographics is the study of the human growth rate, age structure and other
characteristics of human populations.
Age structure diagrams are used to predict the population dynamics in reference to age.
Through these diagrams we are able to study the growth rate of populations.
The Demographic Transition Model
The demographic transition model illustrates the relationship between the economic
developments of a given country in relation to the changes in population patterns.
www.globalchange.umich.edu/.../ human_pop.html
Since the human population is increasing in an exponential growth rate, the amount of
resources available is scarce and limited. The problem with the scarcity of food in certain
parts of the world and influx in food in other parts lies in part in the distribution of
resources between developed and developing countries. Another reason for the
inadequate distribution of food to all parts of the world is due to poor conditions for
harvesting food and poor soil conditions.
Food Sources
The food that humans depend on as their resources are three;
1. Grain production
2. Livestock
3. Ocean Fisheries
There are abundant amounts of grain production and livestock but the ocean fisheries are
in limited supply according to the Worldwatch Institute. The ocean fisheries are suffering
from a combination of ocean pollution, damage to aquatic habitats and over fishing.
The agriculture industry is also suffering; in this case from soil degradation, which is the
removal of soil nutrients and loss of topsoil rich in organic matter, caused by erosion
from the movement of water and wind.
Another reason why there is inefficient soil can be attributed to excessive wetness that
can lead to waterlogged soil, which reduces crop productivity by limiting soil oxygen
supplies needed by plant roots.
More Efficient Energy Distribution
Energy pyramids are used to visualize the transfer of food energy from one tropic level to
another through a food chain.
Approximately only 10% of the energy is transferred to an organism in the next trophic
level. Therefore the food chain with the greater number of organisms would have the
higher loss of unusable energy as if flows through the food chain. From the highest
trophic level to the lowest, the animal at the bottom has the least amount of energy.
In order to the human population to have a future to look forward to, the steps taken
today are essential. Humans are the only species on the Earth which are able to study the
Earth and its physical, chemical and biological nature. They are also the species which
spread the majority of the destructive effects on the Earth.
The following are few examples of potential ecological effects caused by Human Activity.
1. Excessive use of fertilizers
2. Deforestation
3. loss of biodiversity
4. ozone depletion
5. pesticides
6. widespread pollution