6 ANIMAL-LIKE PROTISTS
Objectives
After completing this exercise you should be able to
1. Know the characteristics of Protists.
2. Classification with examples.
3. Identify the Protists and assign them to their classes. (Examples from your manual.)
Introduction
Animal like protists were the first formed animals, hence called as Protozoans. They are single
celled eukaryotic organisms. Their single cell is complex than any particular cell in multicellular
organisms. The diversity of these animals has resulted in categorizing them into five classes.
Characteristics of Protists
1) Protist is a complete organism in single eukaryotic cell.
2) Structures in these cells carry out various functions to maintain homeostasis.
3) Their cells are differentiated into following structures,
Pellicle: Under the plasma membrane, maintains shape but is also flexible.
Cytoplasm: In the Protozoan cell houses various cell structures ectoplasm- peripheral clear and
endoplasm- central granular
Plasma membrane: Gas exchange for cellular respiration and excretion by diffusion
.
Food Vacuole: Formed when Protozoan ingests food through cytopharynx. Food would get
digested here by enzymes.
Egestion Vacuole: After digestion the waste is released by exocytosis through cytopyge
4) Reproduction takes place asexually- Sex cells, gametes are not required for reproduction as
well as sexually- Sex cells, gametes fuse to form zygote that form new organisms
5) Few are parasites
causing various diseases in human and other vertebrates and invertebrates.
Classification of Protozoan – A) Based on their locomotory adaptations –
1) Flagellated Protozoans - Mastigophora eg. Euglena, Trypanosoma
2) Amoeboid Protozoans - Sarcodina eg. Amoeba
3) Ciliated Protozoans - Ciliata eg. Paramecium
4) Stationary Protozoans – Sporozoa eg. Plasmodium
B) Based on recent morphological, biochemical and phylogenetic analyses has given a higher level
classification for Protozoa. It does not use the formal hierarchical rank designations as class and
order, instead is divided into following four supergroups -
