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Unit 3 Populations
Ch. 8 Understanding Populations
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Essential Question
How are population sizes areregulated by nature.
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What is a population?
All the members of the same species living inthe same area at the same time
Refers to a reproductive group in general
Refers to number of individuals in group
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Properties of populations
Populations described in threeways
Size - # of individuals
Density - # of individuals perunit of area or volume
Dispersion distribution orarrangement of individuals
within a space (even, clumped,random)
Properties can be used topredict changes within pop
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Population Growth
Growth rate change in size of popover an amount of time
Growth rate = births deaths
Can be positive, negative or zero
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How fast can pop grow?
Populations usually stay the same dueto environmental factors that killoffspring before they are old enoughto reproduce
Reproductive potential max # ofoffspring an individual can produce
Different for different species
The earlier a species reproduces thehigher the reproductive potential
Exponential Growth pop grows fasterand faster with each generation
Only occurs when there is plenty offood and space and little competitionor predation
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What limits population growth?
Populations rarely grow to theirpotential why?
Limited resources, naturalselection, environmental
changes Carrying capacity maximum
size of a population that anecosystem can supportindefinitely
Limiting resource resourceproduced by ecosystem thatis needed for survival
Competition amongindividuals for food and space
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Population regulation causes of death
Density dependent deaths occur morequickly in a crowded
population Limited resources,disease, predation
Density independent death occurs regardless
of the density Severe weather, natural
disasters
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Closure
How is a population of deer regulatedby nature?
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Essential Question
Describe the 5 major types ofinteractions between species.
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An organisms niche
Niche the unique role of a specieswithin an ecosystem, job
Includes:
Physical home Interactions with other species
Env factors necessary for survival
Pattern of use of habitat (location)
Sometimes niches overlap with otherspecies creating competition forresources
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Ways in which species interact
Competition different individuals attempt touse same resource harms both Indirect species dont come in contact with each
other but use the same resource
Predation organism feeds on another Predator benefits, prey is harmed
Parasitism an organism that lives in or onanother organism and feeds on that organism Parasite benefits, host is harmed
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Mutualism relationship in whichboth species providea benefit to the
other (bacteria instomach, ants inacaicia tree)
Commensalism one species benefits
and the other isneither helped norharmed (barnacleson a whale)
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Symbiosis
Relationship in which two species liveclosely together
Species may coevolve birds andpollinators