Now you might be curious to know how different organisms around us, including humans changed over the years to become what we are today.
By identifying the similarities and differences between organisms, we can trace evolutionary relationships .
Some of these characteristics that make organisms similar or different are visible :
- Green plants photosynthesize
- Animals have 4 limbs
- Whether the skeleton is inside or outside the body etc.
On the other hand, some characteristics are at the cellular level .
Cells are the basic unit of life and all organisms are made up of cells.
But differences in the cellular components and number of cells are basis of differentiation and classification:
- Plant cells have a cell wall but animal cells do not.
- Bacterial cells do not have a well defined nucleus , but plants and animals do.
- All bacterial cells are unicellular (have a single cell) while animals and plants can be multicellular (more than one cell).
Based on these similarities and differences a hierarchy is formed.