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https://en.wikipedia.org/wiki/Beetle

Archostemata contains four families of mainly wood-eating beetles, including reticulated beetles (Cupedidae) and the telephone-pole beetle.[43] The Archostemata have an exposed plate called the metatrochantin in front of the basal segment or coxa of the hind leg.[44] Myxophaga contains about 65 described species in four families, mostly very small, including Hydroscaphidae and the genus Sphaerius.[45] The myxophagan beetles are small and mostly alga-feeders. Their mouthparts are characteristic in lacking galeae and having a mobile tooth on their left mandible.[46]

https://en.wikipedia.org/wiki/Myxophaga

Myxophaga is the second smallest suborder of the Coleoptera after Archostemata, consisting of roughly 65 species of small to minute beetles in four families. The members of this suborder are aquatic and semiaquatic, and feed on algae.

 

Contents [hide]

1 Taxonomy

2 Phylogeny

3 Description

4 Distribution

5 See also

6 Notes

7 References

8 External links

Taxonomy[edit]

There are four extant families in the suborder Myxophaga divided between two superfamilies,[1] containing about 65 described species,[2] and at least two extinct superfamilies of the suborder.[a]

 

Superfamily Lepiceroidea

Family Lepiceridae Hinton, 1936

Superfamily Sphaeriusoidea

Family Hydroscaphidae LeConte, 1874

Family Sphaeriusidae Erichson, 1845

Family Torridincolidae Steffan, 1964

†Superfamily Rhombocoleoidea

†Family Rhombocoleidae

†Superfamily Schizophoroidea

†Family Catiniidae

†Family Schizocoleidae

†Family Schizophoridae

  • J. B. S. Haldane counts fanaticism among the only four really important inventions made between 3000 B.C and 1400 A.D. It was a Judaic-Christian invention. And it is strange to think that in receiving this malady of the soul the world also received a miraculous instrument for raising societies and nations from the dead—an instrument of resurrection.

FOUR INVENTIONS

https://www.marxists.org/archive/haldane/works/1920s/daedalus.htm

But before we proceed to prophecy I should like to turn back to the past and examine very briefly the half dozen or so important biological inventions which have already been made. By a biological invention I mean the establishment of a new relationship between man and other animals or plants, or between different human beings, provided that such relationship is one which comes primarily under the domain of biology rather than physics, psychology or ethics. Of the biological inventions of the past, four were made before the dawn of history. I refer to the domestication of animals, the domestication of plants, the domestication of fungi for the production of alcohol, and to a fourth invention, which I believe was of more ultimate and far-reaching importance than any of these, since it altered the path of sexual selection, focussed the attention of man as a lover upon woman's face and breasts, and changed our idea of beauty from the steatapygous Hottentot to the modern European, from the Venus of Brassempouy to the Venus of Milo. There are certain races which have not yet made this last invention. And in our own day two more have been made, namely bactericide and the artificial control of conception.

FOUR MAJOR COMPLEXES IN THYLAKOID MEMBRANE

https://en.wikipedia.org/wiki/Thylakoid

Thylakoid membranes contain integral membrane proteins which play an important role in light harvesting and the light-dependent reactions of photosynthesis. There are four major protein complexes in the thylakoid membrane:

 

Photosystems I and II

Cytochrome b6f complex

ATP synthase

 

This results in the four major thylakoid protein complexes being encoded in part by the chloroplast genome and in part by the nuclear genome

FOUR MANGANESE IONS

https://en.wikipedia.org/wiki/Photosystem

When photosystem II absorbs light, electrons in the reaction-center chlorophyll are excited to a higher energy level and are trapped by the primary electron acceptors. To replenish the deficit of electrons thus created, electrons are extracted from water by a cluster of four Manganese ions in photosystem II and supplied to the chlorophyll via a redox-active tyrosine.

FOUR LARGE SUBUNITS

https://en.wikipedia.org/wiki/Cytochrome_b6f_complex

The cytochrome b6f complex is a dimer, with each monomer composed of eight subunits.[3] These consist of four large subunits: a 32 kDa cytochrome f with a c-type cytochrome, a 25 kDa cytochrome b6 with a low- and high-potential heme group, a 19 kDa Rieske iron-sulfur protein containing a [2Fe-2S] cluster, and a 17 kDa subunit IV; along with four small subunits (3-4 kDa): PetG, PetL, PetM, and PetN.[3][4] The total molecular weight is 217 kDa.

 

Cytochrome b6f contains seven prosthetic groups.[13][14] Four are found in both cytochrome b6f and bc1: the c-type heme of cytochrome c1 and f, the two b-type hemes (bp and bn) in bc1 and b6f, and the [2Fe-2S] cluster of the Rieske protein. Three unique prosthetic groups are found in cytochrome b6f: chlorophyll a, β-carotene, and heme cn (also known as heme x).[5]

FOUR MANGANESE IONS- FOUR ELECTRONS FOUR PROTONS FOUR REDOX STATES FOUR OXIDIZING EQUIVALENTS- FOUR STEP MECHANIMS

https://en.wikipedia.org/wiki/File:Water_splitting_process.jpg

https://en.wikipedia.org/wiki/Photosystem_II

The oxygen-evolving complex is the site of water oxidation. It is a metallo-oxo cluster comprising four manganese ions (in oxidation states ranging from +2 to +4)[5] and one divalent calcium ion. When it oxidizes water, producing oxygen gas and protons, it sequentially delivers the four electrons from water to a tyrosine (D1-Y161) sidechain and then to P680 itself. The structure of the oxygen-evolving complex is still contentious. The structures obtained by X-ray crystallography are particularly controversial, since there is evidence that the manganese atoms are reduced by the high-intensity X-rays used, altering the observed OEC structure. However, crystallography in combination with a variety of other (less damaging) spectroscopic methods such as EXAFS and electron paramagnetic resonance have given a fairly clear idea of the structure of the cluster. One possibility is the cubane-like structure.[6] In 2011 the OEC of PSII was resolved to a level of 1.9 angstroms revealing five oxygen atoms serving as oxo bridges linking the five metal atoms and four water molecules bound to the Mn4CaO5 cluster; more than 1,300 water molecules were found in each photosystem II monomer, some forming extensive hydrogen-bonding networks that may serve as channels for protons, water or oxygen molecules.[7]

 

The mechanism of water oxidation is still not fully elucidated, but we know many details about this process. The oxidation of water to molecular oxygen requires extraction of four electrons and four protons from two molecules of water. The experimental evidence that oxygen is released through cyclic reaction of oxygen evolving complex (OEC) within one PSII was provided by Pierre Joliot et al.[8] They have shown that, if dark-adapted photosynthetic material (higher plants, algae, and cyanobacteria) is exposed to a series of single turnover flashes, oxygen evolution is detected with typical period-four damped oscillation with maxima on the third and the seventh flash and with minima on the first and the fifth flash (for review, see[9]). Based on this experiment, Bessel Kok and co-workers [10] introduced a cycle of five flash-induced transitions of the so-called S-states, describing the four redox states of OEC: When four oxidizing equivalents have been stored (at the S4-state), OEC returns to its basic S0-state. In the absence of light, the OEC will "relax" to the S1 state; the S1 state is often described as being "dark-stable". The S1 state is largely considered to consist of manganese ions with oxidation states of Mn3+, Mn3+, Mn4+, Mn4+.[5] Finally, the intermediate S-states[11] were proposed by Jablonsky and Lazar as a regulatory mechanism and link between S-states and tyrosine Z.

