Objectives:

Identify basics of protists

Catalyst: Draw diplospirilli, staphylobacilli, streptococci

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PROTISTSunicellular (single celled)

eukaryotic organisms

PROTISTS • Evolved about 2 billion years

after monera• Characteristics in common with

plantae, animalia, and fungi• Protista was created to have a

place for all the “unclassified”

Where did protists come from?

ENDOSYMBIOSIS

HYPOTHESIS

ENDOSYMBIOSIS

HYPOTHESIS1st eukaryotes were formed by the symbiosis (joining

together) of several prokaryotes

ENDOSYMBIOSIS HYPOTHESIS

Proposed by Lynn Margulis

Endosymbi

osis

Hypothesis

3 TYPES OF PROTISTS

•Animal-like

•Plant-like•Fungi-like

Animal-like Protists

Ciliophora

• Aka “cilliates” because they use cillia for movement.

• Cillia are hair like projections that work like oars in the water

• Example = paramecium

Paramecium

Zoomastigina

• Move through the water using flagella

• Flagella are long, whiplike projections (like the tail of a sperm)

Zoomastigina

Sporozoa

• Non-motile (do not move) • All are parasitic• Reproduce using spores• Example: Plasmodium which causes malaria

Plasmodium falciparum

Sarcodina• Use pseudopods (false foot) for movement

• Pseudopods are temporary projections of cytoplasm that help in movement and feeding

• Example = amoeba

AMEOBA

Plantlike Protists

Euglenophyta

• Flagellates with Chloroplasts• Closely related to zoomastinans.

• example = euglena

EUGLENA

Pyrophyta

• Only eukaryote that does not have histones (proteins that tightly coil DNA)

• Most are luminescent (give off light)

• Example: Dinoflagellates

Dinoflagellates

Chrysophyta

•Includes yellow-green algae, golden brown algae, diatoms

•Example: Diatoms

DIATOMDIATOM

Funguslike Protists

2 Phyla of Funguslike Protists

Both are Slime Molds

• Acrasiomycota: cellular slimemolds

• Myxomycota: acellular slime molds

Myxomycota•AKA plasmodial slime molds

•Have 1 cell with thousands of nuclei

MYXOMYCOTA

Acrasiomycota• AKA Cellular Slime Molds

• Spend most of their lives as separate single-celled amoeboid protists

• The individual cells may come together into a great swarm

Protists

• Last part of Chapter 20.• Protists are single celled

eukaryotes. A few forms are multi-cellular.

• Protists often have a very complicated internal structure: a single cell must do all the functions that we have many different cell types to do.

• Protists can be divided into plant-like, fungus-like, and animal-like forms. This division probably has little to do with their evolutionary history.

Protist Phylogeny

• Protists are very diverse, and probably represent several different evolutionary lineages, more distinct from each other than plants, animals, and fungi are.

Fungus-like Protists• Water molds and slime molds• Like fungi, they are heterotrophs: they

get food and energy from other organisms. Many are decomposers of dead organisms.

• Unlike fungi, the fungus-like protists produce motile (moving) cells during part of their like cycle. Also, these protists surround and engulf bacteria as food.

• Slime molds live as separate cells most of their lives, feeding on bacteria. When conditions get harsh, they aggregate into a multicellular slug, which migrates to a new location. The slug then forms a fruiting body that generates spores. The spores from the fruiting body are very hardy.

Slime Molds

• Slime molds can be rather large and colorful.

More Fungus-like Protists

• The water molds include some of the worst plant diseases.

• Phytphthora infestans causes rot in plants. In the 1840’s, Phytophthora caused the potato blight in Ireland. The Irish were poor and overcrowded, and lived mostly on potatoes. The blight caused crop failures in several years, resulting in the deaths of of the population. Many Irish came to the US at that time.

Animal-like Protists

• The animal-like protists are classified according to how they move: amoeba-like, ciliated, or flagellated.

• Amoeba-like protists move by extending pseudopods, part of their cytoplasm, then pulling the rest of the cell along behind. The can surround and engulf their food this way.

• Some amoeba-like protists have hard shells. The foraminiferans are covered in calcium carbonate—chalk, which we use on chalk boards.

Amoebas in Action

Ciliated Protists• Cilia are small hairs

surrounding the protist’s body. The cilia beat in a synchronized pattern to cause movement.

• Paramecium is a typical ciliate. It has a gullet to swallow food, and a contractile vacuole to get rid of excess water.

• Genetics: the DNA used for sexual reproduction is stored in the small micronucleus. A copy of this information is used to run the cell: the copy is kept in the much larger macronucleus.

Flagellates

• Flagellates have a small number of long flagella, long whiplike hairs that beats to propel the cell.

• Some nasty parasites are flagellates, including Giardia lamblia, which causes diarrhea and which is found in most of the surface waters of the US. Another is Trypanosoma brucei, which causes sleeping sickness in Africa. Also Trichmonas vaginalis, a sexually transmitted disease.

Sporozoans• Sporozoans are animal-like protists

that have part of their life cycle inside the cells of their hosts.

• The most important example is Plasmodium, the parasite that causes malaria. Malaria kills 1-2 million people each year.

• Mosquitoes are part of the life cycle. They suck blood from infected humans, ingesting the sporozoans. The sporozoans undergo sexual reproduction in the mosquito’s gut.

• When the mosquito bites another person, the sporozoans infect the blood and liver of the host. The parasites multiply asexually inside the red blood cells, destroying them as they leave.

Algae

• The plant-like protists are called algae. Most are single-celled, but a few form large multicellular seaweed.

• The plant-like protists have chloroplasts. Some, like the Euglena, also have flagella for movement.

• Some, such as the diatoms, have calcium carbonate (chalk) or silica shells.

Algae Blooms

• Algae blooms are the sudden growth of a large population of single celled algae. They occur near the coastlines, with the algae feed on fertilizer runoff and sewage. Algae blooms deplete the oxygen in the water, killing fish and other organisms. Some of the algae also secrete toxins. Red tide and Pfiesteria are examples of this.

Multicellular Algae• The multicellular algae are commonly

called seaweed. They can be classified into red, brown, and green algae. All have chloroplasts, but the pigments in the chloroplasts vary, giving the different colors.

• Some, like kelp, are very large and contain several different types of cells and tissues to do specialized work. These include leaves for photosynthesis, gas-filled bladders for buoyancy, the root-like holdfast, and tubes to transport nutrients throughout the body.

• Algae contain the polysaccharide “agar”, which is tasteless and is used to thicken foods such as soft ice cream.

Green Algae

• The green algae are the ancestors of plants. The term “plant” implies living on the land or derived from plants living on the land. Green algae and plants have very similar chloroplasts.

• Green algae have some unicellular species (such as Chlamydomonas), some simple colonies (such as Volvox), and some relatively complex multicellular organisms (such as Acetabularia).

• Green algae are haploid most of their live cycle, with only a very short diploid phase.