ProtozoaOver all View

By

–V.PARTHASARATHY–Lecturer in Zoology–Vivekananda College,–Tiruvedakam West

Characteristics of Protozoa

• Unicellular OrganizationUnicellular Organization – Since Protozoa are single celled they often rely on other

organisms for some necessities

• ReproductionReproduction::– Asexual:

1. binary fission: cytoplasmic division follows mitosis, producing two organisms

2. budding: 3. multiple fission or schizogeny: cell or organism is split into many

new cells or organisms

– Sexual

Reproduction

Symbiosis: an intimate association between two organisms

Three types of symbiosis:1. Parasitism: one organism lives in or on a

second organism, called the host. – the host is harmed, but usually survives

2. Commensalism: one organism benefits and the other neither benefits nor is harmed

3. Mutualism: both organisms benefit from the relationship

Protozoan Taxonomy

Phylum Sarcomastigophora Subphylum

Mastigophora Subphylum Sarcodina

Phylum Apicomplexa Phylum Ciliophora

SARCOMASTIGOPHORA

Phylum Sarcomastigophora: 18,000 species, largest protozoan phylum

Characteristics:1. Unicellular or Colonial2. Locomotion by flagella, pseudopodia, or

both3. Autotrophic, saprozoic, or heterotrophic4. Single type of Nucleus5. Sexual Reproduction (usually)

LOCOMOTION

Subphylum Mastigophora: locomotion by one or more flagella

Subphylum Sarcodina: locomotion and food gathered by pseudopodia (false foot)

- includes the Amoeba

Pseudopodia- temporary cell extension used for movement and

gathering foodTypes:1. Lobopodia: broad extensions used for locomotion

and engulfing food2. Filopodia: provide constant two-way streaming that

delivers food in a conveyor belt fashion 3. Reticulopodia: similar to filopodia, except they

extend out and form net-like series of extensions4. Axopodia: thin, filamentous and supported by a

central axis of microtubules

The AMOEBA

APICOMPLEXA

Phylum Apicomplexa:

Characterisitics:1. All are parasites2. Apical Complex for penetrating host cells3. Single type of Nucleus4. Usually No Cilia and Flagella5. Life cycles that typically include asexual

and sexual phases

Malaria caused by Plasmodium

Phylum Ciliophora: Characteristics:1. Cilia for locomotion and for the

generation of feeding currents of water.2. Relatively rigid pellicle and more or less

fixed shape3. Distinct cytostome (mouth) Structure4. Dimorphic nuclei, typically larger

macronuclei and one more smaller micronuclei

Ciliophora

Locomotion: cilia• Cilia are generally similar to flagella but are

much shorter, more numerous and widely distributed over the surface of the organism– cilia have evolved into more specialized structures

Trichocysts: used for protection, rodlike or oval structures that can be discharged and stuck to predators

Trichocysts

Body types

Nutrition: • some ciliates possess an oral groove

• cilia sweep food particles down this groove toward the cytopharynx where a food vacuole forms

• some ciliates even possess an anal pore which is used to remove waste from the organism

Genetic Control and Reproduction:

Ciliate have two kinds of Nuclei1. Macronuclei: large polyploid nucleus that

regulates daily metabolic activities2. Micronuclei: one or more small nucleus

which are genetic reserve of the cell

• Ciliates can reproduce asexually by transverse binary fission and occasionally by budding

• Ciliates can reproduce sexually by conjugation

Conjugation:1. Random contact brings individuals of opposite

mating types together (called conjugants)2. Meiosis results in four haploid pronuclei3. Three pronuclei and the macronucleus degenerate.

Mitosis and mutual exchange of pronuclei is followed by fusion of the pronuclei.

4. Conjugants separate. Nuclear divisions that restore nuclear characteristics of species follow. Cytoplasmic divisions may accompany these events

Conjugation