protozoa

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Protozoa

protos "first" + zoia "animal"

PROTOZOOLOGY -is the study of protozoan,

the "animal-like" protists

Protozoans are an extremely diverse assortment

of unicellular eukaryotes

Protozoa

l Lack a cell wall

l Have at least one motile stage in life cycle

l Most ingest their food

l Carry on all life activities within a single cell.

l Can survive only within narrow environmental

ranges.

l Very important ecologically.

l At least 10,000 species of protozoa are symbiotic in

or on other plants or animals.

l Relationships may be mutualistic, commensalistic, or

parasitic.

l More diverse than eukaryotes

Nutrition in Protozoans

l Autotrophs - contain

chloroplasts.

l Heterotrophs - absorb

organic molecules or

ingest larger food

particles.

l Phagocytosis

l Mixotrophs - combine

photosynthesis and

heterotrophic nutrition.

Protozoans Occur in Diverse Habitats

Freshwater and marine species.

l Require moisture

l Free-living and symbiotic species.

l Mutualistic – benefits both.

l Commensalistic – one

benefits, the other is neutral.

l Parasitic – one benefits at

a cost to the other

Locomotion in Protozoans

l Protists have three main methods of locomotion.

l Some protists, like this Euglena,

have one or two long flagella that they can whip around an

propel themselves through the water

lSome, like this Tetrahymena, are covered with numerous, but

shorter, cilia that facilitate movement and/or feeding.

l Others use ameboid movement to get around.

l A pseudopod is extended forward, followed by the rest

of the organism.

l pseudopodia are extensions of the cell cytoplasm used

for locomotion

Form and Function- Locomotion

l Lobopodia – large blunt extensions of the cell body.

l Filopodia – are thin extensions, usually branching.

l Reticulopodia – repeatedly rejoin to form a netlike mesh.

l Axopodia – long thin pseudopodia

supported by axial rods of microtubules

Functional Components- Specialized Organelles

l Nucleus – contains DNA.

l Mitochondria – organelle used in energy production.

l Golgi – part of the secretory system of the ER.

l Plastids – organelles containing photosynthetic pigments.

l Extrusomes – organelles that extrude something from the cell

Nutritions

l Holozoic feeders, or phagotrophs, ingest particles of food.

l Food vacuole – the membrane-bound vesicle containing the

food.

l Food vacuoles fuse with lysosomes containing digestive

enzymes

l Often, the site of phagocytosis is a definite

mouth structure, the cytostome.

l Saprozoic feeding (ingestion of soluble

food) may be by pinocytosis or by transport of solutes

across the cell membrane