1. Protists – The Simplest Eukaryotes
Chapter 20
Biology Concepts and Applications, Eight Edition, by Starr, Evers, Starr. Brooks/Cole, Cengage Learning 2011.

2. 20.1 Harmful Algal Blooms Protist
Eukaryote that is not a fungus, animal, or plant
Aquatic protist
Single-celled and multicellular autotrophs
Heterotrophs
Photosynthetic protists
Take up carbon dioxide and release oxygen
Food source for aquatic animals

3. Harmful Algal Blooms Algal bloom
Population explosion of tiny aquatic producers
Extra nutrients are present and the cells multiply fast
Threatening to the ecosystem
“Red Tide”  algal bloom of reddish pigment protists
Not all algal blooms are red
Not all events are related to tidal changes

4. Harmful Dinoflagellate Blooms
Dinoflagellate bloom – Karenia brevis
Toxin  chemical that is made by one organism and harms another
Brevetoxin  interferes with animal nerve cells by binding to a protein in their cell membrane
Sickens and kills marine invertebrates, fish, sea turtles, sea birds, dolphins, and manatees
Human affects
Tainted food  intestinal problems and nervous system symptoms such as headache, loss of coordination, and paralysis
Inhaling toxin  constricted airways, difficulty breathing, and irrigated nasal membranes, increase risk lung cancer

5. 20.2 A Collection of Lineages
Protists
The simplest eukaryotes
Most are single-celled
Some are multicelled and large

6. Protist Structure Protist cells have a nucleus (eukaryotes)
Most have one or more mitochondria
Many have chloroplasts that evolved from cyanobacteria or from another protist
Dominant stage of life cycle: Haploid or diploid

7. Protist Life Cycle Most reproduce both sexually and asexually Malaria
Haploid stage the divides in human blood and liver cells
Only diploid stage in the parasite’s life is the zygote
Zygote undergoes meiosis within a few hours of fertilization
Silica-shelled cells – diatoms
Diploid-dominant life cycles
Diploid cells divide by mitosis and only the games are haploid

8. Protist Life Cycles
Diatoms
Malaria
Multicelled
algae

9. Protists Nutritional Modes
Heterotrophs, autotrophs, or switch between nutritional modes
Heterotrophic  decomposers, prey on smaller organisms, or live inside larger organisms
Autotrophs  have chloroplasts

10. Protist Diversity
Gene sequencing shows that protists are not a monophyletic group
Collection of lineages, some only distantly related
Evolutionary connections among groups are gradually becoming clear

11. Protist Evolutionary Tree
**Text Figure 20.2 p.312**

12. Comparing Prokaryotes and Eukaryotes

13. Key Concepts: SORTING OUT THE PROTISTS
Protists include many lineages of single-celled eukaryotic organisms and their closest multicelled relatives
Gene sequencing and other methods are clarifying how protist lineages are related to one another and to plants, fungi, and animals

14. 20.3 Ancient Flagellates Flagellated protozoans
Single-celled heterotrophs with one or more flagella
No cell wall, pellicle retains shape
Pellicle  layer of proteins that gives shape to many unwalled, single-celled protists.
Include the most ancient eukaryotic lineages: diplomonads and parabasalids
Both groups lack mitochondria
Both include species that infect humans
Example: Trichomonas vaginalis
Parabasalid that infects the reproductive tract  disease trichomoniasis (6 million infected)

15. Euglenoids and Kinetoplastids
Most euglenoids live in freshwater - Euglena
Flagellated protozoan with multiple mitochondria
Some have chloroplasts that arose by secondary endosymbiosis from a green alga
May be heterotrophic
Contractile vacuoles expel excess water
organelle that collects and expels excess water
Most Trypanosomes are parasites
Have a single giant mitochondrion
Membrane-encased flagellum
Biting insects are vectors

16. Disease-Causing Flagellates
Trichomonas vaginalis
Trypanosoma brucei
Trypanosomes act as vectors for human disease

17. Euglena

18. 20.4 Mineral-Shelled Protozoans
Foraminiferans and radiolarians
Single-celled heterotrophs with a secreted shell
Many openings for pseudopods

19. 20.4 Mineral-Shelled Protozoans
Foraminiferans and radiolarians
Foraminiferans
Heterotrophic single-celled protists with a porous calcium carbonate shell and long cytoplasmic extensions
Ex. Component of plankton
Community of tiny drifting or swimming organisms with small photosynthetic protists inside them
Radiolarians
Heterotrophic single-celled protist with a porous shell or silica and long cytoplasmic extensions
Ex. Component of plankton in tropical water

