Environmental Studies

1. POPULATION ECOLOGY
GRADE 11 CONTENT
PART 1

3. POPULATION ECOLOGY
Population ecology is the study of
populations in relation to environment,
including environmental influences on
density and distribution, age
structure, and population size.

4. POPULATION ECOLOGY TERMINOLOGY
 A species is a group of organisms that can breed and
produce fertile offspring.
 A population is a group of individuals of the same
species living in the same area at the same time.
 Communities are populations that live together in a
defined area.
 Density is the number of individuals per unit area or
volume.
 Dispersion is the pattern of spacing among individuals
within the boundaries of the population.

5. TERMINOLOGY CONTINUED
 Density is the result of an interplay between processes that
add individuals to a population and those that remove
individuals.
 Immigration is the movement of individuals into an areas
from other areas which increases the population size.
 Emigration is the movement of individuals out of a
population causes a decrease in the population size.
 Demography is the study of the vital statistics of a
population and how they change over time. Death rates
and birth rates are of particular interest to demographers.

6. PATTERNS OF DISPERSION
 Clumped- individuals in discrete groups, also
called clustered.
 Uniform- individuals maintain a minimum
distance from other individuals, also called
evenly-spaced.
 Random- individuals spaced independently of
one another.

7. PATTERNS OF DISPERSION

8. THE TWO MAIN PATTERNS OF
POPULATION GROWTH
 Exponential growth/J-pattern: Only one
reproductive chance is given to members of the
population during their entire lifespan. Once individuals
accomplish mission, they die. Many insects and
annual plants reproduce in this manner.
 Logistic growth/S-pattern: Members experience
many reproductive events throughout their lifetime.
Most vertebrates, and trees have this pattern of
reproduction.

9. EXPONENTIAL GROWTH/J PATTERN

10. EXPONENTIAL GROWTH PATTERN
CONTINUED
 Lag phase: Growth is slow because population
base is small.
 Exponential growth phase: Growth is
accelerating. This means that the rate of growth
itself grows.

11. LOGISTIC GROWTH/S PATTERN

12. LOGISTIC GROWTH PATTERN
CONTINUED
 Lag phase: Growth is slow because the population base is
small, organisms adapt.
 Exponential growth phase: Growth is accelerating,
because many offspring are born at a fast rate.
 Deceleration phase: The rate of population growth slows
down – individuals start to die.
 Stable equilibrium phase: Little growth because births
and deaths are about equal. Area has reached its carrying
capacity.
 Carrying capacity (K) is the maximum population size the
environment can support.

13. EXPONENTIAL GROWTH PATTERN VS
LOGISTSIC GROWTH PATTERN
.
In the logistic population growth
model, the rate of increase decline as
carrying capacity is reached.

14. SURVIVAL PATTERNS/ CURVES
Survivorship curves can be classified into three general
types:
 TYPE I- Species have a fewer number of offspring but spend
more time and energy caring for their young . This causes low
death rates in early and middle life then an increase of death
rates is seen in adults.
 Type II- The species produces many offspring and provides
very little care for them hence a constant probability of dying
at any age. n increased death rate in young and less.
 Type III- Species experience high death rates for the young
and a lower, more constant death rate for the survivors.

15. SURVIVAL PATTERNS/CURVES
CONTINUED

16. REFERENCES
 Newberry, T. (2008). Ecology 1 Population Ecology. Available from
slideshare at https://www.slideshare.net/tnewberry/population-ecology-
514438 (Accessed 15 September 2017).
 Tsotsetsi, T.G. (2014) Population Ecology Grade 11. Available from
slideshare at https://www.slideshare.net/ttsotetsi/population-ecology-
32121442 (Accessed 15 September 2017).
 Smith, M.B. (2009). Chapter 3&5 Ecology and population growth.
Available from slideshare at
https://www.slideshare.net/elmochem/chapter-3-5-lecture-ecology-
population-growth (Accessed 15 September 2017).
 Singh, B.R. (2013). Population ecology for epidemiologists. Available
from slideshare at https://www.slideshare.net/singh_br1762/population-
ecology-for-epidemiologists (Accessed 15 September 2017).