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ProtistsChapter 21

+General Characteristics of Protists Protists are eukaryotes, in the Kingdom

Eukarya

Most are unicellular and free-living (not parasites)

Asexual/sexual reproduction

Some live in colonies or are multicellular

Simple organisms because they are mostly unicellular Complex cells because they complete all

life’s functions How is this different from us?

Protists are grouped by their lifestyles rather than evolutionary relationships

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Section 21.2Protist Structure and Function

+ How Do Protists Move in the Environment?

(1) Amoeboid Movement - Movement by changing shape, a process that makes use of cytoplasmic projections called pseudopods Amoeba Feeding

(2) Cilia and Flagella – protists that use cilia (short, numerous structures) ciliates – protists that use flagella ( long, one/two) flagellates

+ How Do Protists Move in the Environment?

(3) Passive Movement – depend on air/water currents and other organisms to carry them around

- form reproductive cells spores that enter the cells of other organisms and live as parasites

* Plasmodium Parasitic protist that causes malaria

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Section 21.3The Ecology of Protists

+ Think About It

After a few days of rain, you notice a small spot of yellow slime at the base of a stand of tall grass. You mark its position. A few days later, you come back, and it has grown and moved away from the mark.

Is it an animal? A fungus? A strange plant? The correct answer is none of the above. It’s a protist called a slime mold.

+ Ecological Signficance : Autotrophic Protists

Use energy from light to make a carbohydrate food source

1) Base of the food chain makes diversity of aquatic life possible

2) Phytoplankton small, free-floating photosynthetic organisms found near the surface of oceans/lakes)

- About half of the Earth’s photosynthesis is carried out by phytoplankton

+ Ecological Signficance : Autotrophic Protists (cont’d)3) Direct source of nourishment

for organisms (shrimp, baleen whales)

4) Recycling wastes grow rapidly and recycle waste materials

+ RECYCLING WASTES Autotrophic Protists

When the amount of waste is excessive, populations of protists can grow to enormous numbers and create an algal bloom, which can disrupt ecosystem homeostasis.

- deplete nutrients from the water

- decomposition of the dead protists can rob water of its oxygen fish die.

Algal blooms of marine protists called dinoflagellates create what is known as a red tide. The buildup of toxins produced by these protists can poison fish and shellfish.

+ Hetertrophic Protists : How do they obtain food?

Engulf/digest food Ameoba: surround a cell/particle and

take it inside themselves and form a food vacuole

Ciliates: use cilia to sweep food particles in gullet indentation one side of the organism

Slime mold: thrives on decaying matter (KEY recyclers)

Protists that Absorb: absorb molecules that other organisms release into environment

- Water molds- grow on dead plants/animalsSaprolegnia

+Symbiotic Protists: Mutualists and Parasites

Symbiosis- relationship in which two species live closely together

Mutualism – both organisms living on one another benefit

- Trichonympha is another example of a mutualistic protist. Trichonympha is a flagellated protist that lives within the digestive system of termites and makes it possible for the insects to digest wood.

Parasitism- one organism benefits at the expense of its host

- Parasitic protists world’s most deadly diseases, like intestinal diseases, African sleeping sickness, and malaria.

+ Intestinal Diseases Water-borne protists are found in streams,

lakes and oceans- Contaminated by animal/human feces can

spread protist parasites intestinal disease

For example, the flagellated protist Giardia causes severe diarrhea and digestive-system problems.

- Even crystal-clear streams may be contaminated with Giardia, which produces tough cysts that can be killed only by boiling water thoroughly or by adding iodine to the water.

+Malaria Malaria - one of the world’s most serious infectious

diseases. Malaria is caused by Plasmodium, a spore-forming protist carried by the female Anopheles mosquito.

Plasmodium requires two hosts to complete its life cycle: an Anopheles mosquito and a human.

+Malaria Malaria - one of the world’s most serious infectious

diseases. Malaria is caused by Plasmodium, a spore-forming protist carried by the female Anopheles mosquito.

Plasmodium requires two hosts to complete its life cycle: an Anopheles mosquito and a human.

+Malaria Malaria - one of the world’s most serious infectious

diseases. Malaria is caused by Plasmodium, a spore-forming protist carried by the female Anopheles mosquito.

Plasmodium requires two hosts to complete its life cycle: an Anopheles mosquito and a human.

+Malaria Malaria - one of the world’s most serious infectious

diseases. Malaria is caused by Plasmodium, a spore-forming protist carried by the female Anopheles mosquito.

Plasmodium requires two hosts to complete its life cycle: an Anopheles mosquito and a human.