20. Key Concepts: GROUPS WITH ANCIENT ROOTS
Two of the earliest lineages of eukaryotic cells are known informally as flagellated protozoans
Foraminiferans and radiolarians are another ancient lineage

21. 20.5 Alveolates
All alveolates have tiny sacs (alveoli) beneath the plasma membrane
All single-celled
Examples:
Ciliates, dinoflagellates, and apicomplexans

22. plasma membrane (blue)
alveolus
plasma
membrane
(blue)
p.322

23. Ciliates Aquatic predators and parasites with many cilia
Example: Paramecium
Food goes in gullet  endocytosis
Digestive waste  exocytosis
Contractile vacuoles that collect and squirt out excess water
Macronucleus  control daily activities
Micronucleus  function in sexual reproduction
Sexual reproduction  swap of micronuclei between two cells
Mostly reproduce ASEXUALLY

24. Fig. 20.7a, p.323

25. contractile vacuole
pellicle
Fig. 20.7b, p.323

26. Dinoflagellates
Aquatic heterotrophs and autotrophs with a cellulose covering, two flagella, and Single-cell
Photosynthetic protists cause algal blooms in nutrient-rich water
Vast majority are marine plankton

27. Apicomplexans Heterotrophs: Parasites living in animal cells
Cell-piercing structure made of microtubules
Reproduce sexually and asexually in host cells
Only gametes have flagella
Example: Plasmodium (malaria)

28. 20.6 Malaria Plasmodium species cause malaria
Leading cause of death – kills 1.3 million/year

29. sporozoites
sporozoites
g Plasmodium zygotes develop inside the gut of female mosquitoes. They
become sporozoites, which migrate to the insect’s salivary
glands.
a Mosquito bites human, bloodstream carries the sporozoites to liver.
b Sporozoites asexually reproduce in liver cells.
d Some of the merozoites enter liver, cause more malaria episodes.
e Others develop
into male, female gametocytes that are released intobloodstream.
merozoite
f Female mosquito
bites, sucks blood
from infected human. Gametocytes in blood
enter her gut, mature
into gametes, which
fuse to form zygotes.
c Offspring (merozoites) enter blood, invade red blood cells, reproduce asexually. They can do so often, over a prolonged period. Disease symptoms (fever, chills, shaking) get more and more severe.
male gametocyte in red blood cell
Fig. 20.9a, p.324

30. merozoites about to rupture a red blood cell
sporozoites
merozoites about
to rupture a
red blood cell
Fig. 20.9b, p.324

31. Key Concepts: THE ALVEOLATES
Ciliated protozoans, dinoflagellates, and apicomplexans are single-celled photoautotrophs, predators, and parasites with a unique layer of tiny sacs under their plasma membrane

32. 20.7 Stramenopiles
“straw-haired”, shaggy flagellum that occurs during the life cycle
Defined by genetic similarities
Types
Water molds
Diatoms
Brown algae

33. Water Molds Grows as nutrient-absorbing filaments Heterotrophs
Most decompose organic debris in aquatic habitats
Few are parasites with economic effects  “plant destroyers”
Closest relatives
Diatoms and brown algae
Both have chloroplasts with a brown accessory pigment (fucoxanthin) that tints them olive, golden, or dark brown.
Chloroplast evolved form red algae

34. Diatoms Single cell, Photosynthetic cells
Brown accessory pigments in its chloroplasts and a two-part silica shell
Live in cool waters, damp soil, lakes, seas
Hard parts accumulate as mineral deposits
Diatoms (silica shells): Diatomaceous earth
Used in filters, abrasive cleaners, and as insecticides that do not harm vertebrates

36. Brown Algae Multicelled, photosynthetic stramenopiles
Brown accessory pigment in its chloroplast
Live in temperate or cool seas
Include microscopic strands and giant kelps
Kelp  the largest protists; pacific northwest, shelter organisms
Commercial uses
Thickeners, emulsifiers, and suspension agents
Ice cream, pudding, jelly beans, toothpaste, cosmetics.

