Organisation of Life
Life can be organised into several different levels of function and complexity. These functional levels are: cells, tissues, organs, systems and organisms.
Levels of Organisation
Every living thing is made up of a cell or a number of cells. A single celled organism is called Unicellular Organism, while those made up of many cells are called Multicellular Organism.
In unicellular organisms, the single cell performs all life functions. It functions independently. Examples are Amoeba, Paramecium, Euglena, Chlamydomonas, etc.
Multi-cellular organisms have various levels of organization within them. Individual cells may perform specific functions and also work together for the good of the entire organism. The cells become dependent on one another. Multi-cellular organisms have the following 5 levels of organisation ranging from simplest to most complex:
Cells are often called the "building blocks of life". They are the smallest unit of life that can replicate. Examples are blood cells, nerve cells, bone cells, muscle cells, etc. The study of cells is called cell biology. Cells consist of cytoplasm enclosed within a membrane, which contains many biomolecules such as proteins and nucleic acids.
A tissue is a group of similar cells from the same origin that together carry out a specific function. Examples are blood, nervous, bone, etc. Example of animals that exist at tissue level is Hydra.
Types of Tissue in Man and their Function
1.Epithelial Tissues: They line and protect the body surface. They help in the formation of skin.
2. Blood Tissues: They transport food and oxygen round the body.
3. Skeletal Tissues: They support the body and aid movement
4. Connective Tissues: They bind other tissue together.
5. Nerve Tissues: They coordinate and transmit nerve impulses.
6. Muscle Tissues: It is for movement for the parts of the body.
Types of Tissues in Plant
Plant tissues are categorised broadly into three tissue systems: the epidermis, the ground tissue, and the vascular tissue. Epidermis - Cells forming the outer surface of the leaves and of the young plant body. Vascular tissue - The primary components of vascular tissue are the xylem and phloem.
Functions of Tissues in Plants
- Vascular Tissues: The vascular tissues include xylem, which conducts water and minerals from the roots upward and throughout the plant, and phloem, which transports dissolved nutrients in all directions within the plant..
- Ground Tissues. They help in photosynthesis and nutrient storage
- Epidermis: They protect against water loss, regulate gas exchange, secrete metabolic compounds, and (especially in roots) absorb water and mineral nutrients.
Organs are a group of tissues in a living organism that have been adapted to perform a specific function. In higher animals, organs are grouped into organ systems; e.g., the esophagus, stomach, and liver are organs of the digestive system. Examples or organs are heart, brain, skin etc.
System is a group of two or more organs that work together to perform a specific function for the organism. Examples are circulatory system, nervous system, skeletal system, etc. The human body has 11 organ systems which are the circulatory, digestive, endocrine, excretory (urinary), immune (lymphatic), integumentary, muscular, nervous, reproductive, respiratory, and skeletal.
These are entire living things that can carry out all basic life processes. Organs can take in materials, release energy from food, release wastes, grow, respond to the environment, and reproduce. Examples or organisms are bacteria, amoeba, mushroom, sunflower, dog, human etc.
Complexity of Organisms
Complexity of organism explains the varying functional capabilities of each level of organisation.
Advantages of Complexity in Organisation
- There is specialisation of various cells.
- Specialisation leads to division of labour.
- There is efficiency.
- One body function does not adversely affect other body functions.
Disadvantages of Complexity in Organisation
- Individual cells are not capable of existing independently and therefore depend on one another’s activity to exist.
- Due to complexity, organisms must obtain enough food and oxygen to activate them and avoid risk of death.
- More effort is needed to eliminate toxic wastes.
- Energy and time are wasted.