1. Why Study Biology?

4. Stem Cell
Stem cells are cells found in most, if not all, multi-cellular organisms. They are characterized by the ability to renew themselves through mitotic cell division and differentiating into a diverse range of specialized cell types. Research in the stem cell field grew out of findings by Canadian scientists Ernest A. McCulloch and James E. Till in the 1960s.[1][2] The two broad types of mammalian stem cells are: embryonic stem cells that are found in blastocysts, and adult stem cells that are found in adult tissues. In a developing embryo, stem cells can differentiate into all of the specialized embryonic tissues. In adult organisms, stem cells and progenitor cells act as a repair system for the body, replenishing specialized cells, but also maintain the normal turnover of regenerative organs, such as blood, skin or intestinal tissues.
As stem cells can be grown and transformed into specialized cells with characteristics consistent with cells of various tissues such as muscles or nerves through cell culture, their use in medical therapies has been proposed. In particular, embryonic cell lines, autologous embryonic stem cells generated through therapeutic cloning, and highly plastic adult stem cells from the umbilical cord blood or bone marrow are touted as promising candidates.[3]
Medical researchers believe that stem cell therapy has the potential to dramatically change the treatment of human disease. A number of adult stem cell therapies already exist, particularly bone marrow transplants that are used to treat leukemia.[27] In the future, medical researchers anticipate being able to use technologies derived from stem cell research to treat a wider variety of diseases including cancer, Parkinson's disease, spinal cord injuries, Amyotrophic lateral sclerosis and muscle damage, amongst a number of other impairments and conditions.[28][29] However, there still exists a great deal of social and scientific uncertainty surrounding stem cell research, which could possibly be overcome through public debate and future research, and further education of the public.
Stem cells, however, are already used extensively in research, and some scientists do not see cell therapy as the first goal of the research, but see the investigation of stem cells as a goal worthy in itself.[30]
[edit] Controversy surrounding human embryonic stem cell research
Main article: Stem cell controversy
There exists a widespread controversy over human embryonic stem cell research that emanates from the techniques used in the creation and usage of stem cells. Human embryonic stem cell research is controversial because, with the present state of technology, starting a stem cell line requires the destruction of a human embryo and/or therapeutic cloning. However, recently, it has been shown in principle that adult stem cell lines can be manipulated to generate embryonic-like stem cell lines using a single-cell biopsy similar to that used in preimplantation genetic diagnosis that may allow stem cell creation without embryonic destruction.[31] It is not the entire field of stem cell research, but the specific field of human embryonic stem cell research that is at the centre of an ethical debate.
Opponents of the research argue that embryonic stem cell technologies are a slippery slope to reproductive cloning and can fundamentally devalue human life. Those in the pro-life movement argue that a human embryo is a human life and is therefore entitled to protection.
Contrarily, supporters of embryonic stem cell research argue that such research should be pursued because the resultant treatments could have significant medical potential. It is also noted that excess embryos created for in vitro fertilization could be donated with consent and used for the research.
The ensuing debate has prompted authorities around the world to seek regulatory frameworks and highlighted the fact that stem cell research represents a social and ethical challenge.

5. Dolly the Sheep
Cloning is the process of making an identical copy of something. In biology, it collectively refers to processes used to create copies of DNA fragments (molecular cloning), cells (cell cloning), or organisms. The term also covers when organisms such as bacteria, insects or plants reproduce asexually.
The term clone is derived from κλών, the Greek word for "twig, branch", referring to the process whereby a new plant can be created from a twig. In horticulture, the spelling clon was used until the twentieth century; the final e came into use to indicate the vowel is a "long o" instead of a "short o"[citation needed]. Since the term entered the popular lexicon in a more general context, the spelling clone has been used exclusively.