37. Fig , p.326

38. Key Concepts: THE STRAMENOPILES
Chrysophytes, diatoms, and brown algae are stramenopiles, most of which are photoautotrophs

39. 20.8 Red Algae
Photosynthetic protist that deposit cellulose in its cell wall
Stores sugars as starch
Has chloroplast containing chlorophyll a (absorb red/violet light) and red pigments called phycobilins (absorb green light)
More phycobilins in deeper water red algae
Can live at greater depths than brown and green algae

40. Red Algae Can survive in deep water (phycobilins)
Chloroplasts evolved from cyanobacteria
Red algae-like plastids occur in dinoflagellates and apicomplexans
Most red algae are multicelled
Cultivated for commercial products

41. Red Algae Commercial use
Agar  Keep baked goods and cosmetics moist, vegetarian substitutes for gelatin
Carrageenan  added to soy milk and dairy products
Nori  dry sheets of red alga Porphyra, wraps kinds of sushi
Alternation of generations
Of land plants and some protists, a life cycle in which haploid and diploid multicelled bodies form
Nori is the haploid body or gametophyte

42. Life Cycle: Porphyra Gametophyte gamete-producing haploid body
Sporophyte
spore-forming diploid body

43. 20.8 Green Algae Photosynthetic protists
Deposits cellulose in its cell wall
Have chloroplasts with chlorophylls a and b
Store carbohydrates as starch grains
Single-cell green algae partner with fungi to form lichens
Studies of green algae helped biologist understand mechanisms of photosynthesis
Determine the most effective wavelengths of light
Clarify the Calvin-Benson cycle

44. Green Algae Chlamydomonas Chlamydomonas Life Cycle
Flagellated single-celled green alga in fresh water
Chlamydomonas Life Cycle
Haploid cells reproduce asexually when conditions favor growth
When nutrients are scares  gametes form by mitosis
Fusion of two gametes produces a diploid zygotes
When conditions are favorable  zygote undergoes meiosis and produces four haploid, flagellated cells

45. Life Cycle: Chlamydomonas
Single celled green alga

46. Key Concepts: CLOSEST RELATIVES OF LAND PLANTS
Red algae, green algae, and land plants all have a cell wall made of cellulose, store sugars as starch, and have chloroplasts that evolved from a cyanobacterial ancestor.
Thought to be descents form a common ancestor
Red algae and green algae are photosynthetic single cells and multicelled forms
One lineage of multicelled green algae is the closest living relatives of land plants

47. 20.9 Amoebozoans Few have a cell wall, shell, or pellicle
Most undergo dynamic changes in shape
Quickly send out pseudopods, move about, and capture food
Amoebas (single cells) and slime molds (“social amoebas”)
Heterotrophic, free-living
Fungal and animal signaling mechanisms may have started in amoebozoan ancestors

48. 20.9 Amoebozoans Amoebas (single cells)
Extend pseudopods to move and to capture prey
Some aid in their host’s digestive process
Some cause disease
50 million people/year are affect by amebic dysentery after drinking water contaminated with pathogenic amoebas

49. Slime Molds Plasmodial slime molds Cellular slime molds
Feed as a multinucleated mass
Can be as big as a dinner plate
Forms a spore-bearing structure when environmental conditions become unfavorable
Cellular slime molds
Feed as a single cell
Individual amoeba-like cells aggregate when food is scarce (mobile “slug”)

50. Life Cycle: Cellular Slime Mold

51. Spores give rise to amoeboid cells.
a Spores give rise
to amoeboid cells.
Spores give rise to amoeboid cells.
e A fruiting
body forms
with resting
spores atop
a stalk.
b Cells feed
and multiply
by mitosis
Mature
fruiting
body
c When food
is scarce, cells
aggregate.
Migrating
slug
stage
d The cells form a
slug. It may start to
develop as a fruiting
body right away, or
migrate about. In the
slug, cells become
prestalk ( red) and
prespore ( tan) cells.
Fig , p.329

52. Amoebozoans

53. Key Concepts: DISTANT RELATIVES OF FUNGI AND ANIMALS
A great variety of amoeboid species formerly classified as separate lineages are now united as the amoebozoans
They are the closest living protistan relatives of fungi and animals

54. Animation: Amoeboid motion

55. Animation: Body plan of Euglena

56. Animation: Cellular slime mold life cycle

57. Animation: Ciliate conjugation

58. Animation: Green alga life cycle

59. Animation: Paramecium body plan

60. Animation: Red alga life cycle