73--a single set

74----> natural selection brings about improved adaptive relations between organisms and environment by favouring the reproduction and survival of those individuals which are found more suited to the( given) environment .

75------>the unfolding of nature wherein newer types of organisms develop from the pre-existing ones through modifications called organic evolution.


76---->most of the amphibians


77----->lamarckism is based on the following

1.internal vital force---there is a vital force in organisms which yends to change them.

2.environment ---- a change in environment brings about direct changes in plants.it produces new needs in animals.

3.new needs---new needs bring about new desires that result in changes of older organs and formation of new organs.

4.use and disuse of organs--- repeated use of an organ
makes it more complex and efficient whereas non-use of an organ brings about its degeneration.

5. inheritance of acquired traits---the traits acquired by an individual in its lifetime is passed on to the next heneration........thats it 8D

73) There may be many possible alleles for any gene , but a diploid cell animal contains only two alleles of each gene or two copies of a single allele ; a haploid gamete contains one copy of each gene , so only one allele.


74) According to Darwin's theory of evolution natural selection is the process by which organisms that are better suited to their environment than others produce more offspring.


75) The process by which changes in the genetic composition of populations of organisms occur in response to environmental changes.