Transcript population studies - GLENEAGLESBIOLOGY

POPULATION STUDIES
Growth of populations
FACTORS INCREASING
POPULATION
• BIRTH
• IMMIGRATION
FACTORS DECREASING
POPULATION
• DEATH
• EMIGRATION
CALCULATING GROWTH RATE
OF A POPULATION
• Growth rate =
(birth rate + immigration rate) – (death rate + emigration rate)
For example
When the growth rate is >0 the population is increasing
When the growth rate is <0 the population is decreasing
Quantifying risk
Which population is at a more significant risk of displaying a significant
decline in population numbers? Why?
Distribution
Measuring Distribution
• A line transect is the best method to use
when measuring changes along a land
surface. Gradual changes in environment
are referred to as environmental gradients
Measuring Abundance
•
There are 3 methods of measuring
abundance
1. Direct observation
2. Quadrat
3. Capture – mark - recapture
Direct observation
• Time consuming
• Involves monitoring a particular area either
by being present on capturing an entire
area by photograph and counting the
individuals present
Quadrat
•
•
Used to measure density of organisms that do not move very much (e.g. plants,
some insects, etc) a quadrat is an effective method used to make predictions on
population numbers.
Quadrat’s involve the marking out of a square area for observation
(usually 1m X 1m)
The following is observed
- The number of individuals of each species is counted or the relative number of each
species is estimated using a scale from abundant (3) to absent (0)
- The percentage of cover is estimated
- The totals of the quadrat are averaged
- The use of a simple mathematic calculation can give the total number or % cover
for each species
AVERAGE DENSITY OF MEMBER SPECIES =
TOTAL NUMBER OF INDIVIDUALS COUNTED ÷ AREA OF EACH QUADRAT x NUMBER OF
QUADRATS
This will give you an average of the number of individuals found per square meter
Capture – mark - recapture
• Commonly used to measure abundance of
mobile species.
• Step 1: Capture: Animals are caught randomly
Step 2: Mark: Each captured animal is marked
then returned to its habitat
Step 3: Recapture: Later a random sample is
taken and the number of marked animals is
compared to the number or unmarked animals
captured. From this information a total
population can be estimates
MARK CAPTURE REMARK
Carrying Capacity
The Carrying capacity of an ecosystem
refers to the levels of life sustaining
resources an environment contains.
It has been estimated that 100km2 of moist tall eucalypt
forest is the minimum area possible to support 10 000
sugar gliders as a viable population.
POPULATION REGULATION
POPULATION REGULATION
OVERVIEW OF POPULATION
RESTORING / CONTROLLING
POPULATIONS
• Student task
Pg 331, 331 of Nelson Biology units 1&2
Write a summary of current methods used
to control and restore population numbers