Population ecology is the study of how population sizes change over time and space due to interactions with the environment. A population is a group of the same species living in the same area that can interbreed. Population ranges and the spacing patterns of individuals within those ranges can change due to environmental factors. A metapopulation consists of distinct populations that interact by exchanging individuals, allowing species to persist even when suitable habitat is fragmented.

2. Population ecology is a sub-field of ecology that
deals with the dynamics of species populations and how
these populations interact with the environment. It is the
study of how the population sizes of species living together in
groups change over time and space.
Population is a summation of all the
organisms of the same group or species, who
live in the same geographical area, and have the
capability of interbreeding.

3. Three characteristics of population
ecology are:
1. Population range, the area throughout
which a population occurs
2. The pattern of spacing of individuals within
that range
3. How the population changes in size
through time.

4. A population’s geographic distribution is termed
its range
Range or distribution of a species is the
geographical area within which that species
can be found.

5. A population’s geographic distribution is termed
its range
Organisms must be adapted for the environment in which
they occur.
Each population has its own requirements – temperature,
humidity, certain types of food, and a host of other factors
– that determine where it can live and reproduce and
where it can’t.

6. Ranges undergo expansion and contraction
Population ranges are not static but change through time.
Factors are, the environment changes like as climates
warmed, species experienced in the elevation at which
they could live.
Population can expand their ranges when they are able
to circumvent inhospitable habitat to colonize suitable,
previously unoccupied areas.

7. 25°
221
_
26°
131
_
27°
151
_
29°
90
_
29°
189
_
28°
254
_
28°
279
_
27°
422
_
27°
403
_
27°
412
_
26°
354
_
25°
322
_
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Temperatures °C (degrees Celsius) in Manila
Rainfall (mm) in Manil
(Average values for each month)

8. Ranges undergo expansion and contraction
The human effect
Humans have served as an agent of
dispersal for many species.

9. Ranges undergo expansion and contraction
Dispersal Mechanism Seeds have
evolved a
number of
different means
of facilitating
dispersal from
their maternal
plant. Some
seeds can be
transported
great distances
by the wind,
whereas seeds
enclosed in
adherent or
fleshy fruits can
be transported
by animals.

10. Individuals in populations exhibit different spacing
patterns
Spacing patterns are the distribution of
a certain specie in a given area or an
environment

11. Individuals in populations exhibit different spacing
patterns
Random Spacing
Random spacing of
individuals within population
occurs when they do not
interact strongly with one
another and when they are
not affected by nonuniform
aspects of their
environment. also known as unpredictable
spacing

12. Individuals in populations exhibit different spacing
patterns
Uniform Spacing
Uniform spacing within a
population may often, but
not always, result from
competition for resources.
also known as even distribution,
or evenly spaced

13. Individuals in populations exhibit different spacing
patterns
Clumped Spacing
Individuals clumped into
groups or clusters in
response to uneven
distribution of resources in
their immediate
environments.

14. A metapopulation comprises distinct populations
that may exchange members
Metapopulation is when species often exist
as a network of distinct populations that
interact with one another by exchanging
individuals, and usually occur in areas in which
suitable habitat is patchily distributed and is
separated by intervening stretches of unsuitable
habitat.

15. The term metapopulation was coined
by Richard Levins in 1970 to describe a
model of population dynamics of insect
pests in agricultural fields, but the idea has
been most broadly applied to species in
naturally or artificially fragmented
habitats. In Levins' own words, it consists
of "a population of populations".
A metapopulation comprises distinct populations
that may exchange members

16. A metapopulation comprises distinct populations
that may exchange members
Dispersal and habitat occupancy
The degree to which populations within a
metapopulation interact depends on the amount
of dispersal; this interaction is often not
symmetrical: Populations increasing in size
tend to send out many dispersers,
whereas populations at low levels tend to
receive more immigrants than they send
off. In addition, relatively isolated populations
tends to receive relatively few arrivals.

17. A metapopulation comprises distinct populations
that may exchange members
Source-sink metapopulations
The populations in the better areas, (the
sources) continually send out dispersers
that bolster the populations in the poorer
habitats (the sinks). In he absence od such
continual replenishment, the sink
populations would have a negative growth
rate and would eventually become extinct.

18. A metapopulation comprises distinct populations
that may exchange members
Metapopulation has two important
implications for the range of species, it
prevents long term extinction and in
source-sink metapopulations, the species
occupies a larger area than it otherwise
might, including marginal areas that could
not support a population without a
continual influx of immigrants.