With the help of suitable examples explain natural selection. [Foreign]
Let us assume that there exist a group of red beetles in some green bushes. Due to variation during sexual reproduction one green beetle evolved among them. This green beetle can pass the colour to its progeny which are green beetles.
Crows cannot see green beetles in green bushes and therefore, cannot eat them. The progeny of green beetles are not eaten while the progeny of red beetles continued to be eaten. As a result there are more and more green beetles in the beetle population. The progeny of green beetles increase due to natural selection which gives survival advantage.
Will geographical isolation be a major factor in the speciation of an organism that reproduces asexually ? Give reason for your answer.
What is meant by the term speciation? List four factors which could lead to speciation. [Delhi]
What are the different ways in which individuals with a particular trait may increase in a population ?
Name five varieties of vegetables which have been produced from ‘wild cabbage’ by the process of artificial selection.
Choose the one term from the following which includes the other three :
broccoli, wild cabbage, cauliflower, cabbage
Explain the mechanism of sex determination in humans. [All India]
Or
With the help of a flow chart explain in brief how the sex of a newborn is genetically determined in human beings. Which of the two parents, the mother or the father, is responsible for determination of sex of a child? [Foreign]
State one characteristic which shows that the birds are very closely related to dinosaurs.
Which of the processes, sexual reproduction or asexual reproduction, brings about maximum variations in the offsprings ?
What type of plants were used by Mendel for conducting his experiments on inheritance ?
Name the various tools of tracing evolutionary relationships which have been used for studying human evolution.
If a 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 ?
Give an example of body characteristics used to determine how close two species are in terms of evolution and explain it. [All India]
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 ?
Can the wing of butterfly and the wing of a bat be considered homologous organs ? Why or why not ?
”The sex of the children is determined by what they inherit from their father and not their mother.” Justify.
An individual cannot pass on to its progeny the experiences of its lifetime.” Justify the statement with the help of an example and also give reason for the same. [Foreign]
(a) Define ‘natural selection’.
(b) “Only variations that confer an advantage to an individual organism will survive in a population”. Do you agree with this statement ? Give reason for your answer.
Write the names of at least three inorganic molecules which helped in the origin of life on the earth.
In human beings, the statistical probability of getting either a male or female child is 50 : 50. Give a suitable explanation.
Distinguish between acquired and inherited traits by giving one example of each. Why are traits acquired during the lifetime of an individual not inherited? [Delhi(C)]
Define the term ‘evolution’. “Evolution cannot be equated with progress”. Justify this statement. [Delhi]
Mendel said that the characteristics or traits of organisms are carried from one generation to the next by internal factors which occur in pairs. What is the modern name for these factors ?
Study the following cross and showing self-pollination in Flf fill in the blank and answer the question that follows
Explain how sexual reproduction gives rise to more viable variations that asexual reproduction. How does this affect the evolution of those organisms that reproduce sexually ?
(a) Why did Mendel choose pea plants for conducting his experiments on inheritance ?
(b) State Mendel’s second law of inheritance.