User:Crunchyjb

Source: Wikipedia, the free encyclopedia.


"M4A1" redirects here. For the World War II tank, see M4 Sherman.
Carbine, 5.56 mm, M4
STANAG Magazines
.

The M4 Carbine is a family of firearms tracing its lineage back to earlier

three-round burst (like the M16A2), while the M4A1 has a "full auto
" option in place of the three-round burst.

Overview

The M4 and variants fire

stock. Original M4 models had a flat-ended telescoping stock, but newer models are now equipped with a redesigned telescoping stock that is slightly larger and the end has a curvature.[1]

stock
.

As with many

armed forces in 2006 and will be manufactured in Malaysia under license by Colt Firearms
.

The M4 was developed and produced for the

XM177
family.

The

corpsmen will also be issued M4A1s instead of the M9, according to the Marine Corps Times.[2]

History and variants

Further information on M4 Carbine variants:
AR-15 variants

Except for the very first delivery order, all U.S. military-issue M4 and M4A1 possess a flat-top

Aimpoint M68 Close Combat Optic
(M68 CCO) being the favorite choices — and a detachable rail-mounted carrying handle. The current government standards are the Colt Model 920 (M4) and 921 (M4A1).

M4/M4A1

The major difference between these models is that the M4 has a "S-1-3" (safe/semi-automatic/3-round burst) trigger group while the M4A1 has a "S-1-F" (safe/semi-automatic/fully automatic) trigger group.

M4 MWS (Modular Weapon System)

M4 MWS (Modular Weapon System) shown with various accessories including M203 grenade launcher, RIS foregrip, removeable carry handle/rear sight assembly, AN/PEQ-2 laser system, and several optional optics.

Colt Model 925 carbines were tested fitted with the

Knight's Armament Corporation
(KAC) M4 RAS under the designation M4E2, but this designation appears to have been scrapped in favor of mounting this system to existing carbines without changing the designation. The U.S. Army Field Manual specifies for the Army that adding the Rail Accessory System (RAS) turns the weapon into the M4 MWS or Modular Weapon System.

M4A1

The M4A1 carbine is a variant of the basic M4 carbine intended for

counter-terrorist and special operations units for close quarters combat because of the carbine's compactness and firepower. These features are also very useful in urban warfare
. Although the M4 does not have as great of an effective range as the longer M16, many military analysts consider engagement with a non-specialized small arm above a range of 300 meters to be unnecessary. It is effective at ranges of 150 meters or less. It has a maximum effective range of about 460 meters.

In the last few years, M4A1 carbines have been refit or received straight from factory with barrels with a thicker profile under the handguard. This is for a variety of reasons such as heat dissipation during full-auto and accuracy as a byproduct of barrel weight. These heavier barrel weapons are also fitted with a heavier buffer known as the H2. Out of three sliding weights inside the buffer, the H2 possesses two tungsten weights and one steel weight, versus the standard H buffer, which uses one tungsten weight and two steel weights. These weapons, known by Colt as the Model 921HB (for Heavy Barrel), have also been designated M4A1, and as far as the government is concerned the M4A1 represents both the 921 and 921HB.

SOPMOD Block I

SOPMOD (Special Operations Peculiar Modification) Block I

holographic
sights).

SOPMOD Block II

A second-generation SOPMOD kit (now known as SOPMOD II) is currently under development, with many different manufacturers competing for a contract. Notable bidders include Knight's Armament Company, Atlantic Research Marketing Systems (ARMS), and Lewis Machine & Tools. Daniel Defense has won the contract for the RIS-II, the next generation of rail handguards.

Variants of the carbine built by different manufacturers are also in service with many other foreign special forces units, such as the

SFW built by Diemaco
of Canada. Although Diemaco was purchased by Colt and renamed Colt Canada, the Diemaco names and related firearms were kept.

Design

M4 with M68 Close Combat Optic and AN/PAQ-4

The M4/M4A1 5.56 mm Carbine is a gas-operated, air-cooled, magazine-fed, selective fire, shoulder-fired weapon with a telescoping stock. A shortened variant of the M16A2 rifle with a 14.5 

XM8 carbine. However, both projects were cancelled.) The M4 Carbine is also capable of mounting the M203 grenade launcher
.

Some features of the M4 and M4A1 compared to a full-length M16-series rifle include:

However, there have been some criticisms of the carbine, such as lower muzzle velocities and louder report due to the shorter barrel, additional stress on parts because of the shorter gas system, and a tendency to overheat faster than the M16A2.

