Structural Organization in Animals and Plants - Class 11 Biology Answers

Question: Which type of plant tissue is responsible for primary growth, leading to an increase in length?

Correct Answer: Apical meristem

Question: Which of the following is a modification of the stem for storage?

Correct Answer: Tuber

Question: Which type of inflorescence has the main axis terminating in a flower, thus limiting further growth?

Correct Answer: Cymose

Question: The vascular tissue in plants responsible for the transport of water and minerals is:

Correct Answer: Xylem

Question: Which of the following is NOT a simple permanent tissue? Correct Answer: Xylem

Question: In dicot stems, the vascular bundles are arranged in a ring. What is their arrangement in monocot stems?

Correct Answer: In a scattered manner

Question: Which part of the flower develops into the fruit after fertilization?

Correct Answer: Ovary

Question: Which animal tissue is responsible for forming the lining of body cavities, ducts, and surfaces?

Correct Answer: Epithelial tissue

Question: Which of the following is a characteristic feature of adipose tissue?

Correct Answer: Specialized for fat storage.

Question: The type of muscle tissue found in the walls of internal organs like the stomach and intestines is:

Correct Answer: Smooth muscle

Question: Which part of the cockroach's digestive system is responsible for grinding food particles?

Correct Answer: Gizzard

Question: The respiratory system of a cockroach involves a network of tubules called:

Correct Answer: Trachea

Question: Which type of plant root is characterized by a single prominent main root with smaller lateral roots?

Correct Answer: Tap root

Question: The outermost protective layer of a plant's stem or root is called the:

Correct Answer: Epidermis

Question: What is the function of companion cells in the phloem?

Correct Answer: Maintaining the pressure gradient in sieve tubes

Question: Which type of connective tissue forms tendons and ligaments? Correct Answer: Dense regular connective tissue

Question: The absence of a cuticle on leaves typically indicates adaptation to which environment?

Correct Answer: Aquatic environment (submerged plants)

Question: Which type of epithelial tissue is characterized by flattened, scale-like cells, ideal for diffusion?

Correct Answer: Squamous epithelium

Question: In a cockroach, the blood is pumped into the hemocoel by the: Correct Answer: Heart

Question: The reproductive system of a female cockroach includes a large ootheca, which is a structure for:

Correct Answer: Egg capsule formation

 

Part A: Plants

Short Questions (2-3 Marks)

Question: Differentiate between tap root system and fibrous root system. Answer:

Tap Root System: Develops from the radicle of the embryo. It consists of a single prominent main root (tap root) that grows vertically downwards, from which several smaller lateral roots branch out. Examples: Dicotyledonous plants like mustard, pea, carrot.

Fibrous Root System: Develops from the base of the stem. It consists of a cluster of slender, adventitious roots of more or less equal size that spread out in the soil. There is no prominent main root. Examples: Monocotyledonous plants like wheat, rice, maize.

Question: What are stipules? Mention their function with an example of modification.

Answer: Stipules are small, leaf-like appendages typically found at the base of the petiole (leaf stalk). Their primary function is to protect the young leaf or bud. In some plants, they get modified for specific functions. For example, in Smilax, stipules are modified into tendrils for climbing.

Question: Name the three basic tissue systems in flowering plants and state their primary functions.

Answer:

Epidermal Tissue System: Forms the outermost protective covering of the plant body. It protects against water loss, mechanical injury, and pathogen invasion.

Ground Tissue System: Constitutes the bulk of the plant body, filling the region between the epidermis and vascular bundles. It is involved in photosynthesis, storage, and support.

Vascular Tissue System: Comprises xylem and phloem. It is responsible for the transport of water and minerals (xylem) and food (phloem) throughout the plant.

Question: Define phyllotaxy. Describe the alternate type of phyllotaxy with an example.

Answer: Phyllotaxy is the pattern of arrangement of leaves on the stem or branch. In alternate phyllotaxy, a single leaf arises at each node in an alternate manner. This arrangement ensures that each leaf receives maximum exposure to sunlight. Examples: China rose, mustard, sunflower.

Question: Differentiate between racemose and cymose inflorescence based on the growth of the main axis.

Answer:

Racemose Inflorescence: The main axis (peduncle) continues to grow indefinitely, and the flowers are borne laterally in an acropetal succession (youngest flowers at the apex, oldest at the base). The terminal bud remains vegetative. Examples: Radish, mustard.

