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.

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.

Cuticle are protective, hydrophobic waxy covering produced by epidermal cells of leaves, young shoots and other aerial parts. It minimizes the water loss through transpiration (with the help of stomata) and also reduces pathogen entry. Lignin hardens the cell wall and provides flexibility, tensile and compressional strength to the cell wall. Suberin is present in cork cell and makes the cell impervious to water.

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.

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. Note: Tendons joint skeletal muscles to bone and ligaments join bones to bones.

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.

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

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