eye |
apartment |
top 10 words in brain distribution (in article): cell light water form produce muscle animal body human brain |
top 10 words in brain distribution (in article): build house state Unite public people service park building world |
top 10 words in brain distribution (not in article): drink lamp plant tissue wine bone structure beer process bottle |
top 10 words in brain distribution (not in article): city store street town home bus road village department country |
times more probable under eye 30 20 10 6 4 2.5 1.25 1 1.25 2.5 4 6 10 20 30 times more probable under apartment (words not in the model) | |
Eyes'" are organs that detect light, and send signals along the optic nerve to the visual and other areas of the brain. Complex optical systems with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system. Image-resolving eyes are present in cnidaria, mollusks, chordates, annelids and arthropods. The simplest "eyes", in even unicellular organisms, do nothing but detect whether the surroundings are light or dark, which is sufficient for the entrainment of circadian rhythms. From more complex eyes, retinal photosensitive ganglion cells send signals along the retinohypothalamic tract to the suprachiasmatic nuclei to effect circadian adjustment. Overview. Complex eyes can distinguish shapes and colors. The visual fields of many organisms, especially predators, involve large areas of binocular vision to improve depth perception; in other organisms, eyes are located so as to maximise the field of view, such as in rabbits and horses. The first proto-eyes evolved among animals 540 million years ago, about the time of the so-called Cambrian explosion. The last common ancestor of animals possessed the biochemical toolkit necessary for vision, and more advanced eyes have evolved in 96% of animal species in 6 of the thirty-something main phyla. In most vertebrates and some mollusks, the eye works by allowing light to enter it and project onto a light-sensitive panel of cells, known as the retina, at the rear of the eye. The cone cells (for color) and the rod cells (for low-light contrasts) in the retina detect and convert light into neural signals for vision. The visual signals are then transmitted to the brain via the optic nerve. Such eyes are typically roughly spherical, filled with a transparent gel-like substance called the vitreous humour, with a focusing lens and often an iris; the relaxing or tightening of the muscles around the iris change the size of the pupil, thereby regulating the amount of light that enters the eye, and reducing aberrations when there is enough light. The eyes of cephalopods, fish, amphibians and snakes usually have fixed lens shapes, and focusing vision is achieved by telescoping the lens — similar to how a camera focuses. Compound eyes are found among the arthropods and are composed of many simple facets which, depending on the details of anatomy, may give either a single pixelated image or multiple images, per eye. Each sensor has its own lens and photosensitive cell(s). Some eyes have up to 28,000 such sensors, which are arranged hexagonally, and which can give a full 360-degree field of vision. Compound eyes are very sensitive to motion. Some arthropods, including many Strepsiptera, have compound eyes of only a few facets, each with a retina capable of creating an image, creating vision. With each eye viewing a different thing, a fused image from all the eyes is produced in the brain, providing very different, high-resolution images. Possessing detailed hyperspectral color vision, the Mantis shrimp has been reported to have the world's most complex color vision system. Trilobites, which are now extinct, had unique compound eyes. They used clear calcite crystals to form the lenses of their eyes. In this, they differ from most other arthropods, which have soft eyes. The number of lenses in such an eye varied, however: some trilobites had only one, and some had thousands of lenses in one eye. In contrast to compound eyes, simple eyes are those that have a single lens. For example, jumping spiders have a large pair of simple eyes with a narrow field of view, supported by an array of other, smaller eyes for peripheral vision. Some insect larvae, like caterpillars, have a different type of simple eye (stemmata) which gives a rough image. Some of the simplest eyes, called ocelli, can be found in animals like some of the snails, which cannot actually "see" in the normal sense. They do have photosensitive cells, but no lens and no other means of projecting an image onto these cells. They can distinguish between light and dark, but no more. This enables snails to keep out of direct sunlight. In organisms dwelling near deep-sea vents, compound eyes have been secondarily simplified and adapted to spot the infra-red light produced by the hot vents in this way the bearers can spot hot springs and avoid being boiled alive. Evolution. Visual pigments appear to have a common ancestor and were probably involved in circadian rhythms or reproductive timing in simple organisms. Complex vision, associated with dedicated visual organs, or eyes, evolved many times in different lineages. Types of eye. Nature has produced ten different