A catkin or ament is a slim, cylindrical flower cluster, with inconspicuous or no petals wind-pollinated but sometimes insect-pollinated. They contain many unisexual flowers, arranged along a central stem, drooping, they are found in many plant families, including Betulaceae, Fagaceae and Salicaceae. For some time, they were believed to be a key synapomorphy among the proposed Hamamelididae known as Amentiferae. Based on molecular phylogeny work, it is now believed; this suggests that the catkin flower arrangement has arisen at least twice independently by convergent evolution, in Fagales and in Salicaceae. Such a convergent evolution raises questions about what the ancestral inflorescence characters might be and how catkins did evolve in these two lineages. In many of these plants, only the male flowers form catkins, the female flowers are single, a cone or other types. In other plants both male and female flowers are borne in catkins. Catkin-bearing plants include many other trees or shrubs such as birch, hickory, sweet chestnut and sweetfern.
The word catkin is a loanword from the old Dutch katteken, meaning "kitten", on account of the resemblance to a kitten's tail. Ament is from the Latin amentum, meaning "thong" or "strap". In Britain, they can be seen in February, when many trees are bare for winter, they can occur in December. Catkins in Fagales Catkins in Salicaceae
Ungulates are any members of a diverse group of large mammals that includes odd-toed ungulates such as horses and rhinoceroses, even-toed ungulates such as cattle, giraffes, camels and hippopotamuses. Most terrestrial ungulates use the tips of their toes hoofed, to sustain their whole body weight while moving; the term means "being hoofed" or "hoofed animal". As a descriptive term, "ungulate" excludes cetaceans, as they do not possess most of the typical morphological characteristics of ungulates, but recent discoveries indicate that they are descended from early artiodactyls. Ungulates are herbivorous, many employ specialized gut bacteria to allow them to digest cellulose, as in the case of ruminants, they inhabit a wide range of habitats, including jungles and rivers. Ungulata, which used to be considered an order, has been split into the following: Perissodactyla, Tubulidentata, Sirenia and Cetacea. However, in 2009 morphological and molecular work has found that aardvarks, sea cows, elephants are more related to sengis and golden moles than to the perissodactyls and artiodactyls, form Afrotheria.
Elephants, sea cows, hyraxes are grouped together in the clade Paenungulata, while the aardvark has been considered as either a close relative to them or a close relative to sengis in the clade Afroinsectiphilia. This is a striking example of convergent evolution. There is now some dispute as to whether this smaller Ungulata is a cladistic group, or a phenetic group or folk taxon; some studies have indeed found the mesaxonian ungulates and paraxonian ungulates to form a monophyletic lineage related to either the Ferae in the clade Fereuungulata or to the bats. Other studies found the two orders not that related, as some place the perissodactyls as close relatives to bats and Ferae in Pegasoferae and others place the artiodactyls as close relatives to bats. Below is a simplified taxonomy with the extant families, in order of the relationships. Keep in mind that there are still some grey areas of conflict, such as the case with relationship of the pecoran families and the baleen whale families.
See each family for the relationships of the species as well as the controversies in their respective article. Ungulata Perissodactyla Hippomorpha Equidae: Horses and zebras Ceratomorpha Tapiridae: Tapirs Rhinocerotidae: Rhinoceroses Artiodactyla Tylopoda Camelidae: Camels and Llamas Artiofabula Suina Tayassuidae: Peccaries Suidae: Pigs Cetruminantia Ruminantia Tragulidae: Chevrotains Cervoidea Antilocapridae: Pronghorn Giraffidae: Giraffes and okapi Cervidae: Deer Moschidae: Musk deer Bovidae: Oxen and antelopes Whippomorpha Hippopotamidae: Hippopotamuses Cetacea Mysticeti Balaenidae: Bowhead and right whales Cetotheriidae: Pygmy right whale Eschrichtiidae: Gray Whale Balaenopteridae: Rorquals Odontoceti Physeteroidea Physeteridae: Sperm whale Kogiidae: Lesser sperm whales Platanistoidea Platanistidae: Indian river dolphins Ziphioidea Ziphiidae: Beaked whales Lipotoidea Lipotidae: Baiji Inioidea Iniidae: Amazonian river dolphins Pontoporiidae: La Plata dolphin Delphinoidea Monodontidae: Beluga and narwhal Phocoenidae: Porpoises Delphinidae: Oceanic dolphins Below is the general consensus of the phylogeny of the ungulate families.
