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Population Ecology

This document discusses several methods for estimating population sizes of plants and animals, including quadrat sampling and capture-mark-recapture. Quadrat sampling involves placing frames on the ground and counting species within. Capture-mark-recapture involves capturing animals, marking them, releasing them, recapturing a sample and using a formula to estimate total population based on marked/unmarked ratios. Population ecology studies how population sizes change over time due to factors like birth/death rates, immigration/emigration, biotic and abiotic influences in the environment.

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Lyana Ahmad
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371 views15 pages

Population Ecology

This document discusses several methods for estimating population sizes of plants and animals, including quadrat sampling and capture-mark-recapture. Quadrat sampling involves placing frames on the ground and counting species within. Capture-mark-recapture involves capturing animals, marking them, releasing them, recapturing a sample and using a formula to estimate total population based on marked/unmarked ratios. Population ecology studies how population sizes change over time due to factors like birth/death rates, immigration/emigration, biotic and abiotic influences in the environment.

Uploaded by

Lyana Ahmad
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PPT, PDF, TXT or read online on Scribd
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Population Ecology

A population is defined as a group of organisms


of the same species occupying a particular
area or habitat.
 Factors including abiotic factors, biotic
factors, birth rate, death rate, immigration
and emigration of the members of a
population determine the size of a population
and how it changes over time.
 The study of the measurement of population
size and factors affecting the population size
is known as population ecology.
Quadrat Sampling Technique
 Usedto estimate population size, density and distribution of
plants or population of immobile animals.
A quadrant consists of a square or rectangular frame made
of metal or wood. Strings are used to subdivide the
quadrant into smaller squares. The frame is pegged to the
ground with a few pieces of string.
 The size of the quadrat depends on the size
and density of the plants sampled.
 In this technique, a number of quadrats are
placed randomly I the area being studied.
 The species found within the quadrat are
counted and recorded.
The distribution of the species
can be determined by:
Frequency of the species
 Frequency is the number of times a particular
species is found when a quadrat is thrown at a
certain number of times.
Density of the species
 Density is the mean number of individuals of the
species per unit area.
Percentage coverage
 Percentage coverage is the percentage of how
much of an area is covered by a species.
Capture, mark, release and recapture
technique
To estimate the population size of
animals which move freely such as
snails and woodlice.
Steps in capture, mark, release and recapture technique
A specific animal sample is captured and marked with a ring, a tag or with
waterproof colored ink, cellulose paint or nail varnish

The marked animals are then released into a general population.

After a suitable period of time, a second animal sample is captured and the number
of marked animals in the second sample is counted and recorded.

Based on the data obtained, the population size of the animal in the area can be
estimated by a formula
Formula:
The assumptions made in this technique:
 The size of the population does not change and is
stable throughout the period of investigation.
 The marked animals are not harmed or predated
upon.
 The animals are captured ay random.
 The marked animals are able to mix randomly
with the other animals before the second
capture.
 Each marked animals has the same probability of
being recaptured as an unmarked animal.
To increase the accuracy of this technique:

 More animals must be captured.


 The animals must be captured at random.
 The markings must be permanent.
 Enoughtime must be allowed for the
marked and unmarked animals to mix.
Abiotic factors which influence the
population distribution of an organisms

 Temperature
 Light intensity
 Humidity
 pH
 Aspect
The End.

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