KCET 2013 Biology Question Paper with Answer and Solution

(D) The correct answer is $D$.
$Taxon$ is a scientific term used to represent a group of organisms at any level or rank in the biological classification system.
It is a general term that can refer to any taxonomic category,such as $Species$,$Genus$,$Family$,$Order$,$Class$,$Phylum$,or $Kingdom$.

(A) The correct answer is $A$.
During the prophase $I$ of meiosis,homologous chromosomes pair up to form a structure known as a bivalent or tetrad.
Each homologous chromosome consists of two sister chromatids joined by a single centromere.
Since a bivalent consists of two homologous chromosomes,it contains a total of $4$ chromatids ($2$ from each chromosome) and $2$ centromeres ($1$ from each chromosome).

(B) The correct answer is $B$.
Electrons from excited chlorophyll molecules of photosystem $II$ ($PS$ $II$) are first accepted by phaeophytin.
Phaeophytin acts as the primary electron acceptor in the light-dependent reactions of photosynthesis.
After receiving the electrons,phaeophytin transfers them to the plastoquinone $(PQ)$ pool,which then initiates the electron transport chain.

(C) The correct answer is $C$. Oxidative decarboxylation occurs during the formation of both acetyl CoA from pyruvate and succinyl CoA from $\alpha$-ketoglutarate.
In these reactions,a carboxyl group is removed as $CO_2$,and $NAD^+$ is reduced to $NADH$.
These steps are key parts of cellular respiration,particularly in the link reaction (pyruvate to acetyl CoA) and the Krebs cycle ($\alpha$-ketoglutarate to succinyl CoA).
$1. \text{Pyruvate} + CoA + NAD^+ \longrightarrow \text{Acetyl CoA} + CO_2 + NADH + H^+$
This reaction is catalyzed by the enzyme pyruvate dehydrogenase.
$2. \alpha\text{-Ketoglutarate} + CoA + NAD^+ \longrightarrow \text{Succinyl CoA} + CO_2 + NADH + H^+$
This reaction is catalyzed by the enzyme $\alpha$-ketoglutarate dehydrogenase.

(B) The correct answer is $B$.
During the transport of carbon dioxide,bicarbonate ions $(HCO_3^-)$ are produced inside the red blood cells $(RBCs)$ and diffuse out into the plasma.
To maintain the electrical neutrality (ionic balance) of the $RBCs$,chloride ions $(Cl^-)$ move from the plasma into the $RBCs$.
This process is known as the chloride shift or the Hamburger phenomenon.

(B) The exchange of gases between the blood and the tissues occurs through the systemic capillaries.
Oxygenated blood reaches the tissues via systemic arteries,which branch into a network of capillaries.
Since the partial pressure of oxygen $(pO_2)$ is lower in the tissue cells compared to the blood in the capillaries,oxygen dissociates from oxyhemoglobin and diffuses into the tissues.
Therefore,the maximum exchange of oxygen from the blood to the cells occurs in the capillaries surrounding the tissue cells.

(A) Pure (oxygenated) blood from the lungs is carried back to the heart by the pulmonary veins,which empty into the left auricle (atrium).
From there,the blood moves to the left ventricle to be pumped to the rest of the body.

(A) $A-q, B-p, C-t, D-r$
$1$. $FSH$ (Follicle-Stimulating Hormone) stimulates the development of ovarian follicles and is involved in the process of ovulation.
$2$. $GH$ (Growth Hormone) is responsible for the normal growth and development of the body.
$3$. Prolactin is a hormone that stimulates the mammary glands to produce milk (milk secretion).
$4$. Oxytocin acts on the smooth muscles of the uterus and stimulates their contraction during childbirth, a process known as parturition.

(A) The correct answer is $A$.
Kingdom Monera consists of prokaryotic organisms,which include $Mycoplasma$,$Eubacteria$,and $Archaebacteria$.
Slime moulds are classified under Kingdom Protista because they are eukaryotic organisms.
Therefore,slime moulds do not belong to Kingdom Monera.

(D) Amphibians of plant kingdom.
Mosses (Bryophytes) and ferns (Pteridophytes) are referred to as the "amphibians of the plant kingdom".
This is because they require water for the process of fertilization, as their male gametes are motile and need a water medium to reach the female gametes.
This dependency on water for reproduction is analogous to the life cycle of amphibians in the animal kingdom.

(D) The correct answer is $D$.
In the phylum $Echinodermata$,adult animals exhibit radial symmetry,while their larval stages exhibit bilateral symmetry.
This transition in symmetry from bilateral in the larval stage to radial in the adult form is a characteristic feature of echinoderms.
In contrast,$Annelids$,$Arthropods$,and $Molluscs$ exhibit bilateral symmetry throughout their life cycles.