Perissodactyla and Artiodactyla include the majority of large land mammals. These two groups first appeared during the late Paleocene spreading to a wide variety of species on numerous continents, have developed in parallel since that time; some scientists believed that modern ungulates are descended from an evolutionary grade of mammals known as the condylarths. The enigmatic dinoceratans were among the first large herbivorous mammals, although their exact relationship with other mammals is still debated with one of the theories being that they might just be distant relatives to living ungulates. In Australia, the marsupial Chaeropus developed hooves, convergent those of artiodactyls. Perissodactyls are said to have evolved from the Phenacodontidae, sheep-sized animals that were showing signs of anatomical features that their descendants would inherit. By the start of the Eocene, 55 million years ago, they had diversified and spread out to occupy several continents. Horses and tapirs both evolved in North America.
Of the 15 families, only three survive. These families were diverse in form and size; the largest perissodactyl, an Asian rhinoceros called Paraceratherium, reached 15 tonnes, more than twice the weight of an elephant. It has been found
Pando known as the trembling giant, is a clonal colony of an individual male quaking aspen determined to be a single living organism by identical genetic markers and assumed to have one massive underground root system. The plant is located in the Fremont River Ranger District of the Fishlake National Forest at the western edge of the Colorado Plateau in south-central Utah, United States, around 1 mile southwest of Fish Lake. Pando occupies 43 hectares and is estimated to weigh collectively 6,000,000 kilograms, making it the heaviest known organism; the root system of Pando, at an estimated 80,000 years old, is among the oldest known living organisms. Pando is thought to be dying. Though the exact reasons are not known, it is thought to be a combination of factors including drought and fire suppression; the Western Aspen Alliance, a research group at Utah State University’s "S. J. & Jessie E. Quinney College of Natural Resources", has been studying the tree in an effort to save it, the United States Forest Service is experimenting with several 5-acre sections of it in an effort to find a means to save it.
A study published in October 2018 concludes that Pando has not been growing for the past 30–40 years. Human interference was named as the primary cause, with the study citing people allowing cattle and deer populations to thrive, their grazing resulting in fewer saplings and dying trees. Pando is thought to have grown for much of its lifetime under ideal circumstances: frequent forest fires have prevented its main competitor, from colonizing the area, a climate shift from wet and humid to semi-arid has obstructed seedling establishment and the accompanying rivalry from younger aspens. During intense fires, the organism survived underground, with its root system sending up new stems in the aftermath of each wildfire. If its postulated age is correct, the climate into which Pando was born was markedly different from that of today, it may have been as many as 10,000 years since Pando's last successful flowering. Additionally, the post glacial climatic conditions have made it problematic for new seeds to sprout.
According to an Organisation for Economic Co-operation and Development report: Clonal groups of P. tremuloides in eastern North America are common, but less than 0.1 ha in size, while in areas of Utah, groups as large as 80 ha have been observed. In the semi-arid western United States, some argue that widespread seedling establishment has not occurred since the last glaciation, some 10,000 years ago. Indeed, some biologists feel; the clone now known as Pando was discovered in 1968 by researcher Burton V. Barnes, who continued to study it through the 1970s. Barnes had described Pando as a single organism based on its morphological characteristics alone. Building on Barnes's earlier work, Michael Grant of the University of Colorado at Boulder re-examined the clone, named it "Pando", claimed it to be the world's most massive organism in 1992. In 2006 the United States Postal Service published a stamp in commemoration of the aspen, calling it one of the forty "Wonders of America." The clonal colony encompasses 43 hectares, weighs nearly 6,000 metric tons, has over 40,000 stems, which die individually and are replaced by new stems growing from its roots.
The average age of Pando's stems is 130 years. The roots are 80,000 years old. Michael Grant in BioScience said:...quaking aspen reproduces via a process called suckering. An individual stem can send out lateral roots that, under the right conditions, send up other erect stems; the process is repeated. This collection of multiple stems, called ramets, all form one, genetic individual termed a clone. Tree experts note that the organism's age cannot be determined with the level of precision found in tree rings, its current 80,000-year designation is based on a complex set of factors, including the history of its local environment, the evidence indicating that there are few if any occurring new aspens in most of the western United States since a climate shift took place 10,000 years ago which eliminated favorable soil conditions for seedlings, the rate of growth, its size, its genome in comparison to the mutations found among aspens born in the modern era. Michael Grant summed it thus: Despite enormous crops of viable seeds, successful seedling establishment appears to be a rare event in the semi-arid West, but the establishment of new trees from seeds appears to be common in the moist, humid forests of New England... aspen establishment from seeds has not occurred in the western United States since the last glaciation, some 10,000 years ago...
