Study Of Tissues And Diversity In Shape And Sizes Of Plants And Animal Cells

Ans. Aerenchyma cells are found in aquatic plants such as Hydrilla.

Second Answer: Aerenchyma is a spongy tissue that develops air channels within the leaves, stems, and roots of halophytic plants. These air channels facilitate the exchange of gases between the shoot and root systems.

Ans. Sclerenchyma cell walls have thick cell walls containing lignin with high levels of cellulose content.

Second Answer: Sclerenchyma cells are characterized by two types of cell walls: primary and secondary. The secondary wall, which is much thicker and heavily lignified (15%–35%), provides significant rigidity and hardness to the cell and surrounding tissue. There are two main types of sclerenchyma cells: fibers and sclereids.

Ans. The differences between Sclerenchyma, Collenchyma, and parenchyma are given in the table below

Second Answer: Ground tissue in plants consists of three main types of simple permanent tissues: parenchyma, collenchyma, and sclerenchyma.

• Parenchyma: It is found throughout the organs of the plants such as roots, stems, leaves, flowers, fruits, and seeds. Parenchyma is a versatile ground tissue that primarily functions as filler tissue in soft plant parts. Examples include the cortex and pith of stems, the cortex of roots, the mesophyll of leaves, the pulp of fruits, and the endosperm of seeds.
• Collenchyma: In herbaceous dicotyledonous stems, collenchyma generally appears as a three- to four-layered hypodermis. It is found mainly near the vascular cambium, a type of outward-growing tissue. It provides structural support to growing shoots and leaves. For example, the stringy texture of celery stalks is due to the presence of collenchyma cells.
• Sclerenchyma: Sclerenchyma fibers are mainly associated with the xylem and phloem of vascular bundles. They occur in various plant parts:  the hypodermis of monocot stems, the pericycle of many dicots, secondary wood, the vascular bundle sheath in monocot stems, and the hypodermis of many leaves.

Ans. There are four types of Animal tissues – Epithelial tissue, Muscle tissue, Nervous tissue, and connective tissue.

• Epithelial tissue: It consists of layers of compactly packed cells that line the surface of the body generally for protection, secretion, and absorption.
• Muscle tissue: It is made up of cells containing contractile filaments that move past each other and change their shapes and sizes.
• Nervous tissue: It is made up of the nerve cells or the neurons that all together form the nervous system, including the spinal cord and brain.
• Connective tissue: It can either be loosely or densely packed and is involved in the structure and support of the body.

Second Answer: Animal cells are organized into various tissues. These tissues differ in structure, function, and developmental origin. There are four main types of animal tissues: epithelial tissue, connective tissue, muscle tissue, and nervous tissue.

Epithelial tissues are classified as Sensory epithelium, Glandular epithelium, Pigmented epithelium, and Absorptive epithelium.

Connective tissues are classified as Connective tissue proper, Vascular tissue, and Skeletal tissue.

Muscle tissues are classified as Cardiac, Smooth, and Skeletal.

Ans. Sclerenchyma is simple permanent tissue generally elongated in shape and the cell wall is thick consisting of lignin and a high level of cellulose content. However, the vacuole is absent in the sclerenchymatous tissue. They are typically dead cells and their wall consists of a few to several pits.

Second Answer: Mature sclerenchyma tissue is composed of dead cells with heavily thickened walls rich in lignin and cellulose (60%–80%). These dead cells provide structural support throughout the plant. Sclerenchyma cells have two types of cell walls: primary and secondary walls.

Ans. A cell is a basic building block or it is a structural, functional, and biological unit of all living organisms. The differences between plant and animal cells are given below:

Second Answer: In biology, the cell is the fundamental unit of life. This membrane-bound structure contains the essential molecules for life and forms the building block of all living things. Some organisms, like bacteria or yeast, exist as single cells. In multicellular organisms like humans and animals, cells differentiate into specialized types as they mature. These specialized cells work together to form tissues, organs, and the entire organism.

The smallest known cells are mycoplasmas, a group of tiny bacteria. Some of these single-celled spheres can be as small as 0.2 micrometers (μm) in diameter, roughly equivalent to 0.000039 inches. In comparison, human cells are about 400,000 times more massive than a single mycoplasma bacterium. However, even human cells are microscopic, typically measuring around 20 μm across.

Ans. Muscle tissue is a highly specialized tissue found in animal cells. It is characterized by its ability to contract and relax, enabling movement. It consists of muscle fibers that help in contraction and relaxation. There are basically 3 types of Muscle tissue-

1. Smooth muscle tissue: Found in the inner lining of the organs.
2. Skeletal muscle tissue: Attached to the bones.
3. Cardiac muscle tissue: Found in the heart only.

Second Answer: Muscle tissue is a highly cellular tissue and well-supplied with blood vessels. It is composed of specialized cells that possess the remarkable ability to shorten or contract, generating the force necessary for body movement.

Ans. The study of plant and animal cells is called cytology.

Second Answer: Cytology comes from the Greek words "cyto" meaning cell and "logos" meaning study. It is a branch of biology that focuses on the structure, function, and behavior of cells.

Ans. Mycoplasma gallisepticum is considered one of the smallest cells, measuring only 0.2–0.3 micrometers (μm) in size. In fact, Mycoplasma are the smallest known living organisms on Earth.

Second Answer: Mycoplasmas are a group of bacteria that are extremely small. They are considered to be the smallest self-replicating organisms known to exist. They do not have a cell wall, which is a rigid structure that surrounds most bacteria and gives them their shape.

Ans. The longest animal cell is a nerve cell, also called a neuron. The length of these cells can be up to 3 feet (1 meter).

Second Answer: A nerve cell, also called a neuron, is a specialized cell found in the nervous system that transmits electrical signals. These signals are essential for coordinating involuntary and voluntary actions, sensations, thoughts, and emotions throughout the body.