Biology

Heredity and Evolution

Question:

Explain with examples how the following are evidences in favour of evolution in organisms.  (i) Homologous organs (ii) Analogous organs (iii) Fossils [Delhi]

Answer:

(i) Forelimb of human and bird are homologous organs. They have same structural design and developmental origin but they have different functions and appearance. Homologous organs help us to understand that the organism has evolved from a common ancestor. The more common characteristics the two species have, the more closely they are related.
(ii) Analogous organs are those organs design and developmental origin but have similar appearance and perform similar functions.
Example: The wings of birds and bats look similar but have different design in their structure. They have a common function of flying but their origins are not common. So, birds and bats are not closely related.
(iii) Fossils and their study is useful in knowing about the species which are no longer alive. They provide evidence and missing links between two classes. They are helpful in forming a sequence of organisms in the pathway of evolution. Thus, fossils have an importance in deciding evolutionary relationship. Archaeopteryx is a fossil bird. It had feathers, fused bones and beak which are exclusively bird structures. It also had some features which are found in reptiles, e.g. teeth in jaw, claws on free fingers and a long tail. This fossil provides a clue that birds have evolved from reptiles.

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Heredity and Evolution

Q 1.

Name the scientist who gave the theory of evolution.

Q 2.

Mention three important features of fossils which help in the study of evolution.

Q 3.

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 ?

Q 4.

What do the following symbols used in the topic on heredity represent ?
(a) TT
(b) tt
(c) XX
(d) XY

Q 5.

(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 ?

Q 6.

In a human, how many chromosmes are present in :
(a) a brain cell ?
(b) a sperm in the testes ?
(c) an egg which has just been produced by the ovary ?
(d) a skin cell ?
(e) a fertilised egg ?

Q 7.

(a) What do you understand by the term ‘variation’ ?
(b) Name two human traits which show variation.

Q 8.

A study found that children with light-coloured eyes are likely to have parents with light-coloured eyes. On this basis, can we say anything about whether the light eye colour trait is dominant or recessive? Why or why not?

Q 9.

What evidence do we have for the origin of life from inanimate matter?

Q 10.

What is heredity?

Q 11.

What is a sex chromosome?

Q 12.

What is meant by the term speciation? List four factors which could lead to speciation. [Delhi]

Q 13.

If we cross pure-bred tall (dominant) pea plant with pure-bred dwarf (recessive) pea plant we will get pea plants of F1 generation. If we now self-cross the pea plant of F2   generation, then we obtain pea plants of F2   generation.
(a) What do the plants of F2 generation look like?
(b) State the ratio of tall plants to dwarf plants in F2 generation.
(c) State the type of plants not found in F2 generation but appeared in F2 generation, mentioning the reason for the same. [All India]

Q 14.

State the meaning of inherited traits and acquired traits. Which of the two is not passed on to the next generation? Explain with the help of an example.

Q 15.

A new born child has an XY pair of chromosmes. Will it be a baby boy or a baby girl ?

Q 16.

What are the four blood groups in humans ?

Q 17.

Give the contrasting traits of the following characters in pea plant and mention which is dominant and which is recessive :
(a) Yellow seed (b) Round seed

Q 18.

Where did life originate on the earth ?

Q 19.

Why are the traits acquired during the lifetime of an individual not inherited ?

Q 20.

Name two animals having homologous organs and two having analogous organs. Name these organs.

Q 21.

Name the various tools of tracing evolutionary relationships which have been used for studying human evolution.

Q 22.

(a) What is meant by a species ? Give two examples of plant species and two of animals.
(b) State the various factors which could lead to the formation of new species.

Q 23.

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 ?

Q 24.

A woman has only daughters. Analyse the situation genetically and provide a suitable explanation.

Q 25.

Evolution has exhibited a greater stability of molecular structure when compared with morphological structures. Comment on the statement and justify your opinion.

Q 26.

Will geographical isolation be a major factor in the speciation of an organism that reproduces asexually ? Why or why not ?

Q 27.

Explain Darwin's theory of evolution.

Q 28.

During which stage can the chromosomes be seen clearly? Write the features of the eukaryotic and prokaryotic chromosomes.

Q 29.

Define variation in relation to a species. Why is variation beneficial to the species? [Delhi]

Q 30.

Describe briefly four ways in which individuals with a particular trait may increase in a population. [Foreign]

Q 31.

What are fossils? What do they tell us about the process of evolution? [All India(C): All India 2011]

Q 32.

Give one example each of characters that are inherited and the ones that are acquired in humans. Mention the difference between the inherited and the acquired characters. [Delhi]

Q 33.

What evidence do we have for the origin of life from inanimate matter? [All India]

Q 34.

Give an example of body characteristics used to determine how close two species are in terms of evolution and explain it. [All India]

Q 35.

How are fossils formed? Describe, in brief, two methods of determining the age of fossils. [All India]

Q 36.

What constitutes the link between one generation and the next ?

Q 37.

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 ?

Q 38.

What type of plants were used by Mendel for conducting his experiments on inheritance ?

Q 39.

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 ?

Q 40.

Fill in the following blanks with suitable words :Fill in the following blanks with suitable words :
(a) Genes always work in …………………
(b) In pea plants, the gene for dwarfness is………………… whereas that for tallness is…………………
(c) Most people have………………… earlobes but some have………………… earlobes.
(d) A human gamete contains………………… chromosomes whereas a normal body cell has………………… chromosomes in it.
(e) All races of man have………………… blood groups.
(f) The………………… chromosomes for a………………… are XX whereas that for a………………… are XY.

Q 41.

Which of the following represent tall plants and which represent short plants (or dwarf plants) ?Which of the following represent tall plants and which represent short plants (or dwarf plants) ?
(a) Tt
(b) tt
(c) TT
Give reason for your choice (The symbols have their usual meaning).

Q 42.

a) Name the scientist who gave the laws of inheritance.
(b) Name an animal in which individuals can change sex. What does this indicate ?

Q 43.

(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 ?

Q 44.

(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

  1.  dwarf plants, and
  2.  tall plants, whose parental cross always produces tall offspring ?

Q 45.

Gregor Mendel’s first law of genetics states “Of a pair of contrasted characters, only one can be represented in a gamete by its internal ‘factor’.
(a) Give the modern name for this ‘factor’.
(b) State where these factors are found in gametes.

Q 46.

Does genetic combination of mother play a significant role in determining the sex of a new born baby ?

Q 47.

(a)What is meant by ‘heredity’ ? What are the units of heredity.
(b) State Mendel’s first law of inheritance.

Q 48.

State whether the following statement is true or false :
Human beings have evolved from chimpanzees.

Q 49.

State one characteristic which shows that the birds are very closely related to dinosaurs.

Q 50.

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 ?