AHSEC| CLASS 12| BIOLOGY| SOLVED PAPER - 2015| H.S. 2ND YEAR
2015
BIOLOGY
(Theory)
Full Marks: 70
Pass Marks: 21
Time: Three hours
The figures in the margin indicate full marks for the questions
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PART-I (BOTANY) MARKS – 35 Page No. 1 - 4 PART-II (ZOOLOGY) MARKS - 35 Page No. 5 – 7 |
Use separate Answer scripts for
Part-I (Botany) and Part-II (Zoology)
Part-I (Botany)
1. What is embryogenesis? 1
Ans:- Embryogenesis is the process by
which a fertilized egg develops into an embryo.
2. What is GMO?
1
Ans:- GMO means genetically modified
organism. These are organisms whose DNA has been altered using genetic
engineering techniques.
3. The micro-organism used 10 produce lactic acid through
fermentation process is known as Lactobacillus. 1
4. Why is apple called a false fruit? 1
Ans:- Apples are considered false fruits
because they develop from parts of the plant other than the ovary. True fruits,
on the other hand, develop from the ovary and do not contain other floral
parts.
5. How many types of artificial asexual reproduction
found in plants? Which type of plants showing grafting? 2
Ans:-
There are four types of artificial asexual reproduction in plants:-
(i) Cutting: A stem or leaf is cut and planted
in the soil. Hormones can be used to stimulate root growth.
(ii) Grafting: A cutting of another plant is
inserted into the stem of that plant which is already rooted in the soil. The
graft tissues join with the rooted plant tissues to form a plant.
(iii) Layering: The stem of a plant is bent down
and covered with soil. Roots emerge from the covered parts of the plant.
(iv) Micropropagation: This method involves growing plants
in the laboratory. It can provide specific nutrients and media for endangered
plants.
Asexual reproduction is a type of reproduction
that does not involve the fusion of gametes or a change in the number of
chromosomes. The offspring are genetically and physically identical to the
parents.
Grafting is a type of artificial vegetative
propagation. It is successful in plants that do not reproduce sexually and do
not produce seeds, such as roses and bougainvillea. Grafting is also used as a
growth control method for fruit trees and ornamental plants such as roses and
junipers.
Or
Describe the
significance of sexual reproduction of plants.
2
Ans:- Sexual reproduction in plants is the process
by which male and female gametes combine to form a zygote. This process is also
known as fertilization.
Sexual reproduction is important for
plants because:-
(i) Provides variation: Sexual reproduction produces variable
offspring, which creates diversity and variation among populations. This
variation helps plants survive and achieve distinctiveness within the species.
(ii) Aid in adaptation: Genetic variation allows
populations to adapt to their environment.
(iii) Helps plants to spread: Sexual reproduction helps plants to
spread into new areas.
(iv) Supports evolution: Sexual reproduction supports
evolution and formation of new species.
(v) Maintains the continuity of the
species: Sexual
reproduction helps in maintaining the continuity of the species.
6. Differentiate between chemical and biological origin
of life. 2
Ans:- The chemical origin of life is the
formation of the first living cell from organic compounds. The biological
origin of life is the proliferation and variation of life forms after the first
prototype cell.
Chemical evolution is a relatively fast process
that involves the evolution of chemicals into organic molecules. Biological
evolution is a very slow process that involves the development of enzymes,
proteins, RNA, and DNA in living cells.
Or
What is meant
by geological time scale? Why is it necessary to determine the age of
fossils? 2
Ans:- The geological time scale is a system that
geologists use to organize the Earth's history into different time intervals.
It represents time based on Earth's rock record and was developed through the
study of rock layers and fossils.
The geological time scale is a table
that shows the sequence and duration of eras, periods and eras, as well as
their major forms of life. It reflects the Earth's evolutionary history, and
provides a framework for studying Earth's history and the evolution of life on
the planet.
Determining the age of fossils is
important for many reasons, including evolutionary studies. Fossils provide
essential evidence for the study of the history and evolution of life on Earth.
The age of a fossil can be
determined by measuring the ratio of the amounts of parent isotopes and
daughter isotopes into which it breaks down. This rate of radioactive decay is
defined as the half-life.
7. What is fermentation? Which micro-organism converts
sucrose into ethyl alcohol? 2
Ans:- Fermentation is a process that
occurs when microorganisms convert glucose into alcohol or lactic acid without oxygen.
This is also known as anaerobic respiration.
Yeast is a microorganism that converts sugar
into alcohol and carbon dioxide during fermentation. The conversion occurs in
the presence of an enzyme called zymase, which is naturally found in yeast.
Some bacteria, such as Zymomonas mobilis, can
also perform alcoholic fermentation.