6. Parmecium vs. Q-tip Cotton

7. Lactobacillus bulgaricus
Lactobacillus is a genus of Gram-positive facultative anaerobic or microaerophilic bacteria[1]. They are a major part of the lactic acid bacteria group, named as such because most of its members convert lactose and other sugars to lactic acid. They are common and usually benign. In humans they are present in the vagina and the gastrointestinal tract, where they are symbiotic and make up a small portion of the gut flora. Many species are prominent in decaying plant material. The production of lactic acid makes its environment acidic which inhibits the growth of some harmful bacteria. Several members of the genus have had their genome sequenced.
Lactobacillus bulgaricus

8. Mimicry Viceroy Monarch Bee Fly Classification
Many types of mimicry have been described. An overview of each follows, highlighting the similarities and differences between the various forms. Classification is often based on function with respect to the mimic (e.g. avoiding harm), though other parameters can also be used, and multidimensional classifications are required to understand the full picture. For this reason, some cases may belong to more than one class, e.g. automimicry and aggressive mimicry are not mutually exclusive, as one describes the species relationship between model and mimic, while the other describes the function for the mimic (obtaining food).
[edit] Defensive
Defensive or protective mimicry takes place when organisms are able to avoid an encounter that would be harmful to them by deceiving an enemy into treating them as something else. Four such cases are discussed here, the first three of which entail mimicry of an aposematic, harmful organism: Batesian mimicry, where a harmless mimic poses as harmful; Müllerian mimicry, where two harmful species share similar perceived characteristics; and Mertensian mimicry, where a deadly mimic resembles a less harmful but lesson-teaching model. Finally, Vavilovian mimicry, where weeds resemble crops, is discussed.
[edit] Batesian
Main article: Batesian mimicry
Several species, including several hoverflies, mimic stinging species of wasp.
In Batesian mimicry the mimic shares signals similar to the model, but does not have the attribute that makes it unprofitable to predators (e.g. unpalatability). In other words, a Batesian mimic is a sheep in wolf's clothing. It is named after Henry Walter Bates, an English naturalist whose work on butterflies in the Amazon rainforest (including The Naturalist on the River Amazons) was pioneering in this field of study.[13][14] Mimics are less likely to be found out when in low proportion to their model, a phenomenon known as negative frequency dependent selection which applies in most other forms of mimicry as well. This is not the case in Müllerian mimicry however, which is described next.
Examples:
Lepidoptera
The Ash Borer (Podosesia syringae), a moth of the Clearwing family (Sesiidae), is a Batesian mimic of the Common wasp because it resembles the wasp, but is not capable of stinging. A predator that has learned to avoid the wasp would similarly avoid the Ash Borer.
Plain Tiger (Danaus chrysippus) - an unpalatable model with a number of mimics.
Common Crow (Euploea core) - an unpalatable model with a number of mimics. See also under Müllerian mimicry below.
and imitate unpalatable Heliconius butterflies such as H. ismenius.[15]
Several palatable butterflies resemble different species from the highly noxious papilionine genus Battus.[15]
Several palatable moths produce ultrasonic click calls to mimic the unpalatable tiger moths.[16]
The False Cobra (Malpolon moilensis) is a mildly venomous but harmless colubrid snake which mimics the characteristic "hood" of an Indian cobra's threat display. The Eastern Hognose Snake (Heterodon platirhinos) similarly mimics the threat display of venomous snakes.
The milk snake resembles the deadly poisonous coral snake.
Octopuses of the genus Thaumoctopus (the Mimic Octopus and the "wunderpus") are able to intentionally alter their body shape and color so that they resemble dangerous sea snakes or lionfish.[17]
Viceroy
Monarch
Bee
Fly

9. Mimicry
Coral Snake
Scarlet King Snake

10. Mimicry
Katydid from Costa Rica
Walkingstick
Caterpillar

11. Biomimicry
“Well, the spider is able to create stronger fiber than the best human efforts to date. And she does this at room temperature, without toxic chemicals and at normal pressure. The diminutive mussel is able to create a glue on the spot that allows him to stick underwater to slippery surfaces better than any genius material scientist’s “breakthrough technologies”. In this book, through these and many other examples, Janine points out that if we open our eyes to the nature around us, we can learn design approaches that will really push technology forward and at the same time help us to minimize our environmental impact.”

