Chapter
9 Heredity and Evolution solved Questions for slow lerner
Very short answer type Question
1) Name the scientist who proposed the
theory of natural selection.
Ans- Charles Darwin.
2) What is micro-evolution?
Ans-Evolution on a relatively small scale
3) Write the expended form of DNA.
Ans-Doxyribo Nucleic Acid
4) Name two human traits which show
variation.
Ans- Colour of eyes and height of an individual.
5) What type of reproduction give rise to
more number of successful variation?
Ans- Sexual reproduction.
6) What is the basis of evolution?
Ans-Selection of variants by environmental factors forms
the basis of evolution.
7) Older fossils are found closer to the
surface-True or False.
Ans- False.
8) What will be the sex of a child who inherit Y
Chromosome from his/her father?
Ans- The sex of the child will be boy.
9) If a trait A exists in 10% of 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?
Ans- Trait B
10) What are fossils?
Ans- Fossils are all the preserved traces or remains of
living organisms of geological past.
Short Answer Type Questions (2 Marks )
1) Differentiate between homologous organs
and analogous organs.Give one example of each.
Ans- Homologous organs have similar basic structure.These
may look different and may perform different functions.e.g.- fore limb of man
and flipper of a whale.
Analogous organs have different basic structure.These
look alike and perform same functions.e.g.- wings of birds and wings of insects.
2) How the study of fossil is considered
significant?
Ans- The study of fossil is considered significant
because-
(i) Fossils
provide direct evidence of past life.
(ii) These
provide convincing proof of organic evolution.
3)
How will you determine the age of fossils?
Ans- The age of fossils can be determined by two ways-
(i) If we
dig into the earth and start finding fossils, it can be assumed that the
fissils closer to the surface are more recent to those found in deeper layers.
(ii) By
detecting the ratio of different isotopes of the same element in the fossil
materials.
4) How does the creation of variations in a
species ensure survival?
Ans- The creation of variations in a species enable them
to adopt according to the changes and the new needs. Thus, they will enable the
survival of the species.
5) Can the wing of a butterfly and the wing
of a bat be considered homologous organs? Why or why not?
Ans- No, the wing oe a butterfly and the wing of a bat
cannot be considered homologous organs they have a common function for flyig
but their origin and structure are not
common . So they are analogous organ.
6) Will geographical isolation be a major
factor in the speciation of a
self-pollinating plant species? Why or why not?
Ans- No, because, new genes do not enter in the
population and no species is formed.Hence, there is a little variation
possible.
7) Explain the importance of fossils in
deciding evolutionary relationships.
Ans- 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
relationships.
8) How does Mendel’s experiment
show that traits may be dominant or recessive?
Ans- Mendel selected and crossed tall pea
plant with dwarf pea plant . The F1 progeny had Tt genotype but the
plant was tall. This shows that T is dominant and t is recessive.
(9) Dead remains of two organisms A and B
were buried. Later , only B's fossils were found , but not A's. Give reasons
Ans: Animal A must not have got preserved or must have
have got fully decomposed by the process of anaerobic bacteria. The other
reason could be that it must have moved away to some other places by the action
of wind or rains etc.
10) Do all variations in a particular
species have equal chances of survival in an environment?
Ans: No, all variations in a particular species do not
have equal chances for survival. The variations which are beneficial for the
species, that is, which help in the better survival of the species have a
better survival as compared to the other variations.
Short Answer Type Questions (3Marks)
1) How is the sex of a new born individual
determined?
Ans- Sex is deternined at the time of fertilisation. A
human male has XY sex chromosome and
produces two types of sperms, either
with X- chromosome or with Y- chromosome.
A human female has XX- chromosome and produce
ova of one type. If the sperm containing X chromosome fuses with ovum , the
individual will be girl and the sperm containing Y chromosome fuses with ovum,
the individual will be boy.
2) What is sex chromosome? Name the two types of sex chromosomes. Mention the chromosomes present in male and female .
Ans- The
chromosome which determine the sex of a person are called sex chromosome.
The two types of sex chromosomes are X chromosome and Y
chromosome.
Sex chromosomes in male -- XY
Sex chromosomes in females -- XX.
3) Explain with an example how traits get
expressed?
Ans- Gene is made
up of a segment of DNA which provide information for protein. Protein is needed
for biochemical process. If the proteins work efficiently,the traits get
expressed in better way.
For erxample, the plant height depends onthe amount of
growth hormone released by protein. If the protein is efficient more growth
hormone will be released and plant will be taller.But tf the protein in
inefficient the plant will be shorter. Thus,
genes control the traits.
4)
Describe the human evolution.
Ans- All human beings belong to a single species that
evolved in Africa.
Few thosand years ago some ancestors left Africa while
other stayed back.
The residents spread across Africa and the migrants
spread acrossthe planet from Africa to West Asia , Central Asia,
Eurasia, South asia, Indonesia, Australia and America.
They went forwards and backwards with groups separating
from each other, or sometime comong together.
Like all other vspecies, they were also living their lives to the best of thiir
ability.
5) Discuss law of segregation
or purity of gametes.
Ans- Both factors or traits are present in pairs and
during gamet formation, the two factors segregate and one gamete is pure for
one character only.After fertilization one trait from male and other trait from
female fuses to restore the paired feature in zygote.
6) What is speciation? How it occurs?
Ans- Origin of new species from existing one, is called
speciation. It nay occur due to the following reasons- Due to
mutation Due to
natural selection.
7) Why are traits acquired during the
lifetime of an individual not inherited?
Ans- Only the traits which are passed on to the DNA of
germ cells are inheritedto the progeny of the organisms reproducing sexually.
Traits acquired during lifetime do not pass on to the DNA of germ cells and
they are not inherited.
8) Who was Mendel? Why was he called the
father of ganetics?
Ans- Gregor Johann Mendel was an Australian geneticist.
he sowed the garden pea and fond flowers of different colours.He formulated the
law of heredity by his experiments. His law gave the base for futher study of
genetics. Threrfore, he was called the father of Genetics.
9).(a) Why Mendel selected garden pea plant
for his experiments. List a reason
(b)What are recessive and dominant genes?
Ans- (a) Mendel selected garden pea plant for his
experiments as these can be self pollinated.
(b) Recessive
genes are not able to express but dominating genes express
10) What is genetics? State any two factors that could lead
to the rise of new species.
Ans: Genetics
is a field of biology that deals with the study of genes, heredity and
variation of different organisms.
Two factors
that could give rise to new species
includes:
1.
Geographical isolation of individuals of a particular population into two or
more groups.
2. Genetic
drift.
11) When is a recessive trait capable of expressing itself?
Write its expression with respect to height of plant (Genotype).
Ans: A recessive trait can be defined as the trait which
is expressed only when the recessive alleles are present in a homozygous
condition, which means that the individual has both the alleles as recessive
alleles.
In pea plant, short plant height is the recessive trait.
It is expressed when the individual plant has both the alleles as 't'. So the
genotype of a plant with short height will be tt.
12) When a pesticide is sprayed on a
population of insects,all insects do not get killed but few of them survive. Give reason.
Ans When a pesticide is sprayed on a field most of the
insects are killed because they are sensitive to the pesticide. A few of the
insects survive because they have variations which made them resistant against the
pesticide, such that the pesticide has no effect on these insects.
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