Structural Organization in Plants and Animals
Table of Content
When we talk about the description of the diverse forms of life on earth, we first learn about observation either through naked eye or by using magnifying lenses and microscopes. The observation results into the description of both morphological (external features) and anatomical (internal features) organization. The morphological and anatomical features come under the structural organization of life forms.
Let’s talk about your last visit to a botanical garden. Probably you are now able to identify the different type of plants on the basis of their difference in height, contour of leaves and the pattern of flower over the branches. Yes, you are right! You are distinguishing the plants of the basis external appearance. An overview of the flowering plants
Figure (A): An overview of the flowering plants
The three Basic Plant Organs: Roots, Stems and Leaves
If you pull out any weed you will see that all of them have roots, stems and leaves. They may or may not be bearing flowering and fruits.
Root system are the portions of the plants which are underground while the portion above the ground forms the shoot system. The latter consist of stems and leaves.
Stem is defined as the rising, shaped-like a cylinder extensions that is formed from the plumule of the germinating seed’s embryo and they always demonstrate negative geotropic, negative hydrotropic but positively phototropic attributes.
Roots are the structures which are usually seen below the soil and are non-photosynthetic, non-nodal and shows positive geotropic, negatively phototropic characteristics
Depending upon the climatic conditions and the habitat they where they grow, plant parts exhibit certain modifications. For example: The spine in opuntia are the modified version of leaves. This is so to reduce the loss of water in the form of vapor.
Figure (B): Opuntia streptacantha showing modified leaves in the form of spines
Not just the leaves, even the stems and roots also show some modification in order to fit into the extreme environment.
The stem may not always be typically like what they are expected to be. They also modify themselves to perform different functions. For example: Potato tubers are modified underground stem in order to store food in them. Stem tendrils developed from axillary buds, are slender and spirally coiled and help plants to climb such as in pumpkins.
Figure (C): Potato tubers, the modified storage form of stem
Even roots modify themselves and change their shape and structure to perform the functions other than absorption and conduction of sap (water along with minerals).
The prop roots hanging from the Banyan tree for support and the pneumatophores of Rhizophora growing in swampy areas are the vertically growing roots that help to get oxygen.
|(a) The pneumatophores of mangroves trees
|(b) The hanging roots of Banyan tree.
The word Anatomy derived from the Greek word “anatemno” means “I cut up, cut open”. It is the branch of biology concerned with the study of the structures of the organisms and their parts.
Plants have cells as the basic unit, cells are organised into tissues and in turn tissues are organised into organs. Different organs in a plant show differences in their internal structure. And internal structure also shows differences in their internal structure.
Anatomical study of flowering plants exhibited quite fascinating arrangement of the internal structures. All three basic plant organs-roots, stems, and leaves-are composed of dermal, vascular and ground tissues.
Figure (E): The three tissue system
Cells from a working animal body through their emergent properties, which arise from successive levels of structural and functional organization. Cells are organized into tissues.
Tissues are the group of cell with a similar appearance and a common function. Tissues are organized into organs. The simplest animals, such as sponges, lack organs or even true tissues.
Groups of organs that work together, providing an additional level of organization and coordination, make up an organ system. For example, the skin is an organ of the integumentary system, which protects against infection and helps regulate body temperature.
Surprisingly, all major complex animals consist of only four types of tissue. Cells, tissues, organs and organ systems split up the work in a way that exhibits division of labour and contribute to the survival of the body as a whole.
The specialized and the complex organ systems of animals are built from a limited set of cells and tissue types. For example, lungs and blood vessels have different functions but are lined by tissues that are of the same basic type and that therefore share many properties.
Figure (F): Schematic representation of types of animal tissues
The four main types of animal tissues are different and broadly classified as:
- Muscular and
Figure (G): Types of animal tissues
Occurring as sheets of cells, epithelial tissues or epithelia (singular epithelium), cover the outside of the body and line organs and cavities within the body.
The word epithelium uses the Greek roots “epi” means ‘on’ or ‘upon’ and “thele” means ‘nipple’. This is so called because the name was originally used to describe the translucent covering of small “nipples” of tissue on the lip.
Because epithelial cells closely packed, often with tight junctions, they function as a barrier against mechanical injury, pathogens, fluid loss. Apart from theses, epithelial also form the interface with the environment.
Figure (H): Types of Epithelial Tissue
They are the most abundant and widely distributed in the body of complex animals. Due to their function in linking and supporting other tissues/organs of the body, they are named so. They are scattered throughout the extra cellular matrix. The matrix generally consists of web of fibers embedded in a liquid, jellylike, or solid foundation.
Figure (I): Types of connective tissues
The tissue type which is responsible for nearly all types of body movement is muscle tissue.
Each muscle is composed of numerous long, cylindrical fibres which are arranged in parallel arrays. These fibres are composed of many fine fibrils, called Myofibrils.
Muscle fibres contract (shorten) and relax (lengthen) in response to stimulation by neurotransmitter signals. Their action moves the body to adjust to the change in the environment and to maintain the position of the various parts of the body.
Nervous or Neural tissue functions in the receipt, processing, and transmission of information.
Nervous tissue contains neurons, which transmit nerve impulses, as well as support cells called Glial or Neuroglial Cells or simply Glia.
Neurons, the basic unit of neural system are excitable cells while glial cells protect and support neuron.
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