Accessories

case in mid-air; the M203 and M68 CCO
are attached

Like all the variants of the M16 assault rifle, the M4 Carbine and the M4A1 Carbine can be fitted with many accessories, such as night vision devices, laser pointers, telescopic sights,

XM26 LSS shotgun
, and anything else compatible with a MIL-STD-1913 Picatinny rail.

Other common accessories include the AN/PEQ-2,

blank-firing attachment
(BFA).

M4 Carbine effectiveness

An April 2002 presentation by the

Natick Soldier Center presented by LTC Charlie Dean and SFC Sam Newland reported on lessons learned from M4 use in Afghanistan (such as use during Operation Anaconda
):

  • 34% of soldiers reported that their M4's handguards rattle and become excessively hot when firing.
  • 15% reported that they had trouble zeroing the M68 reflex sight.
  • 35% added barber brushes and 24% added dental picks to their cleaning kits.
  • Soldiers reported the following malfunctions:
    • 20% reported double-feeding.
    • 15% reported feeding jams.
    • 13% reported that feeding problems were due to magazines.
  • 89% of soldiers reported confidence in the weapon.
  • 20% were dissatisfied with its ease of maintenance.

Soldiers requested the following changes:

  • 55% requested the firearm be made lighter
  • 20% requested a larger magazine
File:TallAfarIraq3rdArmoredCav2006.jpg
Troops armed with M4 Carbines prepare to enter a house on a combat patrol in February 2006 in Tal Afar, Iraq. The 2nd and 4th soldiers from the right have M203 grenade launchers attached.

2007 Dust Test

In the fall of 2007, four carbines were tested in "sandstorm conditions" at

SOF Combat Assault Rifle (SCAR) and the Heckler & Koch HK416. Ten of each type of rifle were used to fire 6,000 rounds each, for a total of 60,000 rounds per rifle type.[3] The M4 suffered significantly more stoppages than its competitors: 882 stoppages, 19 requiring an armorer to fix. In comparison, the most reliable weapon, the XM8, had 116 minor stoppages and 11 major ones. It was followed by the FN SCAR with 226 stoppages, and the HK416 with 233.[4][5] The army now has plans to improve upon the M4. A new cold hammer forge barrel and new more reliable magazines have been their primary focus. The heavier barrel has a longer life and the magazines will reduce the stoppages. The army has stated that if all goes well during testing of the new magazines, they could be ready for combat by spring. The Army realized the need for new magazines when they found that 239 of the 882 failures were the result of problems in the magazine.[6]

Trademark issues

Colt has held a US trademark on the word "M4"[7] Many manufacturers produce firearms that come very close in terms of appearance to a military M4, sometimes colloquially referred to as an "M4-gery" (pronounced ĕm'fôr jə-rē, a

unfair competition, and deceptive trade practices. Heckler & Koch later settled out of court, changing one product's name from "HK M4" to "HK416". However, on December 8th, 2005, a District court judge in Maine granted a summary judgment
in favor of Bushmaster Firearms, dismissing all of Colt's claims except for false advertising. On the latter claim, Colt could not recover monetary damages. More importantly, the court ruled that "M4" was now a generic name, and that Colt's trademark should be revoked.

Users

In addition to the

United States of America (the country of origin), users of the M4 Carbine and its variants include;[citation needed
]

U.S. citizen ownership

Sales of actual M4s by Colt are restricted to military and civilian law enforcement. Only under special circumstances can a private citizen own an official M4 Carbine. While many machine guns can be legally owned with a proper tax stamp from the BATFE, an amendment to the Firearm Owners Protection Act of 1986 barred the transfer to private citizens of machine guns made in the U.S. after May 19, 1986. The only exception was for Special Occupational Taxpayers (SOT): licensed machine gun dealers with demonstration letters, manufacturers, and those dealing in exports and imports. As such, only the earliest Colt M4 prototypes built prior to May 19, 1986 would be legal to own by civilians not in the categories mentioned. However, as US firearms law considers the lower receiver of a M16/M4 type rifle to be the "firearm" (the serial numbered and, in the case of machineguns, registered under federal law, part of the weapon), a registered Colt M16 (much more common than an actual M4) may be configured as an M4 by replacing the M16 upper receiver/barrel assembly with an M4 top half, the burst mechanism with a fully-automatic FCG, and the fixed rifle stock with a 4-position telescoping M4 stock.