Or
What is algal
fertilizer? How does it help in agriculture?
Ans:- Algal fertilizer, also known as algae biomass,
is a type of fertilizer made from microscopic algae. It is rich in nutrients
like nitrogen, phosphorus and potassium, which are essential for plant growth.
Algal fertilizer can be used in a variety of ways in agriculture, including as
a soil amendment, a source of bio-fertilizer, and as a feed supplement for
animals.
Algal biomass can be used as a soil
amendment to improve soil quality, increase water retention, and promote
microbial activity. Algal biomass can also be used as a biofertilizer, which
can provide essential nutrients to plants in a more sustainable and
eco-friendly way than traditional chemical fertilizers.
In addition to its benefits for
plants, algal biomass can also be used as a feed supplement for animals. Algae
are a rich source of proteins, vitamins and minerals, and can be used to
improve the nutritional value of animal feed.
8. What are the principles of bio-technology? 2
Ans:-
Some principles of biotechnology are as follows:-
(i) Isolation of DNA: This technique is essential for the
study of DNA and is important for biotechnology and forensics.
(ii) Restriction enzymes: These enzymes can precisely cut the
double strand of DNA.
(iii) Cloning: This tool allows scientists to make
exact genetic copies of living things.
(iv) Identification of DNA with
desirable genes:
This is important for the progress of biotechnology.
(v) Downstream processing: It is an important part of
industrial biotechnology that involves separating, concentrating and purifying
the target products.
Or
What are
molecular scissors? Give two examples of it.
Ans:- Restriction enzymes are also known as
molecular scissors. These enzymes cut DNA at specific ends and use ligase to
cleave the ends to the other or foreign strand.
Restriction enzymes are used in
recombinant DNA technology. They make random cuts in the DNA. Some examples of
restriction enzymes are: Eco RI, Bam HI, Bgl II, Hae II, Hind II.
9. What is genetically modified crop? Mention its
disadvantages. 2
Ans:- Genetically modified (GM) crops are
plants whose DNA has been altered using genetic engineering techniques. The
goal is to give the plant a new trait that does not occur naturally in the
species.
Some disadvantages of GM crops
include:-
(i) Disrupted gene flow: “Better” traits resulting from
engineering genes may favor an organism.
(ii) Increase in the cost of farming
(iii) Environmental effects: GM crops may release toxins into
the soil, induce pest resistance and disrupt crop biodiversity.
(iv) Allergic reactions: GM crops can cause allergic
reactions in humans.
(v) Deficiency in nutrition: GM crops may lead to deficiency in
nutrition.
(vi) Ethical concerns: There are many ethical concerns
associated with GM crops.
Or
What is the
full form of 'ELISA'? How does it help in detection of disease?
Ans:- ELISA stands for Enzyme-Linked Immunosorbent
Assay. This is a laboratory test that detects the presence of a specific
substance, such as an antibody or protein, in a sample.
ELISA is a commonly used laboratory
test to detect antibodies in the blood. Antibodies are proteins produced by the
body's immune system when it detects harmful substances, called antigens.
10. What are the major abiotic factors of habitat? 2
Ans:-
Some of the major abiotic factors of a habitat include:-
(i) Temperature: A major abiotic factor that affects
both living and non-living organisms.
(ii) Water: An essential abiotic factor for
living organisms and the environment.
(iii) Light: An important abiotic factor of
ecosystem. Light is necessary for photosynthesis, which plants use to prepare
their food.
(iv) Wind: An important abiotic factor that
affects evaporation and transpiration. Wind can also move soil, water, and
other abiotic factors.
(v) Humidity: A main abiotic factor that affects
the behaviour, fitness and distribution of animals.
(vi) Sunlight: A major element in the growth of
trees and plants.
(vii) Altitude: As altitude increases, the air
becomes colder and drier, which can affect the respiratory system of animals.
Or
Differentiate
allelopathy and antibiosis.
Ans:- Allelopathy and antibiosis are
antagonistic relationships between two organisms. However, they differ in the
following ways:-
(i) Effects: Allelopathy can have both positive
and negative effects on the relationships between organisms. Antibiosis has a
negative effect on only one organism.
(ii) Mechanism: In allelopathy members of one
species kill members of another species by secreting toxic chemicals.
Antibiosis involves useful microbes that kill harmful microbes by secreting
chemicals called antibiotics.
(iii) Target: Allelopathy mainly targets plants,
but can also affect some microorganisms. Antibioses target microorganisms
including bacteria, fungi, and some parasites.
(iv) Example: Allelopathy is displayed by plants.
Antibiosis is shown by microbes such as bacteria, fungi and some animals and
plants.
11. Discuss about the technique of hybridization. 3
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