eye layouts — indeed every way of capturing an image has evolved at least once in nature, with the exception of zoom and Fresnel lenses. Eye types can be categorized into "simple eyes", with one concave chamber, and "compound eyes", which comprise a number of individual lenses laid out on a convex surface. Note that "simple" does not imply a reduced level of complexity or acuity. Indeed, any eye type can be adapted for almost any behaviour or environment. The only limitations specific to eye types are that of resolution — the physics of compound eyes prevents them from achieving a resolution better than 1°. Also, superposition eyes can achieve greater sensitivity than apposition eyes, so are better suited to dark-dwelling creatures. Eyes also fall into two groups on the basis of their photoreceptor's cellular construction, with the photoreceptor cells either being cilliated (as in the vertebrates) or rhabdomic. These two groups are not monophyletic; the cnidaira also possess cilliated cells, Pit eyes. Pit eyes, also known as stemma, are eye-spots which may be set into a pit to reduce the angles of light that enters and affects the eyespot, to allow the organism to deduce the angle of incoming light. Found in about 85% of phyla, these basic forms were probably the precursors to more advanced types of "simple eye". They are small, comprising up to about 100 cells covering about 100 µm. The directionality can be improved by reducing the size of the aperture, by incorporating a reflective layer behind the receptor cells, or by filling the pit with a refractile material. Pinhole eye. The pinhole eye is an "advanced" form of pit eye incorporating these improvements, most notably a small aperture (which may be adjustable) and deep pit. It is only found in the nautiloids. Without a lens to focus the image, it produces a blurry image, and will blur out a point to the size of the aperture. Consequently, nautiloids can't discriminate between objects with an angular separation of less than 11°. Shrinking the aperture would produce a sharper image, but let in less light. Spherical lensed eye. The resolution of pit eyes can be greatly improved by incorporating a material with a higher refractive index to form a lens, which may greatly reduce the blur radius encountered — hence increasing the resolution obtainable. The most basic form, still seen in some gastropods and annelids, consists of a lens of one refractive index. A far sharper image can be obtained using materials with a high refractive index, decreasing to the edges — this decreases the focal length and thus allows a sharp image to form on the retina. This also allows a larger aperture for a given sharpness of image, allowing more light to enter the lens; and a flatter lens, reducing spherical aberration. Such an inhomogeneous lens is necessary in order for the focal length | An apartment'" is a self-contained housing unit that occupies only part of a building. Apartments may be owned (by an "owner occupier") or rented (by "tenants"). A common alternative term for apartment is flat'". The term "apartment" is favored in North America, whereas the term "flat" is commonly, but not exclusively, used in the United Kingdom, Ireland and the Commonwealth nations. In Malaysian English, "flat" often denotes a housing block of lesser quality meant for lower-income groups, while "apartment" is more generic and may also include luxury condominiums. In the US, some apartment-dwellers own their own apartments, either as co-ops, in which the residents own shares of a corporation that owns the building or development; or in condominiums, whose residents own their apartments and share ownership of the public spaces. Most apartments are in buildings designed for the purpose, but large older houses are sometimes divided into apartments. The word "apartment" connotes a residential unit or section in a building. In some locations, particularly the United States, the word denotes a rental unit owned by the building owner, and is not typically used for a condominium. In the UK, some flat owners own a share in the company that owns the freehold of the building. This is commonly known as a "share of freehold" flat. The freehold company has the right to collect annual ground rents from each of the flat owners in the building. The freeholder can also develop or sell the building, subject to the usual planning and restrictions that might apply. The word unit'" is a more general term referring to both apartments and rental business suites. The word is generally used only in the context of a specific building. E.g., "This building has three units" or "I'm going to rent a unit in this building", but not "I'm going to rent a unit somewhere." When there is no tenant occupying an apartment, the apartment owner or landlord is said to have a "vacancy". For apartment landlords, each vacancy represents a loss of income from rent-paying tenants for the time the apartment is vacant (i.e., unoccupied). Landlords' objectives are often to minimize the vacancy rate for their units. The owner of the apartment, typically when transferring possession to the occupant, gives him her the key to the apartment entrance and any other keys needed, such