The SAR clade is a monophyletic supergroup made up of the clades Stramenopiles, Alveolata, and Rhizaria. Many of the organisms contained in this supergroup are photosynthetic, and this is also the group that contains the water molds, which you hopefully realize are not actually molds, because these are not fungi; they are protists. So again, just another case where there's a bit of a misnomer in the biological terminology, which hopefully you're starting to see, happens all the time. It's just part of science, unfortunately. Anyhow, Stramenopiles and Alveolates contain chloroplasts, and those chloroplasts likely arose from secondary endosymbiosis, which you might remember was when a eukaryotic cell engulfed another eukaryotic cell that had already undergone endosymbiosis and already had chloroplasts inside of it. Most likely this was a red algae that was being engulfed. So the Stramenopiles are mostly made up of photosynthetic algae, and they are both unicellular and multicellular organisms, and the feature that defines this group are these flagella that have hair-like projections. And you can see in this image of a generic Stramenopile cell, right here, that we have this flagella coming off the cell, and it's got all these little lines coming off of it. Those are supposed to be the hair-like projections. Now, many species in this group exhibit diploid dominant life cycles, and diatoms are no exception. These are unicellular photosynthetic organisms whose key feature is that they're encased in these protective shells. They're actually made of silicon dioxide. So, kind of different from like a seashell, for example. But, different chemically, but kind of the same idea. It's a protective casing for the organism. Now, as you can see in this image here, diatoms come in a wide variety of morphologies. These are all different, you know, shapes and sizes of the diatom's shells, and fun fact, these have actually been arranged by people on slides as an art form. Yeah. Believe it or not, people will take brushes that have a single bristle and work under a microscope, will actually poke around little diatoms and arrange them into a collage like you see here. Pretty pretty funky stuff. And this is not actually a modern thing. People have been doing this kind of art for a really surprisingly long time. Super cool thing about diatoms, even though they're these tiny little microorganisms, they're actually responsible for a lot of Earth's photosynthesis, and they can actually have a noticeable impact on atmospheric carbon. So when they spring up and, you know, there's a large amount of them concentrated in a certain area, you can actually notice a significant dip in the amount of carbon in the air in that area, because they're using up so much of it for photosynthesis. Super cool. Now, gold algae, like we see here, have a distinctive kind of yellowish-brown color. They get that from these yellow and brown carotenoids, which you might remember, carotenoids are a type of photosynthetic pigment in plants. They're usually like an accessory pigment. Here, they're the distinctive pigment that is coloring the organism that we see. Most gold algae are unicellular organisms and even though they contain these chloroplasts, which, just a quick reminder, came from secondary endosymbiosis. Right? So probably a red algae being engulfed. Even though they contain these chloroplasts, many of these organisms are actually mixotrophs. Meaning that they do photosynthesis, but then they also obtain nutrients like heterotrophs as well. So they mix it up. Right? That's where the term comes from. Now lastly, we have brown algae, which you can see in this image here in a multicellular form as a big kelp stalk. But brown algae can also be unicellular. And, it gets its distinctive color from brown carotenoids, similar to gold algae, and a cool thing about these big kelp stalks, right, these are large structures and they'll actually be rooted often at the seafloor. But they want to get close to the surface because that's where the sunlight penetrates best. Right? They're going to get the most sunlight at higher depths, if that makes sense. Higher up, closer to the surface, they're gonna get more sunlight there. So they actually have these little gas-filled chambers in their photosynthetic regions that cause these kelp stalks to float up to the surface, so that they can obtain sunlight more efficiently. And that's why, when you see like big clumps of seaweed or kelp or whatever on the beach, and they have all those little bubbles that are or pods or whatever that are kind of fun to pop open, that's what those are actually for. They're via alteration of generations, and they can be both hetero- via alteration of generations, and they can be both hetero- and isomorphic. We saw examples of that in the lesson on protist life cycles. Now moving on, we have Alveolata, and these protists are, sort of the defining feature of this clade are these membrane-enclosed sacs called alveoli that are right under the plasma membrane. And we're actually going to break up our discussion of different types of Alveolata over a few videos, because I want to get into some specifics about some of these subgroups. So first off, let's talk about dinoflagellates. I have always sort of thought of dinoflagellates as being kind of similar to diatoms, and that's mostly because they both have protective shells and they're both basically plankton. I'm not saying that they're exactly the same. There are many differences, they're in different clades. I'm merely trying to say that there are some parallels between them. Now, dinoflagellates are mostly unicellular, again, mostly aquatic. And they're actually not enclosed by a silicon dioxide shell, but by these two cellulose plates. And you can see in this image of a dinoflagellate here, we have this plate and then this one too. So those are the two plates coming together. And you can see that over in this image, this dinoflagellate looks pretty different. Totally normal, that is the way they're supposed to look, or that's a way they can look, I should say. They come in many shapes and sizes. Now, dinoflagellates rather, have two flagella. Yes. This is sort of where their name is coming from. But these flagella are pretty different. One projects outward and another actually runs around the groove between the two plates. So on this dinoflagellate here, you can probably see this flagella coming off of it. And it might be a little harder to make out, but there's actually flagella running around the side of this organism, kind of doing a loop around it. Right? So those are the two flagella of the organism. Now, roughly half of dinoflagellates are actually heterotrophic and about half are phototrophic. Though many of these phototrophic dinoflagellates are actually mixotrophs. Right? So again, they perform photosynthesis, but they also are going to obtain nutrients in a heterotrophic fashion. Now, most dinoflagellates have chromosomes that lack histones and actually attach directly to the nuclear envelope in a structure called a dinokaryon. And last thing about dinoflagellates, you can see here an example of their life cycle, which is a haploid dominant life cycle. Right? So these cells, These or some of these cells, I should say, are haploid, let me get a new color here, right. So we've got these nice haploid cells, right, these two are haploid and they're gonna fuse together and form this diploid cell, right, n and 2n, trying to show haploid diploid. Right? And then this is eventually going to, go through meiosis and form those haploid cells again. So with that, let's flip the page.
