Hello, everyone. Today, we are going to be talking about the different types of land plants, and how they evolved over time. Alright. So, land plants originally evolved from algae that lived in the water, specifically, green algae because there are different lineages of algae. There's brown algae, red algae, and green algae. Land plants only came from green algae. So, they evolved from these aquatic organisms, and they evolved to live on land, which means they had very specific adaptations to live on land because their environments drastically changed. Now, this change happened around, I believe, 850,000,000 years ago is when plants began to colonize dry land, which is a really long time ago, and they came from these freshwater green algae. And they're gonna have very specific adaptations because, as you can imagine, moving from an aquatic environment to a terrestrial environment has its issues. And some of the adaptations, which you will all learn more about in later lessons, are going to be things like the cuticle, which is a waxy covering of the plants, which helps them retain water because they're no longer living in the water, they're now living in the air. They have the possibility of drying out. They also have things like seeds, vascular tissue, some of them even have pollen, which allows them to reproduce without water, which is very interesting. So, there are many adaptations, which we will learn more about in later lessons. But right now, let's talk about the lineage and the evolution of these land plants. So, land plant, as we normally call them, is a very informal name, which is talking about all of the plants on land. But this is a very informal name, and it's actually very interesting. Land plants also encompass some plants that went back to an aquatic ecosystem, that are now aquatic again. They went from aquatic to terrestrial to aquatic through their evolutionary processes. So land plants, if you wanna be more specific, you're going to call them embryophytes. Embryophytes are a specific type of organism that holds the embryo or the developing offspring inside the tissues of the parent. Don't worry, you'll learn more about that specific quality in later lessons when we talk about plant reproduction. I was just telling you why they have this particular name. Now, there are three types of land plants: nonvascular, seedless vascular, and seed plants. And they did evolve in that particular order. Nonvascular plants came first, then seedless vascular, and then seed plants. The majority of the plants that you think of are gonna be seed plants and they're gonna be the youngest and generally the most specialized plants that live on dry land. But first, let's talk about nonvascular plants. These are gonna be the first plants that actually colonized land, and they're gonna be very similar to the green freshwater algae that they evolved from. So these were the first land plants, and they lacked these particular structures called tracheids. Now, tracheids are going to be a type of plant cell, and tracheids are cells with very thick walls made of lignin. Lignin is like cellulose. It is a very important structural component of most plants, except for nonvascular plants. You'll find that seedless vascular and seed plants have this lignin cell wall component to their anatomy, and this is gonna be very important for structure. This is gonna give them the ability to grow taller and larger. But nonvascular plants, the first land plants didn't have tracheids; they didn't have lignin, so they were not able to grow to great size. So, they could not support large vertical growth. They couldn't grow really tall. Now, you would be knowing this now, you're probably not surprised to hear that nonvascular plants are gonna be things like moss and liverworts, which sound awful, but they're actually not as awful as they sound. So, moss, liverworts, I also believe hornworts are nonvascular plants, and these are gonna be plants that are also called bryophytes, which we'll learn more about in their own lesson. There's a whole lesson on bryophytes. But these are very short plants, very small plants. Moss is kind of like little little tufts of hair or grass on the ground. They don't get very tall. And the reason is, is because they did not evolve tracheids. They're the first land plants, they didn't have this adaptation as of yet. Now, these plants are a gametophyte-dominant life cycle. You will find that the other two types of plants, seedless vascular and seeded plants are not gametophyte-dominant life cycle, they're sporophyte-dominant life cycle. And this means, because they're gametophyte-dominant life cycle, that they are haploid. Most of their life, they only have one set of chromosomes, the majority of their life, their dominant part of their life. Now, they do have some sort of internal water conducting tissue, but they don't have vascular tissue that the larger plants of land today actively have. So they don't have as specialized water and nutrient conducting tissues. So that's also why they're very small. Now, let's go on to the next type of plants. We have the seedless vascular plants. These are going to be the ones that evolved next. Seedless vascular plants are a paraphyletic group, which I'll explain more when we look at the phylogeny down here in just a second. Basically, what that means is seedless vascular plants, that term, that group name encompasses the ancestor of vascular plants, but it doesn't encompass all of the descendants of that ancestor, because the other descendants of that ancestor are gonna be seeded plants and, obviously, they're not seedless vascular plants. They're seeded vascular plants. So, but don't get too much into the specifics. Phylogeny in just a second. Okay. So, what's new about these plants is that they have vascular tissue. That means that they have specialized water conducting and nutrient conducting tissue that acts a lot like our blood vessel does. It is able to transport water and nutrients to the extremities of the plant. This allows the plants to get a lot bigger because they are able to move water and nutrients farther. So, these are also gonna be plants that have a sporophyte-dominant life cycle. Remember that nonvascular are gametophyte-dominant life cycle, seedless vascular plants are sporophyte-dominant life cycle, meaning that most of their life they're gonna be diploid, and they're gonna have two sets of chromosomes in their cells. Also, they evolved lignin like we talked about earlier. And this allows them to have strong vascular networks, and it allows them to support more vertical growth. So these are gonna be larger plants. These are gonna be things like ferns and horsetails are also seedless vascular plants. So, they have vascular conducting tissue. They are able to grow taller because of their lignin, but they don't have seeds as of yet. So, now, let's move on to the seeded vascular plants. So, we just call these seed plants, but these are most of the plants that you think of today whenever you think of a plant. And this is going to encompass the gymnosperms and the angiosperms, two different types of seeded plants. Gymnosperms have naked seeds. These are gonna be things like conifers. Basically, what this means is they don't have an active protection around their seeds, and they don't have any parental part around their seeds. So the opposite of that is gonna be angiosperms. Angiosperms are enclosed seeds. So, you'll...
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
28. Plants
Land Plants
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