Class 9 Science Chapter 6 MCQ

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.

Cellulose is a basic of the cell wall present in plants. The cell wall of almost all the organisms are made up of cellulose whereas lipids along with some proteins forms the basic building blocks of plasma membrane. Plasma membrane is semi-permeable and it is not impervious to water. Lignin is a complex polymer which acts as a cement and hardens the cell wall. It provides flexibility, great tensile and compressional strength to the cell wall and makes the cell wall impermeable. It is present in sclerenchyma cells and not in cork cells. The walls of cork cells are heavily thickened with an organic substance, suberin. Suberin makes these cells impervious to water and gases.

Cardiac muscles show characteristics of both smooth and straight and muscles. These muscles are striated, cylindrical, branched and involuntary in nature. In addition to the light and dark bands, these muscles should densely stained cross bands called intercalated dises. These act as impulse is boosters. Cardiac muscles contract and relax rapidly, rhythmically and tirelessly throughout a lifetime, from early embryonic stage until death. Voluntary muscles are under our control and act accordingly to our need e.g., skeletal muscles. Smooth muscles also known as striated, visceral or involuntary muscles are found in walls of hollow tubular organs like alimentary canal, ducts of glands, urogenital ducts and blood vessels except heart. They show slow contractions but remain contracted for a long period of time.

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.

dipose 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.

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.

Tracheids and vessels are xylem elements and are concerned with the transport of water. They are long tube-like structures with partially or completely dissolved walls to from water pipes (in vessels) and pits in cell wall (in tracheids) for conducting water. Sieve tubes are slender tube-like structure with their end walls perforated by numerous pores and are called seive plates. They are phloem elements and are main food conducting elements. Companion cells possess numerous mitochondria and ribosomes and are supporting units of sieve tubes. Note: Companion cells are associated with sieve tubes and connected to them by numerous plasmodesmata. They help in maintaining pressure gradient in sieve tubes. They are not perforated.

Girth of the stem increases due to lateral meristematic tissues. They are found beneath the bark (called cork cambium) and in vascular bundles of dicot roots and stems (called vascular cambium) as thin layers. This increase in the diameter and girth of the plant is called secondary growth. The apical meristem is situated at the growing tip of stems, root and also at the apices of leaf. They bring about elongation i.e., increase in height (primary growth) of the plant. Intercalary meristem are located at base of leaf and internode and produces an increase in the length of an organ.

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].