populations and communities
DESCRIPTION
Populations and Communities. = Population. A group of individuals of the same species, living in a shared space at a specific point in time. Factors affecting population size. births. deaths. Population. Emigration. Immigration. How big is this population?. 11. 6. 6. - PowerPoint PPT PresentationTRANSCRIPT
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Populations and Communities
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• A group of individuals of the same species, living in a shared space at a specific point in time
= Population
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Factors affecting population size
births deaths
Population
Immigration Emigration
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• How big is this population?
6
11
6
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Counting populations I
- Counting individuals
- Counting by sampling:
Population size =
Average number of individuals per section
xArea of section
total study area
- Counting by recapture %:
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Counting by recapture %
d
d
d
# of marked recaptured animals# of captured animals
# of marked animalsPopulation size=
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Population density
• Factors influencing population density:– Access to water and food– Presence of predators– Parasites, diseases
Pop. Density =# of individuals
Space occupied (area / volume)
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Population distribution
= the way in which individuals are dispersed
within their habitat
clumped
random
uniform
http://www.youtube.com/watch?v=1yKxUNP_XVo&list=PL9CE54703E2B8E92F
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clumpedrandom
uniform
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Ecological factors
= aspect of a habitat that can affect the organisms living there
• amount of light• soil / water pH• terrain• temperature• air humidity
• birth rate• disease• amount of food• predation• competition• human activity
Related to the action of living
organismsPhysical or
chemical origin
Abiotic Biotic
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Limiting factor• A factor that limits the growth of a population– Light– Temperature– Water– Food / nutrients– …
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Limiting factor• Is low temperature limiting growth of vampire
bat population?
• Vampire bat colonies
Mean minimal temperature for January > 10°C
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12 m200 mDistance between nest boxes
Dens
ity (p
airs
/ ha
)
pied flycatcher
Is nesting space limiting?
Providing more nesting spaces increases population density
Nesting space was limiting
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Biological cycles in populations
• Population cycles are composed of alternating rise and fall of population size.• Periods are of fixed duration and are repeated continually.
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Populations
• Counting methods• Density (number/ area)• Distribution (clumped/ random / uniform)• Ecological factors – limiting factors
Polpulation cycles
commuities
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organism
population community
Communities: A set of populations of different species sharing the same habitat
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BiodiversityThe variety of species living in a community
Species richness:Number of different species in a community
Relative species abundance:Number of individuals of one species in relation to total community
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Same species richness;
community 2: species abundance not even
Lower biodiversity
Biodiversity is high when:• number of species high• relative abundance of species similar
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Interactions between individualsCompetition:Living organisms seek access to the same resource in their habitat.
PredationOne feeds on the other.
Mutualism:Interaction between two species beneficial to both.
Commensalism:One organism benefits from relationship while other remains unaffected.
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Competition
interspecific
intraspecific
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Predation:
predator prey
prey may or may not die
parasite hostParasite lives either on or inside the host. Host is harmed from the interaction.
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mutualism
Bee gains foodFlower gains fertilization
Clown fish gains protectionAnemone gains prey (attracted by clown fish)
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Commensalism
Bird gains foodHuman remains unaffected
Bird gains protectiontree remains unaffected