“Animal-Like” Protists:

Protozoans

“Animal-like” Protists: Protozoans

• Kingdom Protista• Four phyla of “animal-like” protists

differentiated by locomotion• All heterotrophs• Protists that live primarily by ingesting food are

called protozoans.

Phylum Zoomastigina - Flagellates

• Move by flagella – long, whip-like structures

• Absorb food through cell membranes

• No shell• Some free-living, some parasites• Most reproduce asexually by

binary fission = genetically identical. Some reproduce sexually as well – gametes formed by meiosis = new combination of genetic information.

Phylum Sarcodina - Sarcodines• Best known sarcodina is

amoeba • Move and feed by use of

pseudopods – temporary projections of cytoplasm

• No body shape, the “blob”• Move by amoeboid movement

– cytoplasm of the cell streams into the pseudopod, and the rest of the cell follows

• Food vacuole temporarily stores food

• Reproduce by binary fission

Amoeboid Movement

Amoeba Anatomy

Food vacuole

Nucleus

Contractile vacuole

Pseudopods

Other Sarcodinas• Heliozoans and radiolarians – these both produce shells of SiO2

(silica)

• Foraminifers – produce shells of CaCO3 (calcium carbonate), used in dating rocks and chalk

Phylum Sporozoa - Sporozoans• Do not move, all are

parasitic• Live in worms, insects, fish,

birds, and humans• Very complex life cycles• Reproduce by means of

spores (groups of cells which invade a new host)

• Also known as Apicomplexans

Plasmodium killing red blood cells

The Life Cycle of PlasmodiumPlasmodium undergoes several stages of development in mosquito’s body

Mosquito bites human, injecting saliva that contains Plasmodium sporozoites

Plasmodium sporozoites

Sporozoites infect liver cells

Liver

Infected liver cells burst, releasing Plasmodium cells that infect red blood cells

Plasmodium cells

Red blood cells

Infected red blood cells burst, releasing Plasmodium cells; some can infect other red blood cells, and others can infect mosquitoes

Anopheles mosquito bites infected human and picks up Plasmodium cells

Phylum Ciliophora – Ciliates

• Cilia – short, hair-like projections used in feeding and/or locomotion

• Found in fresh and saltwater

• Most are free-living• Genus Paramecium

one of the most studied protists

Anatomy of Typical ciliate• Pellicle – “skin”• Trichocysts – small, bottle-shaped structures used for

defense and protection• Macronucleus – daily genetic material• Micronucleus – contains “reserve copy” of cell’s

genes/reproduction genetic material• Gullet – indentation in one side of organism to trap food• Food vacuole – food storage and digestion• Anal pore – excretion• Contractile vacuoles – collect water and when full,

contracts, pumping water out– Why is this necessary?

Paramecium Anatomy

Anal pore

GulletOral groove

TrichocystsLysosomes

Food vacuoles

Contractile vacuole

Micronucleus

MacronucleusCilia

Reproduction of Ciliates• Under most conditions, ciliates reproduce

asexually by mitosis and binary fission – cell splits lengthwise, forming 2 genetically identical cells

• When placed under stress, conjugation may occur

• Conjugation allows for a crossover of genetic information, but in the end, the two cells are genetically the same – the two cells simply swapped half of each other’s genetic information. This does make new combinations of genes though = genetic diversity

Conjugation

Macronucleus

Micronucleus

Conjugation

Macronucleus

Micronucleus

Conjugation

Macronucleus

Micronucleus

Conjugation

Macronucleus

Micronucleus

“Animal-like” Protists and Disease

• Sporozoans – Plasmodium – malaria, Toxoplasma – damages nervous system

• Zoomastigina – Trypanosoma – African sleeping sickness

• Sarcodina – Entamoeba – amebic dysentery

Ecology of “Animal-like” Protists – Helpful

• Serve as food at the base of the food chain

• Trichonympha – live inside termites and help break down cellulose in wood for termites to then digest