12. Biomimicry
A large adhesives company comes to us with a challenge: “We know our products are toxic and not very good: They’re brittle, they dry out, and they have to be reapplied. Furthermore, after we glue things together with our adhesives, they can’t be easily disassembled for recycling. How can we fix all that?”
They come to us because they know we look to the natural world for answers. How does nature adhere? We look at how bacteria stick to the surfaces of a host body, how plants use tendrils to cling to walls, how sea kelp uses its holdfasts to adhere to wet rocks, and how a fly can walk across a ceiling.
The gecko is a beautiful example of nature’s ability to come up with a super-strong adhesive. Do you know how geckos are able to hang on a wall? On the bottom of their feet, they’ve got fins that break up into millions of little bristles, like split ends. Each of those bristles adheres to the nooks and crannies of a surface using positive and negative molecular charges that create what’s called van der Waals forces. They’re the tiniest attractive force there is, but when you combine them by the billions you get one of the strongest adhesives known to man. You can suspend 280 pounds from a fully engaged gecko.
The strength of that adhesive force is only part of the story. When the gecko peels back its toes, it fully releases its bond at 30 degrees. Plus, the gecko can walk through sand and, within just a few steps, can cling to a wall; its toes are self-cleaning structures. The adhesion doesn’t diminish in liquids or in a vacuum. Imagine the uses for a resealable adhesive like this.

13. Burrowing Owl
The Burrowing Owl (Athene cunicularia) is a small, long-legged owl found throughout open landscapes of North and South America. Burrowing owls can be found in grasslands, rangelands, agricultural areas, deserts, or any other dry, open area with low vegetation[1]. They nest and roost in burrows, such as those excavated by prairie dogs. Unlike most owls, burrowing owls are often active during the day, although they tend to avoid the mid-day heat. Most hunting is still done from dusk until dawn, when their owl apomorphies are most advantageous.
Burrowing owls are able to live for at least 9 years in the wild and over 10 years in captivity.[ citation needed ] They are often killed by vehicles when crossing roads, and have many natural enemies, including badgers, coyotes, and snakes. They are also killed by both feral and domesticated cats and dogs.

14. Burrowing Owl Habitat
In 1977, there were about 2,000 breeding pairs of Burrowing Owls in Canada. By 2003 the estimated population was down to fewer than 500 pairs. Over the past decade, they have declined in Canada at a rate of approximatedly 20% per year. Burrowing Owls will likely become extinct in Canada unless this trend is reversed
Seventy-five percent of the native grasslands in Canada are gone. What remains tends to be fragmented by roads, oil and gas well sites, and grain fields. These impacts and their associated activities may be contributing to the decline of our Burrowing Owl.
Habitat change - Much of the prairies native grasslands have been altered and reduced in size by human activities hence decreasing the amount of habitat available to the Burrowing Owl
Fewer burrows - Burrowing Owls put the finishing touches to their underground nest, but do not do much actual digging. For this, they rely on badgers and ground squirrels, which are often considered pests and killed. Fewer of these digging animals mean fewer nest sites for Burrowing Owls.
Lack of Food - Burrowing Owls eat insects and small mammals that tend to live in taller grasses and "weedy" areas. Burrowing Owls need to nest close to these types of areas. Chicks starve when there is not enough food available to the parents. On average, of the nine eggs laid, one will not hatch, while three to six young will not fledge. Hunting perches - Fences, utility poles, hedge-rows and artificial nests for hawks are all new features on the prairie landscape. These perches benefit owl-hunting hawks and may in turn contribute to the decline of the Burrowing Owl. Predation - Although the Burrowing Owl is a predator, it is not at the top of the food chain. Mammals, birds, reptiles, and even house cats kill and eat it. When small mammal populations naturally decline, research suggests that these predators may turn to prey on the Burrowing Owl.
Road kill - It is common for Burrowing Owls to die along roads. Young owls in particular hunt and scavenge on and adjacent to roads at dusk until well after dark. Unfortunately, Burrowing Owls are slow flyers and have difficulty escaping oncoming traffic.
Pesticides - Grasshoppers are one of the most important foods for the Burrowing Owl, but they are also a pest on farms and ranches. It is still not fully known how chemicals sprayed to kill insect pests affect the Burrowing Owl.
Low Productivity - The Burrowing Owl lays more eggs than it can normally raise. Researchers are noticing that when few young are produced in one year, the population is typically lower the following year. When productivity is high, the population may increase (or remain relatively stable) the following year. This low production of owls is one of the reasons that the population continues to decline; work is underway to understand why it is happening.

