The human body, as well as that of other animals, is made up of different levels of structural organisation. From cells to tissues, organs, and organ systems, each level is specialised to perform specific functions for survival. This chapter deals with the study of animal tissues, morphology of some animals, and their structural organisation.
1. Levels of Organisation
- Cellular Level – Seen in sponges where different cells perform different functions but do not form tissues.
- Tissue Level – Found in coelenterates, where cells performing the same function form tissues.
- Organ Level – Present in flatworms, where tissues are organised into organs.
- Organ System Level – Found in higher animals (annelids to chordates), where organs form well-developed systems.
2. Animal Tissues
Animals have four basic types of tissues:
(a) Epithelial Tissue
- Covers body surfaces and lines cavities.
- Types:
- Simple epithelium (single layer; e.g., squamous, cuboidal, columnar, ciliated, glandular)
- Compound epithelium (multiple layers, protective; e.g., skin)
(b) Connective Tissue
- Binds, supports, and connects different tissues/organs.
- Types:
- Loose connective tissue – areolar, adipose
- Dense connective tissue – tendons, ligaments
- Skeletal connective tissue – cartilage, bone
- Fluid connective tissue – blood, lymph
(c) Muscular Tissue
- Responsible for movement.
- Types:
- Striated (skeletal) – voluntary, multinucleated
- Non-striated (smooth) – involuntary, spindle-shaped
- Cardiac – involuntary, branched, found in heart
(d) Nervous Tissue
- Composed of neurons and neuroglial cells.
- Conducts impulses and coordinates body functions.
3. Morphology and Anatomy of Some Animals
For better understanding, the NCERT includes the study of certain organisms:
(a) Earthworm (Pheretima posthuma)
- Body Segmentation – Metamerically segmented with clitellum.
- Digestive System – Complete; pharynx, gizzard, intestine.
- Circulatory System – Closed type with blood vessels and hearts.
- Excretory System – Nephridia.
- Nervous System – Nerve cord and ganglia.
- Reproductive System – Hermaphrodite, with both testes and ovaries.
(b) Cockroach (Periplaneta americana)
- Body Division – Head, thorax, abdomen.
- Digestive System – Foregut, midgut, hindgut.
- Circulatory System – Open type with haemolymph.
- Respiration – Through spiracles and trachea.
- Excretion – Malpighian tubules.
- Nervous System – Nerve cord with ganglia.
- Reproductive System – Sexual dimorphism (male & female separate).
(c) Frog (Rana tigrina)
- Body Division – Head and trunk with two pairs of limbs.
- Digestive System – Stomach, intestine, cloaca.
- Circulatory System – Closed type; three-chambered heart.
- Respiration – Through lungs, skin, and buccal cavity.
- Excretion – Kidneys with ureters opening into cloaca.
- Nervous System – Brain, spinal cord, and nerves.
- Reproductive System – Separate sexes with external fertilisation.
4. Importance of Structural Organisation
- Helps in understanding how different tissues and organs function.
- Provides knowledge of animal morphology and anatomy.
- Useful in medicine, physiology, and veterinary sciences.
✅ Summary:
- Four levels of organisation: cellular, tissue, organ, organ system.
- Four basic animal tissues: epithelial, connective, muscular, nervous.
- Earthworm, cockroach, and frog represent invertebrate and vertebrate structural organisation.
For More Information and Updates, Connect With Us
- Name: Survi
- Phone Number: +91-7488713635
- Email ID: survi@eepl.me
- Our Platforms:
- Digilearn Cloud
- EEPL Test
- Live Emancipation
- Follow Us on Social Media:
- Instagram – EEPL Classroom
- Facebook – EEPL Classroom
- https://eepl.me/blogs/
Stay connected and keep learning with EEPL Classroom!
