10th Class Science Heredity and Evolution Speciation

       Speciation

A species is the organisms consisting of similar individuals, which can breed together and produce fertile off springs. The species can be man or other animals or crops plants. Thus the process of developing new species from the existing species is known as speciation. Normally the new species arises due to the variation, which passed from one generation to the next and get accumulated over the long period of time. This also happens when the population of same species splits up into two separate groups, which then get isolated from each other geographically by the barriers such as mountain ranges, river or the sea.

The main factors which could cause speciation are the geographical isolation, genetic drift caused by drastic changes in the frequencies of particular genes and the variations caused in individuals due to natural selection.

There is no real progress in the field of evolution, rather it is just the production of diversity of life forms and shaping of this diversity by the environmental selection. The only progress in the evolution which appears to us is that the organism with more and more complex body designs have emerged over the ages. It is not that with the appearance of organisms with complex body designs the simpler organisms will disappear. It depends on the environmental condition of the place. For example, one the simplest and primitive life forms called bacteria still inhibits in some of the most inhospitable habitats such as hot springs, deep sea, thermal vents and the ice in Antarctica.

        Which one of the following sex chromosomes give rise to the male child?

(a) XX

(b) XY

(c) YY

(d) XYX

(e) None of these

Answer: (b)

         Name the scientist who gave the theory of evolution.

(a) Darwin

(b) Lamarck

(c) Mendel

(d) Baptiste Pierre

(e) None of these

Answer: (a)

          Which one of the following is not present in the darwins theory of evolution?

(a) Overpopulation

(b) Natural Variation

(c) Struggle for Existence

(d) Use and disuse of organ

(e) None of these

Answer: (d)

         Which one of the following is more in common with us in terms of evolution?

(a) Chinese Boy

(b) Monkey

(c) A chimpanzee

(d) Bacteria                   

(e) None of these

Answer: (c)

• There's no hereditary trait that influences a predisposition to having identical twins.
• Birth rates for identical twins are consistent across populations; it is the same regardless of race, geography or maternal age.

• The changes which arises in an organisms from one generation to the next is called variations.
• These variations is minimum in asexual reproduction and maximum in sexual reproduction,
• The variations results in evolution of new species from preexisting organisms.
• The new born child is male if the Y chromosomes of male combines with the X chromosomes of female, but if the X chromosomes of male combines with the X chromosomes of female, then the new born child is female.
• The transmission of character from one generation to the next is called heredity.
• The DNA is responsible for the transmission of character form one generation to the next.