Bio geographical evidence of evolution, Biology

BIO GEOGRAPHICAL EVIDENCE-

  • The patterns of distribution of animals and plants in different parts of the globe are termed as biogeography.
  • It is believed that around carboniferous period or slightly earlier all the present day continents formed a single large, irregular land mass called Pangaea.
  • Pangaea splited up and the smaller masses (continents) lighter than the underlying earth crust material gradually floated over it to their present position.
  • As the continents drifted away, the sea separated them, forming barriers to free intercontinental movements of organisms. Due to different environmental continents, organisms evolved independently in them.
  • Earlier whole land mass of Globe was one piece called Panagea. 200 - 300 million years ago it got divided as follows -

538_bio geographical evidence.png

  • Sclater (1858) first divided globe in six zoogeographical regions on the basis of avian fauna.
  • A.R.Wallace (1876) divided more scientifically on the basis of entire flora and fauna as:

(i) Oriental region

-

Asia (lower China, West Asia, Malaysia, Indonesia, India, Ceylon)

(ii) Australian region

-

Australia, New Zealand, New Guinea, Tasmania, Hawaiian Island.

(iii) Ethiopian region

-

Africa continent, Madagascar, Egypt, Sahara

(iv) Palaearctic region

-

Europe, Most part of China, Japan, USSR, Siberia, N. Sahara

(v) Nearctic region

-

North America continent (USA, Canada, Alaska, Greenland)

(v) Neotropical region

-

South America continent (Mexico, Galapagos island)

  • Wallace's Line divides Oriental and Australian region.
  • Darwin (1831) during his expedition on H.M.S. Beagle visited Galapagos Islands (900 Km off West coast of South America) and found many endemic (restricted) species.
  • He studied 13 different subspecies of finches (Darwin's finches by David Lack 1947) with different eating habits (originally seed-eating).
  • He reasoned it as suitable adaptation brought by environmental conditions and called the islands as " living laboratory of evolution "
  • Discontinuous (Allopatric) distribution: When closely related genera are found in different regions.
  • This indicated that after arising from common stock they were geographically separated and evolved differently.
  • Due to the geographical barrier they remained isolated and evolved as genera, examples - 2101_bio geographical evidence1.png
  • Continuous (Sympatric) distribution: When closely related genera are found in the same or connected region. e.g. Prototheria and Metatheria are found only in Australian region.
  • Sometimes referred as restricted distribution. endemic fauna.
Posted Date: 10/8/2012 9:21:24 AM | Location : United States







Related Discussions:- Bio geographical evidence of evolution, Assignment Help, Ask Question on Bio geographical evidence of evolution, Get Answer, Expert's Help, Bio geographical evidence of evolution Discussions

Write discussion on Bio geographical evidence of evolution
Your posts are moderated
Related Questions
DNA Replication Deoxyribonucleic acid (DNA) is the carrier of genetic data for all living creatures. An organism's genome, made of DNA, encodes the genetic blueprint for buildi

Explain the Quebec Colony Counter? It is used for counting the number of colonies in a plate. Culture plate is kept on the screen which is illuminated from beneath. Counting is

Explain The proteins stabilize emulsions The proteins stabilize emulsions and contribute  physical  and rheological properties,  like thickness,  viscosity, elasticity   and  r

List the types of Gellan gum.   The three types of gellan gums are: High acetyl gellan (partially deacetylated) Low acetyl gellan (highly deacetylated) High cl

What is reduction? The most commonly understood definition of reduction is the removal of oxygen or addition of hydrogen ions. However, chemically, reduction can be defined as

How does the study of fossils strengthen the theory of evolution? The study of fossils reveals ancient and extinct species having many same structures to others of the present

Food applications of CMC In common with other linear water-soluble polymers, cellulose gum solutions are pseudoplastic that is the viscosity decreases as the  rate of shear inc

Ecological adaptations in animals to desert environment In response to scarcity of water, animats adcipt vario6s strategies to conserve or prevent loss of water. Most of the de

discus the protozoan flagellates of less medical importance ,outlining their development stages,normal habitants and morphological characteristics

Define Reagent for Separation of Amino Acid by Paper Chromatography? The following reagents will be required for carrying out the experiment: 1. Amino acid solution- Weig