1. CHAPTER 29 LECTURE SLIDES
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2. Protists
Chapter 29
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. Brown algae engulfed red algae that already had chloroplasts
Larger bacteria engulfed smaller photosynthetic bacteria
Chloroplasts come from single line of cyanobacteria
Hosts are not monophyletic
Brown algae engulfed red algae that already had chloroplasts
Secondary endosymbiosis

7. 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

8. 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

9. Protista is not monophyletic
Paraphyletic
Does not represent any evolutionary relationships
Grouping 15 major protist phyla into 7 monophyletic groups
60 lineages are still not placed

10. Working model for protists classification

12. Cell surface Cysts Plasma membrane
Extracellular material (ECM) in some
Diatoms – Silica shells
Cysts
Dormant cell with resistant outer covering
Used for disease transmission

13. Locomotion Flagella Cilia Pseudopodia (“false feet”) One or more
Shorter and more numerous than flagella
Pseudopodia (“false feet”)
Lobopods – large, blunt
Filopods – thin, branching
Axopods – thin, long

14. Nutrition Phototrophs Heterotrophs
Phagotrophs – Ingest particulate food matter
Osmotrophs – Soluble food matter
Mixotrophs are both phototrophic and heterotrophic

15. Asexual reproduction Sexual reproduction Typical mode of reproduction
Some species have an unusual mitosis
Mitosis – equal size daughter cells
Budding – one daughter cell smaller
Schizogony – cell division preceded by several nuclear divisions; produces several individuals
Sexual reproduction
May be obligate, or only under stress
Meiosis is a major eukaryote innovation
Union of haploid gametes which are produced by meiosis
Advantage in allowing frequent genetic recombination

16. Multicellularity
From single cells to colonies to true multicellularity
Arisen multiple times
Fosters specialization
Few innovations have had as great an influence on the history of life

17. Diplomonads Unicellular Move with flagella 2 nuclei Giardia
Degenerate mitochondria

18. 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

19. 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

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

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

23. 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

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

25. 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
DNA not complexed with histones

26. 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

28. Other apicomplexans Gregarines Toxoplasma gondii
Found in the intestines of arthropods, annelids, and mollusks
Toxoplasma gondii
Causes infections in humans with immunosuppression
Can cross placental barrier to harm fetus

29. 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

31. Conjugation
Only different mating types can conjugate

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

33. 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

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

36. 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

37. 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)

39. 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

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

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

42. Foraminifera Heterotrophic marine protists
Pore-studded shells called tests, through which thin podia emerge
Use podia for swimming and feeding
Complex life cycles with haploid and diploid generations
Limestones are rich in forams
White Cliffs of Dover

44. 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

45. 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

46. 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
Slug differentiates into a sorocarp