References

  1. ^ Photo of the Colt M4 with the redesigned telescoping stock
  2. ^ http://www.usmc.mil/maradmins/maradmin2000.nsf/9ad58548f0ddc1e58525697a0070ebf9/cbb7191e3979de2b85257302004fdc11
  3. ^ http://www.military.com/NewsContent/0,13319,158468,00.html
  4. ^ http://www.defensetech.org/archives/003909.html
  5. ^ http://www.armytimes.com/news/2007/12/army_carbine_dusttest_071217/
  6. ^ http://www.armytimes.com/news/2007/12/army_m4_hearing_071217w/
  7. ^ US Trademark serial number 76335060 registration number 2734001 http://tess2.uspto.gov/bin/showfield?f=doc&state=75n9nl.3.13

See also

External links

Wikimedia Commons has media related to M4.



"Animalia" redirects here. For the book, see Animalia (book).
For other uses, see User:Crunchyjb (disambiguation).

Animals
Temporal range: Ediacaran – Recent
Clockwise from top-left:
Chrysaora quinquecirrha (a cnidarian), Aphthona flava (an arthropod), Eunereis longissima (an annelid), and Panthera tigris (a chordate
).
Scientific classification
Domain:
Eukaryota
(unranked):
Opisthokonta
Kingdom:
Animalia

Linnaeus, 1758
Phyla

Animals are a major group of

motile – they can move spontaneously and independently. Animals are heterotrophs – they are dependent on other organisms (e.g. plants) for sustenance
.

Most known animal phyla appeared in the fossil record as marine species during the Cambrian explosion, about 542 million years ago.

Etymology

The word "animal" comes from the Latin word animale, neuter of animalis, and is derived from anima, meaning vital breath or soul. In everyday colloquial usage, the word usually refers to non-human animals. The biological definition of the word refers to all members of the Kingdom Animalia. Therefore, when the word "animal" is used in a biological context, humans are included.[1]

Characteristics

Animals have several characteristics that set them apart from other living things. Animals are

blastula stage
, which is a characteristic exclusive to animals.

Structure

With a few exceptions, most notably the

eumetazoans
when the former is used for animals in general.

All animals have

shells, bones, and spicules. During development it forms a relatively flexible framework upon which cells can move about and be reorganized, making complex structures possible. In contrast, other multicellular organisms like plants and fungi have cells held in place by cell walls, and so develop by progressive growth. Also, unique to animal cells are the following intercellular junctions: tight junctions, gap junctions, and desmosomes
.

Reproduction and development

Nearly all animals undergo some form of sexual reproduction. Adults are

ova. These fuse to form zygotes
, which develop into new individuals.

fluorescent dyes undergoing mitosis, specifically early anaphase
.

Many animals are also capable of asexual reproduction. This may take place through parthenogenesis, where fertile eggs are produced without mating, or in some cases through fragmentation.

A

gastrula with a digestive chamber, and two separate germ layers – an external ectoderm and an internal endoderm. In most cases, a mesoderm
also develops between them. These germ layers then differentiate to form tissues and organs.

Most animals grow by indirectly using the energy of

sugars using a process known as photosynthesis. Starting with the molecules carbon dioxide (CO2) and water (H2O), photosynthesis converts the energy of sunlight into chemical energy stored in the bonds of glucose (C6H12O6) and releases oxygen (O2). These sugars are then used as the building blocks which allow the plant to grow. When animals eat these plants (or eat other animals which have eaten plants), the sugars produced by the plant are used by the animal. They are either used directly to help the animal grow, or broken down, releasing stored solar energy, and giving the animal the energy required for motion. This process is known as glycolysis
.

Animals who live close to

eubacteria
form the base of the food chain.

Origin and fossil record

Animals are generally considered to have

eukaryotes
tend to have anterior flagella.

The first fossils that might represent animals appear towards the end of the

earthworms.[6] In addition during the beginning of the Tonian period around 1 billion years ago (roughly the same time that the trace fossils previously discussed in this article date back to) there was a decrease in Stromatolite
diversity which may indicate the appearance of grazing animals during this time as Stromatolites also increased in diversity shortly after the end-Ordovician and end-Permian rendered large amounts of grazing marine animals extinct and decreased shortly after their populations recovered. However some other scientists doubt that these fossils are authentic and have suggested these trace fossils are just the result of natural processes such as erosion.[citation needed]

Groups of animals

sea fan
, Iciligorgia schrammi, and a sea rod, Plexaurella nutans.

The sponges (

Porifera) were long thought to have diverged from other animals early. As mentioned above, they lack the complex organization found in most other phyla. Their cells are differentiated, but in most cases not organized into distinct tissues. Sponges are sessile and typically feed by drawing in water through pores. Archaeocyatha, which have fused skeletons, may represent sponges or a separate phylum. However, a phylogenomic study in 2008 of 150 genes in 21 genera[7] revealed that it is the Ctenophora
or comb jellies which are the basal lineage of animals, at least among those 21 phyla. The authors speculate that sponges—or at least those lines of sponges they investigated—are not so primitive, but may instead be secondarily simplified.

