This document defines key concepts in population ecology including species, populations, communities, density, dispersion, demography, immigration, emigration, and carrying capacity. It describes patterns of dispersion as clumped, uniform, or random and the two main patterns of population growth as exponential/J-shaped or logistic/S-shaped. Exponential growth is characterized by a lag phase, exponential growth phase, and decline, while logistic growth includes lag, exponential, deceleration, and equilibrium phases limited by carrying capacity. Survivorship curves are classified as Type I, II, or III based on mortality rates at different ages.

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).