Structural Organisation in Animals: Class 11 NCERT Biology Guide

Types of Animal Tissues and Their Functions

Animal bodies are made up of different tissues, each specialised for specific functions. In Class 11 NCERT Biology, four main types of tissues are studied:

• Epithelial Tissue: Covers body surfaces and lines cavities. It protects and helps in absorption and secretion. For example, skin epithelium and intestinal lining.
• Connective Tissue: Supports and connects other tissues. Includes loose connective tissue, adipose tissue (fat storage), cartilage, bone, and blood.
• Muscular Tissue: Responsible for movement. There are three types:
• Skeletal muscles (voluntary, striated, attached to bones)
• Smooth muscles (involuntary, found in walls of organs)
• Cardiac muscles (heart muscles, involuntary and striated)
• Neural Tissue: Composed of neurons and neuroglia, it controls and coordinates body activities by transmitting impulses.

Each tissue type plays a vital role in maintaining the animal’s structure and functions.

From Tissues to Organs and Organ Systems

In animals, tissues combine to form organs, which perform specific functions. Multiple organs working together form an organ system. Understanding this hierarchy is crucial for Class 11 students:

• Organs: Examples include the heart, lungs, stomach, and brain. Each organ contains different tissues that contribute to its function.
• Organ Systems: Examples include the digestive system, circulatory system, nervous system, and excretory system.

This organisation ensures efficient functioning and survival of animals.

Control and Coordination in Animals: Neural and Chemical

Control and coordination are essential for animals to respond to stimuli and maintain homeostasis. Class 11 NCERT explains two main types:

• Neural Coordination: Achieved through the nervous system, which includes:
• Central Nervous System (CNS): Brain and spinal cord.
• Peripheral Nervous System (PNS): Cranial and spinal nerves.
• Autonomic Nervous System (ANS): Controls involuntary actions, with sympathetic and parasympathetic divisions.

• Chemical Coordination: Involves hormones secreted by endocrine glands such as the pituitary, thyroid, adrenal glands, and gonads. These hormones regulate growth, metabolism, reproduction, and other physiological processes.

For example, frogs have a well-developed nervous system with a brain divided into forebrain, midbrain, and hindbrain, and endocrine glands that regulate body functions.

Sense Organs and Their Role in Animal Life

Sense organs help animals perceive their environment and react accordingly. Class 11 NCERT Biology highlights key sense organs:

• Eyes: Simple spherical structures in frogs, responsible for vision.
• Ears: Frogs lack external ears but have tympanum for hearing and balance.
• Nose: Nasal epithelium detects smell.
• Tongue and Skin: Contain taste buds and sensory papillae for taste and touch.

These organs send signals to the nervous system, enabling animals to respond quickly to changes and threats.

Comparison of Neural and Chemical Coordination

Understanding the differences between neural and chemical coordination helps clarify how animals control their body:

Both systems work together to maintain balance and respond to internal and external stimuli.

Worked Example: Identifying Tissue Types

Question: Identify the tissue type based on the following description:

• Tissue A is striated, voluntary, and attached to bones.
• Tissue B is non-striated and involuntary, found in the walls of the stomach.

Solution:

• Tissue A is Skeletal Muscle because it is striated and voluntary.
• Tissue B is Smooth Muscle because it is non-striated and involuntary.

This example helps Class 11 students differentiate muscle tissue types based on structure and function.