 

Kok B, Forbush B, McGloin M (June 1970). "Cooperation of charges in photosynthetic O2 evolution-I. A linear four step mechanism". Photochem. Photobiol. 11 (6): 457–75. PMID 5456273. doi:10.1111/j.1751-1097.1970.tb06017.x.

FOUR TERPENE UNITS

https://en.wikipedia.org/wiki/Carotenoid

Carotenoids belong to the category of tetraterpenoids (i.e., they contain 40 carbon atoms, being built from four terpene units each containing 10 carbon atoms). Structurally, carotenoids take the form of a polyene hydrocarbon chain which is sometimes terminated by rings, and may or may not have additional oxygen atoms attached.

https://simple.wikipedia.org/wiki/Genetics

In fact, the genes Mendel studied occurred in only four linkage groups, and only one gene pair (out of 21 possible) is close enough to show deviation from independent assortment; this is not a pair that Mendel studied.

FOUR LAYERS

https://en.wikipedia.org/wiki/Human_tooth_development

The bell stage is known for the histodifferentiation and morphodifferentiation that takes place. The dental organ is bell-shaped during this stage, and the majority of its cells are called stellate reticulum because of their star-shaped appearance. The bell stage is divided into the early bell stage and the late bell stage.[1] Cells on the periphery of the enamel organ separate into four important layers. Cuboidal cells on the periphery of the dental organ are known as outer enamel epithelium (OEE).[2] The columnar cells of the enamel organ adjacent to the enamel papilla are known as inner enamel epithelium (IEE). The cells between the IEE and the stellate reticulum form a layer known as the stratum intermedium. The rim of the enamel organ where the outer and inner enamel epithelium join is called the cervical loop.[23] In summary, the layers in order of innermost to outermost consist of dentin, enamel (formed by IEE, or 'ameloblasts', as they move outwards/upwards), inner enamel epithelium and stratum intermedium (stratified cells that support the synthetic activity of the inner enamel epithelium) What follows is part of the initial 'enamel organ', the center of which is made up of stellate reticulum cells that serve to protect the enamel organ. This is all encased by the OEE layer.

FOUR STAGES

https://en.wikipedia.org/wiki/Rotator_cuff

After experiencing a rotator cuff tear, minimally invasive surgery is needed in order to repair the torn tendon. After surgery, the rehabilitation of the rotator cuff is necessary in order to regain maximum strength and range of motion within the shoulder joint.[9] Physical therapy progresses through four stages, increasing movement throughout each phase. The tempo and intensity of the stages are solely reliant on the extent of the injury and the patient’s activity necessities.[10] The first stage requires immobilization of the shoulder joint. The shoulder that is injured is placed in a sling and shoulder flexion or abduction of the arm is avoided for 4 to 6 weeks after surgery (Brewster, 1993). Avoiding movement of the shoulder joint allows the torn tendon to fully heal.[9] Once the tendon is entirely recovered, passive exercises can be implemented. Passive exercises of the shoulder are movements in which a physical therapist maintains the arm in a particular position, manipulating the rotator cuff without any effort by the patient.[11] These exercises are used to increase stability, strength and range of motion of the Subscapularis, Supraspinatus, Infraspinatus, and Teres minor muscles within the rotator cuff.[11] Passive exercises include internal and external rotation of the shoulder joint, as well as flexion and extension of the shoulder.[11]

FOUR MITOCHONDRIAL LINEAGES

https://investigativegenetics.biomedcentral.com/articles/10.1186/s13323-015-0028-9

a Reconstruction of the mitochondrial phylogeny of 23 female Norfolk Island Polynesian founder descendants. The mitochondrial SNPs defining the branching are displayed on the tree. b Reconstruction of the Norfolk Island pedigree, based on available genealogical and genetic information (n = 1388). Four separate mitochondrial lineages have persisted and are present in the current day population (these are represented by red, pink, blue and light blue in the figure). c Major mitochondrial haplogroup frequencies as inferred from full mitochondrial genome sequencing in the Norfolk Island pedigree

FOUR CELL TYPES

http://owh.adam.com/pages/guide/reftext/html/skin_sys_fin.html

The skin is the largest organ of the body, with a surface area of 18 square feet. Its two main layers are the epidermis (outer layer) and dermis (inner layer). The epidermis has several strata (layers) that contain four cell types. Keratinocytes produce keratin, a protein that gives skin its strength and flexibility and waterproofs the skin surface. Melanocytes produce melanin, the dark pigment that gives skin its color. Merkel's cells are probably involved with touch reception. Langerhans' cells help the immune system by processing antigens (foreign bodies).

http://study.com/academy/lesson/what-is-epidermis-definition-function-layers.html

The epidermis is composed of four main strata, or layers. The outermost layer is called the stratum corneum, which is Latin for ''horny layer.'' While we aren't literally covered in horny scales, this layer is tough nonetheless. It also varies in thickness depending on the body part it covers. If you often go barefoot, the stratum corneum on the sole of your foot is probably quite thick. Compare that to the skin on your eyelids and you can see the drastic difference. 

 

Layers of the Epidermis

 

If we were to take a closer look, we find that the stratum corneum is composed almost exclusively of dead cells. It may come as no surprise that we lose skin cells on a regular basis. In fact, the dead cells of the stratum corneum slough off so often that we end up with a completely new outer layer about every 35 days. 

And how, you may be wondering, do we have any skin left if we are always losing cells? This is where the stratum basale comes in. Just as its name suggests, it is the base or deepest layer of the epidermis. A cell-producing factory, the basale layer contains stem cells which are constantly dividing to make new ones. These fresh new cells make their way up to the stratum corneum to replace those that have sloughed off. This cycle runs on a continual basis, keeping our epidermis healthy and strong. 

