Explain why it is hard to classify organisms in kingdom protista? what are the defining characteristics of the kingdom?

Answer:

1.The main difficulty with classifying organisms in the Kingdom Protista is their extreme diversity which gives rise to a very specific problem: all the rules used to describe them has some major exception. Many protists exhibit characteristics from two or more of the plant, animal and fungus kingdoms.

The only defining rule that applies to all protists is that they are eukaryotes.

2. Some of the main characteristics of the Kingdom Protista are:

- single celled organisms

- primarily aquatic in nature.

- most are are unicellular, with some colonial or multicellular species

- they lack specialized tissue organization.

- they have well defined nucleus with multiple DNA strands

- they have membrane bound organelles (mitochondria for cellular respiration and some species chloroplasts for photosynthesis)

- they can reproduce both sexually and asexually

- they are a major component of plankton

- movement is often achieved through flagella or cilia