Chapter 20

Protists

I. Protists are divided into 3 groups:1. Animallike- must absorb food2. Plantlike- make own food.3. Funguslike

II. Protist- any organism that is not a plant, animal,fungus or a prokaryote (no nucleus).a. Most are unicellular (single-celled)

III. Animallike ProtistsA. Zooflagellates – animal-like protists that swim using flagella.

1. May have one or many flagella for swimming

2. Take in nutrients through the cell membrane.

Trophozoites (pear-shaped)

B. Sarcodines- move by temporary projections in the cell body called pseudopods

Click for movie of amoeba locomotion

1. Surround and engulf their food and store in food vacuoles.

C. Cilliates- Use cillia for feeding and movementi.e. paramecium (see below)

1. cillia- short hair-like structures on the cell membrane.

a. Usually hundreds or thousands of cillia on one cell

2. Trichocysts- parts of the cell membrane that can protrude and act as a defense mechanism

3. Contain 2 nuclei:a. Macronucleus (large) - contains DNA for day-to-day existence.b. Micronucleus (small) - contains a

back-up copy of DNA.

IV. Reproduction in Protists- normally asexual (cloned)a. Conjugation (sexual reproduction)- if

conditions are right two paramecium join and randomly exchange DNA. That exchanged DNA then copies itself and each paramecium gets the new DNA.

V. Sporozoans- can not move on their own so they are parasitic.a. Reproduction by means of a sporozoite which is the sporozoan gone dormant with a protective shell around it (like a shell for a seed)b. Many cause disease i.e. plasmodium falciparum- causes Malaria; carried in the bite of an Anopheles mosquito

Plasmodium attacking and killing red blood cells in a human

                                                                                          

            

Life cycle of Plasmodium

Trypanosoma protist- causes African Sleeping Sickness carried in the excretion of a tseste fly.

Dysentery (severe diarrhea) caused by Entamoeba

Cysts can easily be killed with proper sanitation

VI. Plantlike Protists (Unicellular)- single-celled organisms (algae) that can make their own food

A. Euglena- almost like zooflagellates but contain chloroplasts for photosynthesis

1. No cell wall but a ridged cell membrane called a pellicle

2. Eye Spot – Helps find sunlight

B. Dinoflagellates- half are photosynthetic other half are heterotrophs (must eat food)

1. Flagella stored in grooves called cingulum on cell membrane when not in use

2. Some are luminescent and give off a bluish or redish glow at night

C. Chrysophytes- have gold-colored chloroplasts absorbing different colors of light than green plants

1. Golden-brown or yellowish-green in color

D. Diatoms- produce thin delicate cell walls made of silicon etched in patterns therefore, glasslike

VII. Plant-like Protists (Red, Brown and Green; “pondscum”)- Mostly multicellular; reproduce like plants; have cell walls; no roots or “woody” tissue

1. 3 main groups according to the different types of chlorophyll they have:

A. Red Algae- contain “chlorophyll a” which is very good at absorbing blue light therefore, red algae can live at great depths in the ocean.

1. Red Tides- red algae overtakes an area from eating high concentrations of nitrates from fertilizers that have drained off the land from farming.

B. Brown Algae- “seaweed”; largest and most complex of the algae. 1. All are multicellular

2. Have leaflike structures; look like brown vines or ferns

C. Green Algae- “moss”; can be unicellular; live in colonies or be multicelluar like a plant.1. Identical to plants in almost every way except no roots or woody tissue.

a. Unicellular- single celled

Netrium digitus

b. colonies- individual cells live together and help each other- i.e. volvox

Volvox

c. multicellular- just like a plant; cells are connected and have an individual job for the whole organism. i.e. spirogyra

1000x

300x

VIII. Funguslike Protists- absorb nutrients from dead and decaying organisms. Lack thick cell walls –is made of chitin (kite-in) like true fungi.

A. Chitin- carbohydrate similar to that of an insects’ exoskeleton

1. Slime Molds- unicellular amoeba-like cells that live in the soil.

When nutrients run out they form a colony that builds a fruiting body

(what you see) that contain spores (egglike) that the wind will carry like a seed to new ground.

Various Slime Molds