 

Cross-Section of Epidermis under Microscope

 

Two additional layers are sandwiched between the stratum corneum and stratum basale. The stratum spinosum borders the stratum basale. Here we find spiny keratinocytes that help bond other cells together. Finally, the stratum granulosum lies beneath the stratum corneum. Cells in this layer produce a waxy material that aids in waterproofing the skin. 

While most of our body's epidermis is made up of four layers, on the palms of our hands and the soles of our feet, there is one extra layer of skin. The stratum lucidum is a translucent layer that provides extra thickness to these areas of the skin. 

FOUR GENES

https://en.wikipedia.org/wiki/Migraine

Single gene disorders that result in migraines are rare.[41] One of these is known as familial hemiplegic migraine, a type of migraine with aura, which is inherited in an autosomal dominant fashion.[44][45] Four genes have been shown to be involved in familial hemiplegic migraine.[46] Three of these genes are involved in ion transport.[46] The fourth is an axonal protein associated with the exocytosis complex.[46] Another genetic disorder associated with migraine is CADASIL syndrome or cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy.[2] One meta analysis found a protective effect from an angiotensin converting enzyme polymorphisms on migraine.[47]

There are four types of gene polymorphisms:[6]

https://en.wikipedia.org/wiki/Gene_polymorphism

Seen here is adapted radiation of finch A. (Geospiza magnirostris) into three other species of finches found on the Galapagos Islands. Due to the absence of other species of birds, the finches adapted to new niches. The finches beaks and bodies changed allowing them to eat certain types of foods such as nuts, fruits, and insects.

  1. Geospiza magnirostris

  2. Geospiza parvula

  3. Certhidea olivacea

  4. Geospiza fortis

Single nucleotide polymorphisms (SNPs)[edit]

SNPs are a single nucleotide changes that happen in the genome in a particular location . The Single Nucleotide Polymorphism is known to be the most common form of genetic variation. A major and the cause of this SNPs is the replacement of the nucleotide Cytosine (C) with Thymine (T) in a part of the DNA. SNPs may cause a disease through the affection in a specific gene or regulatory region near this gene resulting in disturbance in the gene's function.[7]

 

Small-scale insertions/deletions[edit]

Small insertions and deletion are called INDELs and this type of gene polymorphism is dependent on insertion or deletion of DNA bases in an organism. Nowadays, two million INDELs have been discovered in approximately seventy-nine various humans genomes. Furthermore, small insertions/ deletions are existed on genes coding exons and this may consider a fundamental factor that leads to diseases inheritance in humans.[8]

 

Polymorphic repetitive elements[edit]

Alu which is a repetitive element from Alu family, can trigger a polymorphism in human genome. Alu element is defined as a small area of DNA sequence with 300 base pairs. Alu element also has a role in RNA polymerase III for its compression of a RNA promoter. It has been found that Alu is repeated in more than 10% of human genome. Insertion and repetitive of Alu element in human genome can cause mutations and disorders that are related to carcinogenesis.[9]

 

Microsatellite variation[edit]

Microsatellites are characterized for the repetition for 1-6 base pairs of DNA sequence. In Genetics, microsatellites are commonly used as a molecular markers especially for identifying the relationship between alleles. Diseases that are correlated with microsatellites are Fragile X Syndrome, Myotonic dystrophy, Friedreich ataxia, Kennedy disease, Huntington disease, Haw river syndrome, and Spinocerebellar ataxia.[10]

FOUR PROCESSES

https://en.wikipedia.org/wiki/Population_genetics

Four processes

2.1 Selection

2.1.1 Dominance

2.1.2 Epistasis

2.2 Mutation

2.3 Genetic drift

2.4 Gene flow

MALES THREE GLANDS FEMALES FOUR GLANDS SPIDER SILK

http://www.chm.bris.ac.uk/motm/spider/page2.htm

There are seven types of silk produced by seven silk glands. A single spider does not possess all seven glands but has at least three if it is male (dragline, attachment and swathing silk) or four if it is female. The additional one is for egg sac silk. The seven types of gland are:

TASTE TETRAHEDRON

 

Henning's tetrahedron

 

 

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Henning's tetrahedron n.

 

Henning’s tetrahedron n.

http://oxfordindex.oup.com/view/10.1093/oi/authority.20110803095930841

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A classification of tastes in terms of a pyramid with a triangular base, its corners representing the fundamental or primary tastes, namely sweet (like sugar or aspartame), sour (like vinegar or lemon juice), salty (like sea water or table salt), and bitter (like quinine or orange peel), and points elsewhere representing other tastes, assumed to be blends of the four primaries. Also called the taste tetrahedron. See also umami. [Named after the German psychologist Hans Henning (1885–1946) who published it in 1927]

 

From: Henning's tetrahedron in A Dictionary of Psychology »

 

Subjects: Psychology.

FOUR WHORLS

https://en.wikipedia.org/wiki/Superman_(gene)

Superman encodes a transcription factor.[3] This protein binds to the DNA through a zinc finger binding motif[3] acts as a regulator of floral homeotic genes, controlling the development of the flowers of Arabidopsis thaliana plants. Arabidopsis thaliana flowers develop in four whorls, which are concentric groups of cells branching off of the growing meristem.[6] Superman has been found to act in the fourth whorl of flowers, which would normally develop into Carpels. Superman normally restricts the effect of another gene called (APETALA3) in the fourth whorl, leaving APETALA3 expression only present in the second and third whorls.[6] APETALA3 is a gene normally associated with the development of a stamen in the third whorl,[7] so by its restriction, we allow for the development of other organs in the fourth whorl (such as the Pistil).

 

A mutation which completely removes superman gene function would result in flowers that carry extra stamens, replacing the pistils which would normally be developing in the fourth whorl. This mutation was named the sup-1 mutation. For the sup-1 mutation, More extreme stamen development is seen from a homozygous mutation than a heterozygous mutation.[8]

DARWIN ON FOUR SUBGROUPS

https://en.wikipedia.org/wiki/File:Finchadaptiveradiation.png

https://en.wikipedia.org/wiki/Darwin%27s_finches

The remaining land-birds form a most singular group of finches, related to each other in the structure of their beaks, short tails, form of body and plumage: there are thirteen species, which Mr. Gould has divided into four subgroups. All these species are peculiar to this archipelago; and so is the whole group, with the exception of one species of the sub-group Cactornis, lately brought from Bow Island, in the Low Archipelago. Of Cactornis, the two species may be often seen climbing about the flowers of the great cactus-trees; but all the other species of this group of finches, mingled together in flocks, feed on the dry and sterile ground of the lower districts. The males of all, or certainly of the greater number, are jet black; and the females (with perhaps one or two exceptions) are brown. The most curious fact is the perfect gradation in the size of the beaks in the different species of Geospiza, from one as large as that of a hawfinch to that of a chaffinch, and (if Mr. Gould is right in including his sub-group, Certhidea, in the main group) even to that of a warbler. The largest beak in the genus Geospiza is shown in Fig. 1, and the smallest in Fig. 3; but instead of there being only one intermediate species, with a beak of the size shown in Fig. 2, there are no less than six species with insensibly graduated beaks. The beak of the sub-group Certhidea, is shown in Fig. 4. The beak of Cactornis is somewhat like that of a starling, and that of the fourth subgroup, Camarhynchus, is slightly parrot-shaped. Seeing this gradation and diversity of structure in one small, intimately related group of birds, one might really fancy that from an original paucity of birds in this archipelago, one species had been taken and modified for different ends. In a like manner it might be fancied that a bird originally a buzzard, had been induced here to undertake the office of the carrion-feeding Polybori of the American continent.[23]