Cymose Inflorescence: The main axis (peduncle) terminates in a flower, thus limiting its growth. The flowers are borne in a basipetal succession (oldest flower at the apex, youngest at the base). Examples: Solanum, jasmine.

 

Long Questions (5-6 Marks)

Question: Describe the internal structure of a dicotyledonous root.

 

Answer: The internal structure of a dicotyledonous root, in a transverse section, shows the following distinct regions:

Epidermis (Epiblema): The outermost single layer of thin-walled, parenchymatous cells. Some epidermal cells elongate to form unicellular root hairs, which absorb water and minerals. The epidermis lacks stomata and cuticles.

Cortex: Lies internal to the epidermis and is made up of several layers of thin-walled parenchymatous cells with intercellular spaces. Its primary function is food storage (e.g., starch).

Endodermis: The innermost layer of the cortex, consisting of a single layer of barrel-shaped cells without intercellular spaces. The radial and tangential walls of endodermal cells have suberin depositions called Casparian strips, which regulate the movement of water and solutes into the vascular cylinder.

Pericycle: A layer of thick-walled parenchymatous cells located just inside the endodermis. It is responsible for the formation of lateral roots and sometimes the secondary cambium.

Vascular Bundles: Radial arrangement, meaning xylem and phloem bundles are separate and arranged on different radii. Typically, there are 2 to 6 xylem and phloem patches (diarch to hexarch condition). Xylem is exarch (protoxylem towards the periphery, metaxylem towards the center).

Conjunctive Tissue: Parenchymatous cells that lie between the xylem and phloem bundles.

Pith: Small or absent in dicot roots, located at the center, and made of parenchymatous cells.

Question: Explain the modifications of stem with suitable examples.

 

Answer: Stems can be modified to perform various functions other than their primary functions of support and conduction. These modifications are broadly categorized as:

Underground Stem Modifications (for perennation and storage):

Rhizome: Horizontal, underground stem with nodes, internodes, scales, and adventitious roots. Stores food and helps in vegetative propagation. Examples: Ginger, Turmeric.

Tuber: Swollen, fleshy tips of underground branches, storing food (starch). Has "eyes" (nodes) that can sprout. Example: Potato.

Corm: Compressed, vertical, underground stem, growing annually. Stores food and has distinct nodes and internodes. Examples: Colocasia, Gladiolus.

Bulb: Highly condensed discoid stem, bearing fleshy scale leaves (storing food) and adventitious roots. Example: Onion, Garlic.

Sub-aerial Stem Modifications (for vegetative propagation and spreading):

Runner: Slender, prostrate branch with long internodes, creeping on the ground. Roots develop at nodes. Example: Grass, Oxalis.

Stolon: Slender lateral branch arising from the base of the main stem, growing upwards and then arching downwards to touch the ground, forming a new plant. Example: Mint, Jasmine.

Offset: Short, thick, lateral branch, typically found in aquatic plants, similar to a runner but with shorter internodes. Example: Pistia, Eichhornia (water hyacinth).

Aerial Stem Modifications (for support, protection, photosynthesis):

Stem Tendril: Slender, spirally coiled structures arising from axillary buds, helping the plant to climb. Examples: Gourd (cucumber, pumpkin), Grapevines.

Thorn: Hard, sharp, pointed structures arising from axillary buds, protecting the plant from Browse animals. Examples: Citrus, Bougainvillea.

Phylloclade: Flattened or cylindrical green stems, typically found in xerophytes, that perform photosynthesis (since leaves are reduced or absent). Example: Opuntia (flattened), Euphorbia (cylindrical).

Cladode: A phylloclade with one or two internodes, often resembling a leaf. Example: Asparagus, Ruscus.

Question: Describe the structure of a typical flower with the help of a well-labelled diagram (diagram not required in answer, only description). Answer: A typical flower is a modified shoot meant for sexual reproduction. It consists of a condensed axis called the thalamus or receptacle, on which various floral organs are arranged in whorls. These organs are:

Calyx: The outermost whorl, composed of sepals. Sepals are typically green and leaf-like, protecting the flower in its bud stage. They can be free (polysepalous, e.g., mustard) or fused (gamosepalous, e.g., cotton).

