please Answer the Above questions
Answers
9ans,
Variation can be defined as the differences among individuals within the same species which develops due to the mixing and assortment of genes of the parents that is passed onto the offspring’s. For example, we keep pets like dogs and cats. There are so many breeds of each one of them and even in the same breed; there are minor differences and variations among individuals.
8ans,
Charles Darwin gave the theory of evolution in his book 'Origin of species'. Adaptive radiation and natural selection are two key concepts of this theory. The main points of this theory are as follows:
1) New forms keep on gradually evolving with time in the history.
2) There is always variation in characteristics of populations which help them to adapt better to the surroundings.
3) Those organisms which adapt themselves better to the surroundings survive and reproduce while others die. This is known as survival of fittest.
4) The organisms which adjust to the changing environments are selected by nature and thus can survive. This is called as natural selection.
5) There is an inheritance of adaptability and the consequence of adaptability is fitness.
Natural selection takes place due to the following reasons:
* Limited natural resources
* Variations in the characters of members of population
* The inheritance of variations to next generation.
Example of natural selection
Industrial melanism: There were a large number of white moths before industrial revolution in England. These moths could easily camouflage against the background of the trees and so were protected from the predators. Thus their numbers increased as a result of reproduction. But after the industrial revolution, soot deposited on the bark of trees and thus white coloured moths became susceptible to the predators and their number started decreasing. The deposition of soot on the trees was advantageous to dark coloured moths as now they were not easily visible to the predators and thus their population started increasing. Thus with the change in the environment, nature selected only on those individuals which were fit to survive in that environment.
b) The three characteristics of Neanderthal man are:
i) Bipedal locomotion
ii) Deep jaw with no chin
iii) Prominent brow ridges and thick skull bones
7ans,
The sex determination is XY type in humans. There are 23 pairs of chromosomes found in human Out of these, 22 pairs are called autosomes which are same in both male and females. The rest one pair is called six chromosome. These vary in males and females. Males have one X chromosome and one Y chromosome(heterogametic). In contrast, females have two copies of the X chromosome (homogametic). All the haploid gamete produced by the female have X chromosome whereas, the gametes produced by the male have either X or Y chromosome. After fusion of the gametes the formed zygote have either XX or XY chromosome, depending upon whether the X or Y chromosome fertilised the ovum. There is fifty-fifty chance of this. On the basis of this fusion, sex of the child is determined which depends on the father not the mother.
6ans,
A good example of independent assortment is Mendelian dihybrid cross. The presence of new combinations - round green and wrinkled yellow, suggests that the genes for the shape of the seed and color of the seed are assorted independently.
Variation is defined as the the change which can be observed at thephenotypic and genotypic level . There are different causes causes of variations like due to natural selection , germinal variation , etc. germinal variation is the variations among the organism due to genetic difference.
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