Darwin's famous image of four finches in quadrant formation

https://en.wikipedia.org/wiki/Darwin%27s_finches

https://simple.wikipedia.org/wiki/Tree_of_life_(biology)

The model of a tree is still considered valid for eukaryotic life forms. Research into the earliest branches of the eukaryote tree suggests a tree with either four supergroups,[6][7] or two supergroups.[8] There does not yet appear to be a consensus; in a review article, Roger and Simpson conclude that "with the current pace of change in our understanding of the eukaryote tree of life, we should proceed with caution".[9]

FOUR EVOLUTIONARY THEORIES

https://www.scientificamerican.com/article/darwins-influence-on-modern-thought/

For 80 years after 1859, bitter controversy raged as to which of four competing evolutionary theories was valid. “Transmutation” was the establishment of a new species or new type through a single mutation, or saltation. “Orthogenesis” held that intrinsic teleological tendencies led to transformation. Lamarckian evolution relied on the inheritance of acquired characteristics. And now there was Darwin’s variational evolution, through natural selection. Darwin’s theory clearly emerged as the victor during the evolutionary synthesis of the 1940s, when the new discoveries in genetics were married with taxonomic observations concerning systematics, the classification of organisms by their relationships. Darwinism is now almost unanimously accepted by knowledgeable evolutionists. In addition, it has become the basic component of the new philosophy of biology.

 

These four insights served as the foundation for Darwin’s founding of a new branch of the philosophy of science, a philosophy of biology. Despite the passing of a century before this new branch of philosophy fully developed, its eventual form is based on Darwinian concepts. For example, Darwin introduced historicity into science. Evolutionary biology, in contrast with physics and chemistry, is a historical science—the evolutionist attempts to explain events and processes that have already taken place. Laws and experiments are inappropriate techniques for the explication of such events and processes. Instead one constructs a historical narrative, consisting of a tentative reconstruction of the particular scenario that led to the events one is trying to explain.

https://en.wikipedia.org/wiki/Jean-Baptiste_Lamarck

Jablonka, Eva (2006). Evolution in Four Dimensions: Genetic, Epigenetic, Behavioral, and Symbolic Variation in the History of Life. Cambridge, MA: MIT Press. ISBN 978-0-262-60069-9.

THE FLOWER IS NAMED AFTER THE CROSS

https://en.wikipedia.org/wiki/Tripterocalyx_crux-maltae

Tripterocalyx crux-maltae is a species of flowering plant in the four o'clock family known by the common names Lassen sandverbena[1] and Kellogg's sand-verbena.

CROSSES ON PLANES

https://en.wikipedia.org/wiki/Military_aircraft_insignia

Of all the early operators of military aircraft, Germany was unusual in not using "round" roundels, but after evaluating several possible markings, including a black, red and white checkerboard, and a similarly coloured roundel, and black stripes, a black "iron" cross on a square white field was chosen as it was already in use on various flags, and to reflect Germany's heritage as the Holy Roman Empire. The German army's mobilization led to orders in September 1914 to paint all-black Eisernes Kreuz (iron cross) insignia with wide-flared arms over a white field — usually square in shape — on the wings and tails of all aircraft flown by its air arm, then known as the Fliegertruppe des Deutschen Kaiserreiches. The fuselage was also usually marked with a cross on each side but this was optional. The form and location of the initial cross was largely up to the painter, which led to considerable variation, and even the white being omitted. An iron cross with explicit proportions superseded it in July 1916, whose initial form was also painted on a white field, although this would be reduced to a 5 cm border completely around the cross in October of the same year — the month of the formation of the Army's Deutsche Luftstreitkräfte in name — even bordering the ends of the flared arms' ends. In March 1918, a straight black cross with narrow white borders on all sides of the cross was ordered, but proportions were not set until April, resulting in many of those repainted in the field having non-standard proportions. This was then replaced by a narrower, straight-armed cross in May that extended the full chord of wings, with the white border restricted to the sides of the cross's bars. In June, it ceased to be used full chord, with the bars all being the same length. The white on any of these could be omitted when used on a white background, such as was used sometimes for the rudder, and was sometimes omitted on night bombers.

 

With the dissolution of the German Army's Luftstreitkräfte in May 1920, military insignia would disappear until the rise of the Nazi party, which imposed new rules on aircraft in 1937, starting with the use of the German red/white/black flag on the tails' starboard side of all aircraft, with the port side showing a Nazi Party flag. When the Luftwaffe's re-establishment was made official, these markings were used by military aircraft, while the 1918 Balkenkreuz crosses were reintroduced, which expanded in their specification to two standardized proportions by July 1939, with differing widths for the quartet of white "flanks" on each insignia. When camouflage was introduced prior to invading Poland, the flags were dispensed with, replacing them with a black and white Hakenkreuz swastika on both sides. During the Second World War, the crosses would be further simplified, leaving only the borders in a contrasting colour. Much like the French roundel, variations would be used on countries allied with Germany, including the Austro-Hungarian Empire (combined it with red-white-red stripes on the wings until 1916), Bulgaria, Croatia (stylized as a leaf), Hungary (reversed colors) and Slovakia (blue cross with a red dot in the middle).

 

After the Second World War was over, West Germany reverted to using a variation of the 1916 iron cross, using the white "flanks" of the Balkenkreuz following the now-curved sides of each arm, while East Germany used a diamond marking based on their flag, with the coat of arms from the flag. Reunification of Germany resulted in the iron cross replacing the East German marking.

