Tissues

This chapter explains how cells in multicellular organisms are organised into tissues, groups of cells similar in structure that work together to perform a particular function. You will learn why plant and animal tissues differ: plants are stationary and need much supportive dead tissue, while animals move and need more living tissue. Plant tissues are divided into meristematic tissue, found at growing regions as apical, lateral and intercalary meristems, and permanent tissue. Simple permanent tissues include parenchyma, collenchyma and sclerenchyma, along with the protective epidermis and cork, and complex permanent tissues are xylem, which conducts water and minerals, and phloem, which transports food. Animal tissues are of four types. Epithelial tissue covers and lines organs and includes squamous, cuboidal, columnar and glandular epithelium. Connective tissue includes blood, bone, cartilage, tendons, ligaments, areolar and adipose tissue. Muscular tissue is striated, unstriated or cardiac, and nervous tissue is made of neurons with a cell body, dendrites and an axon that carry messages through the body.

Detailed Worksheet: Tissues Section A - Definitions (10 marks) 1. What is a tissue? Why do multicellular organisms need tissues? (2 marks) 2. What is meristematic tissue? Name its three types based on location. (2 marks) 3. Name the elements of xylem and phloem. (2 marks) 4. Distinguish between a tendon and a ligament. (2 marks) 5. What is a neuron? Name its three main parts. (2 marks) Section B - Calculations and Applications (15 marks) 6. In a sample of 200 cells from a stem, 120 were parenchyma, 50 collenchyma and 30 sclerenchyma. Find the percentage of each and state which tissue gives mechanical strength. (3 marks) 7. Blood is about 55% plasma and 45% formed elements by volume. An adult has about 5 litres of blood. Find the volume of plasma and of formed elements. Name the three types of blood cells. (3 marks) 8. A nerve impulse travels at about 100 m/s along a motor neuron. How long does it take to travel from the spinal cord to the toe, a distance of 1 m? If a person touches a hot object and the total reflex path is 2 m, find the time taken. (3 marks) 9. Identify the tissue for each function: (i) lining of the blood vessels and lung alveoli (ii) storage of fat below the skin (iii) transport of food in plants (iv) flexibility in the leaf stalk (v) hardness of the husk of a coconut (vi) growth in length of a root tip. (3 marks) 10. The human heart beats about 72 times a minute. How many times does it beat in a day? Which type of muscle makes this possible without tiring, and why? (3 marks) Section C - Diagrams (10 marks) 11. Draw labelled diagrams of the three types of muscle fibres: striated, unstriated and cardiac. (4 marks) 12. Draw a labelled diagram of a neuron. (3 marks) 13. Draw labelled diagrams of parenchyma, collenchyma and sclerenchyma as seen in sections. (3 marks) Section D - Analysis and Higher-order Thinking (15 marks) 14. Compare parenchyma, collenchyma and sclerenchyma on five points: cell wall, cell living or dead, intercellular spaces, location and function. (5 marks) 15. Describe the structure and functions of xylem and phloem. Why is phloem said to carry food in both directions while xylem carries water only upwards? (5 marks) 16. Describe the types of epithelial tissue with one location and function each. Why is the skin made of stratified squamous epithelium? (5 marks) Instructions: Time allowed 2 hours. Attempt all sections. Draw diagrams neatly in pencil and label every part.