Lesson: Heredity and Evolution
Exchange
of genetic material takes place in:
(a)
Vegetative Reproduction
(b)
Asexual Reproduction
(c)
Sexual Reproduction
(d)
Budding
(c)
Two
pink coloured flowers on crossing resulted in 1 red, 2 pink and 1 white flower
progeny. The nature of the cross will be:
(a)
Double Fertilisation
(b)
Self Pollination
(c)
Cross Fertilisation
(d)
No Fertilisation
(b)
A
cross between a tall plant (TT) and short pea plant (tt) resulted in progeny
that were all tall plants because:
(a)
Tallness is the dominant trait
(b)
Shortness is the dominant trait
(c)
Tallness is the recessive trait
(d)
Height of pea plant is not governed by gene ‘T’ or ‘t’
(a)
Which
of the following statement is incorrect?
(a)
For every hormone there is a gene.
(b)
For every protein there is a gene.
(c)
For production of every enzyme there is a gene.
(d)
For every molecule of fat there is a gene
(d)
If
a round, green seeded pea plant (RRyy) is crossed with wrinkled, yellow seeded
pea plant, (rrYY) the seeds produced in F1 generation are:
(a)
Round and yellow
(b)
Round and green
(c)
Wrinkled and green
(d)
Wrinkled and yellow
(a)
In
human males, all the chromosomes are paired perfectly except one. This/this
unpaired chromosome is/ are:
(i)
Large chromosome
(ii)
Small chromosome
(iii)
Y- chromosome
(iv)
X- chromosome
(a) (i) and (ii)
(b)
(iii) only
(c)
(iii) and (iv)
(d)
(ii) and (iv)
(c)
The
maleness of a child is determined by:
(a)
The X chromosome in the zygote
(b)
The Y chromosome in the zygote
(c)
The cytoplasm of germ cell, determines the sex
(d)
Sex is determined by chance
(b)
A
zygote which has an X-chromosome inherited from the father will develop into a:
(a)
Boy
(b)
Girl
(c)
X- chromosome does not determine the sex of a child
(d)
Either boy or girl
(b)
Select
the incorrect statement:
(a)
Frequency of certain genes in a population, change over several generations
resulting in evolution.
(b)
Reduction in weight of an organism, due to starvation is genetically
controlled.
(c)
Loss-weight parents can have heavy weight progeny.
(d)
Traits which are not inherited over generations, do not cause evolution.
(b)
New species may be formed if:
(i) DNA undergoes significant changes in germ cells
(ii) Chromosome number changes in the gamete
(iii) There is no change in the genetic material
(iv) Mating does not take place
(a) (i) and (ii)
(b) (i) and (iii)
(c) (ii), (iii) and (iv)
(d) (i), (ii) and (iii)
(a)
Two pea plants one with round green seeds (RRyy)
and another with wrinkled yellow (rrYY) seeds produce F1 progeny that have
round, yellow (RrYy) seeds. When F1 plants are selfed, the F2 progeny will have
new combination of characters. Choose the new combination from the following:
(i) Round, yellow
(ii) Round, green
(iii) Wrinkled, yellow
(iv) Wrinkled, green
(a) (i) and (ii)
(b) (i) and (iv)
(c) (ii) and (iii)
(d) (i) and (iii)
(b)
A
basket of vegetables contains carrot, potato, radish and tomato. Which of them
represent the correct homologous structures?
(a)
Carrot and potato
(b)
Carrot and tomato
(c)
Radish and carrot
(d)
Radish and potato
(c)
Select
the correct statement:
(a)
Tendril of a pea plant and phylloclade of Opuntia are homologous
(b)
Tendril of a pea plant and phylloclade of Opuntia are analogous
(c)
Wings of birds and limbs of lizards are analogous
(d)
Wings of birds and wings of bat are homologous
(a)
If
the fossil of an organism is found in deeper layers of earth, then we can
predict that:
(a)
The extinction of organism has occurred recently.
(b)
The extinction of organism has occurred thousands of years ago.
(c)
The fossil position in the layers of earth is not related to its time of
extinction.