(D) The levels of organization in animals are classified as follows:
$1$. $A$. Organ level: $Fasciola$ (Platyhelminthes) exhibits organ level of organization.
$2$. $B$. Cellular aggregate level: $Spongilla$ (Porifera) exhibits cellular aggregate level of organization.
$3$. $C$. Tissue level: $Obelia$ (Cnidaria) exhibits tissue level of organization.
$4$. $D$. Organ system level: $Pheretima$ (Annelida) exhibits organ system level of organization.
Therefore,the correct matching is $A-q, B-r, C-s, D-p$.

(C) The correct option is $C$.
$1$. Scorpion,Spider,and Cockroach all belong to the phylum Arthropoda. $A$ characteristic feature of arthropods is the presence of a ventral solid nerve cord.
$2$. In option $A$,Sea urchin (Echinodermata) does not have jointed appendages; these are characteristic of Arthropoda.
$3$. In option $B$,Taenia (Platyhelminthes) is acoelomate and does not exhibit metameric segmentation.
$4$. In option $D$,Sea anemone (Cnidaria) exhibits radial symmetry,not bilateral symmetry.

The correct answer is $(D)$ Vinca.
The provided floral formula is: $\oplus$

(A) The correct answer is $A$.
Stomata are small pores present on the surface of leaves.
The opening and closing of these stomata are regulated by the turgor pressure changes within the $guard cells$.
When $guard cells$ become turgid, the stoma opens, and when they become flaccid, the stoma closes.
These cells are specialized epidermal cells that surround the stomatal pore.

(C) The correct option is $C$.
In the given diagram of a typical flower:
$A$ represents the Sepals (Calyx),which are the outermost whorl.
$B$ represents the Pistil (Gynoecium),which is the female reproductive part.
$C$ represents the Stamens (Androecium),which are the male reproductive parts.
$D$ represents the Petals (Corolla),which are the brightly colored parts of the flower.
Therefore,the correct sequence is $A$-Sepals,$B$-Pistil,$C$-Stamens,$D$-Petals.

(B) The correct answer is $B$.
An angiosperm embryo sac,also known as the female gametophyte,typically follows the $Polygonum$ type of development.
It consists of $7$ cells: $1$ egg cell,$2$ synergids,$3$ antipodal cells,and $1$ large central cell.
Although there are $7$ cells,there are $8$ nuclei because the central cell contains $2$ polar nuclei,while the other $6$ cells each contain $1$ nucleus.

(B) Statement $A$ is correct: Ovulation typically occurs around the $14^{\text{th}}$ day of a $28$-day menstrual cycle due to the $LH$ surge,making this the most fertile period for conception.
Statement $B$ is incorrect: Vasectomy is a surgical method of male sterilization where the vasa deferentia are cut and tied. The method used for female sterilization is called tubectomy.
Therefore,Statement $A$ is correct and Statement $B$ is incorrect.

(C) The correct answer is $C$.
Chancre (a painless ulcer) and rashes all over the body are characteristic symptoms of syphilis, which is caused by the bacterium $Treponema pallidum$.
$A$. Gonorrhoea is caused by $Neisseria gonorrhoeae$ and typically presents with genital discharge and pain during urination.
$B$. $AIDS$ is caused by the $HIV$ virus and primarily weakens the immune system, leading to various opportunistic infections.
$D$. Fever is a general clinical sign or symptom associated with many conditions and is not a specific disease characterized by chancres.

(A) . Klinefelter's syndrome.
Gynaecomastia,which is the development of enlarged breast tissue in males,is a characteristic symptom of Klinefelter's syndrome.
Klinefelter's syndrome is a genetic condition caused by chromosomal aneuploidy where males possess an extra $X$ chromosome,resulting in an $XXY$ genotype.
This condition leads to symptoms such as reduced testosterone levels,small testes,reduced fertility,and the development of female-like secondary sexual characteristics,including gynaecomastia.

(B) The correct statement is $B$.
$A$ back cross is defined as the cross of an $F_1$ hybrid with either of its parents ($P_1$ or $P_2$).
$A$ test cross is a specific type of back cross where an individual of unknown genotype (usually $F_1$ or $F_2$ generation) is crossed with a homozygous recessive parent.
Since a test cross is a subset of back crosses,it is correct to say that every test cross is a back cross,but not every back cross is a test cross.

(C) The correct answer is $C$.
Paleontology is the branch of biology and geology that deals with the study of fossil animals and plants.
It focuses on the analysis of fossils to understand ancient life forms,their structure,and their evolutionary history.

(B) $Interferons$ are protein molecules produced by virus-infected host cells.
They help in the defense against viral infections by signaling neighboring cells to enhance their antiviral defenses.
While normal cells can produce other proteins,$Interferons$ specifically come from infected cells.

(B) $EcoRI$ is a restriction enzyme isolated from the bacterium $Escherichia$ $coli$. It cuts $DNA$ at the palindromic sequence $5'-GAATTC-3'$,specifically between the $G$ and $A$ on each strand. This staggered cleavage produces single-stranded overhangs known as sticky ends,which facilitate the joining of $DNA$ fragments.