Morphology: Types & Divisions

Morphology is a branch of biology that studies the size, form, and arrangement of body parts of living organisms. It is studied under two headings like internal morphology (anatomy) and external morphology. 

• Morphology is divided into different branches like Cellular Morphology, Tissue Morphology, Organ Morphology, and Organism Morphology. 
• All morphological concepts are based on Homology and analogy, Body plan and symmetry, and the Morphological basis of classification.
• Homologous structures in plants and animals are similar in embryonic development but different in function
• Whereas analogous structures are different in embryonic development but similar in function.

Most animals and plants exhibit spherical, radial, or bilateral symmetry. In bilateral symmetry, the body can be sliced in half in only one plane to get all parts as that of human beings. Most microorganisms, plant, and animal taxa are morphologically distinct from one another.

Key Terms: Morphology, Anatomy, External, Internal, Homologous Organs, Analogous Organs, Cellular, Tissue, Organ, Organism 

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What is Morphology ?

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Morphology (Gk Morphe=form) is the description of the forms like sizes, shapes, colours, patterns, and structures of microbes, plants, and animals. It can be external morphology and internal morphology. 

• Morphology is a branch of biology that deals with the study of the form and organisation of living organisms. 
• It examines how organisms are built as per their specific structural traits. 
• It studies both the external and internal structures of living things. 
• It studies the forms, shapes, and interactions of microorganisms, animals, and plants. 
• In medicine, it deals with the study of the structure and elements of an organism.

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Types of Morphology

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There are two types of morphology. They are internal morphology and external morphology:

• External Morphology: In external morphology external forms of roots, stems, leaves, flowers, and fruits of plants; heads, trunks, and limbs in animals are studied.
• Internal Morphology (Anatomy): In internal morphology, the internal structure of roots, stems, leaves, flowers, and fruits of plants; head, bodies, limbs, bones, blood vessels, intestines, lungs, heart and other internal organs of animals are studied.

Read More: Tropism in Plants

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Divisions of Morphology

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There are different divisions of morphology which are listed below:

Cellular Morphology

The basic structural and functional unit of all organisms is the cell. 

• Cells of different organisms and organs have different shapes and sizes.
• Epithelial cells have walls that prevent objects from moving freely from one side to the other. 
• The squamous epithelium has cells with a broad body, cuboidal epithelium with cube-like cells, and columnar epithelium with rectangular and elongated cells.
• The fat-storing cells are called adipocytes, which have large and spherical cells.
• Nerve cells or neurons are thin and very long.

Tissue Morphology

A group of cells which are similar in structure and function are called tissues. Tissues show similar morphological features and functions.

• A long, twisted bundle of cells are formed by skeletal muscle cells. 
• Lung tissue is composed of epithelial cells that have grape-like cell sacs (alveoli) to effectively exchange oxygen and carbon dioxide. 
• Walking and running cause stress on the cartilage.

Organ Morphology

A group of tissues meant for a certain function are called organs. Organs of a kind show similar patterns of structure and function. 

• The heart of all human beings has four chambers. 
• The two lower chambers are called the ventricles which have thicker muscular walls. 
• The two upper chambers are called the ventricles which have thinner and less muscular walls. 
• The walls of the ventricles are more muscular as they have to pump blood to all portions of the body.
• In organ morphology roots, stems, leaves, flowers, and fruits of plants; heads, bodies, limbs, bones, and internal organs of animals are studied.

Organism Morphology

The description of the whole organism is the highest level in morphology. 

• The two fundamental symmetries in animals are bilateral symmetry (lobster) and radial symmetry (starfish). 
• The fin shape for swimming, limb shape for sprinting, and wing shape for flying are other examples of the diverse morphology of organisms.

Read More: Flower Structure

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Fundamental Concepts of Morphology

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The fundamental concepts of morphology are:

• Homology and analogy
• Body plan and symmetry
• Morphological basis of classification

Homology and Analogy

Based on origin and functionality body organs are classified as follows:

• Homologous structures: They are similar in embryonic development but different in function. Eg. Human arms, bird wings, and whale pectoral fins are all homologous structures with similar bone, muscle, nerve, and blood vessel patterns.
• Analogous structures: They are different in embryonic development but similar in function. Eg. Wings of butterflies and birds, flippers of dolphins and penguins.

Homology and Analogy

Body Plan & Symmetry

Most animals and plants exhibit spherical, radial, or bilateral symmetry.

• Asymmetry: Organisms with no plane of symmetry. Eg. Amoebas, slime moulds, and some sponges
• Spherical Symmetry: Spherically symmetrical body can be sliced in half in any plane. Eg . Heliozoa
• Radial Symmetry: The body has distinct top and bottom and body sections radiating from a central axis and can be sliced in half in any plane. Eg. Starfish and mushrooms.
• Bilateral Symmetry: The body can be sliced in half in only one plane to get all parts. Eg. Other animals, and humans.

Body Plan & Symmetry

Morphological Basis of Classification

Most microorganisms, plant, and animal taxa are morphologically distinct from one another. 

• Closely related species of microorganisms, plants and animals can many times be distinguished from one another using colour, patterns, proportion and size.
• The morphological relationships can be described as homology and homoplasy.
• Homology: The traits indicate that they have a common ancestry.
• Homoplasy: The traits indicate that the species have evolved separately through convergent or parallel evolution.

Read More:

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Things to Remember

• Morphology is the study of the form and organisation of living organisms.
• Morphology is of two types - internal morphology and external morphology
• The fundamental concepts of morphology are Homology and analogy, Body plan and symmetry, and the Morphological basis of classification.
• Homologous structures are similar in embryonic development but different in function.
• Analogous structures are different in embryonic development but similar in function.
• Most animals and plants exhibit spherical, radial, or bilateral symmetry.
• In bilateral symmetry, the body can be sliced in half in only one plane to get all parts.
• Most microorganisms, plant, and animal taxa are morphologically distinct from one another.

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Previous Year Questions

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