(d)
Time of extinction cannot be determined.
(b)
Which
of the following statements is not true with respect to variation?
(a)
All variations in a species have equal chance of survival.
(b)
Change in genetic composition results in variation.
(c)
Selection of variants by environmental factors, forms the basis of evolutionary
processes.
(d)
Variation is minimum in asexual reproduction.
(a)
A trait in an organism is influenced by:
(a) Paternal DNA only
(b) Maternal DNA only
(c) Both maternal and paternal DNA
(d) Neither by paternal nor by maternal DNA
(c)
Select
the group which shares maximum number of common characters
(a)
Two individuals of a species
(b)
Two species of a genus
(c)
Two genera of a family
(d)
Two genera of two families
(a)
According to the evolutionary theory, formation of
a new species is generally due to:
(a) Sudden creation by nature
(b) Accumulation of variations over several
generations
(c) Clones formed during asexual reproduction
(d) Movement of individuals from one habitat to
another
(b)
From
the list given below, select the character that can be acquired, but not
inherited:
(a)
Colour of eye
(b)
Colour of skin
(c)
Size of body
(d)
Nature of hair
(c)
The
two versions of a trait (character) that are brought in by the male and female
gametes are situated on:
(a)
Copies of the same chromosome
(b)
Two different chromosomes
(c)
Sex chromosomes
(d)
Any chromosome
(a)
Select
the statements that describe characteristics of genes:
i) Genes are specific sequence of bases
in a DNA molecule.
ii) A gene does not code for proteins.
iii) In individuals of a given species,
a specific gene is located on a particular chromosome.
iv) Each chromosome has only one gene.
(a) (i) and (ii)
(b)
(i) and (iii)
(c)
(i) and (iv)
(d)
(ii) and (iv)
(b)
In peas, a pure tall plant (TT) is crossed with a
short plant (tt). The ratio of pure tall plants to short plants in F2 is:
a) 1: 3
b) 3: 1
c) 1: 1
d) 2: 1
(c)
The number of pair (s) of sex chromosomes in the zygote of humans is:
(a)
One
(b)
Two
(c)
Three
(d) Four
(a)
The theory of evolution of species by natural
selection, was given by:
(a) Mendel
(b) Darwin
(c) Morgan
(d) Lamarck
(b)
Some dinosaurs had feathers although they could not
fly, but birds have feathers that help them to fly. In the context of evolution
this means that:
(a) Reptiles have evolved from birds.
(b) There is no evolutionary connection between
reptiles and birds.
(c) Feathers are homologous structures in both the
organisms.
(d) Birds have evolved from reptiles.
(d)
How sex of a new-born is determined in humans?
Sex of a
new born human is genetically determined i.e., genes inherited from parents
decide whether the new born will be a boy or a girl. If a father’s sperm with X
chromosome fertilizes the mother’s egg, it results in development of a girl
child. Whereas, if a sperm with Y chromosome fertilizes the egg, it results in
the development of a male child.
Do genetic combinations of a mother play a
significant role in determining the sex of a new born?
No, it does
not. Mothers have a pair of X-chromosomes. Sex of a new-born is determined by
the 23rd chromosome in the sperm. All children inherit an ‘X’
chromosome from their mothers regardless of whether they are boys or girls. So,
the genetic combination of a mother has no role in determining the sex of a new
born.
Mention three important features of fossils that
help in study of evolution.
Fossils preserved
traces of living organisms. The three important features of fossils are given
below.
(a) It helps
in determining the sequence of appearance of a particular character in a
particular group of species.
(b) It helps in establishing evolutionary traits among organisms and
their ancestors.
(c) It helps
in establishing the time period in which a particular species lived.
Why do all the gametes formed in human females have
an X chromosome?
Human
females have two X chromosomes called sex chromosomes. During gametogenesis, one
X chromosome enters each gamete. Hence all the gametes formed in human female possess
an X chromosome.
In human beings, the statistical probability of
getting either a male or a female child is 50:50. Give a suitable explanation.