Table of contents
- 1. Introduction to Biology2h 40m
- 2. Chemistry3h 40m
- 3. Water1h 26m
- 4. Biomolecules2h 23m
- 5. Cell Components2h 26m
- 6. The Membrane2h 31m
- 7. Energy and Metabolism2h 0m
- 8. Respiration2h 40m
- 9. Photosynthesis2h 49m
- 10. Cell Signaling59m
- 11. Cell Division2h 47m
- 12. Meiosis2h 0m
- 13. Mendelian Genetics4h 41m
- Introduction to Mendel's Experiments7m
- Genotype vs. Phenotype17m
- Punnett Squares13m
- Mendel's Experiments26m
- Mendel's Laws18m
- Monohybrid Crosses16m
- Test Crosses14m
- Dihybrid Crosses20m
- Punnett Square Probability26m
- Incomplete Dominance vs. Codominance20m
- Epistasis7m
- Non-Mendelian Genetics12m
- Pedigrees6m
- Autosomal Inheritance21m
- Sex-Linked Inheritance43m
- X-Inactivation9m
- 14. DNA Synthesis2h 27m
- 15. Gene Expression3h 20m
- 16. Regulation of Expression3h 31m
- Introduction to Regulation of Gene Expression13m
- Prokaryotic Gene Regulation via Operons27m
- The Lac Operon21m
- Glucose's Impact on Lac Operon25m
- The Trp Operon20m
- Review of the Lac Operon & Trp Operon11m
- Introduction to Eukaryotic Gene Regulation9m
- Eukaryotic Chromatin Modifications16m
- Eukaryotic Transcriptional Control22m
- Eukaryotic Post-Transcriptional Regulation28m
- Eukaryotic Post-Translational Regulation13m
- 17. Viruses37m
- 18. Biotechnology2h 58m
- 19. Genomics17m
- 20. Development1h 5m
- 21. Evolution3h 1m
- 22. Evolution of Populations3h 52m
- 23. Speciation1h 37m
- 24. History of Life on Earth2h 6m
- 25. Phylogeny2h 31m
- 26. Prokaryotes4h 59m
- 27. Protists1h 12m
- 28. Plants1h 22m
- 29. Fungi36m
- 30. Overview of Animals34m
- 31. Invertebrates1h 2m
- 32. Vertebrates50m
- 33. Plant Anatomy1h 3m
- 34. Vascular Plant Transport2m
- 35. Soil37m
- 36. Plant Reproduction47m
- 37. Plant Sensation and Response1h 9m
- 38. Animal Form and Function1h 19m
- 39. Digestive System10m
- 40. Circulatory System1h 57m
- 41. Immune System1h 12m
- 42. Osmoregulation and Excretion50m
- 43. Endocrine System4m
- 44. Animal Reproduction2m
- 45. Nervous System55m
- 46. Sensory Systems46m
- 47. Muscle Systems23m
- 48. Ecology3h 11m
- Introduction to Ecology20m
- Biogeography14m
- Earth's Climate Patterns50m
- Introduction to Terrestrial Biomes10m
- Terrestrial Biomes: Near Equator13m
- Terrestrial Biomes: Temperate Regions10m
- Terrestrial Biomes: Northern Regions15m
- Introduction to Aquatic Biomes27m
- Freshwater Aquatic Biomes14m
- Marine Aquatic Biomes13m
- 49. Animal Behavior28m
- 50. Population Ecology3h 41m
- Introduction to Population Ecology28m
- Population Sampling Methods23m
- Life History12m
- Population Demography17m
- Factors Limiting Population Growth14m
- Introduction to Population Growth Models22m
- Linear Population Growth6m
- Exponential Population Growth29m
- Logistic Population Growth32m
- r/K Selection10m
- The Human Population22m
- 51. Community Ecology2h 46m
- Introduction to Community Ecology2m
- Introduction to Community Interactions9m
- Community Interactions: Competition (-/-)38m
- Community Interactions: Exploitation (+/-)23m
- Community Interactions: Mutualism (+/+) & Commensalism (+/0)9m
- Community Structure35m
- Community Dynamics26m
- Geographic Impact on Communities21m
- 52. Ecosystems2h 36m
- 53. Conservation Biology24m
27. Protists
Eukaryotic Supergroups: Exploring Protist Diversity
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