Among the other phyla, the Ctenophora and the

diploblastic. The tiny Placozoans
are similar, but they do not have a permanent digestive chamber.

The remaining animals form a

triploblastic, i.e. all three germ layers are well-developed, and tissues form distinct organs. The digestive chamber has two openings, a mouth and an anus, and there is also an internal body cavity called a coelom or pseudocoelom. There are exceptions to each of these characteristics, however – for instance adult echinoderms
are radially symmetric, and certain parasitic worms have extremely simplified body structures.

Genetic studies have considerably changed our understanding of the relationships within the Bilateria. Most appear to belong to two major lineages: the

Rhombozoa, and Orthonectida. The Myxozoa
, single-celled parasites that were originally considered Protozoa, are now believed to have developed from the Bilateria as well.

Deuterostomes

Superb Fairy-wren
, Malurus cyaneus

Deuterostomes differ from the other Bilateria, called protostomes, in several ways. In both cases there is a complete digestive tract. However, in protostomes the initial opening (the archenteron) develops into the mouth, and an anus forms separately. In deuterostomes this is reversed. In most protostomes, cells simply fill in the interior of the gastrula to form the mesoderm, called schizocoelous development, but in deuterostomes it forms through invagination of the endoderm, called enterocoelic pouching. Deuterostomes also have a dorsal, rather than a ventral, nerve chord and their embryos undergo different cleavage.

All this suggests the deuterostomes and protostomes are separate, monophyletic lineages. The main phyla of deuterostomes are the

Echinodermata and Chordata. The former are radially symmetric and exclusively marine, such as starfish, sea urchins, and sea cucumbers. The latter are dominated by the vertebrates, animals with backbones. These include fish, amphibians, reptiles, birds, and mammals
.

In addition to these, the deuterostomes also include the

Hemichordata or acorn worms. Although they are not especially prominent today, the important fossil graptolites
may belong to this group.

The Chaetognatha or arrow worms may also be deuterostomes, but more recent studies suggest protostome affinities.

Ecdysozoa

Yellow-winged Darter
, Sympetrum flaveolum

The

Tardigrada
, are close relatives of the arthropods and share these traits.

The ecdysozoans also include the

Nematoda or roundworms, the second largest animal phylum. Roundworms are typically microscopic, and occur in nearly every environment where there is water. A number are important parasites. Smaller phyla related to them are the Nematomorpha or horsehair worms, and the Kinorhyncha, Priapulida, and Loricifera
. These groups have a reduced coelom, called a pseudocoelom.

The remaining two groups of protostomes are sometimes grouped together as the Spiralia, since in both embryos develop with spiral cleavage.

Platyzoa

Bedford's flatworm
, Pseudobiceros bedfordi

The

Platyhelminthes, the flatworms. These were originally considered some of the most primitive Bilateria, but it now appears they developed from more complex ancestors.[8]

A number of

Gastrotricha.[9]

The other platyzoan phyla are mostly microscopic and

Cycliophora.[10] These groups share the presence of complex jaws, from which they are called the Gnathifera
.

Lophotrochozoa

Roman snail
, Helix pomatia

The

Annelida.[11][12] The former includes animals such as snails, clams, and squids, and the latter comprises the segmented worms, such as earthworms and leeches. These two groups have long been considered close relatives because of the common presence of trochophore larvae, but the annelids were considered closer to the arthropods,[13] because they are both segmented. Now this is generally considered convergent evolution, owing to many morphological and genetic differences between the two phyla.[14]

The Lophotrochozoa also include the

Phoronida, and possibly the Bryozoa or moss animals.[20]

Model organisms

Main articles: Model organism and Animal testing

Because of the great diversity found in animals, it is more economical for scientists to study a small number of chosen species so that connections can be drawn from their work and conclusions extrapolated about how animals function in general. Because they are easy to keep and breed, the fruit fly Drosophila melanogaster and the nematode Caenorhabditis elegans have long been the most intensively studied metazoan model organisms, and were among the first lifeforms to be genetically sequenced. This was facilitated by the severely reduced state of their genomes, but the double-edged sword here is that with many genes, introns and linkages lost, these ecdysozoans can teach us little about the origins of animals in general. The extent of this type of evolution within the superphylum will be revealed by the crustacean, annelid, and molluscan genome projects currently in progress. Analysis of the starlet sea anemone genome has emphasised the importance of sponges, placozoans, and choanoflagellates, also being sequenced, in explaining the arrival of 1500 ancestral genes unique to the Eumetazoa.[21]

An analysis of the homoscleromorph sponge Oscarella carmela also suggests that the last common ancestor of sponges and the eumetazoan animals was more complex than previously assumed.[22]

Other model organisms belonging to the animal kingdom include the mouse (

Danio rerio
}.

