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Also, in stacked shells the layer separating the shells will resemble the sediment surrounding the fossil and in multilayer the layer between shells will resemble the primary shell more than the surrounding sediment. [3] Cathodoluminescence can be used to distinguish pathological egg shell from egg shell that has been altered diagenetically ...
The related term Aufwuchs (German "surface growth" or "overgrowth", pronounced [ˈaʊ̯fˌvuːks] ⓘ) refers to the collection of small animals and plants that adhere to open surfaces in aquatic environments, such as parts of rooted plants. Periphyton serves as an important food source for invertebrates, tadpoles, and some fish.
Revertant somatic mosaicism is a rare recombination event with a spontaneous correction of a mutant, pathogenic allele. [19] In revertant mosaicism, the healthy tissue formed by mitotic recombination can outcompete the original, surrounding mutant cells in tissues such as blood and epithelia that regenerate often. [ 19 ]
In the shell gland (similar to a mammalian uterus), mineralization starts at the mammillae and around the outermost membrane fibers. [11] The shell gland fluid contains very high levels of calcium and bicarbonate ions. The thick calcified layer of the eggshell forms in columns from the mammillae structures, and is known as the palisade layer.
Fossil fish eggs have an extensive record going at least as far back as the Devonian and spanning into the Cenozoic era. The eggs of many different fish taxa have contributed to this record, including lobe-finned fish, placoderms, and sharks. Occasionally eggs are preserved still within the mother's body, or associated with fossil embryos.
Alternation of generations (also known as metagenesis or heterogenesis) [1] is the predominant type of life cycle in plants and algae. In plants both phases are multicellular: the haploid sexual phase – the gametophyte – alternates with a diploid asexual phase – the sporophyte.
In genetics, a maternal effect occurs when the phenotype of an organism is determined by the genotype of its mother. [1] For example, if a mutation is maternal effect recessive, then a female homozygous for the mutation may appear phenotypically normal, however her offspring will show the mutant phenotype, even if they are heterozygous for the mutation.
For each plant, an overview (upper row; scale bar corresponds to 1 mm) and a close-up (bottom row; scale bar equals 0.5 mm) are shown. A: Haploid wild-type moss plant completely covered with leafy gametophores and close-up of wild-type leaf. B–E: Different mutants. [1] A knockout moss is a kind of genetically modified moss.