as a common key to the building or any other common areas and a mailbox key. When the occupant(s) move out, these keys are typically returned to the owner. Apartment types and characteristics. Apartments can be classified into several types. In the US the typical terms are a Studio'", "'efficiency'", bedsit, or bachelor style apartment. These all tend to be the smallest apartments with the cheapest rents in a given area. These kinds of apartment usually consist mainly of a large room which is the living, dining, and bedroom combined. There are usually kitchen facilities as part of this central room, but the bathroom is its own smaller separate room. Moving up from the efficiencies are "'one-bedroom apartments'", in which one bedroom is separate from the rest of the apartment. Then there are "'two-bedroom'", "'three-bedroom'", etc. apartments. Small apartments often have only one entrance. Large apartments often have two entrances, perhaps a door in the front and another in the back. Depending on the building design, the entrance doors may be directly to the outside or to a common area inside, such as a hallway. Depending on location, apartments may be available for rent "'furnished'" with furniture or "'unfurnished'" into which a tenant usually moves in with their own furniture. A "'garden apartment'" has some characteristics of a townhouse: each apartment has its own entrance, and apartments are not placed vertically over one another. However, a garden apartment is usually only one story high and never more than two stories; they are often one-bedrooms and almost never more than two-bedrooms. Some garden apartment buildings place a one-car garage under each apartment, with pedestrian entrances from a common courtyard open at one end. The grounds are more landscaped than for other modestly scaled apartments. (Alternately, "garden apartment" can refer to a unit built half below grade, putting its windows at garden level. Laundry facilities may be found in a common area accessible to all the tenants in the building, or each apartment may have its own facilities. Depending on when the building was built and the design of the building, utilities such as water, heating, and electricity may be common for all the apartments in the building or separate for each apartment and billed separately to each tenant (however, many areas in the US have ruled it illegal to split a water bill among all the tenants, especially if a pool is on the premises). Outlets for connection to telephones are typically included in apartments. Telephone service is optional and is practically always billed separately from the rent payments. Cable television and similar amenities are extra also. Parking space(s), air conditioner, and extra storage space may or may not be included with an apartment. Rental leases often limit the maximum number of people who can reside in each apartment. On or around the ground floor of the apartment building, a series of mailboxes are typically kept in a location accessible to the public and, thus, to the mailman too. Every unit typically gets its own mailbox with individual keys to it. Some very large apartment buildings with a full-time staff may take mail from the mailman and provide mail-sorting service. Near the mailboxes or some other location accessible by outsiders, there may be a buzzer (equivalent to a doorbell) for each individual unit. In smaller apartment buildings such as two- or three-flats, or even four-flats, garbage is often disposed of in trash containers similar to those used at houses. In larger buildings, garbage is often collected in a common trash bin or Dumpster. For cleanliness or minimizing noise, many lessors will place restrictions on tenants regarding keeping pets in an apartment. In some parts of the world, the word apartment refers to a new purpose-built self-contained residential unit in a building, whereas the word "flat" means a converted self-contained unit in an older building. An industrial, warehouse, or commercial space converted to an apartment is commonly called a loft. When part of a house is converted for the ostensible use of a landlord's family member, the unit may be known as an "in-law" apartment or "granny flat", though these (sometimes illegally) created units are often occupied by ordinary renters rather than family members. In Canada these suites are commonly located in the basements of houses and are therefore normally called "basement suites" or "mother-in-law suites." In Milwaukee vernacular architecture, a Polish flat is an existing small house or cottage that has been lifted up to accommodate the creation of a new basement floor housing a separate apartment, then set down again; thus becoming a modest two-story flat. In Russia, a communal apartment'" («коммуналка») is a room with a shared kitchen and bath. A typical arrangement is a cluster of five or so apartments with their common kitchen and bathroom and their own front door, occupying a floor in a pre-Revolutionary mansions. Traditionally a room is owned by the government and assigned to a family on a semi-permanent basis. It is possible to "privatize" a room by paying a large sum of money to the government; then it can legally be sold. |