origin of eukaryotes. prokaryotes no true nucleus no plastids internal membrane systems are folds of...
TRANSCRIPT
![Page 1: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/1.jpg)
Origin of Eukaryotes
![Page 2: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/2.jpg)
Prokaryotes
• No true nucleus• No plastids
• Internal membrane systems are folds of plasma membrane
• True nucleus• Specialized plastids
• Internal membrane systems independent of plasma membrane
Eukaryotes
![Page 3: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/3.jpg)
Trends in Increased Prokaryote Complexity
• Multicellular prokaryotes with specialized cells
• Complex bacterial communities
• Compartmentalization of different functions within single cells
Heterocyst of Anabaena
![Page 4: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/4.jpg)
Trends in Increased Prokaryote Complexity
• Multicellular prokaryotes with specialized cells
• Complex bacterial communities
• Compartmentalization of different functions within single cells
• These trends are important because eukaryotes had to evolve from prokaryotes
![Page 5: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/5.jpg)
Origins of Eukaryotes
• Earliest evidence - 1.5 billion years
• Acritarchs resemble cysts produced by living autotrophic protists
• Development of oxygen atmosphere
Electron micrograph of an acritarch.
![Page 6: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/6.jpg)
Models Proposed for the Evolution of Eukaryotes
Autogenous Model - eukaryotic cells evolved from specialization of internal membranes
derived from plasma membrane of prokaryotes
![Page 7: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/7.jpg)
Autogenous Model
• Single-membranes organelles formed by folding of inner membrane only
• Double-walled organelles by complete invagination
![Page 8: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/8.jpg)
Autogenous Model
![Page 9: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/9.jpg)
Endosymbiotic Model
Predecessors of eukaryotes where symbionts, with small specialized species (endosymbionts)
living within larger prokaryotes
![Page 10: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/10.jpg)
Fig. 22.12b
Endosymbiotic Model
![Page 11: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/11.jpg)
Model uses chloroplasts and mitochondria as examples
• Chloroplasts were photosynthesizing prokaryotes
• Mitochondria evolved from aerobic heterotrophs (emphasis on role of Krebs cycle)
![Page 12: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/12.jpg)
Chloroplast
Mitochondrion
![Page 13: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/13.jpg)
The Model was Controversial
The endosymbiotic model differs from evolution as we discussed earlier
It is a merger of evolutionary lineages giving rise to a new form of life
![Page 14: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/14.jpg)
But,
Supporting evidence has strengthened validity
e.g., mitochondrial and chloroplast DNA
Also, symbiosis is a common phenomenon in nature
![Page 15: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/15.jpg)
Kingdom Protista
• First eukaryotic organisms
• Typically thought of as the unicellular eukaryotes
• Some colonial and multicellular species
• Addition of multicellular forms justified by similarities in cell structure and life cycles
![Page 16: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/16.jpg)
![Page 17: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/17.jpg)
Unicellular, but Complex
• Genesis of protists reveals rise of – true nucleus– specialized organelles– 9 + 2 flagella and cilia– mitosis– meiosis
• Share common ancestry with multicellular eukaryotes
![Page 18: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/18.jpg)
Protistan Systematics
• As would be expected, it is difficult to develop phylogenetic relationships among the protistans– Poor fossils (except those with external covering– Some features (e.g., flagella and autotrophy)
arose and have been lost more than once over their evolution
• Phyla are placed into supergroups (Table 28.1)
![Page 19: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/19.jpg)
Protistan Systematics
• Evolutionary Relationships– Cellular structure– Gene sequences
• Evolutionary relationships constantly changing
• Systematics
• Relationships into supergroups
![Page 20: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/20.jpg)
Informal Classification – Ecological Roles
Protozoa – animal-like heterotrophic Protista
Ciliate consuming diatoms
Algae – autotrophic protists
![Page 21: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/21.jpg)
Informal Classification – Ecological Roles
Fungus-like protists
![Page 22: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/22.jpg)
Informal Classification – Motility
Ciliates
Flagellates
![Page 23: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/23.jpg)
Informal Classification – Motility
Amoeboid
![Page 24: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/24.jpg)
Life Processes??
Although unicellular, protistans can carry out all life processes
![Page 25: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/25.jpg)
Osmoregulation – Water Balance
Vacuoles increase effective surface area in large cells.
Contractile vacuoles in freshwater microbial eukaryotes such as Paramecium are used to excrete excess water.
