Class XI – Biology – Paper – 1

Ans. a) Tigon and liger

Ans. a) Nephron

Ans. b) Silicon

Ans. b) Ventral surface

Ans. a) Pleura

Ans. a) PEP carboxylase

Ans. a) No urea

Ans. d) Cutaneous respiration

Ans. b) Meristematic region

Ans. a) Naked seeds

Ans. d) 20.83%

Ans. b) Higher pH

Ans. c) A is true but R is false.

Ans. b) Both A and R are true but R is not the correct explanation of A.

Ans. c) A is true but R is false.

Ans. b) Both A and R are true but R is not the correct explanation of A.

Ans. In gymnosperms, vessel elements are not present in xylem, whereas, these are main constituents in angiosperms. In the phloem of gymnosperms, companion cells are not associated with the sieve elements. In angiosperms, companion cells are associated with the sieve elements of phloem.

Ans. When breathing takes place by diffusion through the skin, it is called cutaneous respiration. When breathing takes place through the lungs, it is called pulmonary respiration. When a frog is underwater, it breathes by cutaneous respiration. When a frog is on land, it breathes by pulmonary respiration.

Ans.

Ans. A taxon is a particular level of hierarchy in the system of classification of living beings. The following figure gives taxa at different hierarchical levels:

Kingdom

Phylum

Class

Order

Family

Genus

Species

Ans. It is due to photorespiration. With an increase in temperatures as on a hot summer day, the affinity of RuBP carboxylase for CO₂ reduces. It increases for O2. Therefore, more and more photosynthetically fixed carbon is lost by photorespiration.

Ans. Girdling experiments cannot be done in monocots. The stem of monocot has vascular bundles scatter all over the width of the stem. Hence, we cannot reach a specific band of phloem for girdling.

Ans. Bryophytes commonly grow in moist, shaded areas in hills. These are also called amphibians of the plant kingdom because, these can live in soil, but are dependent on water for sexual reproduction.

Some bryophytes grow in diverse habitats, such as

i. Aquatic, e.g. Riccia, Ricciocarpus, Riella

ii. Epiphyte, e.g. Radula, Dendroceros

iii. Saprophyte, e.g. Buxbaumia, Cryptothalius

iv. Dry habitats, e.g. Polytrichum

v. Deserts, e.g., Tortula desertorum

vi. Dry rocks, e.g., Porella

Ans. The amphibians are adapted to dual/ double mode of life that is on land as well as in water called amphibians animals. Adults move on land by the limbs and breath by lungs. There are no marine forms. Aquatic forms e.g. Newt and Salamanders have gills. Frogs and toads are terrestrial. Toad occurs on dry land but the frog is found near water in marshy zones. Tree frogs like Hyla and Rhacophorus are arboreal (live on the trees). They do not have a tail but adhesive discs on toes and web, frog produces in water.

Ans.

Ans. A bioassay means “the evaluation of the effect of a substance on a living organism under controlled conditions. ” Two bioassays used to examine auxin activity in plants are the following:

a. The avena Curvature Test and

b. Root Growth Inhibition Test.

Ans. Abscisic acid (ABA): It is a phytohormone that acts antagonist to gibberellins. Gibberellin was initially extracted from the fungus named Gibberella fujikuroi. Two bioassays of this growth hormone are the following:

a. Shoot elongation is some dwarf stems and

b. Barley Endosperm test.

Ans. The different parts of cranial bones are as follows: 

1. A- FRONTAL

2. B-PARIETAL

3. C-TEMPORAL

4. D-OCCIPITAL

5. E-ETHMOID

Ans. The mandible is the only movable bone in the skull of the man.

Ans. On the basis of the presence or absence of a red pigment called myoglobin, the skeletal muscles are classified into red and white muscles.

Ans. The normal activities of the heart are intrinsically regulated, i.e., autoregulated by the specialised muscles, (nodal tissue). Thus, the heart is known as a myogenic heart. 

The neurogenic heartbeat is initiated by a nerve impulse, e.g., annelids and most arthropods. The rate of its formation and conduction is regulated by the following

i. Neural Regulation: In medulla oblongata, a special neural centre is present, which can moderate, the cardiac function through the Autonomic Nervous System (ANS).

ii. Hormonal Regulation: Adrenaline and noradrenaline hormones secreted by the medulla of adrenal gland has a significant role in regulating heartbeat and thus increasing the cardiac output. The noradrenaline accelerates the heartbeat, while adrenaline does this function at the time of emergency.

Ans. Hypertension is another name for high blood pressure which is the force exerted by the blood against the walls of the blood vessels. The pressure depends on the work being done by the heart and the resistance of the blood vessels.

Some of its Causative factors are:

i. Age: The risk of high blood pressure increases as a person becomes older because the blood vessels become less flexible.

ii. Ethnic background: African-American people have a higher risk of developing hypertension than other people. Hypertension also presents more severely in African-American people and is less responsive to certain medications.

iii. Obesity and being overweight: People who are overweight or have obesity are more likely to develop high blood pressure.

Ans. It is representing impulse conduction through an axon.

Ans. Na+ moves inside the membrane and polarity of the membrane is reversed at point A.

Ans. The potential difference at point A is known as the action potential.

Ans. In basidiomycetes asexual spores are not found, vegetative reproduction occurs by fragmentation, and sexual organs are absent.

