Download Population Dynamics in Ecosystems and Human Impact

Population Dynamics in
Ecosystems
Bio.2.1.4, Bio.2.2.1, Bio.2.2.2
K. Nifong
Population Dynamics
• Populations often change size over
time.
• Some increase in size, others
decrease.
• We will concentrate on population
growth:
• How fast?
• For how long will growth continue?
Population Growth Around the
World since 1 A.D.
• Population Density: # of individuals
per unit area
http://desip.igc.org/mapanim.html
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Population Dynamics
# of Individuals
• Population growth can be linear:
Time
Population of lions.
http://www.fotosearch.com/DGV119/029069/
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Population Dynamics
• Population growth can be
exponential:
# of Individuals
J-Shaped Curve
Population of Seagulls..
Time
http://www.acclaimimages.com/_gallery/_pages/0018-0312-3010-5037.html
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Population Growth
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• Exponential growth: when the number of organisms grows by a constantly
increasing rate.
• Ideal situation with unlimited resources.
• Results in a population
Population Dynamics
• R-selected: organisms that grow out
of control, exponentially
• Exponential growth can occur for
short periods of time, but cannot
continue forever!
http://www.sgnhs.org/mouse.html
• Why?
• What limits exponential growth?
Mice and weeds are examples of
r-selected organisms
http://montana.plant-life.org/page_weeds.htm
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Population Dynamics
Population growth can be logistic:
http://animaltrial.com/animals/Elephantpictures/africanelephantherdpict.html
# of Individuals
S-Shaped Curve
Population of Elephants….
Logistic Growth: a population’s
growth slows or stops following
a period of exponential growth.
Time
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Population Dynamics
• Carrying Capacity: The number of
organisms of one species that a
habitat or environment can hold
http://buten.net/max/My2001/10_monkeys/index_10_monkeys.html
• Once carrying capacity (k) is
reached, the population maintains
at that size.
• These populations of organisms
are called
k-selected.
http://www.wildlife-pictures-online.com/image-files/xfamily.jpg
Most primates and Elephants are
k-selected
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# of Individuals
Population Dynamics
k
http://www.wildlife-pictures-online.com/image-files/xelecalf3a.jpg
Time
For logistic growth, population
sizes always level out at the
carrying capacity (k)
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Characteristics of K and R selected organisms
• K-selected organisms:
•
•
•
•
•
Big
Usually mammals (parental care)
Longer life span
Stable environments
Humans, bears, elephants
• R-selected organisms:
http://www.theglobalroad.com/zoo/polar1/polar0025.shtml
•
•
•
•
•
Small bodied
Often insects
Short Life span
Mature early, lots of offspring
Mosquitoes, bacteria.
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http://classroomclipart.com/cgibin/kids/imageFolio.cgi?action=view&link=Animals/Insec
ts/Ants&image=P7190888AB.jpg&img=&tt=
• Limiting Factors: Biotic or abiotic
factors that restrict or prevent the
existence, numbers, reproduction, or
distribution of organisms.
http://www.yukonman.com/pictures2-8.asp
http://www.fotosearch.com/COR356/110000/
• Ex. A predator such as a lynx is a
limiting factor for a prey such as a hare.
• Ex. A cold snowy winter is a limiting
factor for thousands of species that
would die under those conditions.
• Ex. In brackish water, fish can’t pass
from salt water to fresh water. The
salinity of the water is a limiting factor.
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Population Dynamics
Population Dynamics
• Limiting Factors can be biotic or
abiotic.
• *List examples of each!
http://www.facethewind.com
Abiotic
Biotic
http://www.spottycat.com/marlos/emporium/cougar/bigcat11.jpg
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Population Dynamics
• Density Dependent Factors: Factors
that limit the size of a population and
only exist when populations get too
big
http://gbgm-umc.org/umcor/00/eth6.stm
• Ex. Disease, competition, parasites,
and a limited amount of food.
• These would not have caused so
many problems had the population
remained small.
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Population Dynamics
http://www.naturia.per.sg/buloh/birds/Ardea_cinerea.htm
• Predation: One animal constantly
consuming another, limits its’
population size
• Ex. Owls keeping a mouse population
small, or hunters keeping deer
numbers in check.
• Ex: Lynx and Hare
• Predator can’t eat all prey or food will
be gone for good.
http://www.colostate.edu/Depts/CoopExt/4DMG/Pests/spiders.htm
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Lynx Chases Hare
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Lynx and Hare Graph
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Population Dynamics
• Competition: A density dependent factor.
Individuals competing for limited food
source or other resources.
• Crowding and Stress: Not completely
understood, but causes:
•
•
•
•
•
fighting
Infertility
decreased parental care
decreased immunity to disease
death
• Parasitism and Disease: parasites limit the
growth of a population by causing diseases
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Population Dynamics
Floods
• Density Independent Factors: Limiting
factors that would affect all
populations regardless of size
• Most are abiotic factors.
• Ex. Floods, hurricanes, drought,
habitat destruction.
http://www.danieldesign.com/otherlinks.htm
Volcanic Eruptions
Fire
http://www.arenal.net/
http://www.worldphotos.com/s/worldphotos/weather.html
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