A somatic cell in human male has XY chromosomes. If
one gametocyte undergoes meiosis, it produces two sperms. In which one sperm
gets X chromosome and another gets Y chromosome. Since the ratio of male
gametes containing X chromosome and those containing Y chromosome is 50:50, the
statistical probability of male or a female infant is also 50:50.
A smaller population of a species faces greater
threat of extinction than a larger population. Provide a suitable genetic
explanation.
Limited number of individuals in a species imposes extensive inbreeding,
resulting in negligible variations through successive generations. Since the
number of individuals is small, the population is always exposed to the dangers
of sudden changes in environment. In many such cases, individuals fail to cope
up with the environmental changes, therefore they become extinct.
What are homologous structures? Give an example. Is it necessary that
homologous structures always have a common ancestor?
Homologous structures have a common basic design but perform different
functions.
Example: The fore limbs of reptiles, amphibians and mammals have common
ancestor, but are variously modified to carry out different activities.
Yes, it is necessary that homologous structures always have a common
ancestor.
Does the occurrence diverse animals on Earth, also suggest
their diverse ancestry? Discuss this point in light of evolution.
No, diversity of animals on Earth does not suggest
their diverse ancestry. Animals have a vast diversity in structures on Earth
that is based on certain common characters. We can group these animals into
different groups and subgroups. For example, all animals without notochord are
grouped under invertebrates.
Given the pair of contrasting traits of the
following characters in pea plant and mention which is dominant and recessive.
(i) Yellow seed
(ii) Round seed
Green seed is the
contrasting trait of yellow seed.
Wrinkled seed is the
contrasting trait of round seed.
i.
Yellow
dominant
Green recessive
ii.
Round
dominant
Wrinkled recessive
Why did Mendel choose pea plant for his experiments?
Mendel chose pea plants for the following reasons.
(a) It is easy to grow
(b) It has short life span. This helps in conducting
many experiments in a short period.
(c) It has easily distinguishable characteristics.
(d) It has large size flowers.
(e) It undergoes self-pollination.
A woman has only daughters. Analyse the genetic situation
and provide a suitable explanation.
Birth of a male or female child depends on the
presence of X or Y chromosome in the sperm that fertilizes the egg. Therefore, the
father genetically contributes towards the birth of a girl child or a male
child.
Does geographical isolation of individuals of a
species lead to formation of a new species? Provide a suitable explanation.
Yes, geographical isolation of
individuals of a species leads to the formation of a new species. Geographical
isolation, initially imposes limitations for sexual reproduction of the
separated population, thereby leading to a gradual genetic drift.
Slowly,
the separated individuals start reproducing among themselves and generate new
variations. Continuous accumulation of those variations for a few generations
may ultimately lead to the formation of a new species.
Bacteria have a simpler body plan when compared with
human beings. Does it mean that human beings are more evolved than bacteria?
Provide a suitable explanation.
Evolution
cannot always be equated with progress or better body designs. So, it does not
mean that simple body designs are inefficient. When we take complexity of a body
design as a criterion for evolution, then human beings are more evolved than
bacteria.
On the
other hand, if we take the ability to survive in almost all kinds of habitat as
a criterion; bacteria, having a simple body design, are still the most evolved organisms
found on earth. From this perspective, bacteria appear to be more evolved than
human beings.
All human
races like Africans, Asians, Europeans, Americans and others might have evolved
from a common ancestor. Provide a few evidences in support of this view.
All human beings on this earth have the capability
to interbreed. This shows that all of them belong to the same species, and they
all show maximum number of common characters. Some of the common characters in
human beings are as follows:
·
Similar
size of the brain
·
Same
body design
·
Bipedal
locomotion
·
Hair
on body
·
Ability
to communicate using language
·
Social
behaviour
Similarity in traits indicates common ancestry for
all human beings.
Differentiate between inherited and acquired
characters. Give one example for each type.
Inherited characters |
Acquired characters |
Traits that are passed on from parents to
offspring. |
Traits that appear in an individual’s lifetime,
but cannot be transmitted to the next generation. |
Traits alter the genotype and phenotype. |
Traits that alter only the phenotype. |
Traits are the result of genetic recombination. |
Traits that are the result of individual’s
response to environmental challenges. |
Examples: Hair colour, eye colour, skin colour, seed
colour, etc. |
Examples: Muscular body, loss of a body part in an
accident, hair loss, etc. |
Give reasons why acquired characters are not
inherited.
