Download Population Ecology - HRSBSTAFF Home Page

Population Ecology
Biology 11
Ecology
• The study of the relationships
the living organisms have with
each other and their
environment.
• Dependant on interactions
between organisms, as well as
between individuals and their
environment.
Symbiotic relationships
• Symbiosis (meaning “living together”) is a direct
interaction between two species where at least
one of the two species benefits from the
association.
• The host is the larger of the two species and the
more independent in the symbiotic relationship.
Types of symbiotic relationships
• Parasitism is a type of symbiotic relationship in
which one organism (the parasite) benefits at the
expense of the other organism (the host) (+/relationship).
The tick receives the blood it needs to live, but the dog is
damaged by the ticks transmitting disease in its blood.
Types of symbiotic relationships
• Mutualism is a type of symbiotic relationship in
which both organisms benefit and neither are
harmed (+/+ relationship)
Ex: Bees & flowers
Types of symbiotic relationships
• Commensalism is a type of symbiotic
relationship in which one organism benefits and
the other organism is unaffected (+/0
relationship).
Ex: Clownfish and sea anemone
A habitat is a place or region having a
particular combination of biotic and abiotic
characteristics. Organisms adapt to the
habitats within which they usually live.
• Ex: The taiga (Boreal forest) biome
covers a large part of central and
northern Canada, Europe and Asia. From
the North to the South and from the East
to the West, the taiga varies greatly in
density and type of tree. Also, each
biome can contain an assortment of
different habitats. Each habitat contains
its own combination of organisms and
abiotic conditions.
The study of ecology
happens at many levels,
from individual organisms
to populations, from
communities to
ecosystems.
• A population is a group of
individuals of the same
species (organisms that
resemble one another in
appearance, behaviour,
chemistry and genetic
makeup) who occupy the
same geographical region.
Demography: the study of populations.
• Regarding the size, density age structure and
growth of populations.
• The density of a population corresponds with
the number of individuals per unit of volume or
surface area.
• Dispersion indicates how individuals of a
population are spread within the geographical
limits (uniform or in compact masses).
Population dispersion
• The general pattern in which individuals are
distributed through a specific area.
Demographic growth
•
Births and immigration increase a population. On the
contrary, deaths and emigration reduce a population.
The size of a population is affected by the following 4
factors:
• Birth rate: The number of new individuals in a
population due to reproduction.
• Mortality rate: The number of deaths within a
population.
• Immigration: The number of individuals arriving in a
new region.
• Emigration: The number of individuals leaving the
population.
The growth rate is the number of births or
immigration minus the number of deaths or
emigration in a given time period.
• Changes in the size of the population:
Variation
in the size
of a population =
in a given
period of time
The number
of births
within
this interval
of time
The number
of deaths
within
this interval
of time
IF:
• Birth rate + immigration > mortality rate + emigration,
the population is increasing.
• Birth rate + immigration < mortality rate + emigration,
the population is decreasing.
• Birth rate + immigration = mortality rate + emigration,
the population is unchanging.
Population growth
• Population growth can be
represented by the following
model:
•
•
•
A: Exponential growth phase
(logarithmic): The phase in which
the number of individuals increases
rapidly (exponentially).
B: Transitional growth phase: The
phase in which the growth rate
slows considerably – the population
continues to increase, but at a much
slower rate.
C: Stationary phase (Plateau
phase): The phase in which the
number of individuals has stabilized
and there is not more growth
(carrying capacity).
Causes of the exponential phase:
• Abundant resources
• Little competition between habitants
• Favourable abiotic factors (temperature, oxygen levels, etc.)
• Little predation or illness
Causes of the transitional phase:
• There is an increase in competition for resources
• There is an increase in predation
• Illness starts to spread due to demographic growth
Causes of the stationary phase:
• Less space
• Limited food resources (consequently, there is a decrease in birth rate)
• There are more predators
• Easier for illness to spread
Population pyramids
• A graph that shows the distribution of various age groups in a
population (typically that of a country or region of the world),
which forms the shape of a pyramid when the population is
growing.
• Used in Ecology to determine the overall age distribution of a
population; an indication of the reproductive capabilities and
likelihood of the continuation of a species.
Carrying capacity
• The maximum
population of a species
that a given
environment can
support.
•
http://www.rareconservation.org/blog/index.php?paged=2
Seychelles Paradise Flycatcher
need approx an acre of mixed
forest per couple. They live on a
small island in North-East
Madagascar.
4 factors that determine carrying capacity
1) Energy and matter
• Limited by the quantity of
light energy.
• Limited by the quantity of
water, carbon and other
materials.
http://www.condorjourneysadventures.com/costarica_nature.asp
http://weathersavvy.com/Q-Climate_DesertsHot.html
4 factors that determine carrying capacity
2) Food chains
• Limited by the quantity of
available food (lowest
tropic level)
• Limited by predators
(highest tropic level)
http://www.intarttiles.com/robertekennedy.htm
4 factors that determine carrying capacity
3) Competition
• Competition for food, water,
sexual partners and space.
• Intraspecific Competition:
between individuals of the
same species.
• Interspecific Competition:
between different species.
http://www.maxi-fond-ecran.com/fond-ecran-photo-paon/paon/telecharger-fondecran-photo-paon-p18507.html
http://www.tnstate.edu/ganter/B412%20Lab2%20PlantComp.html
http://www.allposters.com/-st/Elephant-Posters_c646_p3_.htm
4 factors that determine carrying capacity
4) Population density
• The number of individuals
who can live in a region
at the same time.
http://reliableanswers.com/images/wallpaper/penguin_party.jpg
http://www.naturetrek.co.uk/wildlife-holidays/wildlife-holidays.asp?ID=3
Density dependent factors
• When the density surpasses biotic
capacity, we call it overpopulation.
• Overpopulation can:
• Increase stress and the
propagation of illness and
parasites.
• Increase aggression and
negligence of babies.
• When this happens, the population
will decrease.
• Other density-dependent factors
include: disease, reproductive rates,
predator/prey relationships,
competition, availability of mates, etc.
http://www.envirowarrior.com/animalabusers-the-worst-polluters/
Density independent factors
Limits the population
regardless of its size.
-Forest fire
-Earthquake
-Volcanic eruption
-Tornado
http://tiee.ecoed.net/vol/v3/issues/frontier_sets/yellowstone/sci_teaching.html