It is associate unbroken series of species against in associate root to descendant sequence with every later species having evolve from one that now preceded it.
Number of living organism
- Till now we have 2.5 million of species of animals and plants. All to an estimate 5.3 million species present over Earth.
- We discovered only 50% of total species.
- Insects are 53.1%.
- Vascular plants 17.6 %.
- Animals 19.9%.
- Fungi, algai, protist 9.4%.
We have incomplete series of organism from ancestor to descendant is incomplete due to following reason.
- Incomplete Fossil record
We have incomplete Fossil record, we know that invertebrates and soft bodies animals rarely develop fossils.
- Undiscovered animals
Many animals not yet discovered.
iii. Undiscovered fossils
We do not have complete record of Fossil, many of them still buried in soil.