CRUCIFORM

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1166713/

The single-stranded character of cytosine bases in three cruciform structures has been assessed by an examination of reactivity towards sodium bisulphite. Unpaired cytosine residues undergo deamination at C4 to give deoxyuracil, and propagation in an ung Escherichia coli host results in C-G----T-A transition mutations, detectable by restriction cleavage or sequence analysis. Very high frequencies of such mutations have been found at cruciform loops, confirming their unpaired character, with almost zero background mutation frequencies elsewhere. A low level of modification was observed at the four-way junction of a cruciform. The results indicate that the optimal cruciform loop size is four bases, with loose 'breathing' at the first base pair at the top of the cruciform stem at 37 degrees C, and little or no opening of base pairs at the four-way junction.

CRUCIFORM

http://rna.cshl.edu/content/free/chapters/15_rna_world_2nd.pdf

The same argument had been made in support of the familiar tRNA cruciform almost a decade earlier, but there was a difference. The cruciform was identified initially because it is one of three maximally base-paired structures that could be proposed for the first tRNA sequence (Holley et al. 1965). As soon as a few more tRNAs were sequenced, it was obvious that the cruciform was right. From the point of view of Fox and Woese, the number of base pairs in an RNA helix dia- gram is irrelevant, and when they began, it was not obvious that a unique, maximally paired structure exists for 5S rRNA. Six years later, the phylo- genetic approach was applied with spectacular results to the sequence of 16S rRNA (Noller and Woese 1981).

TETRAMERIC

https://en.wikipedia.org/wiki/Aminoacyl_tRNA_synthetase

Class II has three highly conserved sequence motifs. It aminoacylates at the 3'-OH of a terminal adenosine on tRNA, and is usually dimeric or tetrameric (two or four subunits, respectively). Although phenylalanine-tRNA synthetase is class II, it aminoacylates at the 2'-OH.

THE PASSION FRUIT REPRESENTS THE CRUCIFIXION OF JESUS- THE CROSS IS THE QUADRANT

https://en.wikipedia.org/wiki/Passiflora_edulis

The passion fruit is so called because it is one of the many species of passion flower, leading to the English translation of the Latin genus name, Passiflora.[1] Around 1700, the name was given by missionaries in Brazil as an educational aid while trying to convert the indigenous inhabitants to Christianity; its name was flor das cinco chagas or "flower of the five wounds" to illustrate the crucifixion of Christ, with other plant components also named after an emblem in the Passion of Jesus.[5]

At least four subspecies are known:

https://en.wikipedia.org/wiki/Treponema_pallidum

Treponema pallidum pallidum, which causes syphilis

T. p. endemicum, which causes bejel or endemic syphilis

T. p. carateum, which causes pinta

T. p. pertenue, which causes yaws

http://www.savyondiagnostics.com/chlamydia

Chlamydia is composed of four species: C.trachomatis, C.pneumoniae (TWAR), C.psittaci and C.pecorum. 

FOUR LAYERS BASAL LAMINA

https://en.wikipedia.org/wiki/Basal_lamina

The layers of the basal lamina ("BL") and those of the basement membrane ("BM") are described below:

 

 

 

Name Part of BL? Part of BM? Notes

lamina lucida / lamina rara interna[1] yes yes electron-lucid layer[2] containing the glycoprotein laminin

lamina densa yes yes electron-dense layer[3] composed of type IV collagen

lamina lucida / lamina rara externa yes yes Similar composition to lamina rara interna. Some sources do not consider this a distinct layer.

lamina reticularis[4] no yes The three above layers of the basal lamina typically sit on top of the reticular lamina, which is synthesized by cells from the underlying connective tissue and contains fibronectin. The exception is when two epithelial layers abut one another as in the alveoli of the lungs and glomeruli of the kidneys, in which the basal lamina of one epithelial layer fuses with that of the other.

https://answersingenesis.org/biology/microbiology/laminin-and-the-cross/

Romans 1:20 makes it clear that we can know God through what He has made. God certainly designed the laminin protein and gave it a structure that allows it to perform the function He designated for it. In fact, one of the early papers on the structure and function of laminin said this: “Globular and rodlike domains are arranged in an extended four-armed, cruciform shape that is well suited for mediating between distant sites on cells and other components of the extracellular matrix” (emphasis mine).1

 

The supremacy of Christ that is talked about in Colossians 1:15–20 is probably one of my favorite passages in all of Scripture. Paul begins talking about Christ as Creator and moves to Christ as Redeemer. These are truths not because they appeal to our unaided reasoning, but because they are revealed in God’s Word.

TRANSCENDENT FOURTH GROUP

https://en.wikipedia.org/wiki/Nilotic_languages

According to linguist Joseph Greenberg, the language family is divided up into three subgroups:[4]

 

Eastern Nilotic languages such as Turkana and Maasai

Southern Nilotic languages such as Kalenjin and Datooga

Western Nilotic languages such as Luo and Dinka

Before Greenberg's reclassification, Nilotic was used to refer to Western Nilotic alone, with the other two being grouped as related "Nilo-Hamitic" languages.[5]

 

Blench (2012) treats the Burun languages as a fourth subgroup of Nilotic.[6] In previous classifications, the languages were included within the Luo languages. Starostin (2015) treats the Mabaan-Burun languages as "West Nilotic" but outside the Luo level.[7]

FOUR VOCAL REGISTERS

https://en.wikipedia.org/wiki/Vocal_register

Vocal registers arise from different vibratory patterns produced by the vocal cords. Research by speech pathologists and some vocal pedagogists has revealed that the vocal cords are capable of producing at least four distinct vibratory forms, although not all persons can produce all of them. The first of these vibratory forms is known as natural or normal voice;[9] another name for it is modal voice, a term currently widely used in both speech pathology and vocal pedagogy publications. In this usage, modal refers to the natural disposition or manner of action of the vocal cords. The other three vibratory forms are known as vocal fry, falsetto, and whistle. Each of these four registers has its own vibratory pattern, its own pitch area (although there is some overlapping), and its own characteristic sound. Arranged by the pitch areas covered, vocal fry is the lowest register, modal voice is next, then falsetto, and finally the whistle register.[4][9]

 

While speech pathologists and scholars of phonetics consistently divide the voice into these four registers, vocal pedagogists are divided on this issue. Indiscriminate use of the word register has led to much confusion and controversy about the number of registers in the human voice within vocal pedagogical circles. This controversy does not exist within speech pathology and the other sciences, because vocal registers are viewed from a purely physiological standpoint that is concerned with laryngeal function. Various writers concerned with the art of singing state that there are anywhere from one to seven registers present. The diversity of opinion in this area is quite wide and there is no one consensus or point of view.[9]

https://en.wikipedia.org/wiki/Head_voice

Pamelia S. Phillips. "Identifying the Fab Four of Singing Voices". Wiley Publishing. Retrieved 18 February 2007. Bass is the lowest of the voice types...