15. Endangered Species African wild dog
fill the same ecological niche as a woodpecker. It is the world's largest nocturnal primate, and is characterized by its unique method of finding food; it taps on trees to find grubs, then gnaws holes in the wood and inserts its elongated middle finger to pull the grubs out.
The Aye-aye is an endangered species not only because its habitat is being destroyed, but also due to native superstition. Besides being a general nuisance in villages, ancient Malagasy legend said that the Aye-aye was a symbol of death. It is viewed as a good omen in some areas, however, but these areas are a minority.
Researchers in Madagascar report remarkable fearlessness in the Aye-aye; some accounts tell of individual animals strolling nonchalantly in village streets or even walking right up to naturalists in the rainforest and sniffing their shoes. Therefore, it is no wonder that displaced animals often raid coconut plantations or steal food in villages. It is not unlike the Common Raccoon in this regard.
However, public contempt goes beyond this. The Aye-aye is often viewed as a harbinger of evil and killed on sight. Others believe that should one point its long middle finger at you, you were condemned to death. Some say the appearance of an Aye-aye in a village predicts the death of a villager, and the only way to prevent this is to kill the Aye-aye. The Sakalava people go so far as to claim Aye-ayes sneak into houses through the thatched roofs and murder the sleeping occupants by using their middle finger to puncture the victim's aorta.[6]
Incidents of Aye-aye killings increase every year as its forest habitats are destroyed and it is forced to raid plantations and villages. Because of the superstition surrounding it, this often ends in death. Fortunately, the superstition can prevent people from hunting them for food.
African wild dog
Aye-aye: endangered species of madagascar. Most primitive of all living
Primates. Resembles a cat-like squirrel

16. Endangered Species Cucumber Tree Largetooth Sawfish Almiqui
While it is not yet extinct, it is still an endangered species, in part because it only breeds a single litter of one to three in a year, and, like the Agouti, because of predation by species that were introduced by humans.
Largetooth Sawfish (Pristis microdon) is a large, Endangered species of sawfish that is wide-ranging in the Indo-West Pacific, in freshwater or inshore coastal waters. The distinctive rostrum that gives the species its name is highly sought after, but is also often responsible for the species becoming entangled in fishing nets as bycatch. Virtually all known populations have experienced very serious declines. The species is also threatened by habitat loss and degradation
Atelopus varius is a Critically Endangered harlequin toad that was once abundant in Costa Rica and western Panama. Declines began at Monteverde in 1988, and by 1996 it was believed to be extinct in Costa Rica. Serious population crashes have also taken place in Panama, although it has been recorded there as recently as A small population was rediscovered in Costa Rica in The cause of its decline is possibly a result of the fungal disease, chytridiomycosis, the incidence of which may be related to extreme climatic events, in particular drought. Atelopus varius is a Critically Endangered harlequin toad that was once abundant in Costa Rica and western Panama. Declines began at Monteverde in 1988, and by 1996 it was believed to be extinct in Costa Rica. Serious population crashes have also taken place in Panama, although it has been recorded there as recently as A small population was rediscovered in Costa Rica in The cause of its decline is possibly a result of the fungal disease, chytridiomycosis, the incidence of which may be related to extreme climatic events, in particular drought.
The Cucumber Tree (Dendrosicyos socotrana) is an unusual Vulnerable endemic from the island archipelago of Soqotra, Yemen. The species is very well adapted to withstand drought conditions and should therefore be better able than many species to tolerate any drying out of the Archipelago due to climate change. However, in times of severe drought, trees are cut-down, pulped and fed to livestock, and in some areas this has resulted in its almost total eradication. Declining habitat quality is also preventing regeneration of the plant.
Almiqui

