Heirarchy of life forms and classification.pptx

Heirarchy of life forms and classification.pptx

1. Classification, why and how? Living world is full of diversity and complexity Organisms are categorized in different super groups and subgroups to make their study easier Biology is an ongoing enquiry about the nature of life and classification of life forms is a part of it. Biologist use different criterions for classification based on the characteristics of life. Morphology – External structure and appearance Anatomy – Internal structure and appearances Biochemical pathways – various chemical reactions occurring inside the body Ecological – Various adaptation to suit their environmental requirements

2. Hierarchy of life

3. Common thread weaves this hierarchy The study of life reveals unifying themes Organization - living organisms are highly ordered in structure Information – life processes involves expression and transmission of information Energy and matter processing - Life requires transfer and transformation of energy and matter Interactions at every level of hierarchy -Interaction leads to emergence of new properties in biological systems Idea of evolution makes logical sense of everything we know about living organisms

4. The Cell Cells are as fundamental to biology as atom is for chemistry Cell is the simplest collection of matter that can be considered a living entity All cells are related by their descent from earlier cells Although cells can differ substantially from one another they share common features Discovered by Robert hook in 1665 Cell theory was developed by Schlieiden and Schwann in 1839

5. Classification based on cellularity Unicellular organisms Composed of single cell Microscopic in nature Division of labor is at organelle level Includes both eukaryotes and prokaryotes Life span is short Asexual reproduction is predominant Bacteria, amoeba, paramecium, yeast Multicellular organisms Composed of more than one cells Mostly macroscopic Division of labor is at cellular level Only eukaryotes Shows longer lifespan Both asexual and sexual mode of reproduction Humans, elephants, whales, trees