Class 9 Science Chapter 6 MCQ

The gymnosperms are characterized by the presence of tracheids as their major conducting tissues. These are elongated dead cells with hard lignified walls. They conduct water and do not have open ends like the vessels.

The conducting tissues in plants conduct different shapes and have different structures. The primary conducting tissues of plants are xylem and phloem. Xylem conducts water from roots to the other parts of the plant, whereas phloem transports food and other material from the leaves to other parts of plants.

Areolar tissue is a loose and cellular connective tissue. Its matrix consists of two kinds of fibres, i.e., the white collagen fibres (which changes into boiling in water) and the yellows elastic fibres or elastin. Several other kinds of irregular cells, (example, fibroblasts), which can engulf bacteria and prevent infection (example, macrophages) are also present in the matrix. It is the simplest and most widely distributed connective tissue. It joins skin to muscles, fills spaces inside organs and is found around muscles, blood vessels and nerves. It acts as supporting and packing tissue between organs lying in the body cavity. Matrix of the tissue is important in diffusion of oxygen and nutrients from small blood vessels. It helps in repairing of tissues and to combat foreign toxins. Dislocation of joints occurs when there is an abnormal separation in joint, which are held together by ligament. Therefore, ligament break and may result in dislocation of bone. Areolar tissues join skin to muscles, fills spaces inside organs and is found around muscles, blood vessels and nerves. Hence are not concerned with bones. Tendon break may cause inflammation and occurs due to factors including age, body weight, nutrition, sports etc. Cartilage is specialised connective tissue, which is compact and less vascular. The cartilage cells (chondroblasts) are widely spaced and the matrix is reinforced by fibres. Cartilage occurs at the joints of bones, in the nose, ear, trachea and larynx. It helps in smootheing the surface at the joints. It lends support and provide flexibility to the body parts. Adipose tissue consists of oval and round cells filled with fat globules, scattered in the matrix. This tissue is found below the skin, between internal organs and in the yellow bone marrow. It stores fat and acts as an insulator. Cuboidal epithelium help in absorption, excretion and secretion, whereas bones and cartilage are specialized connective tissue and they provide support to the internal organs.

Each nerve cell or neuron is composed of three parts. i)Cyton or cell body: It contains central nucleus and cytoplasm with characteristic deeply stained particles called “Nissl’s granules” (i.e. clumps of ribosome). ii) Dendron: These are short processes arising from cyton and further branching into dendrities. ii)Axon : It is a single long cylindrical process of uniform diameter which forms fine branches terminally. The dendrites receives impulses and the axon takes impulses away from the cell the body. Tendon are the connective tissue, which join skeletal muscles to bones, hence nervous tissue is absent is them. Nervous tissue is specialized to transmit messages within our body. It contains highly specialized unit cells called nerve cells or neurons. They have the ability to receive stimuli from within or out-side the body and to conduct (send) impulses (signals) to different parts of the body. Brain, spinal cord are all associated with the regulation of body activity and are composed of nervous tissue.

Contractile proteins are found in muscles, as they are associated with the movement of body or limbs. The contraction and relaxation of contractile proteins, present in muscles bring about movement of limbs, internal organs etc. The bones are the major supporting tissues which form the endoskeleton of a vertebrate body. Blood is a fluid connective tissues responsible for transport of oxygen, nutrients, hormones etc. and for producing antitoxins and antibodies etc. Cartilage provides support and flexibility to the body parts and smoothens surface at joints. Note: Bones, blood and cartilage all are different types of connective tissues and are not responsible for movement of any of the body parts.

Tendons are cord-like, strong, inelastic, structures that join skeletal muscles to bones. A tendon is a white fibrous tissue which has great strength but limited flexibility. It consists of parallel bundles of collagen fibres, between which are present, rows of fibroblasts (called tendinocytes).

Smooth muscles are found in the walls of hollow visceral organs. They do not work according to our will. They are involved in peristaltic movement of gastro-intestinal tract and male genital tract. Cardiac muscles are present in the heart. They contract and relax rapidly, rhythmically and tirelessly. They help to pump the blood to various parts of the body. The working of both smooth and cardiac muscles is involuntary while skeletal or straited in muscles are moving to our will and are voluntary in action.

Explanation: Parenchyma serves as the packing tissue in plants therefore they do not have intercellular spaces. Collenchymatous tissues are mechanical tissues in the plants and are characterized by the deposition of cellulose at the corners of the cell, which leads to localised thickening of the cell wall. Apical and intercalary meristem bring primary growth (increase in height) and secondary growth (increase in diameter) respectively and are classified under meristematic tissues. Meristematic tissues are dividing units of the plants and contain dense cytoplasm and large nucleus with few or no vacuoles at all.

The cell walls of sclerenchyma are greatly thickened of lignin. Sclerenchyma cells are dead cells and they are devoid of protoplasm. The cells of sclerenchyma are closely packed without intercellular spaces.

Here, all these statements are correct. Hence, your answer will be option [D].