Part of the rationale behind current age estimates for aspen clones is that sexual reproduction is frustrated by the rarity of a favorable suite of conditions in semi-arid environments... High levels of genetic variation and excesses of heterozygotes are found in semi-a
The flowering plants known as angiosperms, Angiospermae or Magnoliophyta, are the most diverse group of land plants, with 64 orders, 416 families 13,164 known genera and c. 369,000 known species. Like gymnosperms, angiosperms are seed-producing plants. However, they are distinguished from gymnosperms by characteristics including flowers, endosperm within the seeds, the production of fruits that contain the seeds. Etymologically, angiosperm means a plant; the term comes from the Greek words sperma. The ancestors of flowering plants diverged from gymnosperms in the Triassic Period, 245 to 202 million years ago, the first flowering plants are known from 160 mya, they diversified extensively during the Early Cretaceous, became widespread by 120 mya, replaced conifers as the dominant trees from 100 to 60 mya. Angiosperms differ from other seed plants in several ways, described in the table below; these distinguishing characteristics taken together have made the angiosperms the most diverse and numerous land plants and the most commercially important group to humans.
Angiosperm stems are made up of seven layers. The amount and complexity of tissue-formation in flowering plants exceeds that of gymnosperms; the vascular bundles of the stem are arranged such that the phloem form concentric rings. In the dicotyledons, the bundles in the young stem are arranged in an open ring, separating a central pith from an outer cortex. In each bundle, separating the xylem and phloem, is a layer of meristem or active formative tissue known as cambium. By the formation of a layer of cambium between the bundles, a complete ring is formed, a regular periodical increase in thickness results from the development of xylem on the inside and phloem on the outside; the soft phloem becomes crushed, but the hard wood persists and forms the bulk of the stem and branches of the woody perennial. Owing to differences in the character of the elements produced at the beginning and end of the season, the wood is marked out in transverse section into concentric rings, one for each season of growth, called annual rings.
Among the monocotyledons, the bundles are more numerous in the young stem and are scattered through the ground tissue. They once formed the stem increases in diameter only in exceptional cases; the characteristic feature of angiosperms is the flower. Flowers show remarkable variation in form and elaboration, provide the most trustworthy external characteristics for establishing relationships among angiosperm species; the function of the flower is to ensure fertilization of the ovule and development of fruit containing seeds. The floral apparatus may arise terminally from the axil of a leaf; as in violets, a flower arises singly in the axil of an ordinary foliage-leaf. More the flower-bearing portion of the plant is distinguished from the foliage-bearing or vegetative portion, forms a more or less elaborate branch-system called an inflorescence. There are two kinds of reproductive cells produced by flowers. Microspores, which will divide to become pollen grains, are the "male" cells and are borne in the stamens.
The "female" cells called megaspores, which will divide to become the egg cell, are contained in the ovule and enclosed in the carpel. The flower may consist only of these parts, as in willow, where each flower comprises only a few stamens or two carpels. Other structures are present and serve to protect the sporophylls and to form an envelope attractive to pollinators; the individual members of these surrounding structures are known as petals. The outer series is green and leaf-like, functions to protect the rest of the flower the bud; the inner series is, in general, white or brightly colored, is more delicate in structure. It functions to attract bird pollinators. Attraction is effected by color and nectar, which may be secreted in some part of the flower; the characteristics that attract pollinators account for the popularity of flowers and flowering plants among humans. While the majority of flowers are perfect or hermaphrodite, flowering plants have developed numerous morphological and physiological mechanisms to reduce or prevent self-fertilization.
Heteromorphic flowers have short carpels and long stamens, or vice versa, so animal pollinators cannot transfer pollen to the pistil. Homomorphic flowers may employ a biochemical mechanism called self-incompatibility to discriminate between self and non-self pollen grains. In other species, the male and female parts are morphologically separated, developing on different flowers; the botanical term "Angiosperm", from the Ancient Greek αγγείον, angeíon and σπέρμα, was coined in the form Angiospermae by Paul Hermann in 1690, as the name of one of his primary divisions of the plant kingdom. This included flowering plants possessing seeds enclosed in capsules, distinguished from his Gymnospermae, or flowering plants with achenial or schizo-carpic fruits, the whole fruit or each of its pieces being here regarded as a seed and naked; the term and its antonym were maintained by Carl Linnaeus with the same sense, but with restricted application, in the names of the orders of his class Didynamia. Its use with any
North America is a continent within the Northern Hemisphere and all within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the west and south by the Pacific Ocean, to the southeast by South America and the Caribbean Sea. North America covers an area of about 24,709,000 square kilometers, about 16.5% of the earth's land area and about 4.8% of its total surface. North America is the third largest continent by area, following Asia and Africa, the fourth by population after Asia and Europe. In 2013, its population was estimated at nearly 579 million people in 23 independent states, or about 7.5% of the world's population, if nearby islands are included. North America was reached by its first human populations during the last glacial period, via crossing the Bering land bridge 40,000 to 17,000 years ago; the so-called Paleo-Indian period is taken to have lasted until about 10,000 years ago. The Classic stage spans the 6th to 13th centuries.
