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Outside the stele lies the endodermis, which is the innermost cell layer of the cortex. The concept of the stele was developed in the late 19th century by French botanists P. E. L. van Tieghem and H. Doultion as a model for understanding the relationship between the shoot and root, and for discussing the evolution of vascular plant morphology. [2]
Curled up Selaginella tamariscina Wallace's Selaginella (Selaginella wallacei). Selaginella, also known as spikemosses or lesser clubmosses is a genus of lycophyte.It is usually treated as the only genus in the family Selaginellaceae, with over 750 known species.
The geographic cycle, or cycle of erosion, is an idealized model that explains the development of relief in landscapes. [1] The model starts with the erosion that follows uplift of land above a base level and ends, if conditions allow, in the formation of a peneplain. [1]
In evolutionary biology, punctuated equilibrium (also called punctuated equilibria) is a theory that proposes that once a species appears in the fossil record, the population will become stable, showing little evolutionary change for most of its geological history. [1]
Two useful introductions to the fundamental theory underlying the unit of selection issue and debate, which also present examples of multi-level selection from the entire range of the biological hierarchy (typically with entities at level N-1 competing for increased representation, i.e., higher frequency, at the immediately higher level N, e.g., organisms in populations or cell lineages in ...
Orthogenesis, also known as orthogenetic evolution, progressive evolution, evolutionary progress, or progressionism, is an obsolete biological hypothesis that organisms have an innate tendency to evolve in a definite direction towards some goal (teleology) due to some internal mechanism or "driving force".
In plant anatomy and evolution a microphyll (or lycophyll) is a type of plant leaf with one single, unbranched leaf vein. [1] Plants with microphyll leaves occur early in the fossil record, and few such plants exist today. In the classical concept of a microphyll, the leaf vein emerges from the protostele without leaving a leaf gap. Leaf gaps ...
Recurrent evolution also referred to as repeated [1] [2] or replicated [3] evolution is the repeated evolution of a particular trait, character, or mutation. [4] Most evolution is the result of drift , often interpreted as the random chance of some alleles being passed down to the next generation and others not.