17. Golden lion tamarin

18. Global Warming
Global warming is the increase in the average measured temperature of the Earth's near-surface air and oceans since the mid-20th century, and its projected continuation.
The average global air temperature near the Earth's surface increased 0.74 ± 0.18 °C (1.33 ± 0.32 °F) during the 100 years ending in 2005.[1] The Intergovernmental Panel on Climate Change (IPCC) concludes "most of the observed increase in globally averaged temperatures since the mid-twentieth century is very likely due to the observed increase in anthropogenic (man-made) greenhouse gas concentrations"[1] via an enhanced greenhouse effect. Natural phenomena such as solar variation combined with volcanoes probably had a small warming effect from pre-industrial times to 1950 and a small cooling effect from 1950 onward.[2][3]
These basic conclusions have been endorsed by at least 30 scientific societies and academies of science,[4] including all of the national academies of science of the major industrialized countries.[5][6][7] While individual scientists have voiced disagreement with some findings of the IPCC,[8] the overwhelming majority of scientists working on climate change agree with the IPCC's main conclusions.[9][10]
Climate model projections summarized by the IPCC indicate that average global surface temperature will likely rise a further 1.1 to 6.4 °C (2.0 to 11.5 °F) during the twenty-first century.[1] This range of values results from the use of differing scenarios of future greenhouse gas emissions as well as models with differing climate sensitivity. Although most studies focus on the period up to 2100, warming and sea level rise are expected to continue for more than a thousand years even if greenhouse gas levels are stabilized. The delay in reaching equilibrium is a result of the large heat capacity of the oceans.[1]
Increasing global temperature is expected to cause sea level to rise, an increase in the intensity of extreme weather events, and significant changes to the amount and pattern of precipitation, likely leading to an expanse of tropical areas and increased pace of desertification. Other expected effects of global warming include changes in agricultural yields, modifications of trade routes, glacier retreat, species extinctions and increases in the ranges of disease vectors.
Remaining scientific uncertainties include the amount of warming expected in the future, and how warming and related changes will vary from region to region around the globe. Most national governments have signed and ratified the Kyoto Protocol aimed at reducing greenhouse gas emissions, but there is ongoing political and public debate worldwide regarding what, if any, action should be taken to reduce or reverse future warming or to adapt to its expected consequences.

19. List of Endangered Species
Abarema josephi
Abarema killipii
Abarema longipedunculata
Abarema obovata
Abarema oxyphyllidia
Abarema racemiflora
Abarema turbinata
Abarema villifera
Abdulmajidia chaniana
Abdulmajidia maxwelliana
Abies beshanzuensis
Abies bracteata (Bristlecone Fir)
Abies cephalonica (Greek Fir)
Abies chengii
Abies fanjingshanensis
Abies fraseri (Fraser Fir)
Abies hickelii
Abies hidalgensis

20. List of Endangered Species
Abies koreana (Korean Fir)
Abies nebrodensis (Sicilian Fir)
Abies numidica (Algerian Fir)
Abies pinsapo (Spanish Fir)
Abies squamata (Flaky Fir)
Abies yuanbaoshanensis
Abies ziyuanensis
Abrawayaomys ruschii (Rushi's Rat)
Abrocoma boliviensis (Bolivian Chinchilla Rat)
Abronia montecristoi
Aburria aburri (Wattled Guan)
Abutilon eremitopetalum (Hidden-petaled Abutilon)
Abutilon menziesii
Abutilon sachetianum
Abutilon sandwicense (Greenflower Indian Mallow)
Acacia albicorticata

21. List of Endangered Species
Acacia anegadensis
Acacia ankokib
Acacia aulacocarpa
Acacia belairioides
Acacia bucheri
Acacia campbellii
Acacia caraniana
Acacia cernua
Acacia condyloclada
Acacia crassicarpa
Acacia daemon
Acacia densispina
Acacia dolichostachya
Acacia ferruginea
Acacia flagellaris
Acacia gaumeri
Acacia koaia

22. Human Biology

23. Human Biology
Autopsy
An autopsy, also known as a post-mortem examination, necropsy, or obduction, is a medical procedure that consists of a thorough examination of a corpse to determine the cause and manner of death and to evaluate any disease or injury that may be present. It is usually performed by a specialized medical doctor called a pathologist.
Autopsies are either performed for legal or medical purposes. A forensic autopsy is carried out when the cause of death may be a criminal matter, while a clinical or academic autopsy is performed to find the medical cause of death and is used in cases of unknown or uncertain death, or for research purposes. Autopsies can be further classified into cases where external examination suffices, and those where the body is dissected and an internal examination is conducted. Permission from next of kin may be required for internal autopsy in some cases. Once an internal autopsy is complete the body is reconstituted by sewing it back together.
The prefix 'auto-' means 'self', and so autopsy means 'to see for oneself'; it is used more broadly of personal examination of an object, as well as its specific usage for the post-mortem examination of a human corpse.

