Already have an account? Get multiple benefits of using own account!
Login in your account..!
Remember me
Don't have an account? Create your account in less than a minutes,
Forgot password? how can I recover my password now!
Enter right registered email to receive password!
Many definitions of species have been offered, but none of them proved to be satisfactory. The definitions did not categorically provide the basis to decide whether two similar groups are distinct species or only sub-species. Again what is the criterion to decide the distinctness of a species? Some tried to specify the degree of difference that would distinguish a species from another. Apart from the difficulty in quantifying such differences, there are also other problems. Certain forms which show very little morphological differences proved to be very distinct species. In other cases, such as Homo sapiens, undoubtedly a single species, different races have pronounced differences. The discontinuity between groups, it appears, depends less on the degree of differences and more on the constancy of differences. Another approach to define species was to distinguish related organisms on their inability to breed. Many definitions of species have relied upon such interspecific sterility and sterility of offsprings, that is hybrid sterility. This proposition also has certain inherent problems. It is not easy to identify cases in which organisms do not interbreed, and those which can breed, but do not do so for certain reasons. At these times, sterility cannot be deemed to be an appiopriatc criterion for defining species. Nevertheless, reproductive isolation or inability to breed has been the commdn element in the definition of species provided by many evolutionary biologists, be it Dobzhansky, Goldschmidt or Ernst Mayr. Reproductive isolation, the discussion of which follows later in this unit, has been the basis for defining the species and speciation.' Such an isolating mechanism becomes a barrier for the flow of genes between related populations and the concept of biological species centres around this phenomenon.
What is the Rh typing of the mother and of the fetus in the hemolytic disease of the newborn? In a hemolytic disease of the newborn the mother is Rh- and the fetus Rh+. In thes
Classification of zoonoses More than 300 zoonoses of diverse etiologies are recognized. Thus, a very large number of zoonoses call for classification, especially for teaching
Suspensor - Pollen Biology The structure and function of suspensor have not been given adequate attention. During the last decade, however, investigations have produced notewo
How do the availability of water and light and the climate affect the growth of a population? The availability of water and light and the climate are abiotic factors that limi
Explain Objective Anti-arrhythmic pacemaker defibrillators? After reading this unit, you should be able to: 1 describes the classification of ant arrhythmic drugs; 2 understand
is there a difference between the giant asiatic bees apis dorsata and Philippine giant bees apis breviligula
Describe about The implant surgeon The implant surgeon should have basic knowledge of the macroscopic and microscopic anatomy of the jaw bones with their associated neurovascul
Explain the Changes in Body Tissue Compartments - Underweight? The severity of nutritional deprivation determines the extent of changes in the body tissue compartments. The fir
What are stains? Microorganisms are difficult to be seen in living state because of their minute, colourless and transparent nature. Moreover, there is limitation of insufficie
Q. Into which two groups can the nitrogen-containing bases that form RNA and DNA be classified? What is the criterion used in to that classification? The nitrogen-containing ba
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!
whatsapp: +1-415-670-9521
Phone: +1-415-670-9521
Email: [email protected]
All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd