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
THYROI D DISORDERS - (A ) Hyperthyroidism (Hypersecretion of thyroid hormone). Graves' disease or Basedow's disease or Parry's disease or exophthalmic goitre . It is a

What are DNA ligases? How do these enzymes participate in the recombinant DNA technology? The DNA ligases are enzymes specialized in tying the complementary DNA chains that for

What is crystallization of a virus? What is the importance of this process? Crystallization is the method of transformation of viral components into organized solid particles.

how do i prove in a diagram that water is needed for photosynthesis


HUMA N HEART (MAMMALIAN HEART) - Position - Situated in thoracic cavity in pericardial cavity close to its front wall. Its broad base faces upward and backward. Its narrow a

Iodine  deficiency Iodine is an important component of thyroid hormones, which play active role in several physiological process such as control of basal metabolic rate, oxidat

What is the most excellent identification hypothesis for a plant tissue seen under the microscope having most cells undergoing cell division? The most excellent hypothesis is t

Q. What is the name given to conditions in which the own immune system of the individual is the agent of diseases? What are some examples of these conditions? Diseases caused b

Medical status of the patient Conditions like osteoporosis, history of radiotherapy, use of bisphosphonates which can affect the success of the treatment should be considered b