Organisation Of Life: According to Biology
One of the main factors considered in classifying living things is the complexity of the organisms, others are referred to as multicellular, consisting of many cells. A single celled organism is itself sufficient and is adapted to its environment just as a multicellular organism. Amoeba, Euglena and paramecium are complete functional entities and perform all fundamental functions of living things such as feeding, reproduction, excretion etc.
In these organisms, the level of body organisation is by units known as organelles e.g. contractile vacuole flagella, cilia, nucleus etc.
Levels of Organisation
At the centre of the cell is a spherical and dense body called the nucleus which is clearly separated from the material around it. The material is the endoplasm and it has food vacuoles of various sizes suspended in it and a large contractile vacuole. The simple cell that makes up the amoeba is capable of carrying out all life processes.
As we progress upwards in the evolutionary line, body organisation becomes more complex and complicated as body functions cannot be performed by single cells. For example, Hydra is a multicellular animal made up of many cells which are arranged in two layers; that is an outer ectoderm and an inner endoderm separated by a jelly like material known as mesoglea.
This shows clearly that Hydra has a more complicated body structure than either Paramecium,. Euglena or. Amoeba. because it has different types of cells which perform different functions. The cells of the ectoderm. Within Hydra, there are sting cells which perform a particular function. Such a collection of similar cells performing the same function is known as a tissue. We can therefore say that Hydra consist of tissues, just as cells specialise to perform different functions, tissues are organised in such a way as to perform specific functions e.g. a muscle tissue consists of cells adapted in such a way for contraction and to cause movement.
Nervous tissues are adapted for transmission of nerve impulses while conducting tissues made of phloem and companion cells are specialised for conducting food substances in plants.
Another example of a tissue is the bone tissue which has its cells widely spaced. In between the cells is the matrix containing calcium salts. The bone is described as a solid. Tissues performing a specific function in a living organism is called an organ. In plants, the leaves, stems and roots are organs while in animals, examples of organs include the eyes for sight, the heart for pumping blood round the body, the kidneys which are used for excretion, and the brain which coordinates nervous activities.
A collection of organs working in a coordinated fashion for the benefit of an organism is referred to as a system. The brain, spinal cord, and nerve fibers form the nervous system in man. Order systems found in man include the digestive, respiratory, circulatory, reproductive, excretory, muscular and skeleton systems. In like manner we also refer to the excretory and respiratory systems of plants.
The climax of organization in higher living things is the aggregation of systems to form an organism. All the cells, tissues, organs and systems within the organism do not function independently of one another but are all coordinated in maintaining the life of organism. Thought everything is centred on division of labour, they function harmoniously for the benefit of the organism. This uniform function enables the organism to exhibit certain specific characteristics that only common on living things.
Living things are organised for survival. This shows why higher organisms have been successful because they have been able to adapt to variations which are not too drastic will die if their environment becomes flooded for a long period. The same thing will happened to the mahogany tree if the environment suddenly becomes dry and less humid. Thus the complexity of higher organisms has its advantages and disadvantages.
The more structures an organism processes, the more complex its body organisation becomes. The rat for instance has a more complex body organisation than Paramecium which has no specialised structure like blood, heart, kidneys and lungs, Because of the simple body organisation of lower plants and animals, their body functions are limited and in most cases restricted to specific conditions, They are restricted to an aquatic environment because they cannot develop feature that can enable them to adapt to other environments. The complex organisation of higher organisms allows for better division of labour which enables them to perform complicated tasks. It enhances their efficiency and therefore adaptability to their environment.
A disadvantage of complex body organisation in higher organisms is the problem of keeping be all the parts functioning well as individual cells have lost their Independence. However complicated the body organisation is, all parts must work in a coordinated fashion for the benefit of the organism. In higher organisms must be coordinated by hormones and a nervous system.
The complex body organisation is also accompanied by basic changes in the body plan. The result is the need for an efficient transport system.
Major Sources and Forms of Energy
Energy is defined as the ability to do work. All living things require energy to carry out their body functions. Energy is required for all processes in the body like talking, moving, thinking, growth and breathing. Weather we are awake or sleep, energy is continuously being used in the body, This energy is obtained from a process called Respiration. Essentially, respiration is a sequence of chemical reactions which releases energy from food materials.
Through respiration food is 'burned' to release energy. The process can be likened to the combustion of fuel in the be engine of a car.
Sources of Energy - According to Biology
(a) The Sun: This is the ultimate source of energy on the earth's surface. Energy from the sun reaches the earth in the form of heat and and light. Living things are directly or indirectly dependent on sunlight for the ultimate source of food and therefore energy. This is so, because plants absorb sunlight, and through the process of photosynthesis food is manufactured,
Animals, on the other hand, feed on plants or other animals. Since food is the availability of food is ultimately dependent on sunlight, we can say that the sun is the ultimate source of energy. Organic fuel like coal and petroleum products are the remains of plants that were trapped millions of years ago.
(b) Catabolism: A lot of activity which requires energy takes place within cells. Such activities include chemical synthesis, transfer of materials and transformation of energy, etc.
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