Cell is the fundamental unit of life.
It took a lot of time for organisms to be multi cellular. This is because cells needed a way to communicate with each other and for a such mechanism to evolve it took time.
Life is a concept that is hard to define. However there are certain activities that can be used to define life.
Activities that define life;
- Order and Organization
- Metabolism ( anabolism and catabolism)
- Growth and development
There are three linages of modern day organisms
The former two linages comes under Prokaryots who lack a defined nucleus. Prokaryotes have a simple cellular organization.
Eukaryotes have a membrane bound nucleus which contains most of the cellular DNA. They have specialized organelles and a complete cytoskeleton.
even though eukaryotes and prokaryotes are different they share a number of structural and functional properties such as;
- Structure of biomembranes
- structure of DNA
- The process of DNA replication
- The process of Protein synthesis
- Production of ATP
Found in multicellular organisms. Able to renew themselves from mitotic division and differentiate into a diverse range of specialized cells.
Two broad types of mammalian stem cells are;
- Embryonic stem cells (Isolated from the inner cell mass of Blastocysts, 5 days after Morula)
- Adult stem cells (found in adult tissues)
Plants also have stem cells in;
- Shoot tips
- Root tips