Corolla: The second whorl, made up of petals. Petals are usually brightly colored and scented to attract pollinators. They can be free (polypetalous, e.g., rose) or fused (gamopetalous, e.g., sunflower).

Androecium: The male reproductive whorl, consisting of stamens. Each stamen comprises:

Filament: A slender stalk.

Anther: A bilobed structure containing pollen sacs, where pollen grains (male gametes) are produced.

Gynoecium (Pistil): The female reproductive whorl, located at the center of the flower. It consists of one or more carpels. Each carpel (or pistil) typically has three parts:

Ovary: The swollen basal part containing ovules (which develop into seeds after fertilization).

Style: A slender stalk connecting the ovary to the stigma.

Stigma: The receptive tip that receives pollen grains.

Flowers can be complete (all four whorls present) or incomplete, and can be unisexual (having only androecium or gynoecium) or bisexual (having both).

Part B: Animals (Cockroach Focus)

Short Questions (2-3 Marks)

Question: What are the four primary types of animal tissues? Briefly state their main functions.

Answer:

Epithelial Tissue: Covers body surfaces, lines internal organs and cavities. Functions in protection, secretion, absorption, and excretion.

Connective Tissue: Supports and binds other tissues, transports substances, and stores energy. Examples include bone, cartilage, blood, adipose tissue.

Muscular Tissue: Responsible for movement. Three types: skeletal (voluntary), smooth (involuntary), and cardiac (involuntary, heart).

Nervous Tissue: Transmits electrical signals (nerve impulses) to coordinate and control body activities. Composed of neurons and neuroglia.

Question: Describe the function of Malpighian tubules in cockroaches.

Answer: Malpighian tubules are the main excretory organs in cockroaches (and other insects). They are thin, filamentous, yellow structures that open into the hindgut. They absorb nitrogenous waste products (primarily uric acid) and excess water from the hemolymph and then discharge them into the alimentary canal for elimination along with feces. This process helps in osmoregulation and excretion.

Question: What is the function of the gizzard (proventriculus) in the digestive system of a cockroach?

Answer: The gizzard, also known as the proventriculus, is a part of the foregut in the cockroach. It has an outer layer of thick circular muscles and an inner cuticle forming six highly chitinous plates (teeth). Its function is to grind the food particles into finer pieces, aiding in mechanical digestion, before the food enters the midgut.

Question: Briefly explain how respiration occurs in a cockroach.

Answer: Respiration in a cockroach is direct and occurs through a network of tracheal tubes. These tubes open to the outside through 10 pairs of small pores called spiracles, located on the lateral sides of the body (2 pairs on the thorax, 8 pairs on the abdomen). Air enters and exits through the spiracles, diffusing directly into the tracheae and then into finer tracheoles, which deliver oxygen directly to the body cells, and collect carbon dioxide. This system bypasses the circulatory system for gas exchange.

Long Questions (5-6 Marks)

Question: Describe the different types of epithelial tissues based on their structure and location, with an example for each.

 

Answer: Epithelial tissues are broadly classified based on the number of cell layers and the shape of the cells.

Based on Number of Cell Layers:

Simple Epithelium: Composed of a single layer of cells. Its primary functions are absorption, secretion, diffusion, and filtration.

Squamous Epithelium: Single layer of flattened, irregular cells with irregular boundaries. Appears like tiles on a floor.

Location: Walls of blood vessels, air sacs of lungs, lining of coelom.

Function: Filtration (glomerulus), diffusion (alveoli), formation of a smooth lining.

Cuboidal Epithelium: Single layer of cube-like cells.

Location: Ducts of glands (e.g., salivary glands), tubular parts of nephrons, thyroid follicles.

Function: Secretion and absorption. In some regions (e.g., kidney tubules), it provides mechanical support.

Columnar Epithelium: Single layer of tall and slender cells with nuclei usually at the base.

Location: Lining of stomach, intestine, gall bladder.

Function: Secretion (mucus, digestive enzymes) and absorption. If they bear cilia (ciliated columnar), they help in moving particles or mucus in a specific direction (e.g., bronchioles, fallopian tubes).

Pseudostratified Epithelium: Appears multilayered but is actually a single layer of cells of different heights, with nuclei at different levels. All cells touch the basement membrane. Often ciliated and secretes mucus.

