Populations Notes

7/26/2019 Populations Notes

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Populations

Wednesday, August 26, 2015

9:29 AM

Ecology - study of interactions of organisms with their environment

Environment - abiotic portion (physical factors, temperature, rainfall)

Biotic portion (other organisms)

Environmental factors include both of these

Levels of organization

Individuals - how they interact with environment

Populations - groups of individuals of same species living in same area orhabitat

ommunity - populations of all species that occupy a habitat - larger scale

Ecosystems - communities and their interactions with the physicalenvironment - species type of interactions with physical environment -

biotic and abiotic

Biosphere - envelope of life covering earth - things that go on ecologicallyon one part of the globe have an e!ect on other parts of the globe

Population ecology -

Populations - individuals of same species living in an area

!i"#ult to tell $%en one population leaves o& fro' anot%er population

(ne feature of populations of parti#ular interest is if t%is is a gro$ing, de#lining ort%e nu')er of population individuals staying t%e sa'e

*o$ fast t%ese population #%anges are o##urring rapid, slo$ly de#lining rapidly+endangered spe#ies


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-ro$t% rate

"rowth rate # birth rate (br) (and immigration) - death rate (dr) (andemigration)

"rowth rate # birth rate - death rate

# net number of individuals added to the population in a given time period

.gnoring i''igration and e'igration

If br $ dr than population will grow

If br # dr than population will remain at constant si%e (%ero populationgrowth - %pg)

If br & dr than population will decline

Buc'et analogy - with water in it, amount of water, indicator of si%e ofpopulation

wo things going on

aucet going - putting more water into buc'et (birth rate)

Buc'et has hole in it - water leaving the buc'et through bottom (deathrate)

*ater going in at certain rate, water going out at certain rate

+i%e of population - total amount of water at a particular time

ore water going in - bigger br

Bigger hole - bigger dr

"rowth with unlimited resources -

/nli'ited resour#es in t%e environ'ent

a'ple one individual +fe'ale gives )irt% to 2 fe'ale o&spring $%i#% in turnea#% %ave 2 fe'ale o&spring

2 2 3 4 16 2 63 et#

.n t%is #ase, t%e population dou)les every generation


3/8

7%ere are no restri#tions on t%ese o&spring t%at are produ#ed plenty of food ea#%o&spring a)le to gro$ up and produ#e

Eponential growth

. shaped growth curve

!ou)ling ti'e ti'e for t%e population to dou)le in size #o'pare population and%o$ fast t%ey are gro$ing

"rowth with Environmental /imits

/imited resources in the environment

!ensity dependent li'iting fa#tors as population in#reases t%e deat% rate

in#reases +fun#tion as population size due to and de#rease )irt% rate


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o Predators predators 8ey in )e#ause t%ey are an a)undant resour#eo o'petition every individual is fa#ed $it%

/imited space

/imited food - every other individual is eating it as wello !isease easier trans'itted )e#ause t%ey are #lose to ea#% ot%er

Populations are also li'ited )y density independent fa#tors

ad $eat%er 8no#8s it )a#8 and %as to start over again

s-shaped growth curve

/ogistic growth

+tart out - population fairly small, grow fairly eponentially, as populationgets larger and larger - runs o! at resourceli'itation population levels o& point )irt% rate ; deat% rate population is #arrying #apa#ity

Population gro$s until it rea#%es t%e #arrying #apa#ity t%en re'ains at t%at level

arrying capacity (')is population size t%at #an )e supported )y t%e resour#esavaila)le in t%e environ'ent

(vers%ooting t%e #arrying #apa#ity going )eyound #arrying #apa#ity and severe#onse


5/8

ras% overs%oots and t%an de#lines t #o'e )a#8 destroy vegetation


6/8

Polonesian easter island - stonehedge

Easter island - etremely isolated from mainland and other islands

Polonesians - coloni%ed easter island

122 ad,

+mall population, lots of trees, birds, and some native mammals

+ame thing happened li'e the reindeer

Population got up to 'ay)e 20 t%ousand individuals )ut not enoug% resour#es tosupport t%e' for a long period of ti'e

Population under$ent $ars, #anni)alis', et#

onse3uences - overshoot and environment destroyed so carryingcapacity signi4cantly reduced

As population gre$, started using up all trees on island for ?re$ood and so on

.sland people $ould ta8e )oats out into t%e o#ean and ?s% and used a lot of ?s%fro' o#ean

%opped do$n every tree on island dis#overed )y europeans $it%out trees

@o trees ; no )oats to ?s%, no nesting )irds

7%ey )roug%t #%i#8ens to eat )ut not enoug% food to support 20 t%ousand people

@u')ers $ere a)out 2 t%ousand $%en dis#overed )y europeans

=eprodu#tive strategies referred to as life %istory patterns

7%ere are di&erent reprodu#tive strategies

Loo8 at dandelions in your la$n individual dandilion %undreds of seeds

*u'an spe#ies not %undreds of o&spring, 12 )a)ies at ti'e, 5 or fe$er overlifeti'e

o'e spe#ies lots of )a)ies

(t%ers not 'any )a)ies at all


7/8

W%y is t%is t%e #aseB

nviron'entCliving #onditions for populations relations%ip )et$een t%at andreprodu#tion strategies

7$o etre'e situations

5 - selected species

6 - selected species

7 species reproductive strategy is an adaptation to living conditions forthe population

5 selected species - seem to be below carrying capacity of environment

most of the time, grow rapidly

5 is growth rate parameter to loo' at population growth

ocus on rapid reproduction - females are ma'ing lots of babies, not largebabies, caring for babies in particular way, many small babies andfre3uent reproduction - a lot of species

5abbits, many insects, weedy plants

Lots of )a)ies )etter #%an#e of o&spring )etter surviving to net generation

onstant ponential gro$t%

Dre


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Population of other species are almost always near '

Population 8ept near 8 )y #o'petition for resour#es

7%ese spe#ies are 8sele#ted

Do#us on %aving #o'petetive o&spring t 'a8e lots of )a)ies, 'a8e a fe$ )a)ies, %ig%

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