24. Elephantiasis
Elephantiasis, or Lymphatic Filariasis, is a rare disorder of the lymphatic system caused by parasitic worms such as Wuchereria bancrofti, Brugia malayi, and B. timori, all of which are transmitted by mosquitos. Inflammation of the lymphatic vessels causes extreme enlargement of the affected area, most commonly a limb or parts of the head and torso. It occurs most commonly in tropical regions and particularly in parts of Africa.
Elephantiasis is characterized by the gross enlargement of a limb or areas of the trunk or head. There is an abnormal accumulation of watery fluid in the tissues (edema) causing severe swelling. The skin usually develops a thickened, pebbly appearance and may become ulcerated and darkened. Fever, chills and a general feeling of ill health (malaise) may be present.
Elephantiasis may also affect the male and female genital organs. In a male, there may be enlargement of the scrotum, and the penis may be retracted under skin which has become thickened, nonelastic, hot and painful. The spermatic cords may become thickened.
The external parts of the female genital organs (vulva) may also be affected by elephantiasis. A long, tumorous mass covered by thickened and ulcerated skin may develop between the thighs. There may also be an enlargement of the lymph nodes of the legs.
The extreme enlargement of the limbs and other areas of the body characterized by elephantiasis, is the result of obstruction of the lymph flow and possibly of blood circulation. The lymphatic blockage can be due to recurrent attacks of a bacterial infection which causes inflammation of the lymphatic vessels (streptococcal lymphangitis). When the lymphatic obstruction is large enough, back pressure in the lymphatic channels produces dilation of the superficial vessels, resulting in extreme swelling. Without medical intervention, the cycle continues until the affected area is grotesquely enlarged. Death of surrounding tissues may also occur from an obstructed blood supply (gangrene).
Recent studies have shown that a possible cause of elephantiasis in Africa may be related to the red soil on which certain barefooted populations live. It is believed that small chemical particles found in the soil may enter the skin through the bare feet. These particles then lodge in the lymphatic tissues and produce irritating effects. The traumatized tissue is then vulnerable to streptococcal infection.

25. Venus Fly Trap Only carniforous plant. Here it is eating a mealworm
Like other plants, Venus' Flytraps gather nutrients from gases in the air and nutrients in the soil. However, they live in poor soil and are healthier if they get nutrients from insects. Carnivorous plants live all over the world but Venus' Flytraps live only in select boggy areas in North and South Carolina. Because of people's fascination with these plants, they collected many of them and they became endangered. Venus' Flytraps today are grown in greenhouses.
The leaves of Venus' Flytrap open wide and on them are short, stiff hairs called trigger or sensitive hairs. When anything touches these hairs enough to bend them, the two lobes of the leaves snap shut trapping whatever is inside. The trap will shut in less than a second. The trap doesn't close all of the way at first. It is thought that it stays open for a few seconds in order to allow very small insects to escape because they wouldn't provide enough food. If the object isn't food, e.g., a stone, or a nut, the trap will reopen in about twelve hours and 'spit' it out.
When the trap closes over food, the cilia. finger-like projections, keep larger insects inside. Fold your hands together lacing your fingers to see what the trap looks like. In a few minutes the trap will shut tightly and form an air-tight seal in order to keep the digestive fluids inside and bacteria out.
If an insect is too large it will stick out of the trap. This allows bacteria and molds on the insect to thrive. Eventually the trap turns black, rots and falls off.
The trap constricts tightly around the insect and secretes digestive juices, much like those in your stomach. It dissolves the soft, inner parts of the insect, but not the tough, outer part called the exoskeleton. At the end of the digestive process, which takes from five to twelve days, the trap reabsorbs the digestive fluid and then reopens. The leftover parts of the insect, the exoskeleton, blow away in the wind or are washed away by rain. The time it takes for the trap to reopen depends on the size of the insect, temperature, the age of the trap, and the number of times it has gone through this process.

