HEREDITY AND EVOLUTION SOLVED EXERCISES QUESTIONS [Biology Term-2 CHAPTER - 13]
Q.1. What is heredity?
Ans:- Heredity refers to the transmission of characters or
traits from the parents to their offspring.
Q.2. Name the plant on which Mendel performed his
experiments?
Ans:- Garden Pea (Pisum sativum.)
Q.3. Define variation?
Ans:-Variation refers to the differences in the characters or
traits about the individuals of a species.
Q.4. Define a gene?
Ans:- Gene is a small segment of DNA on a chromosome
occupying specific position in which is a hereditary determinant or unit of a
biological function.
Q.5.Write the expanded form of DNA?
Ans:- DNA - Deoxyribonucleic Acid.
Q.6. What are the components of chromosome?
Ans:- Each chromosome is double or replicated and consists of
two thread like structures called chromatids attached to each other at
centromere.
.Each chromatid has a number of dense areas arranged linearly
which are known as chromomeres. They represent the areas of active genes.
.Internally each chromosome has two spirally coiled threads
called chromonemata embedded in matrix. These are DNA molecules.
Q.7. What is a retrovirus?
Ans:- A virus having RNA (Ribonucleic acid) as genetic
(heredity) material is called Retrovirus. For example, Human immunodeficiency
virus (HIV) is a retrovirus.
Q.8. What is sex chromosome?
Ans:- A chromosome which is associated with sex determination
is called sex chromosome.
Q.9. How is sex determined in human beings?
Ans:- Sex is determined at the time of fertilisation and the
two sexes are produced in approximately equal numbers. A human male has XY
sex-chromosomes and produces two types of sperms (heterogametic). Either with
X-chromosome or with Y-chromosome.
A human female has XX sex-chromosomes and produce ova of one
type (homogametic) all with X-chromosomes.
Parents Male Female
Gametes X Y X
Progeny XX XY
Female
(50%) Male (50%)
Q.10. What do you understand by evolution?
Ans:-Evolution is the sequence of gradual changes which takes
place in the primitive organisms over million of years in which new species are
produced.
Q.11. Define homologous organs?
Homologous organs are those organs which have the same basic
structure and developmental origin but have different functions and appearance.
Ans:- e.g., The forelimb of a frog, a bird and a man seem to
be built from the same basic design of bones, but they perform different
functions.
Q.12. Explain Darwin’s theory of evolution?
Ans:- According to Darwin’s theory of evolution:
(i) There is natural variation within any population and some
individuals have more favourable variations than others..
(ii) Population remains fairly constant even though all
species produce a large number of off springs.
(iii) This is due to ‘competition’ or struggle for existence
between same and different species.
(iv) The struggle for survival within population eliminates
the unfit individuals and those with ‘favourable variations’ survive and pass
on these variations to their progeny to continue. This is called natural
selection.
(v) The favourable variations are accumulated over a long
time period leading to the origin of a new species.
Q13. Define genetics. What is the contribution of Mendel in
this branch of biology?
Ans:- genetics is the branch of biology which deals with the
study of heredity and variation.
Contribution of Mendel : Mendel done his experiments on
garden pea(pisum sativum) and discovered the scientific principles which govern
patterns of inheritance i.e. the principle of inheritance. He explained the
contrasting characters are controlled by units which he called Factors.
Today these factors are called genes.
Q14. Where are the genes located? What is the chemical nature
of gene?
Ans:- Genes are located on chromosomes. Chemically, genes are
made of DNA(deoxy ribonucleic acid).
Q15. During which stage of cell division can chromosome be
seen? Write the features of prokaryotic and eukaryotic chromosome.
Ans:- Chromosomes can be seen during the metaphase stage
of the cell division.
FEATURES OF
PROKARYOTIC CHROMOSOME: Prokaryotes
(bacteria) have a single chromosome. The chromosome is circular and made up of
a DNA molecule associated with a few proteins.
EUKARYOTIC CHROMOSOME: Eukaryotes contain many chromosomes. Each is made up
of a DNA molecule and more number of basic proteins. The chromosomes are
not circular but rod shaped.
Q 16. Who provided the evidence of DNA as a genetic material?
Write the names of components of DNA?
Ans:- Griffith, Avery , McLeod and McCarty established that DNA
is the genetic material.
Components of DNA: A DNA molecule consists of two polynucleotide chains. Each
nucleotide consists of (a) nitrogenous base (Adenine/guanine/Thymine or
Cytosine) ,a pentose sugar(deoxyribose) and a phosphate group.