![Page 26: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/26.jpg)
Figure 27.10 Contractile Vacuoles Bail Out Excess Water
![Page 27: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/27.jpg)
Nutrition
• Phagotrophy
• Osmotrophy
• Autotrophy
• Mixotrophy
![Page 28: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/28.jpg)
Defense
• Mucilage
• Trichocysts
• Bioluminescence
• Toxins
![Page 29: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/29.jpg)
![Page 30: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/30.jpg)
27.3 How Did the Microbial Eukaryotes Diversify?
Food vacuoles are formed by protists when solid food particles are ingested by endocytosis.
The food is digested in the vacuole. Smaller vesicles pinch off—increasing surface area for products of digestion to be absorbed by the rest of the cell.
![Page 31: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/31.jpg)
Cell surfaces
Many microbial eukaryotes have diverse means of strengthening their surfaces.
Cytoskeleton
Internal structures that provide support and rigidity
![Page 32: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/32.jpg)
27.3 How Did the Microbial Eukaryotes Diversify?
Some amoebas make a “shell” or test from bits of sand beneath the plasma membrane.
Diatoms form glassy cell walls of silica. These walls are exceptionally strong, and perhaps enhanced defense against predators. Frustule
![Page 33: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/33.jpg)
Figure 27.12 Cell Surfaces in the Microbial Eukaryotes
![Page 34: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/34.jpg)
34
Asexual Reproduction
• All protists can reproduce asexually
• Many produce cysts with thick, protective walls that remain dormant in bad conditions
• Many protozoan pathogens spread from one host to another via cysts
![Page 35: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/35.jpg)
35
Sexual Reproduction
• Eukaryotic sexual reproduction with gametes and zygotes arose among the protists
• Generally adaptive because it produces diverse genotypes
• Zygotic and sporic life cycles
![Page 36: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/36.jpg)
36
• Zygotic life cyclesMost unicellular sexually
reproducing protistsHaploid cells transform into
gametes+ and – mating strainsThick-walled diploid zygotes
Survive like cysts
![Page 37: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/37.jpg)
37
![Page 38: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/38.jpg)
38
• Sporic life cycle Many multicellular green and brown
seaweeds Also known as alternation of generations 2 types of multicellular organisms
Haploid gametophyte produces gametes
Diploid sporophyte produces spores by meiosis
Red seaweed variation involves 3 distinct multicellular generations
![Page 39: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/39.jpg)
39
![Page 40: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/40.jpg)
40
![Page 41: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/41.jpg)
41
• Gametic life cycleAll cells except the gametes are
diploidGametes produced by meiosisDiatoms
Asexual reproduction reduces the size of the daughter cells
Sexual reproduction restores maximal size
![Page 42: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/42.jpg)
42
![Page 43: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/43.jpg)
43
• Ciliate sexual reproduction – Conjugation Most complex sexual process in protists Have 2 types of nuclei (single
macronucleus and one or more micronuclei)
Macronuclei are the source of the information for cell function
2 cells pair and fuse – conjugation Micronuclei undergo meiosis,
exchange, fusion and mitosis
![Page 44: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/44.jpg)
44
![Page 45: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/45.jpg)
Phylum Chlorophyta
• Green algae, diverse group
• unicellular, aggregates, colonial, multicellular
• Believed to be the group that gave rise to plants– multicellular and colonial forms– alternation of generation
![Page 46: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/46.jpg)
![Page 47: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/47.jpg)
Origins of Multicellularity
• Probably arose from colonial protistan– something resembling Volvox– (Volvox is only an example!!!!!!)
• Coordination and cooperation between cells
• Specialized reproductive cells– Volvox - locomotion and reproduction
• Ancestor probably flagellated
![Page 48: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/48.jpg)
Alternation of Generation
• Life cycles that show an alternation between a multicellular haploid form and a multicellular diploid form
• Sporophyte - Diploid; produces reproductive cells (haploid) called spores
• Gametophyte - Haploid; produces haploid gametes. Fusion of gametes produces diploid form
![Page 49: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/49.jpg)
Fig. 28.20
![Page 50: Origin of Eukaryotes. Prokaryotes No true nucleus No plastids Internal membrane systems are folds of plasma membrane True nucleus Specialized plastids](https://reader036.vdocuments.net/reader036/viewer/2022062408/56649ea35503460f94ba7a4f/html5/thumbnails/50.jpg)
Thus, the presence of alternation of generation and other similarities suggests a linkage between the Chlorophyta and the
Plant Kingdom