1. Chapter 21
Protists

2. I. Characteristics of Protists
A. Diversity
1. Characteristics
Various ways of metabolizing food
a. photosynthetic
b. ingest food
c. absorb food

3. Some move by flagella or cilia
Found almost everywhere there is water
Many have mechanisms responding to stimuli in their environment. Many have structures called eyespots.

4. 2. The First Eukaryotes
Evolved about 1.5 billion years ago
Two important eukaryotic features evolved among protists
a. sexual reproduction
b. multicellularity

5. B. Reproduction
1. Asexual reproduction in unicellular protists
A mature haploid (n) cell divides by mitosis
Haploid cells called zoospores are produced and remain within the wall of the parent cell
Zoospores then break out of the parent cell

6. 2. Sexual reproduction in unicellular protists
A haploid (n) cell divides by mitosis to produce haploid gametes
A pair of gametes fuse
The pair sheds their cell walls and fuse into a diploid (2n) zygote with a think protective wall called a zygospore
In favorable environmental conditions meiosis within the zygospore produces haploid (n) cells that break out of the zygospore

8. 3. Sexual reproduction in multicellular protists
a. Alteration of generations
Characterized by two distinct multicellular processes
i. sporophyte generation
- diploid, spore-producing phase
ii. Gametophyte generation
- haploid, gamete-producing phase

9. Step 1: Adult sporophyte’s (2n) reproductive cells, sporangia, produce haploid (n) spores by meiosis
Step: 2 Spores grown into multicellular haploid gametophytes
Step 3: The mature gametophyte produces haploid gametes
Step 4 Haploid gametes fuse into diploid zygotes
Step 5: Diploid zygotes divide by mitosis to form new diploid sporophytes

10. Gametophyte generation Diploid (2n) Sporophyte Generation
Haploid (n)
Gametophyte generation
Diploid (2n)
Sporophyte Generation
mitosis

11. b. Conjugation
Two protists temporarily unite to exchange nuclear material
The nucleus of one cell passes through the bridge made by the fusion into the adjacent cell

12. Unicellular heterotrophs Amoebas
II. Amoebas and Forams
Unicellular heterotrophs
Amoebas
Protists that move by using flexible, cytoplasmic extensions called pseudopodia
In a process called ameboid movement, a pseudopodium bulges form the cell, stretches outward, and anchors itself to a nearby surface
Live in both fresh and salt water
Reproduce by fission, dividing into two cells
Concept Map Protist Diversity

13. B. Foraminifera
Typically live in marine sand or attach themselves to other organisms or rocks
Characterized by their porous shells, or tests, made of calcium carbonate

14. III. Algae
Strict phototrophs
A. Green Algae
Freshwater unicellular and multicellular organisms
Contain the same pigments found in the chloroplasts of plants
most have sexual and asexual reproductive stages

15. B. Red Algae
Multicellular organisms found in warm ocean waters
- contributes to the great coral reefs
Red pigment is efficient at absorbing the light that penetrates deep waters
Life cycle involves alternation of generations

16. C. Brown Algae
Multicellular organisms found mostly in marine environments
Kelp is among the largest organisms on Earth
Reproduce by alternation of generations

17. IV. Diatoms
Photosynthetic
Unicellular
Unique double shells made of silica
Found in oceans and lakes
Important producers in the food chain

18. Diploid (2n) individuals that reproduce asexually
- the two halves of the shell separate, and each half regenerates another matching half
- tend to get smaller and smaller with each generation
- when an individual gets too small it slips out of its shell, grows to full size, and regenerates a new shell

19. V. Flagellates
Move using flagella
A. Dinoflagellates
Unicellular phototrophs
Most are marine and make up plankton
Have a protective coat made of cellulose

20. Most have two flagella
1. one encircles the body like a belt
2. the other beats perpendicular to it causing it to spin through water like a top
Reproduce asexually by mitosis
Some produce powerful toxins that are associated with the poisonous “red tides”

21. B. Euglenoids
Live in freshwater
Unicellular, asexual
1/3 contain chloroplasts and are photosynthetic
Others lack chloroplasts, ingest their food, and are heterotrophic
A light-sensitive organ called the eyespot helps orient the organisms movements towards light

22. C. Kinetoplasts
Unicellular
Heterotrophs
Most reproduce asexually
Some live symbiotically in the guts of termites, where they provide the enzymes that digest wood
Others cause diseases such as African sleeping sickness

23. D. Ciliates
Most complex of the protists
Have large numbers of cilia used for movement
Unicellular
Heterotrophs
Most form vacuoles for ingesting nutrients and regulating their water balance

24. Most have two types of nuclei
1. micronuclei
- contain normal chromosomes that divide by mitosis
2. macronuclei
- contain small pieces of DNA derived from the micronuclei
Most reproduce by mitosis, with the body splitting in half
Engage in sexual reproduction through conjugation

25. VI. Protistan Molds
Heterotrophs
Cell walls contain different carbohydrates than fungal cell walls

26. A. Cellular slime molds
Individual organisms behave as separate amoebas in soil
In the event of environmental stress, they gather together and form multicellular colonies called slugs
- each slug develops a base, a stalk, and a swollen tip that develops spores
- each spore releases and becomes a new individual

27. B. Plasmodial Slime Molds
A group of organisms that move along as a mass of cytoplasm, or plasmodium
Engulf bacteria and other organic material as they move
Contains many nuclei that are not separated by cell walls

28. Under stress, the plasmodium divides into smaller mounds
- each mound produces a stalk tipped with a capsule in which haploid spores develop
- in favorable conditions, the spores germinate and become haploid cells
- the haploid cells fuse into diploid zygotes that undergo mitosis and form a new plasmodium

29. C. Oomycetes
Water molds, white rusts, an downy mildews in fresh water
Either parasites or feed on dead organic matter

30. VII. Sporozoans
Parasitic in hosts
Form spores during their reproduction cycle
Nonmotile
Unicellular
Life cycle involves both asexual and sexual reproduction
- sexual reproduction between a male and female gamete results in a zygote with a think-walled structure that makes it resistant to unfavorable conditions

31. VIII. Protists and Health
A. Beneficial protists
Single largest group of photosynthesizers on the planet
- help to support food chains
Live in the digestive tracts of humans and animals
- cattle could not digest the cellulose in the hay and grass they eat without the aid of protists

32. B. Malaria
3 million people die from malaria each year
- die of anemia, kidney failure, or brain damage
1. Malaria Life Cycle
Spread by the bite of certain mosquitoes

33. Three stages
a. sporozoite
A mosquito injects saliva containing about 1,000 protists into a human
These sporozoites infect the liver where they divide and reproduce

34. b. Merozoite
The second generation cells from the liver infect red blood cells and divide
Red blood cells rupture, releasing the merozoites and toxic substances that prevents the blood from clotting

35. c. Gametes
Some merozoites develop into gametes
When eaten by a mosquito, male and female gametes fuse into a zygote
The zygotes divide in the mosquito and form sporozoites

36. Active Reading p. 11