26. Listeria
Listeria monocytogenes is a bacterium commonly found in soil, stream water, sewage, plants, and food.[1] Each bacterium is Gram-positive and rod-shaped. Listeria are known to be the bacteria responsible for listeriosis, a rare but lethal food-borne infection that has a devastating case fatality rate of 25%[2] (Salmonella, in comparison, has a less than 1% mortality rate[3]). They are incredibly hardy and able to grow in temperatures ranging from 4°C (39°F), the temperature of a refrigerator, to 37°C (99°F), the body's internal temperature[1]. Furthermore, listerosis's deadliness can be partially attributed to the infection's ability to spread to the nervous system and cause meningitis.[1] Finally, Listeria has a particularly high occurrence rate in newborns because of its ability to infect the fetus by penetrating the endothelial layer of the placenta.[2]
Listeria uses the cellular machinery to move around inside the host cell: it induces directed polymerization of actin by the ActA transmembrane protein, thus pushing the bacterial cell around.
Listeria monocytogenes, for example, encodes virulence genes which are thermoregulated. The expression of virulence factor is optimal at 37 degrees Celsius and is controlled by a transcriptional activator, PrfA, whose expression is thermoregulated by the PrfA thermoregulator UTR element. At low temperatures, the PrfA transcript is not translated due to structural elements near the ribosome binding site. As the bacteria infects the host, the temperature of the host melts the structure and allows translation initiation for the virulent genes.
[edit] Mechanism of infection
The majority of Listeria bacteria are targeted by the immune system before they are able to cause infection. Those that escape the immune system's initial response, however, spread though intracellular mechanisms and are therefore guarded against circulating immune factors (AMI).[2]
To invade, Listeria induces macrophage phagocytic uptake by displaying D-galactose receptors that are then bound by the macrophage's polysaccharide receptors (Notably, in most bacterial infections it is the host cell, not the bacteria, that displays the polysaccharide). [3] Once phagocytosed, the bacteria is encapsulated by the host cell's acidic phagolysosome organelle. [1] Listeria, however, escapes the phagolysosome by lysing the vacuole's entire membrane with secreted hemolysin, [4] now characterized as the exotoxin listeriolysin O.[1] The bacteria then replicate inside the host cell's cytoplasm. [2]
Listeria must then navigate to the cell's periphery to spread the infection to other cells. Outside of the body, Listeria has flagellar-driven motility, sometimes described as a "tumbling motility." However, at 37°C, flagella cease to develop and the bacteria instead usurps the host cell's cytoskeleton to move. [2] Listeria, inventively, polymerizes an actin tail or "comet" [4], using host-produced actin filaments [5] with the promotion of virulence factor ActA[2]. The comet forms in a polar manner [6] and aids the bacteria's migration to the host cell's outer membrane. Gelsolin, an actin filament severing protein, localizes at the tail of Listeria and accelerates the bacterium's motility.[6] Once at the cell surface, the actin-propelled Listeria pushes against the cell's membrane to form protrusions called filopods[1] or "rockets". The protrusions are guided by the cell's leading edge [7]to contact adjacent cells which subsequently engulf the Listeria rocket and the process is repeated, perpetuating the infection.[2] Once phagocytosed, the Listeria is never again extracellular: it is an intracytoplasmic parasite [4] like Shigella flexneri and Rickettsia.[2]
[edit] Epidemiology
The Center for Science in the Public Interest has published a list of foods that have sometimes caused outbreaks of Listeria: hot dogs, deli meats, raw milk, cheeses (particularly soft-ripened cheeses like feta, Brie, Camembert, blue-veined, or Mexican-style “queso blanco”), raw and cooked poultry, raw meats, ice cream, raw vegetables, raw and smoked fish and the green lip mussel.[8]
[edit] Prevention
The prevention of Listeria as a food illness involves effective sanitation of food contact surfaces. Alcohol has proven to be an effective topical sanitizer against Listeria. Quaternary ammonium can be used in conjunction with alcohol as a food contact safe sanitizer with increased duration of the sanitizing action. Nonflammable Alcohol Vapour in carbon dioxide NAV-CO2 systems or sodium hypochlorite are frequently used to sanitize surfaces to prevent Listeria.
[edit] Modern relevance/future research
Listeria is an opportunistic pathogen: it is most prevalent in the elderly, pregnant mothers, and AIDS patients. With improved healthcare leading to a growing elderly population and extended life expectancies for AIDS patients, physicians are more likely to encounter this otherwise rare infection (only 0.7 per 100,000 healthy people are infected with virulent Listeria each year).[1] Better understanding the cell biology of Listeria infections, including relevant virulence factors, may help us better treat Listeriosis and other intracytoplasmic parasites. Researchers are now investigating the use of Listeria as a cancer vaccine, taking advantage of its "ability induce potent innate and adaptive immunity."[5][9]
[edit] Treatment
Antibiotics effective against Listeria species include ampicillin, vancomycin, ciprofloxacin, linezolid, azithromycin, and cotrimoxazole.
[edit] Future treatment options
Intralytix has created a virus spray with bacteriophages to be applied to food for the prevention of Listeriosis by killing six strains of L. monocytogenes bacterium.[10] EBI Food Safety has created and put a similar product on the market, LISTEX P100. LISTEX P100 prevents Listerios in food by using bacteriophages for killing Listeria. [11]
Listeriosis or "circling disease" is a bacterial disease that is common in ruminants and may also affect pigs, dogs, cats, some wild animals, and humans. Encephalitis is the most common form of the disease in ruminant animals. In young animals, visceral or septicemic infections may occur. Intra-uterine infection of the fetus via the placenta frequently results in abortion in sheep, goats, and cattle. Listeria moncytogenes is the bacteria that causes listeriosis. The bacteria can live almost anywhere – soil, manure piles, grass, and the digestive tract of animals. Grazing animals may ingest the bacteria and further contaminate the vegetation and soil. Animal-to-animal transmission occurs via the fecal-oral route. Listeria thrive in aerobic conditions where the pH is 5.4 or higher and don't do well in acidic conditions. As a result, the top layers of silage or improperly preserved silage harbor large numbers of the bacteria, and disease is often associated with the feeding of silage. The incubation period is 10 to 18 days after the bacteria is ingested.

