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
Q. Class Reptilia identity card. How are they characterized according to examples of representing beings, basic morphology, skin, respiration, circulation, nitrogen waste, thermal

Q. What is Normalisation of Inverted T-Waves? In patients with flat or inverted T-waves at rest, the evolution to an upright T-wave has been considered by some to be a sign of

OXIDATION OF PYRUVATE TO ACETYL CoA The oxidation of  pyruvate  to acetyl CoA is  the irreversible route from glycolysis  to the citric acid cycle. What is citric acid cycle?

Woodland Stage - Hydrarch When the lowland has been built up to an extent where the soil is saturated perhaps only in spring and early summer, certain species of shrubs and tr

Explain the characterstics of Acute AR Murmur ? Characteristic: Relatively low pitched, decrescendo diastolic murmur, which may end part way through diastole. These murmurs ar

Copper deficiency Copper deficiency may be primary or secondary (conditional). Primary copper deficiency occurs due to its inadequate dietary intake; whereas secondary copper d

Sally Subcloner wants to clone a fragment into pUC19 (Map above - From New England Biolabs). Her fragment was a protein coding gene of 2.7 kb, and had Xho I sites on either end (a

Define the Fats requirement to avoid underweight problem?   We know that fats are concentrated source of energy (1g = 9 Kcals). Fats are capable of increasing the energy val

Glycogen synthesis and degradation in the liver and muscle is very similar. Which of the following enzymes is not used in both muscle and liver for these metabolic pathways? -ph

Some organisms contain enzymes that condense a fatty alcohol and a fatty acid to generate wax esters. Draw decanol, plamitic acid (C16:0 fatty acid) and the resulting wax ester gen