53.Phylum Protozoa – General characteristic and classification · Biology · MU Pleven

53.Phylum Protozoa – General characteristic and classification.

Introduces protozoa as unicellular eukaryotes, then covers their general characteristics such as nuclear structure, cysts and body covering. It goes on to describe locomotion by pseudopodia, flagella, cilia or none, and nutrition by holozoic, saprozoic and parasitic methods. Reproduction (asexual and sexual forms), trophozoite and cyst stages, and medical importance follow. A table groups the phylum into four groups with their locomotion and example species.

Inside: 7 sections · 4 labelled pictures · 1 table · 13 flashcards · 2 min

Topic 53 of 63 in the MU Pleven syllabus for Biology (Medicine, Year 1). The free AceMed note covers it in 7 sections, about 249 words (2 min of reading), with 13 flashcards.

Phylum Protozoa

Protozoa are unicellular, eukaryotic organisms in which all vital life processes are carried out within a single cell. They may be free-living or parasitic, and many species are of major medical importance as causative agents of human disease.

General Characteristics

Protozoa possess a true nucleus enclosed by a nuclear membrane and contain typical eukaryotic organelles such as mitochondria, Golgi apparatus, and endoplasmic reticulum. Although they do not form tissues or organs, their cellular organization is highly specialized.

Key characteristics include:

Unicellular and microscopic
Eukaryotic cell structure
Body covered by a plasma membrane or pellicle
Some species form cysts, which are resistant stages important for survival and transmission

Locomotion

Locomotion varies according to the group:

Pseudopodia – movement by cytoplasmic extensions
Flagella – long whip-like structures
Cilia – numerous short hair-like structures
Some protozoa are non-motile

Nutrition and Metabolism

Protozoa obtain nutrition by different methods:

Holozoic – ingestion of solid food particles
Saprozoic – absorption of dissolved nutrients
Parasitic – deriving nutrients from the host

Respiration and excretion occur mainly by diffusion through the cell membrane. In freshwater protozoa, contractile vacuoles maintain osmoregulation.