How did Microphylls and Megaphylls evolve?
Evolution. The telome theory proposes instead that both microphylls and megaphylls originated by the reduction; microphylls by reduction of a single telome branch, and megaphylls by evolution from branched portions of a telome.
How many times have megaphylls evolved?
… Leaves are thought to have evolved between 2 and 11 times in vascular plants (lycophytes, ferns, and seed plants). Leaves in lycophytes are commonly termed microphylls while leaves in ferns and seed plants are termed megaphylls [1][2][3] [4] .
When did megaphyll leaves evolve?
About 350 million years ago
About 350 million years ago, plants first evolved megaphylls, the leaf type of modern seed plants and ferns. A megaphyll typically has a complex venation pattern, and arises from a stem which has leaf gaps, or regions of parenchyma tissue where the vascular strand leads into the leaf base.
Are Microphylls and Megaphylls homologous?
Microphylls and megaphylls are two types of leaf structures, which occur in vascular plants. Both develop independently from euphyllophyte leaf precursor structures. They are not homologous structures. Moreover, they differ from each other by means of leaf veins and leaf gaps.
When did seeds evolve?
about one million years ago
Seed plants appeared about one million years ago, during the Carboniferous period. Two major innovations were seeds and pollen. Seeds protect the embryo from desiccation and provide it with a store of nutrients to support the early growth of the sporophyte.
What is the evolutionary significance of megaphylls?
The evolutionary significance of megaphylls is that they increase the surface area for photosynthesis. Megaphylls are leaves. They provide a large surface area to maximize photosynthesis. Leaves increase the surface area of the plant body and serve as the primary photosynthetic organ of vascular plants.
Is a Microphyll a true leaf?
The leaves of lycophytes are microphylls. The leaves of other plants are called megaphylls, and they will have multiple or branching veins. The extension of the vascular system into the flaps of tissue creates a true leaf, in this case a microphyll.
Are ferns Homosporous or heterosporous?
Ferns are mostly homosporous, though some are heterosporous. The heterosporous state is a more advanced condition, that seems to have evolved independently in several groups of plants. The haploid spores are formed by meiosis inside the sporangium.
How did gymnosperms evolve?
Seed ferns gave rise to the gymnosperms during the Paleozoic Era, about 390 million years ago. True seed plants became more numerous and diverse during the Carboniferous period around 319 million years ago; an explosion that appears to be due to a whole genome duplication event.
When did fruit evolve?
Angiosperms evolved during the late Cretaceous Period, about 125-100 million years ago. Angiosperms have developed flowers and fruit as ways to attract pollinators and protect their seeds, respectively.
What is the evolutionary significance of megaphylls quizlet?
What can be said about the evolution of megaphylls and Stomates?
The megaphylls evolved after the stomates. Stomates were required for the simultaneous evolution of megaphylls. Some groups with megaphylls lack stomates. Megaphylls required the loss of stomates during evolution.
Where did microphylls and megaphylls come from?
Of those, two prevailing hypotheses explained the origin of microphylls from enations (small unvascularized flaps of tissue that characterized early vascular plants), and that of megaphylls from three-dimensional (3D) branching systems of undifferentiated photosynthetic axes [7].
Can a megaphyll be considered a euphyllophyte?
Although it is now accepted that leaves evolved independently in several euphyllophyte lineages, ‘megaphyll’ has grown to reflect another type of homology, that of euphyllophyte leaf precursor structures. However, evidence from the fossil record and developmental pathways fails to indicate homology and suggests homoplasy of precursor structures.
Is the leaf trace divergence associated with megaphylls?
In many plants nested among the megaphyll-bearing euphyllophytes, leaf trace divergence is not associated with a leaf gap (e.g. the non-protostelic Equisetum, cladoxylalean pteridophytes and all extant seed plants [5] ).
What does Zimmermann’s telome theory of megaphyll leaf evolution?
Megaphyll leaf evolution was a critical event in Earth history that had major consequences for the biotic regulation of the global environment. Zimmermann’s telome theory has been widely accepted for over seventy years as the leading explanation for this evolutionary innovation.