Bio geographical evidence of evolution, Biology

Assignment Help:

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.

Related Discussions:- Bio geographical evidence of evolution

How many chromosomes and chromatin strands, Drosophila has 4 bivalents (hom...

Drosophila has 4 bivalents (homologous chromosomes) formed at Meiosis I. How many chromosomes and chromatin strands are present in each of the following stages- Anaphase of mito

All or None Response, All or None Response A very weak stimulus does n...

All or None Response A very weak stimulus does not result in an action potential. The stimulus must have a certain strength to evoke an excitation. This is the threshold value

Process of respiration, Process of Respiration Respiratory and Circul...

Process of Respiration Respiratory and Circulator System Gaseous exchange that is intake of oxygen and output of carbon dioxide, takes place at the respiratory surface since

Indicate the probablilities of producing, Two gene loci, A and B, assort in...

Two gene loci, A and B, assort independently, and alleles A and B are dominant over alleles a and b. Indicate the probablilities of producing .... an AB phenotype from a cross AaBb

Techniques of blood pressure recording, Precautions It is a common obs...

Precautions It is a common observation that BP recordings are variable when taken by different individuals. To decrease this variability it is important that certain precautio

What are the typical vegetation, What are the typical vegetation and the ty...

What are the typical vegetation and the typical fauna of the tundra? Tundra has vegetation formed mainly by mosses and lichens. In the fauna the densely furred animals, like ca

What are prophylactic measures against hiv infection, Q. What are some prop...

Q. What are some prophylactic measures against HIV infection? The major prophylactic measures against HIV infection are: the use of condoms in sexual relations, not to share ne

Lampbrush chromosomes, LAMPBRUS H CHROMOSOMES Discovered by Rucker...

LAMPBRUS H CHROMOSOMES Discovered by Ruckert . Lampbrush Chromosomes were seen in Oocytes of several different animals like shark, amphibians, reptiles and birds. (Most

Why poriferans and cnidarians do not have excretory systems, Poriferans and...

Poriferans and cnidarians do not have excretory systems. Do platyhelminthes have an excretory system? Platyhelminthes have a primitive excretory system made of flame cells (als

Homo erectus, Homo erectus first arose about 1.6 million years ago and is b...

Homo erectus first arose about 1.6 million years ago and is believed to have lived for atleast 600,000 years at a time when the transition to Homo sapiens took place. The fosSil fi

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd