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The image I’ve chosen depicts two different kinds of speciation. On the left, the original population is physically divided in a process called allopatric speciation. Over time, the physical barrier forces a genetic separation, resulting in a new species. Since the two species are now in differing environments, they will thrive under different conditions. On the right, sympatric evolution is displayed. The species of fish is not physically separated however, the species does become reproductively isolated. Some fish may adapt to deeper pressures, a colder environment, or a preference in diet. Both forms of evolution result in a new species.

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The fungus I have chosen Hydnellum peckii, also known as the bleeding tooth fungus or Devil’s Tooth. As an adolescent, the mushroom is covered in soft, velvety hairs. The feature that gives the Devil’s Tooth its signature nickname is the red sap that oozes from its pores caused by the surrounding soil becoming saturated, resulting in osmosis and a buildup of pressure that eventually bursts out of the organism. In addition, the mushroom has small tooth-like protrusions under the cap where the spores are produced. The mature fungus has a much less exciting appearance, losing the velvety hairs and bright red sap. The mushroom’s root system, or mycelia, lay just below the surface and can extend up to 11 feet away. It exists in a symbiotic relationship with the coniferous trees in mountainous areas of North America, Europe, Iran, and South Korea. While the Devil’s Tooth is non-toxic, the bitter taste renders it basically inedible but it is not completely useless; researchers have found a presence of thelephoric acid which could someday aid in the developing a cure for Alzheimer’s disease.

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American Association for the Advancement of Science

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Hydnellum peckii. Photo Credit: Bernypisa [CC BY-SA 3.0], via Wikimedia Commons.

In the same way that you may have to be convinced that a raisin really used to be a grape before it aged and dried out, you also might be surprised to learn about the difference between a young Bleeding Tooth Fungus ( Hydnellum peckii) and its adult counterpart. The adult mushroom is beige and rather dull in appearance. When young and actively growing, however, this whitish mushroom appears to bleed from its pores, inspiring some of its colorful names (it's also known as Devil's Tooth).

This gooey red liquid is actually a sap of sorts caused by a process called guttation. When the soil surrounding the fungus' root system becomes very wet, it may force water into the roots through the process of osmosis. This creates pressure throughout the organism, which eventually builds up enough to force liquid to the surface of the fungus. Although scientists have not yet decided what this liquid is exactly, they know it appears red thanks to a pigment found within the fungus.

In addition to its most graphic feature, the Bleeding Tooth Fungus has small toothlike projections underneath the mushroom cap, where its spores are produced. When young, the mushroom's surface is covered in soft "hairs" that can give it a velvety texture, but these fall off as the mushroom matures. As with similar fungi, beneath each mushroom lies an interconnected mass of mycelia, its root system. The mycelia can spread widely just beneath the surface of the forest floor-up to 11 feet away from where the mushroom appears.

Located in forested, often mountainous, areas in North America, Europe, Iran, and South Korea, the Bleeding Tooth Fungus has a symbiotic relationship with the coniferous trees amongst whose roots it is located. The trees provide the fungus with access to a fixed source of carbon dioxide, while the fungus produces enzymes that convert amino acids and minerals found in the soil into forms that the host trees can better use. The fungi's presence is indicative of an old, species-rich forest, and scientists express concern when it disappears from an area, as seems to be happening in areas of Europe, where nitrogen deposits caused by pollution may be a problem.

The Bleeding Tooth Fungus is not toxic, but tastes so bitter as to be inedible, despite one of its other names (Strawberries and Cream, because of its resemblance to a fruit danish). However, the mushroom is valued by natural dyers, who dry it and use it alone to create a beige dye or combine it with mordants (substances, such as allum or iron, that cause a dye to set into fabric and other surfaces) to create blue-green hues. Scientists have found that extracts from the Bleeding Tooth Fungus contain the chemical compound atromentin, which like heparin, can be used as an anti-coagulant to keep blood clots from forming and which also has anti-bacterial properties and may be an option for treating the most common strain of bacterial pneumonia. Researchers are also looking at another chemical found in the Bleeding Tooth Fungus, thelephoric acid, which may someday be used to treat Alzheimer's disease.

Learn more about other types of fungi in these Science NetLinks resources: Mycologist Debbie Viess leads an inventory of the mushrooms in Muir Woods as part of BioBlitz 2014 in Golden Gate National Parks. In this video, AAAS's Bob Hirshon talks with a team from the University of Arizona who are hunting for fungi that spend their entire lives inside plants. Listen to this Science Update to hear about a fungus attack in Italy that dates back to World War II. And in The Case of the Vanishing Golden Frogs lesson, find out what might be causing these amphibians to die off.

Are you interested in finding out more about symbiotic relationships? Listen to this Science Update on Three-Way Symbiosis. The Ecology of Your Skin lesson series deals with bacteria and microbes that live on our skin.

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Weird & Wonderful Creatures: Bleeding Tooth Fungus

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Hydnellum peckii. Photo Credit: Bernypisa [CC BY-SA 3.0], via Wikimedia Commons. In the same way that you may have to be convinced that a raisin really used to be a grape before it aged and dried out, you also might be surprised to learn about the difference between a young Bleeding Tooth Fungus ( Hydnellum peckii) and its adult counterpart.

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Flowering plants have been historically classified into two types. The classification came from John Ray in 1682 and later a botanist by the name of Antoine Laurent in 1789. Monocots are angiosperms that form one narrow structure during germination. Their petals are formed in groups of three. Their leaves have narrow, parallel veins while the Dicots leaves have oval, net-like veins. The Dicots have two cotyledons and have four or five petals. They are the largest group of angiosperms with around 200,000 species. Dicots are paraphyletic, having not evolved from a single lineage, while the Monocots are monophyletic.

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Monocot vs. Dicot: Differences and Examples

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Learn the differences and similarities between monocot and dicot regarding root, seed, stem, leaf, and flower, along with a few examples.

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Cnidaria is a phylum containing around eleven species that are more complex than sponges, but less than sea stars. Members of this species are radially symmetrical, meaning that the body parts emerge outward from the center. Hydroids, jellyfish, anemones, and coral are all Cnidarians. All of them contain tentacles with stinging cells called cnidocytes and a coiled, thread-like stinger called a nematocyst. Most also contain a toxin in the stinger. Most are not harmful to humans but certain jellyfish can deliver a highly painful, and sometimes fatal, sting to humans. They can either come in a polyploid or medusoid body type. The polyploid generally has an upward facing mouth while the medusoid generally has a downward facing mouth. All cnidarians have a blind gut, food goes in the mouth and once digested gets spit out the same mouth.

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Cnidarians: Squishy Stingy animals! | JONATHAN BIRD'S BLUE WORLD

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The body’s functions operate in order to stay in equilibrium no matter the external environmental factors. Homeostasis is seen in the regulation of temperature, pH, oxygen levels, blood glucose concentration, and others. Cells make up tissues, which make up organs, which make up organ systems that all work together to maintain homeostasis. Change is detected by disruptors that send out effectors to regulate the change back to the set point. The five parts of the reflex loop are the sensor, set point, error detector, controller, and effector. Sensors measure a change in values from the set point. The controller interprets the signals and decides the appropriate effectors to send in response. Receptors monitor the change to generate a response to the effector organ. All of these components come together to form a negative feedback loop, a positive feedback loop reinforces stimulus to continue.

