With the help of an example, explain how variation leads to evolution.
Some amount of variations are produced even during asexual reproduction but it is very small. The number of variations produced during sexual reproduction is, however, very large. It is due to these variations that no two human beings look alike. The number of successful variations is maximized by the process of sexual reproduction, so we can conclude that the variation is a necessity for organic evolution. Example: Animal reproduced by sexual reproduction show large number of variations.
(a) If a normal human cell has 46 chromosomes, how many chromosomes will be there in a human (;) sperm cell, and (ii) zygote ?
(b) What sizes of plants are produced if both parents have genes Tt ?
a) Name the scientist who gave the theory of origin of life on earth. What is this theory ?
(b) How are those species which are now ‘extinct’ studied ?
How are fossils formed? Describe, in brief, two methods of determining the age of fossils. [All India]
Name the first scientist who studied the inheritance of traits from one generation to the next.
Will geographical isolation be a major factor in the speciation of an organism that reproduces asexually ? Why or why not ?
Only variations that confer an advantage to an individual organism will survive in a population. Do you agree with this statement ? Why or why not ?
Explain with examples how the following are evidences in favour of evolution in organisms. (i) Homologous organs (ii) Analogous organs (iii) Fossils [Delhi]
Give an example of body characteristics used to determine how close two species are in terms of evolution and explain it. [All India]
If the trait A exists in 10% of a population of an asexually reproducing species and a trait B exists in 60% of the same population, which trait is likely to have arisen earlier ?
(a) What is the genotype of dwarf plants which always produced dwarf offspring ?
(b) What is the genotype of tall plants which always produced tall offspring ?
(c) What is the genotype of
A woman has only daughters. Analyse the situation genetically and provide a suitable explanation.
What do you understand by the double helical structure of DNA? Who proposed this structure?
Define variation in relation to a species. Why is variation beneficial to the species? [Delhi]
(a) What will you get in the F1 and F2 generations in the following cross ?
Pure tall pea plant x Pure dwarf pea plant
(b) Is it an example of monohybrid cross or dihybrid cross ?
Out of the wing of a bird, wing of an insect and the wing of a bat :
(a) which two are homologous organs ?
(b) which two are analogous organs ?
Fill in the following blanks with suitable words :Fill in the following blanks with suitable words :
(a) The human forelimb and bat’s forelimb are an example of……………………organs whereas an insect’s wing and a bat’s wing are an example of…………………organs.
(b) The evolution of eye is an example of evolution by…………………
(c) The scientific name of all human beings is……………………..
(d) Broccoli has evolved from……………..by the process of artificial selection.
(e) The theory of natural selection for evolution was proposed by………………………
Out of bacteria, spider, fish and chimpanzee, which organism has a better body design in evolutionary terms ? Give reason for your answer.
(a) Define ‘speciation’. Explain how speciation occurs.
(b) Will geographical isolation be a major factor in the speciation of a self-pollinating plant species ? Give reason for your answer.
In evolutionary terms, can we say which among bacteria, spiders, fish and chimpanzees have a ‘better body design’ why or why not ?
The human beings who look so different from each other in terms of colour, size and looks are said to belong to the same species. Why? Justify your answer. [All India(C)]
How is the equal genetic contribution of male and female parents ensured in the progeny? [Delhi]
What is meant by the term speciation? List four factors which could lead to speciation. [Delhi]
The gene for red hair is recessive to the gene for black hair. What will be the hair colour of a person if he inherits a gene for red hair from his mother and a gene for black hair from his father ?
(a)What is meant by ‘heredity’ ? What are the units of heredity.
(b) State Mendel’s first law of inheritance.
State whether the following statement is true or false :
Human beings have evolved from chimpanzees.
The forelimbs of a frog, a bird and a man show the same basic design (or basic structure) of bones. What name is given to such organs ?
Bacteria have a simpler body plan when compared with human beings. Does it mean that human beings are more evolved than bacteria ? Explain your answer.
Do genetic combination of mothers play a significant role in determining the sex of new born?
Why are the small numbers of surviving tigers a cause of worry from the point of view of genetics ?
Give an example of characteristics being used to determine how close two species am in evolutionary terms ?
”The sex of the children is determined by what they inherit from their father and not their mother.” Justify.