Ans. i. Aquatic habitats

ii. On decaying wood

Ans. a) Ascomycetes are commonly known as sac-fungi as they are produced in a sac-like structure known as ascus.

b) Dikaryon formation is the characteristic feature of ascomycetes and basidiomycetes.

Ans. Agaricus

Agaricus is a fleshy saprophytic fungus with over 300 species and contains both edible and poisonous species. It is found in wet and damp climates. It grows on wood and in humus-rich soil.

Ans. Rhizome – Ginger, turmeric. Banana

Bulb – Tulips, Lilies, Daffodils, Onion, Garlic

Corm – Colocasia, Yam, Saffron

Tuber – Potato, Artichokes

Ans. ii. It has nodes and internodes. Such nodes and internodes are not found in the roots.

Ans. iii. Modified stem in the potato is underground and it becomes swollen because food gets accumulated to form tubers.

Ans. No. Many different parts of plants, like the stem, leaves and fruits, get modified to act as underground structures that can perform functions other than those of roots.

Ans. A pair of homologous chromosomes are genetically different because in a set of homologous chromosomes, one of the chromosomes belongs to the male parent and the other comes from the female parent. Therefore, one of a pair will contain paternal genes and the other will contain maternal genes.

However, a pair of sister chromatids are genetically identical before crossing over as the chromatids are formed from the replication of DNA during the ‘S’ phase of interphase. DNA replication ensures that the DNA content is doubled with identical genes being copied from the original DNA. Therefore, there is no genetic variation because there is no exchange of genetic material between sister chromatids.

If crossing over occurs, then it would be possible for some genes to be exchanged between the chromatids of homologous chromosomes that have chiasmata, thus leading to genetic variation.

Ans. Meiosis is called reduction division because the number of chromosomes in daughter cells becomes half of the number of chromosomes in mother cells. In spite of this, meiosis enables the conservation of specific chromosome number of each species. In fact, has there been no meiosis, organisms would not have been able to evolve to sexual mode of reproduction. We know that fertilization involves fusion of male and female gametes. Thus, zygote gets the chromosome pool from two cells and the number of chromosomes in a zygote becomes double that of the gametes. To ensure conservation of specific chromosome number after fertilization, it is necessary that the gametes should have half the number of chromosomes compared to what it is in somatic cells.

Ans. Electron Transport System (ETS): The metabolic pathway by which the electrons passes from one carrier to another is known as the electron transport system. It is operative in the inner mitochondrial membrane of mitochondria. The electrons from NADH produced in the mitochondrial matrix during the citric acid cycle are oxidised by an NADH dehydrogenase (Complex I). Electrons are then transferred to Ubiquinone that receives reducing equivalents via FADH, {generated during oxidation of succinate) by the activity of Succinic dehydrogenase (Complex II) in TCA. Reduced ubiquinone is oxidised with the transfer of electrons to cytochrome V via Cytochrome V complex (complex III). Cytochrome V acts carrier for transfer of electrons between complex III and complex IV. Complex IV refers to cytochrome c oxidase complex having cytochromes a and centres.

Ans. The energy released during the electron transport system is utilized in synthesizing ATP with the help of ATP synthase (complex V). This complex consists of two major components, F1 and F0. The F1 headpiece is a peripheral membrane protein complex and contains the site for synthesis of ATP from ADP and inorganic phosphate. F0 is an integral membrane protein complex that forms the channel through which protons across the inner membrane. The passage of protons through the channel is coupled to the catalytic site of the F1 component for the production of ATP. For each ATP produced, 2H+ passes through F0 from the intermembrane space to the matrix down the electrochemical proton gradient.

Ans. Structure of Plasma Membrane: Fluid mosaic model of the plasma membrane was suggested by S. Singer and G. Nicholson in 1972. According to this model, the lipids and proteins are arranged in a mosaic fashion. The matrix is the highly viscous fluid of two layers of phospholipids having two types of protein molecules-extrinsic and intrinsic proteins. The phospholipids layer is bimolecular and their hydrophilic ends are pointed towards top and bottom respectively. Peripheral 0extrinsic) proteins are superficially arranged on either side and can be easily separated. They have enzymatic properties and also make membrane as selectively permeable. Integral (intrinsic) proteins are tightly held in place by strong hydrophilic or hydrophobic interactions or both are difficult to remove from the membranes.

Ans. Prokaryotic Cells. In prokaryotic cells nuclear membrane is absent. It means that genetic materials are without an envelope. Cell lumen is filled with a fluid called cytoplasm. Cytoplasm contains ribosomes as well. Bacteria, and blue green algae are prime examples of prokaryotes. Cell Envelope. Most prokaryotic cells, particularly the bacterial cells, have a chemically complex cell envelope. The cell envelope consists of a tightly bound three layered structure i.e., the outermost glycocalyx followed by the cell wall and then the plasma membrane. Although each layer of the envelope performs distinct function, they act together as a single protective unit. The plasma membrane is semi-permeable in nature and interacts with the outside world. This membrane is similar structurally to that of the eukaryotes. A special membranous structure is the mesosome which is formed by the extensions of plasma membrane into the cell. These extensions are in the form of vesicles, tubules and lamellae. They help in cell wall formation, DNA replication and distribution to daughter cells. They also help in respiration, secretion processes, to increase the surface area of the plasma membrane and enzymatic content. In some prokaryotes like cyanobacteria, there are other membranous extensions into the cytoplasm called chromatophores which contain pigments.