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Homeostasis is a term that was first coined by physiologist Walter Cannon in 1926, clarifying the ‘milieu intérieur’ that fellow physiologist Claude Bernard had spoken of ­­in 1865.[1] ‘Homeo,’ Latinized from the Greek word ‘homio,’ means ‘similar to,’ and when combined with the Greek word ‘stasis,’ meaning ‘standing still’ gives us the term that is a cornerstone of physiology. Carl Richter proposed that behavioral responses were also responsible for maintaining homeostasis in addition to the previously proposed internal control system, while James Hardy gave us the concept of a setpoint or desired physiological range of values that homeostasis accomplishes.[2]

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Endogenous Cushing syndrome is caused by chronic exposure to excess glucocorticoids. An excess secretion of adrenocorticotropic hormone (ACTH) from the pituitary gland causes a production of cortisol by the adrenal glands. Symptoms vary greatly because excess cortisol affects multiple of the body’s systems. Symptoms may include diabetes, glucose intolerance, and osteoporosis, along with others. Neuropsychiatric symptoms may also arise, although the role they play is not fully understood. Theories suggest it may be a decreased brain volume in the hippocampus caused by prolonged cortisol exposure. Patients have seen psychiatric and neurocognitive improvements after their hormone level has been normalized. An early diagnosis and treatment of hypercortisolism may help alleviate psychiatric symptoms.

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The desert biome covers around 20% of the Earth’s surface. The top soil layer can be rocky, sandy, or gravely. Deserts usually get around 20” of rain per year. Flora and fauna of this biome are adapted to conserve water. The Organ Pipe Cactus pictured has an enlarged stem to store water as well as spines to deter thirsty animals. Hot, dry deserts are known as arid deserts and they have little rainfall throughout the year. Semi-arid deserts have hot, dry Summers with more rainfall in the Winter. Cold deserts such as the Antarctic also have little rainfall but they have much lower temperatures in comparison.

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Image

Walter Meayers Edwards

The desert biome covers about one-fifth of Earth's surface. This biome has a layer of soil that can either be sandy, gravelly, or stony, depending on the type of desert. Deserts usually get at most 50 centimeters (20 inches) of rainfall a year, and the organisms that live in deserts are adapted to this extremely dry climate.

Plants in deserts have adaptations to conserve water. For example, cacti have enlarged stems to store water, as well as spines to protect these water reserves from thirsty animals. Animals such as the black-tailed jackrabbit ( Lepus californicus) are also adapted to life in the desert: Their extra-long ears help to transfer out excess heat from their body into the air.

The four main types of desert include hot and dry deserts, semi-arid deserts, coastal deserts, and cold deserts. In hot and dry deserts, also known as arid deserts, the temperatures are warm and dry year-round. Some famous arid deserts include the Sahara Desert that covers much of the African continent and the Mojave Desert located in the southwest of the United States. Semi-arid deserts are a bit cooler than hot and dry deserts. The long, dry summers in semi-arid deserts are followed by winters with some rain. Semi-arid deserts are found in North America, Greenland, Europe, and Asia. Coastal deserts are a bit more humid than other types of deserts. Although heavy fogs blow in from the coast, rainfall is still rare. The Atacama Desert of Chile in South America is an example of a coastal desert. Cold deserts are still dry but have extremely low temperatures in comparison to the other types of deserts. The Antarctic is an example of a cold desert.

Director

Tyson Brown, National Geographic Society

Author

National Geographic Society

Production Managers

Gina Borgia, National Geographic Society

Jeanna Sullivan, National Geographic Society

Program Specialists

Sarah Appleton, National Geographic Society, National Geographic Society

Margot Willis, National Geographic Society

Last Updated

October 19, 2023

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Deserts are extremely dry environments that are home to well-adapted plants and animals. The main types of deserts include hot and dry deserts, semi-arid deserts, coastal deserts, and cold deserts.

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Evolutionary relationships can be represented by a tree of life. Each species is represented by a branch that flows back to a common ancestor between the two species. If you keep following the tree back to the root, you will come to a common ancestor between all species. The tree only represents the species that we have recorded, there very well may be deep sea species yet to be discovered. The tree of life also excludes species that are extinct. As recently as 2022, a branch was added to represent close to 600 species of fungi. Closest to the trees roots are the prokaryotes, followed by the eukaryotes such as plants, animals, fungi, and protists. Protists have more biodiversity than any other eukaryote; if you balled up all of them on Earth they would weigh roughly twice the amount of all of the animals.

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Biological Diversity, Butts, and the Tree of Life: Crash Course Biology #18