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8/2/2019 Lec 3 - Distribution and Abundance
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Distribution & Abundance ofOrganisms
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Why are some organisms found in oneplace but not in other places?
The kangaroo only found in Australia andnot other places and with unevendistribution in Australia
This also goes for many other animal and
plant species around the globe
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Environmental componentsAffect the distribution and abundance of organisms
Figure 50.2
Kangaroos/km2
> 20
1020
510
150.11
< 0.1Limits ofdistribution
Climate in northern Australiais hot and wet, with seasonaldrought.
Red kangaroosoccur in most
semiarid and aridregions of theinterior, whereprecipitation isrelatively low andvariable fromyear to year.
Southeastern Australiahas a wet, cool climate.
Southern Australia hascool, moist winters andwarm, dry summers.
Tasmania
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Darwin, Wallace & others recognized broadpatterns of geographic distribution of plants andanimals Biogeographic realms associated
with Continental Drift due to Plate Tectonicsand the breakup of Pangaea
Biogeography study of the past and presentdistribution of individual species of plants and
animals
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BiogeographicalRealms
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NorthAmericanPlate
CaribbeanPlateJuan de FucaPlate
Cocos Plate
PacificPlate
NazcaPlate
SouthAmericanPlate
AfricanPlate
Scotia Plate AntarcticPlate
ArabianPlate
Eurasian Plate
PhilippinePlate
IndianPlate
AustralianPlate
Plate Tectonics
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Many important geological processesOccur at plate boundaries or at weak points in the
plates themselves
Volcanoes andvolcanic islands
TrenchOceanic ridge
Figure 26.19
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Figure 26.20
India collided withEurasia just 10 millionyears ago, forming theHimalayas, the tallestand youngest of Earthsmajor mountainranges. The continentscontinue to drift.
By the end of theMesozoic, Laurasiaand Gondwanaseparated into thepresent-day continents.
By the mid-Mesozoic,
Pangaea split intonorthern (Laurasia)and southern(Gondwana)landmasses.
Ce
nozoic
Eurasia
AfricaSouth
AmericaIndia
Madagascar
Antarctica
Laurasia
Mesozoic
At the end of thePaleozoic, all ofEarths landmasseswere joined in thesupercontinent
Pangaea.Paleozoic
251
135
65.5
0
Millionsofy
earsago
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What limits the distribution of
organisms in the naturalenvironment?
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What are the factors involved?
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A series of questions are askedby Ecologists
What are these Questions?
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Biogeography
Provides a good starting point for understandingwhat limits the geographic distribution of species
Figure 50.6
Species absentbecause
Yes
No
Dispersallimits
distribution? Behaviorlimits
distribution? Biotic factors(other species)
limitdistribution? Abiotic factors
limitdistribution?
Yes
No
Yes
No
Area inaccessibleor insufficient time
Habitat selection
Predation, parasitism,competition, disease
WaterOxygenSalinitypHSoil nutrients, etc.
TemperatureLightSoil structureFireMoisture, etc.
Chemicalfactors
Physicalfactors
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Species dispersal contributes to thedistribution of organisms: why nokangaroos in America, Africa, Asia? possibly because they could not getthere because of barriersto dispersal.
Dispersal is critical in understandinggeographic isolation and patterns ofcurrent distribution of organisms
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Species Transplants
Dispersal is a key factor for limitingdistribution
Some organisms can disperse andsurvive in new areas but cannotreproduce.
So success is determined by the ability forcompleting at least one life cycle in thenew habitat/environment.
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Transplant Experiment
To answer questions concerningdistribution we must first determine
whether the limitation on distribution results
from
inaccessibility of the particular areato a species.
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One way to determine this isby conducting a transplant
experiment
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Transplant Experiment Concept
Moving individuals of a species to anunoccupied area and determine if they cansurvive and reproduce successfully.
Two (2) outcomes of Transplant Experiment: successful
limited distribution is due to areainaccessibility, too short time to reach, area notrecognized by organisms as suitable
potential range > actual rangeunsuccessful
limited by behaviour, biotic or abiotic factors
potential range = actual range
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Accidental Transplants IntroducedSpecies
African Honey Bees
Unpredicted and undesirable consequences African honey bee (Apis millifera scutellata) an aggressive
species brought to Brazil in 1956 to breed a new variety withthe Italian honey bee (Apis millifera ligustica)
It escaped and have been spreading since and thesebees may drive out colonies of the Italian honey bees
These bees are aggressive towards humans and
domestic animals and will impact on the domestichoney bee industry
What will limit its northward and southward
distribution?
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In-text figurePage 577
Kudzu Vine
(from Japan)
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1918
2000
Expansion of thefire ant in southern
states (FromArgentina)
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Figure 22-17 (2)Page 576
Sea lamprey(attached to lake trout)
Argentina fire ant Eurasian muffleBrown tree snake Common pigeon(Rock dove)
Formosan termite Zebra mussel Asian long-hornedbeetle
Asian tiger mosquito Gypsy moth larvae
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Figure 22-17 (1)Page 576
Purple looselife European starling African honeybee(Killer bee)
Nutria Salt cedar(Tamarisk)
Marine toad Water hyacinth Japanese beetle Hydrilla European wild boar(Feral pig)
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Tens Rule generally 1 out of 10
introduced species gets establishedand 1 out of 10 established species
becomes a pest!