SS 1 Biology (1st, 2nd & 3rd Term) Biology

Organization of Life

Organization of life is defined as the existence of life from a single called organisms to a multicellular organisms with complex form that perform different functions

Levels of Organization

1  First level (cell): A cell which is the functional and structural unit of protoplasm bounded by a membrane is the first level of organization. It contains nucleus and cytoplasmic materials. Some living things or organisms exist as a cell capable of carry out all the characteristics of living things they have cytoplasmic structure such as pseudopodia, cilia, flagella and vacuole e.t.c. amoeba, paramecium and Euglena.

  1. Second level (Tissue): A tissue is a collection of cells which are similar in structure and perform similar the same position in the body in which they exist. The only organism that exists at tissue level is hydra. Examples of tissues are blood, xylem tissue, phloem tissue, parenchyma, and collenchyma.
  2. Third level (Organ): An organ is a collection of different tissues that perform a common function or functions, some organs can carry out more than one function, for example kidney excretes metabolic of water in the body. Examples of organs are root, stem, leaves, bulb, nose, ears, brain, spinal cords, taste, buds ovaries and urinary bladder
  3. Fourth level (System): A system is a set of organs which cooperate to carry out one of the vital function of life. For examples the digestive system is made up of organs such as the mouth, oesophagus stomach, pancreas, duodenum and ileum, large intestine and anus.

Complexity of organization in higher organ

The advancement in the evolutionary trend of both plant and animals shows that there is a gradual complexity in the organization from one level to the next unicellular to multicellular and their bodies shows advancement over the unicellular organism. Their bodies are performing different functions. The specialized parts are made up of tissues, organs and system which make up higher organisms more efficient to carryout various activities of life

Advantages of Complexity

  1. There is specialization of various cells
  2. Division is allowed for efficient exploitation of the environment

iii.        It increases adaptation to environment

  1. It leads to increase in size of organisms
  2. In unicellular organisms all other activities stop when reproduction is about to take place but complex organisms do not.

Disadvantages of Complexity

  1. Individual cells are not capable of existing independently and therefore depend on one another for activities to exist
  2. Area to volume diminishes

iii.        In higher organism ability to regenerate decreases


Questions to practice

1a.       State one difference each between hydra and mammals with respect to :

  1. Level of Organizations
  2. Body symmetry

iii.     Number of body layer


  1. State 4 advantages of the body complexity of higher animal
  2. In terms of body complexity, relate the body functions of higher animals and Amoeba
  3. In tabular forms, group the following objects according to their level of organization. Blood cell, blood, onion bulb, leaf, stem, ear, tongue, amoeba, paramecium, Nervous system, respiratory system, hydra and mango fruit

2a.       State five differences between monocotyledonoea and dicotyledoneca

  1. State the principal features of the following groups of an organisms
  2. Co-elenterata     ii, Amphibia     iii. Fishes      iv. Reptiles     v. Bird     vi. Mammals


See also






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