History of classification

Carolus Linnaeus known as the father of modern taxonomy

Carolus Linnaeus (Carl von Linné), in the first hierarchical classification. Since then biologists have begun emphasizing evolutionary relationships, and so these groups have been restricted somewhat. For instance, microscopic protozoa
were originally considered animals because they move, but are now treated separately.

In

Amphibia, Aves, and Mammalia. Since then the last four have all been subsumed into a single phylum, the Chordata
, whereas the various other forms have been separated out. The above lists represent our current understanding of the group, though there is some variation from source to source.

See also

Look up crunchyjb in Wiktionary, the free dictionary.

Notes

  1. ^ "Animal". The American Heritage Dictionary (Forth ed.). Houghton Mifflin Company. 2006.
  2. ^ National Zoo. "Panda Classroom". Retrieved 2007. {{cite web}}: Check date values in: |accessdate= (help); Unknown parameter |accessmonthday= ignored (help)
  3. ^ Jennifer Bergman. "Heterotrophs". Retrieved 2007. {{cite web}}: Check date values in: |accessdate= (help); Unknown parameter |accessmonthday= ignored (help)
  4. ^ Davidson, Michael W. "Animal Cell Structure". Retrieved 2007. {{cite web}}: Check date values in: |accessdate= (help); Unknown parameter |accessmonthday= ignored (help)
  5. ^ Saupe, S.G. "Concepts of Biology". Retrieved 2007. {{cite web}}: Check date values in: |accessdate= (help); Unknown parameter |accessmonthday= ignored (help)
  6. PMID 9756480. Retrieved 2007-08-20. {{cite journal}}: Cite uses deprecated parameter |authors= (help
    )
  7. ^ Dunn et al. 2008. "Broad phylogenomic sampling improves resolution of the animal tree of life". Nature 06614.
  8. PMID 10082465. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: date and year (link
    )
  9. ^ Todaro, Antonio. "Gastrotricha: Overview". Gastrotricha: World Portal. University of Modena & Reggio Emilia. Retrieved 2008-01-26.
  10. PMID 21708760. Retrieved 2008-01-26.{{cite journal}}: CS1 maint: date and year (link
    )
  11. ^ "Biodiversity: Mollusca". The Scottish Association for Marine Science. Retrieved 2007-11-19.
  12. ^ Russell, Bruce J. (Writer), Denning, David (Writer) (2000). Branches on the Tree of Life: Annelids (VHS). BioMEDIA ASSOCIATES.
  13. doi:10.1093/sysbio/41.3.305. {{cite journal}}: Check date values in: |date= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help
    )
  14. ISSN 0022-2844. Retrieved 2007-11-19. {{cite journal}}: Check date values in: |date= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help
    )
  15. ^ Collins, Allen G. (1995), The Lophophore, University of California Museum of Paleontology {{citation}}: Check |author-link= value (help); External link in |author-link= (help)
  16. PMID 10781043. {{cite journal}}: Check date values in: |date= (help
    )
  17. ^ Passamaneck, Yale J. (2003), "Woods Hole Oceanographic Institution", Molecular Phylogenetics of the Metazoan Clade Lophotrochozoa (PDF), p. 124
  18. PMID 11527461. {{cite journal}}: Check date values in: |date= (help
    )
  19. PMID 11801741. Retrieved 2007-11-19. {{cite journal}}: Check date values in: |date= (help
    )
  20. ISBN 9780470016176. Retrieved 2008-01-19.{{cite journal}}: CS1 maint: date and year (link
    )
  21. ^ N.H. Putnam; et al. (Jul 2007). "Sea anemone genome reveals ancestral eumetazoan gene repertoire and genomic organization".
    PMID 17615350. {{cite journal}}: Explicit use of et al. in: |author= (help)CS1 maint: date and year (link
    )
  22. PMID 17090697. Retrieved 2008-01-19.{{cite journal}}: CS1 maint: date and year (link
    )

References

  • Klaus Nielsen. Animal Evolution: Interrelationships of the Living Phyla (2nd edition). Oxford Univ. Press, 2001.
  • Knut Schmidt-Nielsen. Animal Physiology: Adaptation and Environment. (5th edition). Cambridge Univ. Press, 1997.

External links
Wikispecies has information related to Animalia.

Retrieved from "https://en.wikipedia.org/w/index.php?title=User:Crunchyjb&oldid=1168399020"