Scientists surmise that an early charophyte-like alga isthe ancestor of land pla

Question

Scientists surmise that an early charophyte-like alga isthe ancestor of land plants. Starting with bryophytes, describespecific features that evolved in this group of plants that allowedfor a move to land. Explain how these adaptations wereadvantageous. Next, describe and explain the adaptations found inseedless vascular plants that made them better suited to a landexistence. Explain why both groups of plants (bryophyte andseedless vascular) are limited to moist environments. Finally,explain how the adaptations found in seed plants allowed them totake over the world!

Explanation / Answer

1. Specific features that evolved in the bryophyte phyla andhow they are adventageous:
Spores
The spores of the bryophyte germinate and growinto gametophytes, when dispersed into moist soils or tree bark.The gametophytes of the bryophyte phyla are the dominant stage ofthe life cycle, which means they are larger and are able to livelonger than the sporophyte. Protonema Germinating moss spores produce a mass of green, branched,one-cell-thick filaments known as protonema. This structure, with alarge surface area, embellishes the ability to absorb water as wellas minerals. Gametophore Each bud of the protonema has an apical meristem that givesrise to a gamete-producing structure called a gametophore or"gamete bearer." To give you a picture, a protonemajoined with one or more gametophores make up the body of a mossgametophyte. Organs Although constrained by the lack of a rigid vascular tissue,the thin structure of the bryophyte organs make it possible todistribute materials without specialized vascular tissue. Rhizoids The gametophytes of the bryophyte are anchored by long,tissue-less, tubular single cells or filaments of cells known asrhizoids. Rhizoids lack specialzed conducting cells and do not playa major role in water and mineral absorption. Gametangia A mature gametophyte forms gametangia that produce gametes andare covered by a protective tissue. Eggs are produced in archegoniaand sperm is produced by each antheridium. This allows somebryophyte to be bisexual as well as have the ability to reproduceasexually. Sporophytes The sporophyte produces haploid spores by meiosis that developinto gametophytes. Bryophytes have the smallest sporophytes of allextant plants and consist of a foot, seta, and capsule. The footabsorbs nutrients from the gametophyte. The seta conducts thesenutrients to the sporangium, also called a capsule, which uses themto produce spores (via meiosis). One capsule is capable ofproducing up to 50 million spores. Stomata Hornwort and moss sporophytes have specialized pores thatsupport photosynthesis by allowing the exchange of CO2 and O2between the outside air and the sporophyte interior. Thesepores are the main route by which water is loss from thesporophyte through evaporation. In hot, dry conditions, thestomata close thereby minimizing water loss. Hornwort and moss sporophytes have specialized pores thatsupport photosynthesis by allowing the exchange of CO2 and O2between the outside air and the sporophyte interior. Thesepores are the main route by which water is loss from thesporophyte through evaporation. In hot, dry conditions, thestomata close thereby minimizing water loss. 2. (Generalized) Adaptations found in seedless vascularplants: *Life cycles with dominant sporophytes (complex alternation ofgenerations) *Transport in vascular tissues called xylem,lignin, and phloem *Well-developed roots and leaves *Spore bearing leaves called sporophylls *Well-developed roots and leaves *Spore bearing leaves called sporophylls 3. Why both groups are limited to moist environments: Bryophyte and seedless vascular sperm areflagellated and require a film of water to reach the eggs. 4. Seed plants dominate: The seed is "analogous to a detachable and mobile version of apregnant woman's womb." It consists of an embryo and its foodsupply, surrounded by a protective coat. Seed plants have theability to survive the harshest of environments and exposure to UVradiation in sunlight. Water is not needed for fertilization andcan remain dormant for years after being released from the parentplant I hope the information provided helps answer your questions aswell as in understanding the material. Good luck with your studies!

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