FOUR REGISTERS

https://en.wikipedia.org/wiki/Head_voice

This view is that since all registers originate in laryngeal function, it is meaningless to speak of registers being produced in the head. The vibratory sensations which are felt in the head are resonance phenomena and should be described in terms related to resonance, not to registers. These vocal pedagogists prefer the term "head voice" over the term register and divide the human voice into four registers: the vocal fry register, the modal register, the falsetto register, and the whistle register. This view is more consistent with modern understandings of human physiology and in keeping with stroboscope videos of laryngeal function during vocal phonation.[1] Tarneaud says, "during singing, the vibration of the vocal folds impresses periodic shakes on the laryngeal cartilage which transmits them to the bones in the thorax via the laryngeal depressors, and to the bony structures in the head via the laryngeal elevators. Singers feel these shakes in the form of thoracic and facial vibrations". These internal phonatory sensations produced by laryngeal vibrations are called "resonance" by singers and teachers of singing.[12] There are seven parts of the human body that act as resonators and of those seven the three most effective resonators that help amplify and create the most pleasing sounds are all located in the head: the pharynx, the oral cavity, and the nasal cavity.[1]

FOUR REGISTERS HUMAN VOICE

https://en.wikipedia.org/wiki/Modal_voice

In speech pathology, the modal register is one of the four identifiable registers within the human voice. It is above the vocal fry register and overlapping the lower part of the falsetto register. That view is also adopted by many vocal pedagogists, but some vocal pedagogists may view vocal registration differently. In singing, the modal register may also overlap part of the whistle register. A well trained singer or speaker can phonate two octaves or more within the modal register with consistent production, beauty of tone, dynamic variation, and vocal freedom.[2] The modal register begins and ends in different places within the human voice. The placement of the modal register within the individual human voice is one of the key determining factors in identifying vocal type.[3]

FOUR VOCAL REGISTERS

https://en.wikipedia.org/wiki/Falsetto

It is produced by the vibration of the ligamentous edges of the vocal cords, in whole or in part. Commonly cited in the context of singing, falsetto, a characteristic of phonation by all genders, is also one of four main spoken vocal registers recognized by speech pathology.

FOUR BASIC SHAPES

https://verobella.files.wordpress.com/2015/08/face-shapes.jpg

https://verobella.wordpress.com/2015/08/10/the-right-bangs-for-your-face-shape/

Second, there are four basic face shapes we all work with: round, oval, square and heart.

MOST FACES FOUR CATEGORIES

http://modernteenstyle.com/why-the-shape-of-your-face-matters-eye-on-fashion-modern-teen-style/

Did you know that faces have a particular shape? It’s true! Most faces fall into one of four shape categories: Oval. Square. Round. and Heart!

http://modernteenstyle.com/wp-content/uploads/2016/03/faceshapes.jpg

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HEART IS ANOTHER WAY TO SAY LONG

http://www.cielodrive.com/archive/topping-off-the-well-groomed-man/

http://www.cielodrive.com/archive/wp-content/uploads/2013/07/face-types.jpg

There are several important factors to be considered before the haircut begins. Probably the most critical is the shape of the face. There are four basic types:

1. Long: The hair should be cut lower on the top than with other face shapes, but not necessarily shorter. A part is desirable for this shape of face. The sides should be full in order to

make the top of the head seem lower. An oblong face is a problem because it can tend to look even longer if the sides are too short and a lot of hair is worn on the top. I try to bring the face down into more of a compact unit by lowering the sideburns and making them fuller. Many times a high forehead goes along with an oblong face. In this event, I try to bring some hair to the forehead by combing it flat down over the top of the forehead. This is the only way to proportion such a face.

2. Round: This is a very common shape, generally associated with a heavy person. The round face automatically has a compact appearance. With Jackie Gleason, I had to thin down the appearance of the face. The more hair on the sides as well as on the top, the thinner the face will appear. The sideburns should be lowered, not to the point where they will look ridiculous, like cowboy sideburns, but a little lower than normal, below the cheekbone—not long enough to be conspicuous, however. A part can easily be worn with this shape of face.

3. Square: This is very similar to a round face as far as the design is concerned. To thin down the appearance of the face, it is absolutely necessary that the hair be full on the sides. This also helps balance off the jowly look. The hair can also be full over the top, but the fullness is not as critical as on the sides. The sideburns should also be a little lower than normal. With a square face you can carry as much hair as you like. A part also can be worn. Vic Damone has a square face, but his hair is extremely curly, so I have to get the fullness and yet keep it short. This is accomplished by daily washing, and cutting the hair at the break of the first wave. The daily washing pulls out some of the wave and gives the hair fullness. It springs out and looks long and full even though it’s short.

4. Triangular and Oval: You can do just about anything with these shapes that the hair will permit. You can comb it into a part or wear the hair without one. The sideburns should be normal in length, and should balance off with the cheekbone. Barry Goldwater has an oval face, but I would definitely suggest a high part in his case, because of recession in front. I would cut him “conservative”—close on the sides and on the top.

THE FOUR CLUSTERS OF HOX

http://www.pnas.org/content/100/25/14603.full

First, it was shown that mammals have four Hox clusters, called A, B, C, and D (8), a condition which seems to be true for all tetrapods.

 

Hox genes play a key role in animal body plan development

 

Although the data for jawless vertebrates and cartilagenous fishes (sharks and relatives) are still incomplete, the most parsimonious scenario also associates the earlier Hox cluster duplications, leading to the four clusters found in humans, with major adaptive radiations (5, 19). One duplication might have occurred before the radiation of jawless vertebrates and one probably occurred before the radiation of the jawed vertebrates.

I'm a paragraph. Click here to add your own text and edit me. It's easy.

FAMOUS FOUR WINGED FLY
https://en.wikipedia.org/wiki/Hox_gene
The third thoracic segment, or T3, bears a pair of legs and a pair of halteres (highly reduced wings that function in balancing during flight). Ubx patterns T3 largely by repressing genes involved in wing formation. The wing blade is composed of two layers of cells that adhere tightly to one another, and are supplied with nutrient by several wing veins. One of the many genes that Ubx represses is blistered, which activates proteins involved in cell-cell adhesion, and spalt, which patterns the placement of wing veins. In Ubx loss-of-function mutants, Ubx no longer represses wing genes, and the halteres develop as a second pair of wings, resulting in the famous four-winged flies. When Ubx is misexpressed in the second thoracic segment, such as occurs in flies with the "Cbx" enhancer mutation, it represses wing genes, and the wings develop as halteres, resulting in a four-haltered fly.

