Biology Essay Example | Topics and Well Written Essays - 500 words - 10

Biology - Essay Example All living things are composed of one (unicellular) or more (multicellular) cells. All the cells gather energy and utilize energy for growth, reproduction, repairing processes etc. Many different types of cells perform different jobs and together co-ordinate and keep living beings alive. Unicellular (one celled) organisms are bacteria and paramecium, while fungi, plants and animals are multicellular (many cells). The living things are classified into prokaryotes and eukaryotes. Bacterial cells are prokaryotes with simple structure without complex organelle system. Figure 1.A (1) shows prokaryotic cell structure of unicellular bacteria and Figure 1. B shows many bacterial cells. Bacteria are the smallest organism on our planet. Plant cells (Figure 2) (2) form plants. Animal cells (Figure 3) (3) form animals. The plants and animal cells are eukaryotes having larger size than eukaryotes and have complex organelle system. Cells put together form tissues. Tissues form organs. The organs put together form organ system. The organ systems put together make plants and animals. The organelle nucleus in the eukaryotic cell accommodates deoxyribose nucleic acid (DNA) which is a blueprint of our life. The DNA houses the intelligence needed to determine the characteristic shape (structure) and job (function) of all living creatures. We get this DNA from our parents which decides our physical make up, our intelligence, and it reflects our personality. DNA of a cell decides the characteristic role of that cell it has to play in our body. This double helix DNA is like a spiral staircase. DNA can be extracted from any living things and can be seen in a test tube with naked eye in the form of long ropy strings. This DNA is made up of four nucleotides A, T, C and G (Figure 4) (4). The various permutations and combinations of these nucleotides differentiate each living being. It decides who and how we should be. The human beings