Learning Through Art Alternation of Generations Life Cycle in Ulva
Streptophytes and Reproduction of Green Algae
Land plants and closely-related green algae (charophytes) are classified as Streptophytes; the remaining dark-green algae are chlorophytes.
Learning Objectives
Discuss the full general similarities of green algae and land plants
Key Takeaways
Cardinal Points
- In that location is a diverse array of green algae including single-celled or multicellular species, which can reproduce both sexually or asexually.
- The nomenclature of dark-green algae is challenging because they acquit many of the structural and biochemical traits of plants.
- Species of dark-green algae that are closely related to embryophytes are classified as charophytes while the remaining light-green algae are classified as chlorophytes.
- Like plants, charophytes take chlorophyll a and b, shop carbohydrates every bit starch, take jail cell walls consisting of cellulose, and undergo similar jail cell-partition processes.
- Charophytes take unique reproductive organs that differ considerably from that of other algae.
Fundamental Terms
- streptophytes: a subphylum consisting of several orders of green algae and embryophytes
- Charophyta: a segmentation of green algae that includes the closest relatives of the embryophyte plants
- Chlorophyta: a segmentation of green algae that are considered more distantly related to plants
Streptophytes
Until recently, all photosynthetic eukaryotes were considered members of the kingdom Plantae. The chocolate-brown, red, and gold algae, withal, accept been reassigned to the Protista kingdom. This is considering, apart from their ability to capture light free energy and fix CO2, they lack many structural and biochemical traits that distinguish plants from protists. The position of green algae is more than cryptic. Green algae include unicellular and colonial flagellates, most with two flagella per prison cell, also as various colonial, coccoid, and filamentous forms, forth with macroscopic seaweeds, all of which add together to the ambiguity of green algae classification since plants are multicellular.
Chara vulgaris: A representative charophyte alga is Chara vulgris, or common stonewort, which is a multicellular branching species that can abound upwardly to 120m long.
Greenish algae contain the same carotenoids and chlorophyll a and b as state plants, whereas other algae have different accessory pigments and types of chlorophyll molecules in addition to chlorophyll a. Both green algae and land plants also store carbohydrates as starch. Cells in greenish algae divide forth prison cell plates called phragmoplasts and their jail cell walls are layered with cellulose in the same manner every bit the cell walls of embryophytes. Consequently, land plants (embryophytes) and closely-related greenish algae ( Charophyta ) are now function of a new monophyletic grouping chosen Streptophyta. The remaining dark-green algae, which are more distantly related to plants, belong to a grouping chosen Chlorophyta that includes more than 7000 different species that live in fresh or brackish water, in seawater, or in snowfall patches.
The Charophyta are a division of green algae that includes the closest relatives of the embryophyte plants. Charophyta are a small but important group of plants which evidence marked differences from both the Thallophyta and the Bryophyta. They are all specialized water plants. The reproductive organs consist of antheridia and oogonia, although the structure of these organs differs considerably from the corresponding organs in the Algae.
Charales
Algae in the guild Charales live in fresh water and are often considered the closest-living relatives of embryophytes.
Learning Objectives
Identify the principle features of charophyte algae
Key Takeaways
Key Points
- The construction of charophyte algae consists of a thallus, which is the main stem, and branches that arise from nodes which bear both male and female reproductive structures.
- Although charophyte algae practice non exhibit alteration of generations, they share a number of adaptations to life on land with embryophytes, including the encasement of eggs in protective enclosures.
- As new Deoxyribonucleic acid sequence analysis techniques develop, revisions may need to be made in our understanding of plant evolution, such as indications that greenish algae in the order of Zygnematales may exist more-closely related to embryophytes than is Charales.
Cardinal Terms
- Charales: light-green algae in the partition Charophyta which are light-green plants believed to be the closest relatives of the greenish state plants
- sporopollenin: a combination of biopolymers observed in the tough outer layer of the spore and pollen wall
Charales
Green algae in the order Charales, and the coleochaetes, microscopic green algae that enclose their spores in sporopollenin, are considered the closest-living relatives of embryophytes. The Charales tin can be traced every bit far back as 420 one thousand thousand years. They alive in a range of fresh water habitats and vary in size from equally small as a few millimeters to equally large as a meter in length. A representative species of Charales is Chara, which is often called muskgrass or skunkweed because of its unpleasant aroma.
Charophyte algae: A representative charophyte alga, Chara, is a noxious weed in Florida, where information technology clogs waterways.
In Charales, large cells course the thallus: the main stem of the alga. Branches arising from the nodes are made of smaller cells. Male and female person reproductive structures are found on the nodes; the sperm take flagella. Dissimilar state plants, Charales practice not undergo alternation of generations in their lifecycle. Like embryophytes, Charales showroom a number of traits that are meaning in their adaptation to land life. They produce the compounds lignin and sporopollenin. They form plasmodesmata, which are microscopic channels that connect the cytoplasm of adjacent cells. The egg and, later, the zygote, form in a protected chamber on the parent plant.
New information from recent, extensive DNA sequence assay of green algae indicates that the Zygnematales are more closely-related to the embryophytes than the Charales. The Zygnematales include the familiar genus Spirogyra. As techniques in Dna assay better and new information on comparative genomics arises, the phylogenetic connections between species volition probably continue to change. Clearly, plant biologists accept yet to solve the mystery of the origin of state plants.
Source: https://courses.lumenlearning.com/boundless-biology/chapter/green-algae-precursors-of-land-plants/
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