Ecology Ppt Ch. 5

1. Chapter 5 - Populations
By: Alan Kim, Thomas Huh, Gianna Mor, and Audrey Raulli

2. 3-1: How Populations Grow
Characteristics of Populations:
Population Growth:
Population density is
the number of
individuals per unit area
● Geographic distribution, density, and growth rate
are three important characteristics of a
population.
● Population density can vary tremendously
depending on the species and its ecosystem
● The number of births, the number of deaths, and the number of
individuals that enter or leave the population can affect
population size.
● A population grows if its birthrate is greater than its death rate. If
the death rate is greater than the birth rate, the population
shrinks.
Immigration is the
movement of
individuals into an area
occupied by an existing
population
Emigration is the
movement of
individuals out
of an area
Audrey Raulli

3. 3-1: How Populations Grow
Exponential Growth:
Logistic Growth:
● Exponential growth occurs when the individuals in a population
reproduce at a constant rate.
● A population will grow exponentially under ideal conditions and
unlimited resources.
● In an exponential growing population, the number of individuals
increases slowly. However, over time the population become larger.
● Logistic growth is a growth pattern in which a population’s
growth rate slows or stops following a period of exponential
growth.
● The growth of a population slows or stops as resources become
less available.
Carrying capacity: the largest
number of individuals of a
population that a given
environment can support
Audrey Raulli

4. 5-2: Limits to grow
Limiting factors
A limiting factor is a factor that
causes population growth to
decrease.
There are two kinds of limiting
factors density-dependent
factors and density
independent factors.
Thomas Huh and Alan Kim

5. 5-2: Limits to grow
Density dependent factors
These density dependent factors, are factors that
depend on the size of the population, include
competition,predation, parasitism and, disease.
Competition- This is when populations become more
crowded, organisms compete with one another for
food, water space, sunlight, and other important
necessities.
Predation:populations in nature are often controlled by
predation, this is one of the best ways to control the
population
Parasitism and Disease:Parasitism and Disease both
depend on the size of the population in order to
spread around. These organisms are similar toThomas Huh and Alan Kim

6. 5-2: Limits to grow
Density independent factors
These factors affect all populations in a
similar way, regardless of the size of
the population.
Unusual weather, natural disasters,
seasonal cycles, and certain human
activities-such as damming rivers and
clear cutting forests- are all examples
of density independent limiting factors
Thomas Huh and Alan Kim

7. 5-3 Human Population Growth
Historical Overview:
Like the populations of many other living organisms,
the size of the human population tends to increase
with time.
The size of the human population has increased over
time. After a long, start, the worldwide population
expanded following improvements in medicine,
sanitation, agriculture, energy use, and technology.
Patterns of Population Growth:
Birth rates, death rates, and the age structure of a
population help predict why some countries have
high growth rates while other countries grow more
slowly.Gianna Mor

8. 5-3 Words to know
Demography- Scientific study of human
populations.
Demographic Transition- Change in a
population from high birth and death rates to
low birth and death rates.
Age-Structure Diagrams- Graph of the numbers
of males and females within different age
groups of a population.
Gianna Mor