1. CHAPTER 29
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2. Protists
Chapter 29

3. Eukaryotic Origins Eukaryotic cells differ from prokaryotes
Presence of a cytoskeleton
Compartmentalization (nucleus and organelles)
Appearance of eukaryotes in microfossils occurred about 1.5 BYA

4. The nucleus and endoplasmic reticulum arose from infoldings of prokaryotic cell membrane

5. Many organelles evolved via endosymbiosis between an ancestral eukaryote and a bacterial cell
Mitochondria
Aerobic bacteria engulfed by larger bacteria

6. Endosymbiosis supported by
DNA inside mitochondria and chloroplasts
DNA similar to bacteria DNA in size and character
Ribosomes inside mitochondria similar to bacterial ribosomes
Chloroplasts and mitochondria replicate by binary fission – not mitosis

7. Defining Protists Most diverse of the four eukaryotic kingdoms
United on the basis that they are not fungi, plants, or animals
Vary considerably in every other aspect
Unicellular, colonial, and multicellular groups
Most are microscopic but some are huge
All symmetries
All types of nutrition

8. Working model for protists classification

10. Locomotion Nutrition Flagella Cilia Pseudopodia (“false feet”)
One or more
Cilia
Shorter and more numerous than flagella
Pseudopodia (“false feet”)
Nutrition
Phototrophs
Heterotrophs

11. Asexual reproduction Sexual reproduction Typical mode of reproduction
Some species have an unusual mitosis
Mitosis – equal size daughter cells
Budding – one daughter cell smaller
Sexual reproduction
Meiosis is a major eukaryote innovation
Union of haploid gametes which are produced by meiosis
Advantage in allowing frequent genetic recombination

12. Diplomonads
Unicellular
Move with flagella
2 nuclei
Giardia

13. Parabasalids Live in termite guts Trichomonas vaginalis – STD
Host cellulose degrading bacteria
Trichomonas vaginalis – STD
Undulating membrane for locomotion
Use flagella
Lack mitochondria – derived trait

14. Euglenozoa Among the earliest eukaryotes to possess mitochondria
1/3rd have chloroplasts and are autotrophic
May become heterotrophic in the dark
Others lack chloroplasts and are heterotrophic
All have a flexible pellicle
No sexual reproduction

15. © Andrew Syred/Photo Researchers, Inc.
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Euglena
Two anterior (and unequal) flagella
Contractile vacuoles – collect excess water
Stigma – movement towards light
Numerous small chloroplasts
Concept of a single Euglena genus is now being debated a.
6.5 µm
© Andrew Syred/Photo Researchers, Inc.

17. Kinetoplastids 2nd major group in Euglenozoa
Unique, single mitochondrion
Trypanosomes cause human diseases
African sleeping sickness – tsetse fly
Chagas disease – skin contact with urine or blood of infected wild animal

18. Difficult to control because organisms repeatedly change their protective coat
Release of sterilized flies
Traps scented like cows but treated with insecticides
Sequencing of genomes revealed core of common genes in all 3 – hope for single drug target

19. Alveolata Flattened vesicles called alveoli Dinoflagellates
Apicomplexans
Ciliates
Common lineage despite diverse modes of locomotion

20. Dinoflagellates Photosynthetic, unicellular with flagella
Live in aquatic environments
Some are luminescent
Do not appear to be directly related to any other phylum
“Red tide” are “blooms” – fish, birds, and marine mammals may die from toxins

21. Apicomplexans Spore-forming animal parasites
Apical complex is a unique arrangement of organelles at one end of the cell
Enables the cell to invade its host
Plasmodium causes malaria
Complex life cycle – sexual, asexual, different hosts
Eradication focused on eliminating mosquito vector, drug development, vaccines
DDT-resistant mosquitoes

23. Other apicomplexans Toxoplasma gondii
Causes infections in humans with immunosuppression
Can cross placental barrier to harm fetus

24. Ciliates 3rd group of apicomplexans
Feature large numbers of cilia arranged in longitudinal rows or spirals around the cell
Pellicle – tough but flexible outer covering
2 types of nuclei
Micronucleus – without will reproduce asexually
Macronucleus – essential for function
Have two types of vacuoles
Food vacuoles – digestion of food
Contractile vacuoles – regulation of water balance

26. Stramenopila Brown algae, diatoms, and oomycetes
Very fine hairs on their flagella
A few species have lost their hairs during evolution

27. Brown algae Not plants Conspicuous seaweeds of northern regions
Life cycle involves alternation of generations
Sporophyte – multicellular and diploid
Gametophyte – multicellular and haploid
Not plants

29. Diatoms Phylum Chrysophyta Photosynthetic, unicellular organisms
Unique double shells made of silica
Some move using raphes
Two long grooves lined with vibrating fibrils

30. Oomycetes “Water molds” Either parasites or saprobes
Were once considered fungi
Motile zoospores with two unequal flagella
Produced asexually
Undergo sexual reproduction
Found in water or on land
Phytophthora infestans
Irish potato famine (1845–1847)
400,000 people died

31. Rhodophyta Red algae range from microscopic to very large
Lack flagella and centrioles
Have accessory photosynthetic pigments within phycobilisomes
Origin has been a source of controversy
Tentatively, treated as a sister clade of Chlorophyta (green algae)

33. Choanoflagellida Most like common ancestor of all animals
Single emergent flagellum, surrounded by funnel-shaped contractile collar
Structure matched in sponges
Use collar to feed on bacteria
Have a surface tyrosine kinase receptor found in sponges

34. Protists Without a Clade
Amoebas are paraphyletic
Rhizopoda (True amoebas)
Move by means of cytoplasmic projections called pseudopods

35. Actinopoda (Radiolarians)
Glassy exoskeletons made of silica
Needlelike pseudopods

36. Foraminifera Heterotrophic marine protists
Pore-studded shells called tests, through which thin podia emerge
Use podia for swimming and feeding
Limestones are rich in forams
White Cliffs of Dover

38. Slime molds Were once considered fungi Include two lineages
Plasmodial slime molds
Huge, single-celled, multinucleate, oozing masses
Cellular slime molds
Single cells combine and differentiate, creating an early model of multicellularity

39. Plasmodial slime molds
Stream along as a plasmodium
Nonwalled, multinucleate mass of cytoplasm
Form called feeding phase
Ingests bacteria and other organic material
When food or moisture is scarce, organism forms sporangia, where spores are produced

40. Cellular slime molds
Important group for the study of cell differentiation because of their relatively simple developmental systems
Individual organisms behave as separate amoebas
Move through soil ingesting bacteria
When food is scarce, organisms aggregate to form a slug