FOUR WINGED COMMON ANCESTOR OF FLIES

https://blogs.lt.vt.edu/lijingyi/2014/04/14/hox-genes-are-involved-in-evolution-of-two-winged-drosophila-biol-5104-blog-9/

As we learnt from the text book, the four-winged Drosophila is the phenotype (a homeotic transformation of the halteres of the third thoracic segment changed into the wings normally associated with the second thoracic segement) that results from a Ubx gene mutation. But, of course, there are many insects, such as dragonflies, butterflies, and bees, which normally have four wings. Is two-winged flies evolved from four-winged ancestors, or opposite?

 

To investigate this question, I look up the text book of evolution. In fact, all the phylogenetic relationship of various insect groups and evidence from the fossil record indicate that the ancestor of all these winged insects was one with four wings. During the lineage leading to files, the wings of the third thoracic segment were modified into halteres. This is not surprising, at least for me. In my point of view, flies are very successful animals and should be more evolutionary than most insects. And also I think evolution of wings from halteres is harder than degeneration of halteres from wings. But, how this evolutionary event happened in history? Scientists have at least three hypotheses to explain the transition from four-winged to two-winged insects.

 

About 60 years ago, the first hypothesis is that the four-winged common ancestor of flies and dragonflies lacked the Ubx gene. Somewhere in the evolutionary lineage leading to flies, Ubx appeared and resulted in the transformation of the third thoracic wings into halteres. But after the development of molecular biology, it is discovered that Ubx gene is present throughout the insects, this hypothesis could be rejected.

Four mating-type genes control sexual differentiation in the fission yeast.

 

https://www.ncbi.nlm.nih.gov/pubmed/2900761

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FOUR WINGED ANCESTOR

https://www.facebook.com/groups/409519862782589/

1A,B). Dipterans evolved from a four-winged ancestor, with the resulting posterior flight appendages, the halteres, being morphologically distinct and reduced in size compared to wings. In Drosophila, the Hox gene Ultrabithorax (Ubx) controls the differential development between wing and haltere. Ubx is expressed throughout haltere development but not in the developing wing (Struhl 1982; Beachy et al. 1985; White and Wilcox 1985a) (Fig. ​(Fig.1C,D).1C,D). Reduced Ubx function in imaginal discs or in Ubx mutant clones results in transformation of haltere tissue into wing tissue (Lewis 1963; Morata and Garcia-Bellido 1976; Morata and Kerridge 1981; Kerridge and Morata 1982) (Fig. ​(Fig.1E).1E). Total loss of Ubx function in the developing halteres results in the complete transformation of halteres to wings, giving rise to a four-winged fly (Lewis 1978) (Fig. ​(Fig.1F).1F). Conversely, mutations that cause ectopic expression of Ubx in the developing wing disc [e.g., Contrabithorax (Cbx)] (Cabrera et al. 1985; White and Akam 1985; White and Wilcox 1985b; Castelli-Gair et al. 1990) transform wing into haltere tissue (Lewis 1955, 1978, 1982; Morata and Lawrence 1975; Casanova et al. 1985; Micol and García-Bellido 1988; González-Gaitán et al. 1990). Although these spectacular Ubx mutant phenotypes have been known for decades, no Ubx-regulated genes in the haltere have been identified.

FOUR TISSUE TYPES

http://www.pnas.org/content/112/52/15946.full

We used normalized read counts from the blast-annotated contigs to examine differential gene expression (RNA-seq) across the four tissue types (T1 body wall; Scr RNAi wing, T2 wing, T3 wing). After filtering out contigs with low expression (<20 total reads, or a zero reading in at least one library of each tissue type), remaining contigs (n = 12,429) had expression levels that tended to be highly correlated (R generally >0.82) across the replicate tissue libraries [using log2 (normalized read count + 0.01)]. This was not true for libraries T1_1 and T3_3, which had correlation coefficients all <0.83 with replicates of the same tissue type and as low as <0.57 across tissue types. For that reason, those two libraries (T1_1, T3_5) were judged to be of reduced quality and were excluded from subsequent analyses.

TIC TAC TOE FOUR IN A ROW

 

https://www.youtube.com/watch?v=SQZd-2J9Mmk

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TIC TAC TOE FOUR IN A ROW

http://thestuffofsuccess.com/2015/05/10/hp-envy-creates-tic-tac-toe-its-four-in-a-row-hpsmartmom-cmyk-myprintly/

My task – create a craft/project with the photo paper. I feel like I have been using my new HP Envy printer daily anyway so that should be an easy task. We decided (my daughter and I) to make a board game called Tic Tac Toe It’s Four In A Row. It is a spinoff of the famous Tic Tac Toe that we all know so well.

http://www.sightwordadventures.com/blog/tic-tac-toe-four-in-a-row

Tic-Tac-Toe and Four-In-A-Row are games that seem to have been around forever, and even toddlers know how to play them. Make these games a learning exercise by adding the Sight Words.

CROSS INCISIONS

http://www.medindia.net/education/familymedicine/incision-drainage-abscess-incision.htm

Peri-rectal abscesses require fair sized, crucial (cross shaped) incision to prevent the development of fistula in ano.

https://kitchenalia.wordpress.com/how-to/how-to-peel-a-tomato/

First, make a cross incision in the top of the tomato. (If the tomato is super big, you might want to make the incisions at the top and bottom.)

CROSSHATCHING INCISION

http://www.sciencedirect.com/science/article/pii/S0385814615300109

In previous experiments, the crosshatching incision has been shown to be an effective method for the correction of cartilaginous deviations. Although the settings of the experiments were different from that of septoplasty, the crosshatching incision has been considered a useful method for septoplasty. Therefore, we attempted to determine the efficacy of the crosshatching incision technique under actual septoplasty surgical settings.

 

Methods

 

Commercial pig ear cartilages were used for the following experiments: firstly, the crosshatching incision was performed with the cartilage in a partially fixed state (in order to approximate caudal and dorsal fixation of septal cartilage); secondly, for the purpose of approximating L-strut preservation in septoplasty, the crosshatching incision was performed while excluding a marginal area of 1 cm on any two contiguous borders. After the experiments, the change of curvature was assessed.

CRUCIFORM

https://www.intechopen.com/books/chromosomal-abnormalities-a-hallmark-manifestation-of-genomic-instability/acquired-chromosomal-abnormalities-and-their-potential-formation-mechanisms-in-solid-tumours

Figure 16. A model of long inverted repeat (LIR)-induced gene amplification. A cruciform near 5′ boundary of an amplicon unit can cause the fork stalling during replication. Hairpins formed at both leading and lagging strand templates may slow the DNA synthesis. Both cruciform and hairpin structures could trigger a rereplication between two microhomology (mh) sites located 5′ and 3′ boundaries of the amplicon, leading to the formation of head-to-tail tandem duplication.