Acquired characters appear in an individual because of his/her response
to external stimuli. These characters do not produce any change in the DNA of the
germ cells. Only those characters that have a gene for them can be inherited.
Since there is no gene for the acquired characters, they cannot be inherited.
Evolution exhibits a
greater stability of molecular structure when compared with morphological
structures. Comment on the statement and justify your opinion.
Morphological
structures can be easily seen by us. Life began as a simple form of unicellular
organisms. Gradually, it evolved into many complex organisms. Whatever
diversity we see around us, is because of the diversity in the morphological
structure such as size, form and other morphological features. Thus, it can be
said that morphological structures show least stability.
On the
other hand, molecular structures are found at the molecular level. All the
organisms are made up of same biomolecules such as DNA, RNA, protein, lipid,
carbohydrates, etc. Even though, the number of biomolecules varies from
organism to organism, their structures remain the same in every organism. Hence, it can be said that molecular
structures show greater stability when compared to the morphological
structures.
In the
following crosses write the characteristics of the progeny.
Cross |
Progeny |
(a) |
........................... ........................... |
(b) |
........................... ........................... |
(c) |
........................... ........................... |
(d) |
........................... ........................... |
(a) RRYY Round, yellow
(b) RRYY Round, yellow
RrYy
Round, yellow
RRyy
Round, green
Rryy
Round, green
rrYY Wrinkled,
yellow
rrYy
Wrinkled, yellow
rryy
Wrinkled, green
(c) rryy Wrinkled, green
(d) RrYy Round, yellow
Study the
following cross showing self-pollination in F1, and fill in the blank and
answer the question that follows:
Parents RRYY x rryy
Round, yellow wrinkled, green
F1
RrYy x
?
Round, yellow
RrYy
Round, yellow
In
question 44, what are the combinations of character in the F2 progeny? What are
their ratios?
I. Round yellow (RRYY) and (RrYy) 9
II. Round green (RRyy) and (Rryy) 3
III. Wrinkled yellow (rrYY) and (rrYy) 3
IV. Wrinkled green (rryy) 1
This can be shown by the following Punette Square:
The ratio is 9: 3: 3: 1
Give the
basic features of the mechanism of inheritance.
Characters
are controlled by genes. Each gene controls one character. There may be two or more
forms of genes. One form may be dominant over the other. These genes are
present in DNA. DNAs; in turn are present in the form of chromosomes. Every
trait is present in pairs, i.e. alleles. Out of a pair of contrasting traits,
one is present in a particular chromosome and the other in another chromosome.
This ensures that, when gametes are formed, one trait goes to one gamete and
another goes to the other one. This forms the basis of the law of segregation
as proposed by Mendel.
In his monohybrid,
cross experiment, Mendel crossed a pure-bred tall plant with a pure-bred short
plant. In F1 generation, the gene governing the tallness dominated. So, the all
the plants in F1 generation were tall. However, in F2 generation, some plants
were tall while others were short. This could be possible because of
recombination of gametes during fertilization.
Give reasons for the
appearance of new combinations of characters in the F2 progeny.
Appearance
of a new combination of characters in F2 progeny can be explained by
illustrating dihybrid cross as was carried out by Mendel.
During the dihybrid
cross, Mendel crossed the pure bred of tall plants having round seeds with pure
bred of short plants having wrinkled seeds. It was observed that all the F1
generation plants were tall with round seeds. This indicated that the traits of
tallness and round seeds were dominant. However, genes for recessive traits
were present in all the plants.
Later, the self-breeding
of F1 generation seeds yielded F2 generation. The F2 generation plants had the
characters of tall with round seeds (9 plants), tall with wrinkled seeds (3
plants), short with round seeds (3plants) and short with wrinkled seeds (1
plant). The tall-wrinkled seeds and short-round seeds were the new combination,
which developed only when the traits were inherited independently.