EVOLUTION OF PTERIDOPHYTES EPUB DOWNLOAD
A pteridophyte is a vascular plant (with xylem and phloem) that reproduces by spores and lacks . Ilia J.; Schneider, Harald (May ). "Genome evolution of ferns: evidence for relative stasis of genome size across the fern phylogeny".Taxonomy · Ecology. Marcus Lehnert: Diversity and evolution of pteridophytes. 3. Chapter I. Ferns as species: systematics and phylogeny. “Móhala maka'í ke oho o ke kupu kupu.”. The pteridophytes evolved in the Silurian period and subsequently got diversified in the Lower Devonian. There are controversies regarding their origin and.
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Andrewsalso is a believer of polyphyletic origin for vascular plants.
Occurrence of such plants made Andrews to believe that several algal groups independently attempted the invasion of the land. These groups gave rise to different groups of vascular plants.
Life forms of Pteridophyta, their origin and evolution.
He believes that the morphological diversity exhibited by psilophyta, lycophyta etc. Based on the paleopalynological studies, Leclercqproposed a polyphyletic origin for vascular plants. According to her, land plants must have had their origin somewhere during the Precambrian era.
This assumption evolution of pteridophytes supported by the discovery of fossil spores probably of land plants in the rock strata belonging to ordovician and cambrian periods.
Pteridophytes: Origin, Classification and Importance | Botany
She considers the simple psilophytes like Rhynia as the descendants of complex race that existed prior to the Devonian period.
Axelrod supported the polyphyletic origin of Leclercq and elaborated it by his own palaeopalynological discoveries. Merker also believes evolution of pteridophytes the algal origin.
He recognises five main evolutionary lines: He also agrees with Leclercq that Rhyniaceae are simple due to reduction and not due to primitiveness. In his essay on the Phytogeny of Carmophyta, Lam has evolution of pteridophytes a di-phyletic origin for vascular plants.
The two independent lines are psilopsida and lycopsida which arose from Thallophyta independently somewhere during the Cambrian period. Psilopsida gave rise to three groups viz. The last mentioned group gave rise to protoangiosperms and angiosperms.
The lycopsid stock gave rise to coniferopsida.
Pteridophytes: Meaning, Origin and Economic Importance
There are mainly two objections evolution of pteridophytes this hypothesis: Mehra the ancestors of land plants are to be found among the green algae. He opposed the polyphyletic origin of vascular plants.
While agreeing that the different groups of pteridophytes diverged from the very beginning, he argued that all of them have come from a common group. Mehraenvisages the origin of a hypothetical group Protoarchegoniatae from the chaetrophoraceous ancestors.
From these protoarchcgoniates two evolution of pteridophytes viz.
In-spite of the innumerable theories proposed, it may be said that the problem remains as before i. However, it seems quite possible evolution of pteridophytes bryophytes and Pteridophytes evolved parallely from some algal ancestor which in all probability could be a green algal stock.
Origin and early evolution of land plants
Sporophytic Generation of Pteridophytes: It is the sporophytic generation which constitutes the main plant body in pteridophytes. In any description whenever we refer to the evolution of pteridophytes body of a ptcridophyte, we mean the sporophyte.
There is a great variety in the nature and organisation of the sporophytic plant body in pteridophytes. The simplest sporophyte in an extant member is to be found in Psilotum.
The plant body here is a naked, branched evolution of pteridophytes with no evidence of roots. The axis is distinguishable into an underground prostrate system and an erect aerial system. Rhizoids help in anchoring the plant to the substratum.
There are no leaves.