THREE V FOUR BINDING DOMAINS (ALZHEIMER CAUSE)

https://en.wikipedia.org/wiki/Tau_protein

Six tau isoforms exist in human brain tissue, and they are distinguished by their number of binding domains. Three isoforms have three binding domains and the other three have four binding domains. The binding domains are located in the carboxy-terminus of the protein and are positively charged (allowing it to bind to the negatively charged microtubule). The isoforms with four binding domains are better at stabilizing microtubules than those with three binding domains. The isoforms are a result of alternative splicing in exons 2, 3, and 10 of the tau gene.

 

They differ in either zero, one, or two inserts of 29 amino acids at the N-terminal part (exon 2 and 3), and three or four repeat-regions at the C-terminal part (exon 10). So, the longest isoform in the CNS has four repeats (R1, R2, R3 and R4) and two inserts (441 amino acids total), while the shortest isoform has three repeats (R1, R3 and R4) and no insert (352 amino acids total).

 

The longest isoform in the CNS has four repeats (R1, R2, R3, and R4) and two inserts (441 amino acids total), whereas the shortest isoform has three repeats (R1, R3, and R4) and no insert (352 amino acids total). All of the six tau isoforms are present in an often hyperphosphorylated state in paired helical filaments from AD.

TAW AND CROSS

https://en.wikipedia.org/wiki/Tau

In ancient times, tau was used as a symbol for life or resurrection, whereas the eighth letter of the Greek alphabet, theta, was considered the symbol of death.

In Biblical times, the taw was put on men to distinguish those who lamented sin, although newer versions of the Bible have replaced the ancient term taw with mark (Ezekiel 9:4) or signature (Job 31:35). Its original sound value is a voiceless alveolar plosive, IPA /t/

The symbolism of the cross was connected not only to the letter chi but also to tau, the equivalent of the last letter in the Phoenician and Old Hebrew alphabets, and which was originally cruciform in shape; see Cross of Tau

An essay written around 160 AD, attributed to Lucian, a mock legal prosecution called The Consonants at Law — Sigma v. Tau in the Court of Seven Vowels, contains a reference to the cross attribution. Sigma petitions the court to sentence Tau to death by crucifixion, saying:

Men weep, and bewail their lot, and curse Cadmus with many curses for introducing Tau into the family of letters; they say it was his body that tyrants took for a model, his shape that they imitated, when they set up structures on which men are crucified. Stauros (cross) the vile engine is called, and it derives its vile name from him. Now, with all these crimes upon him, does he not deserve death, nay, many deaths? For my part I know none bad enough but that supplied by his own shape — that shape which he gave to the gibbet named stauros after him by men

Tau is usually considered as the symbol of Franciscan orders due to St. Francis' love for it, symbol of the redemption and of the Cross. Almost all Franciscan churches have painted a tau with two crossing arms, both with stigmata, the one of Jesus and the other of Francis; usually members of the Secular Franciscan Order wear a wooden τ in a string with three knots around the neck

TETRADS

https://en.wikipedia.org/wiki/Evolutionary_history_of_plants

The first evidence of plants on land comes from spores of mid-Ordovician age (early Llanvirn, ~470 million years ago).[17][18][19] These spores, known as cryptospores, were produced either singly (monads), in pairs (dyads) or groups of four (tetrads), and their microstructure resembles that of modern liverwort spores, suggesting they share an equivalent grade of organisation.[7] Their walls contain sporopollenin – further evidence of an embryophytic affinity.[20] It could be that atmospheric 'poisoning' prevented eukaryotes from colonising the land prior to this,[21] or it could simply have taken a great time for the necessary complexity to evolve.[22]

 

Trilete spores similar to those of vascular plants appear soon afterwards, in Upper Ordovician rocks.[23] Depending exactly when the tetrad splits, each of the four spores may bear a "trilete mark", a Y-shape, reflecting the points at which each cell squashed up against its neighbours.[17] However, this requires that the spore walls be sturdy and resistant at an early stage. This resistance is closely associated with having a desiccation-resistant outer wall—a trait only of use when spores must survive out of water. Indeed, even those embryophytes that have returned to the water lack a resistant wall, thus don't bear trilete marks.[17] A close examination of algal spores shows that none have trilete spores, either because their walls are not resistant enough, or in those rare cases where it is, the spores disperse before they are squashed enough to develop the mark, or don't fit into a tetrahedral tetrad.[17]

 

Heterosporic plants, as their name suggests, bear spores of two sizes – microspores and megaspores. These would germinate to form microgametophytes and megagametophytes, respectively. This system paved the way for ovules and seeds: taken to the extreme, the megasporangia could bear only a single megaspore tetrad, and to complete the transition to true ovules, three of the megaspores in the original tetrad could be aborted, leaving one megaspore per megasporangium.

 

A Late Silurian sporangium, artificially colored. Green: A spore tetrad. Blue: A spore bearing a trilete mark – the Y-shaped scar. The spores are about 30-35 μm across

MEGAPHYLLS FOUR TIMES FOUR GROUPS

https://en.wikipedia.org/wiki/Evolutionary_history_of_plants

The more familiar leaves, megaphylls, are thought to have separate origins – indeed, they appeared four times independently, in the ferns, horsetails, progymnosperms, and seed plants.[55] They appear to have originated from dichotomising branches, which first overlapped (or "overtopped") one another, and eventually developed "webbing" and evolved into gradually more leaf-like structures.[53] So megaphylls, by this "teleome theory", are composed of a group of webbed branches[53] – hence the "leaf gap" left where the leaf's vascular bundle leaves that of the main branch resembles two axes splitting.[53] In each of the four groups to evolve megaphylls, their leaves first evolved during the Late Devonian to Early Carboniferous, diversifying rapidly until the designs settled down in the mid Carboniferous.[55]

TETRAGONAL FOUR MICROSPORANGIA

http://cdn.yourarticlelibrary.com/wp-content/uploads/2013/10/image37.png

http://www.yourarticlelibrary.com/biology/stamen-male-reproductive-organ-in-flowering-plants/11816/

It is a bilobed tetragonal oblong knoblike fertile part of stamen. Each anther lobe contains two long and cylindrical pollen sacs or microsporangia. Thus a dithecous anther is tetrasporangiate while monothecous stamen is bisporangiate. Rarely, an anther lobe has only one microsporangium, e.g., Wolffia or there is just one microsporangium per anther, e.g., Arceuthobium. The four microsporangia of an anther lie at its four comers.

FOUR TYPES OF LAYERS

http://www.yourarticlelibrary.com/biology/stamen-male-reproductive-organ-in-flowering-plants/11816/

Microsporangial wall has four types of layers epidermis (common anther covering), endothecium, 1-3 middle layers and tapetum