Location: Trachea, large bronchi.

Function: Trapping and moving mucus/particles.

Compound (Stratified) Epithelium: Composed of two or more cell layers. Primarily protective.

Location: Skin (epidermis), lining of buccal cavity, pharynx, esophagus.

Function: Provides protection against mechanical and chemical stresses. Can be keratinized (e.g., skin) or non-keratinized (e.g., buccal cavity).

 

Question: Elaborate on the circulatory system of a cockroach.

Answer: The circulatory system of a cockroach is of the open type, meaning the blood (hemolymph) does not flow within closed vessels but rather circulates in open spaces or sinuses within the body cavity.

Hemolymph: The circulatory fluid is called hemolymph. It is colorless and lacks respiratory pigments (like hemoglobin), so it does not play a role in oxygen transport. It contains plasma and hemocytes (phagocytic cells). Its primary functions include transporting nutrients, hormones, and waste products, and providing hydrostatic pressure.

Heart: The heart is an elongated, muscular, tubular structure located dorsally along the midline of the thorax and abdomen. It consists of 13 segmentally arranged, funnel-shaped chambers. Each chamber has a pair of ostia (small, slit-like openings) on its lateral sides, which allow hemolymph to enter the heart from the surrounding pericardial sinus.

Aorta: The anterior-most chamber of the heart continues forward as a narrow tube called the anterior aorta, which opens into the head sinus.

Sinuses (Hemocoel): The entire body cavity of the cockroach is a hemocoel, divided into three main sinuses by two horizontal membranes (dorsal and ventral diaphragms):

Pericardial Sinus: Dorsal-most, surrounds the heart.

Perivisceral Sinus: Middle, surrounds the visceral organs (digestive tract).

Perineural Sinus: Ventral-most, surrounds the ventral nerve cord.

Circulation Pathway:

Hemolymph from the hemocoel enters the heart chambers through the ostia when the heart relaxes (diastole).

During contraction (systole), the ostia close, and the hemolymph is pumped anteriorly through the successive chambers and out through the anterior aorta into the head sinus.

From the head sinus, the hemolymph flows posteriorly into the perivisceral and perineural sinuses, bathing the organs directly.

Muscular contractions of the body wall and diaphragms help in the movement of hemolymph.

Finally, the hemolymph re-enters the pericardial sinus and then the heart through the ostia, completing the cycle.

The open circulatory system is less efficient than a closed system for rapid transport but is sufficient for the metabolic needs of insects, especially since oxygen is delivered directly by the tracheal system.

 

Question: Describe the male reproductive system of a cockroach.

 

Answer: The male reproductive system of a cockroach is well-developed and consists of a pair of testes, vasa deferentia, an ejaculatory duct, accessory reproductive glands (mushroom gland and phallic gland), and external genitalia (phallomeres).

Testes: A pair of three-lobed, whitish, flattened structures located laterally in the 4th-6th abdominal segments. They are responsible for producing spermatozoa.

Vasa Deferentia: From each testis, a thin, short tube called the vas deferens arises. These two vasa deferentia join in the middle to form a common ejaculatory duct.

Ejaculatory Duct: A common median duct that extends posteriorly and opens to the outside through the male gonopore, which is located ventral to the anus.

Accessory Reproductive Glands:

Mushroom Gland (Utricular Gland): A large, white, mushroom-shaped gland located at the junction of the vasa deferentia and ejaculatory duct. It consists of two types of tubules:

Longer peripheral tubules: Secrete a nourishing fluid for spermatozoa.

Shorter central tubules: Form the inner layer of the spermatophore (a capsule containing spermatozoa).

Phallic Gland (Conglobate Gland): A long, tubular, accessory gland located ventral to the ejaculatory duct. Its secretion forms the outermost layer of the spermatophore.

Spermatophore: The spermatozoa are stored in seminal vesicles, which are part of the mushroom gland, and are later glued together in the form of bundles called spermatophores. These spermatophores are discharged during copulation.

External Genitalia (Phallomeres/Gonapophyses): The male cockroach possesses asymmetrical chitinous structures called phallomeres or gonapophyses around the male gonopore. These are chitinous exoskeletal extensions that help in copulation and anchoring the male to the female during sperm transfer. There are typically three phallomeres: right phallomere, left phallomere, and ventral phallomere