27. Why are Flamingos Pink?
Flamingos filter-feed on brine shrimp. Their oddly-shaped beaks are specially adapted to separate mud and silt from the food they eat, and are uniquely used upside-down. The filtering of food items is assisted by hairy structures called lamellae which line the mandibles, and the large rough-surfaced tongue. The flamingo's characteristic pink colouring is caused by the Beta carotene in their diet. The source of this varies by species, but shrimp and blue-green algae are common sources; zoo-fed flamingos may be given food with the additive canthaxanthin, which is often also given to farmed salmon. Flamingos produce a "milk" like pigeon milk due to the action of a hormone called prolactin (see Columbidae). It contains more fat and less protein than the latter does, and it is produced in glands lining the whole of the upper digestive tract, not just the crop. Both parents nurse their chick, and young flamingos feed on this milk, which also contains red and white blood cells, for about two months until their bills are developed enough to filter feed.[4]
Flamingos frequently stand on one leg. The reason for this behavior is not fully known. One common theory is that tucking one leg beneath the body may conserve body heat,[5] but this has not been proven. It is often suggested that this is done in part to keep the legs from getting wet, in addition to conserving energy. As well as standing in the water, flamingos may stamp their webbed feet in the mud to stir up food from the bottom.
Young flamingos hatch with grey plumage, but adults range from light pink to bright red due to aqueous bacteria and beta carotene obtained from their food supply. A well-fed, healthy flamingo is more vibrantly coloured and thus a more desirable mate. A white or pale flamingo, however, is usually unhealthy or malnourished. Captive flamingos are a notable exception; many turn a pale pink as they are not fed carotene at levels comparable to the wild. This is changing as more zoos begin to add prawns and other supplements to the diets of their flamingos.