unit 3 populations

8/2/2019 Unit 3 Populations

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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

unit 3 populations

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