KINGDOM KINGDOM PROTISTAPROTISTA

PROTISTSPROTISTS• Very diverse group

– >60,000 known species

• Most are unicellular– Some are colonial– Some are multicellular

• Not “simple” at the cellular level– A unicellular organism must carry out all basic

functions of life within a single cell– Cells within a multicellular organism can become

specialized, and need not carry out all such functions

• Protists show amazing diversity in cell organization, methods of reproduction, metabolic needs and habitats.

• They inhabit aquatic and terrestrial environments.

• Protists are the most nutritionally diverse eukaryotic group–Most are aerobic, and possess

mitochondria–Some protists are heterotrophic;

others are autotrophic

Protists are divided into Protists are divided into 3 main groups3 main groups

1. Animal-like protists (Protozoa)

2. Plant-like protists (Algae)

3. Fungus-like protists

Animal-like ProtistsAnimal-like Protists• All protozoa are heterotrophic

• Some absorb nutrients through their cell membrane, whereas others “engulf” larger food particles.

• Most protozoa are motile and are divided into phyla based on their means of locomotion.

Phylum SarcodinaPhylum Sarcodina• Ancestors lost their

permanent motile structures.

• Found in fresh and salt water and inside the bodies of animals. Some of these cause disease.

• Reproduction is both sexual and asexual.

Types of Types of ReproductionReproduction

• Asexual Reproduction - only one parent is needed, resulting in offspring that are genetically identical to the parent -- clones.

• Sexual Reproduction - requires two parents who exchange genetic material, resulting in offspring with a mix of inherited genes.

• The best known sarcodine is the ameba. • Amebas are unicellular organisms that

continually change shape• Move and capture food by pseudopods,

or “false feet.” • This movement by pseudopods is called

amoeboid movement.• Amebas reproduce asexually by binary

fission.• They are commonly found in freshwater

ponds, lakes and streams.

Ameba Video ClipAmeba Video Clip

Amebas can cause Amebas can cause disease!disease!

• They can cause amebic dysentery.

• Common in tropical regions

• Lives in the large intestine of humans and feeds on the intestinal wall causing bleeding.

• A person becomes infected by eating food or water contaminated with the cysts of the ameba.

Radiolarians and Radiolarians and ForamsForams

• Also belong to the phylum Sarcodina.• Surrounded by protective shells that contain silicon. They

have very long thin pseudopods.• When these organisms die, their shell settle to the bottom

of the ocean.

The White Cliffs of The White Cliffs of Dover are made of old Dover are made of old

foram shellsforam shells

Phylum CiliophoraPhylum Ciliophora• e.g., Paramecium

• Many possess numerous cilia

– Motile structures

– Beat in synchronized fashion

• Prey on bacteria, algae, each other

• ~65% are free-living and motile

– Others attach to some substrate

– Some form colonies

A Microscopic Predator – A Microscopic Predator – two ciliates meet for two ciliates meet for

lunchlunch

DidiniumDidinium sp. sp.DidiniumDidinium sp. sp.

ParameciumParamecium sp. sp.ParameciumParamecium sp. sp.

Ciliates Video ClipCiliates Video Clip

• Cilia are important in movement and to move food into the oral groove.

• Food particles are enclosed and digested in food vacuoles.

• Some ciliates have contractile vacuoles which collect and excrete excess water from the cell. Most aquatic protists have a contractile vacuole.

• Ciliates do not change shape.

• They have a rigid outer covering called a pellicle that maintains their shape.

• Beneath the pellicle, some ciliates have trichocysts which are barbed structures that are discharged for defense or capturing of prey.

• Reproduce sexually and asexually

–Similar to most protozoans in this regard

• Asexual process is “binary fission”

–In this process the cell divides into two genetically identical cells.

• Sexual process is “conjugation”

–Two cells join and exchange their micronuclei before the cells divide.

CONJUGATIONCONJUGATION

Phylum Phylum ZoomastiginaZoomastigina• Also called the zooflagellates.

• These protists move by beating a long whip like flagella.

• Some have one flagella while others may have many.

• Most are unicellular.• Some are free living but most live in the

bodies of animals.• Reproduce both asexually and sexually.

TrypanosomaTrypanosoma in Blood – in Blood – causes African sleeping causes African sleeping

sicknesssickness

African Sleeping African Sleeping SicknessSickness

• The parasite multiplies in the blood and releases toxins that cause fever, weakness and sleepiness.

• Lives in the blood of wild and domestic animals, but can be passed to humans through a bite from a tsetse fly.

Not all zooflagellates Not all zooflagellates are harmful!are harmful!

• Another zooflagellate lives in the digestive tract of termites.

• The protist breaks down the wood that the termite eats and then both absorb the nutrients.

Phylum SPOROZOAPhylum SPOROZOA• These are non motile parasitic protozoa.• They get their name because they produce

spores during asexual reproduction.• The spores allow the spread of the parasite to

new hosts.• The life cycles of sporozoans are complex and

involve growth and reproduction in more than one kind of host.

• The best know members are of the genus Plasmodium, which causes malaria.

MALARIAMALARIA• Has infected > 100 million people

– ~1 million die yearly in Africa alone• Shaking, chills, fever, sweats caused by the toxins

that are released when the red blood cells of the host are destroyed by the reproducing Plasmodia.– Symptoms subside, but can reoccur.

• Transmitted to humans by mosquitoes– Females of genus Anopheles

• Sexual reproduction takes place in the gut of the mosquito and the asexual phase occurs in the liver and blood of the human host.

Malaria VideoMalaria Video

Life cycle of plasmodium on Pg. 645 of text.