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प्रश्न
"Natural selection and speciation leads to evolution." Justify this statement.
उत्तर
Natural selection is the phenomenon by which the nature selects those species which possess survival advantage over the other species. According to theory of natural selection, there is "struggle for existence" within the species of a population for the environmental resources and this struggle leads to survival of certain organisms and elimination of the less competent species. Thus, in this competition, some organisms might undergo genetic changes which help them in their survival. The better adapted organisms would, thus, survive and pass on their traits to next generation, gradually leading to evolution.
Speciation is a process of formation of new species from the existing one due to reproductive isolation of a part of its population. This reproductive isolation can occur due to geographical isolation of a part of population.
With time, the genetic drift will accumulate different variations in each of the geographically separated sub-populations. Ultimately, all the individuals of these two groups will isolate reproductively, thus, leading to formation and evolution of new species. Thus, we can say that both natural selection and speciation lead to the evolution of species on earth.
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संबंधित प्रश्न
The palisade cells of a species of plant contain 28 chromosomes. How many chromosomes will there be in each gamete produced by the plant?
(a) 56
(b) 28
(c) 14
(d) 4
In peas, a pure tall plant (TT) is crossed with a pure short plant (tt). The ratio of pure tall plants to pure short plants in F2 generation will be ______.
Will geographical isolation be a major factor in the speciation of a self-pollinating plant species? Give reason for your answer.
Define 'natural selection'.
The human species has genetic roots in ______
Which of the following statement is incorrect with respect to variations?
(a) all variations in a species have equal chance of survival
(b) change in genetic composition results in variations
(c) selection of variations by environmental factors forms the basis of evolutionary process
(d) variations are the minimum in asexual reproduction
Read the following statement and justify same in your own words with the help of suitable example.
Geographical and reproductive isolation of organisms gradually leads to speciation.
In the following Question, the Assertion and Reason have been put forward. Read the statements carefully and choose the correct alternative from the following:
Assertion: Speciation is the reproductive isolation amongst once interbreeding population.
Reason: Genetic drift, Natural selection, and Severe DNA change can cause speciation.
Add a note on allopatric speciation.
Complete the following chart:
| Animals | Connecting link between | |
| (1) | Balanoglossus | ______ |
| (2) | ______ | Annelida and Arthropoda |
| (3) | Lung fishes | ______ |
| (4) | ______ | Reptiles and mammals |
| (5) | Seymouria | ______ |
| (6) | Fishes and Amphibia |
