Protists

O’Connor

Protists

• organisms, comprising those eukaryotes that cannot be classified in any of the other kingdoms as fungi, animals, or plants.

• they are unicellular or

• they are multicellular without highly specialized tissues.

How do they “eat”?

• Protists obtain nutrients & digest nutrients in a complex acquirement & assimilation system.

• Most protists also feed on bacteria.

• Protists acquire their food material through internal digestion.

• They extend their cell wall & cell membrane around the food material to form a food vacuole via endocytosis.

Protozoa

• animal-like protists

• mostly single-celled, motile protists that feed by phagocytosis, though there are numerous exceptions.

• generally too small to be seen without magnification.

• Some protists are heterotrophs

• Some protists are autotrophs

• Some get nutrients by decomposing organic matter

Protozoa are grouped by method of locomotion into

• Flagellates with long flagella e.g., Euglena Amoeboids

• with transient pseudopodia e.g., Amoeba Ciliates

• with multiple, short cilia e.g., aramecium Sporozoanon

• mobile parasites; some can form spores e.g., Toxoplasma

Algae, the plant-like protists

• include many single-celled organisms that are also considered protozoa, such as Euglena

• which many believe have acquired chloroplasts through secondary endosymbiosis

• Others are non-motile, and some (called seaweeds) are truly multicellular

• Chlorophytes- green algae, are related to higher plants– e.g., Ulva

• Rhodophytes- red algae – e.g., Porphyra

• Heterokontophytes- brown algae, diatoms, etc. – e.g., Macrocystis

Molds

• Slime molds, water molds & downy mildews are fungus like protists that decompose organic material to obtain nutrients.

• Plasmodial and cellular slime molds change in appearance and behavior before producing reproductive structures

Slime Mold

Water Mold

Downy Mildew