lec 3 - distribution and abundance

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!

lec 3 - distribution and abundance

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