Q17.What do you understand by the double helical structure of
DNA? Who proposed this structure?
Ans:-J.D.Watson & F.H.C.Crick proposed the double helical
structure of DNA.
The important features of the model are:
i)DNA molecule consists of two polynucleotide strands forming
a double helix.
Each helical turn has a length of 3.4nm in which ten
nucleotides present.
ii)Each polynucleotide stand has a backbone of sugar and
phosphate. The nitrogenous base is attached to the sugar.
iii)The nitrogenous bases of the two stands of a double helix
form a pair with the help of hydrogen bonds. Adenine pairs with Thymine
,whereas the guanine pairs with Cytosine. Such a specific pairing of the bases
is called complimentary pairing.
A and T are complimentary to each other and G is
complimentary to C. The hydrogen bonding between the nitrogenous bases holds
the two strands together as a result of which the base pairs remains stacked
between the two strands.
This structure can be compared with the steps of a spiral
staircase.
Q18.Describe the different types of chromosomes.
Ans:- depending on the position of the centromere,a
chromosome may have either equal arms, or one long and one short arm.
Accordingly, four types of chromosomes are known :
Metacentric:It is a chromosome with the centromere near the middle and
the two arms are almost equal in length.
Sub-metacentric:In this type of chromosome the centromere is situated closer
to one end. As a result , one arm of the chromosome is long and one is slightly
short.
Acrocentric:It is the type of the chromosome which has the centromere
near the end. In this case one arm is very long and the other one is very
short.
Telocentric:In this type of the chromosome, the Centromere is situated at
the tip of the chromosome.
Q19.How many types of nitrogenous bases are present
in DNA?Name them.
Ans:-In DNA two types of nitrogenous bases are present. These
are (i)PURINES which are adenine and guanine (ii)PYRIMIDINES which are Thymine
and cytosine.
Q.20.How do embryological studies provide evidence for
evolution?
Ans:- The similarities in embryonic development reinforce the
idea of evolution from common ancestors. The sequence of embryonic development
in different vertebrates shows striking similarities. Notochord and gill clefts
appear in the embryos of all vertebrates.
Q.21. Define evolution. And Describe the contribution of Lamarck?
Ans:- Evolution is the sequence of gradual changes which
takes place in the primitive organisms over millions of years in which new
species are produced.
Contribution of Lamarck:
(i) Lamarck proposed a theory called “The Theory of
inheritance of Acquired Characters” to explain the origin and evolution of
species.
(ii) The theory was explained in his book ‘Philosophic
Zoologique.
Q.22. What are homologous organs? How do they provide
evidence in support of evolution?
Ans:- Homologous organs are those organs which have the same
basic structure and developmental origin but have different functions and
appearance.
Homologous organs support evolution:
(i) The similarities of structure and origin of organs
indicate that all vertebrates had common ancestors. For example, the forelimbs
of humans, whale and bat show structural similarities but functional
dissimilarities. Forelimbs in humans used for grasping or holding the things,
in whale for swimming and in bat for flying.
(ii) All the organs and systems of the vertebrates show
fundamental similarities i.e. homology, which indicate towards common ancestry.
Thus, homologous point that organic evolution has taken place.
Q.23. Define the following terms?
Ans:- (i) Vestigial organs: Vestigial organs are those organs,
which are rudimentary and functionless in the evolved forms but are well
developed and functional in the ancestral forms. Eg: Vermiform appendix in
human beings.
(ii) Analogous organs : Are those organs which have different
basic structure and developmental origin but have similar appearance and
perform similar functions. Eg: The wings of and insect and a bird have
different structures, but they perform the same function of flying.
Q.24. 1.
What are transgenic organisms? Which property of DNA is used as a tool in
genetic engineering?
Ans:-The organisms that contain a segment of foreign DNA are
known as transgenic organisms.The complimentary property of the nucleotides of
DNA.is the most powerful tool in genetic engineering.
Q.25. Explain how the sex of the child is determined at the
time of conception in human beings.
Ans:- Male human beings have XY sex-chromosomes and female human
beings have XX sex-chromosomes. If a sperm carrying x-chromosome fertilizes
with the ovum, then sex of the baby will be female. If a sperm carrying
y-chromosome fuses with the ovum, the sex of the baby will be male.
For more solved paper X : Biology Visit
10th Science SA-2 Chapter wise Test Papers Links
| |
very useful...
ReplyDelete