The Pre-Columbian era ended in 1492, the transatlantic migrations—the arrival of European settlers during the Age of Discovery and the Early Modern period. Present-day cultural and ethnic patterns reflect interactions between European colonists, indigenous peoples, African slaves and their descendants. Owing to the European colonization of the Americas, most North Americans speak English, Spanish or French, their culture reflects Western traditions; the Americas are accepted as having been named after the Italian explorer Amerigo Vespucci by the German cartographers Martin Waldseemüller and Matthias Ringmann. Vespucci, who explored South America between 1497 and 1502, was the first European to suggest that the Americas were not the East Indies, but a different landmass unknown by Europeans. In 1507, Waldseemüller produced a world map, in which he placed the word "America" on the continent of South America, in the middle of what is today Brazil, he explained the rationale for the name in the accompanying book Cosmographiae Introductio:... ab Americo inventore... quasi Americi terram sive Americam.
For Waldseemüller, no one should object to the naming of the land after its discoverer. He used the Latinized version of Vespucci's name, but in its feminine form "America", following the examples of "Europa", "Asia" and "Africa". Other mapmakers extended the name America to the northern continent, In 1538, Gerard Mercator used America on his map of the world for all the Western Hemisphere; some argue that because the convention is to use the surname for naming discoveries, the derivation from "Amerigo Vespucci" could be put in question. In 1874, Thomas Belt proposed a derivation from the Amerrique mountains of Central America. Marcou corresponded with Augustus Le Plongeon, who wrote: "The name AMERICA or AMERRIQUE in the Mayan language means, a country of perpetually strong wind, or the Land of the Wind, and... the can mean... a spirit that breathes, life itself." The United Nations formally recognizes "North America" as comprising three areas: Northern America, Central America, The Caribbean.
This has been formally defined by the UN Statistics Division. The term North America maintains various definitions in accordance with context. In Canadian English, North America refers to the land mass as a whole consisting of Mexico, the United States, Canada, although it is ambiguous which other countries are included, is defined by context. In the United States of America, usage of the term may refer only to Canada and the US, sometimes includes Greenland and Mexico, as well as offshore islands. In France, Portugal, Romania and the countries of Latin America, the cognates of North America designate a subcontinent of the Americas comprising Canada, the United States, Mexico, Greenland, Saint Pierre et Miquelon, Bermuda. North America has been referred to by other names. Spanish North America was referred to as Northern America, this was the first official name given to Mexico. Geographically the North American continent has many subregions; these include cultural and geographic regions. Economic regions included those formed by trade blocs, such as the North American Trade Agreement bloc and Central American Trade Agreement.
Linguistically and culturally, the continent could be divided into Latin America. Anglo-America includes most of Northern America and Caribbean islands with English-speaking populations; the southern North American continent is composed of two regions. These are the Caribbean; the north of the continent maintains recognized regions as well. In contrast to the common definition of "North America", which encompasses the whole continent, the term "North America" is sometimes used to refer only to Mexico, the United States, Greenland; the term Northern America refers to the northern-most countries and territories of North America: the United States, Bermuda, St. Pierre and Miquelon and Greenland. Although the term does not refer to a unifie
Plants are multicellular, predominantly photosynthetic eukaryotes of the kingdom Plantae. Plants were treated as one of two kingdoms including all living things that were not animals, all algae and fungi were treated as plants. However, all current definitions of Plantae exclude the fungi and some algae, as well as the prokaryotes. By one definition, plants form the clade Viridiplantae, a group that includes the flowering plants and other gymnosperms and their allies, liverworts and the green algae, but excludes the red and brown algae. Green plants obtain most of their energy from sunlight via photosynthesis by primary chloroplasts that are derived from endosymbiosis with cyanobacteria, their chloroplasts contain b, which gives them their green color. Some plants are parasitic or mycotrophic and have lost the ability to produce normal amounts of chlorophyll or to photosynthesize. Plants are characterized by sexual reproduction and alternation of generations, although asexual reproduction is common.
There are about 320 thousand species of plants, of which the great majority, some 260–290 thousand, are seed plants. Green plants provide a substantial proportion of the world's molecular oxygen and are the basis of most of Earth's ecosystems on land. Plants that produce grain and vegetables form humankind's basic foods, have been domesticated for millennia. Plants have many cultural and other uses, as ornaments, building materials, writing material and, in great variety, they have been the source of medicines and psychoactive drugs; the scientific study of plants is known as a branch of biology. All living things were traditionally placed into one of two groups and animals; this classification may date from Aristotle, who made the distincton between plants, which do not move, animals, which are mobile to catch their food. Much when Linnaeus created the basis of the modern system of scientific classification, these two groups became the kingdoms Vegetabilia and Animalia. Since it has become clear that the plant kingdom as defined included several unrelated groups, the fungi and several groups of algae were removed to new kingdoms.
However, these organisms are still considered plants in popular contexts. The term "plant" implies the possession of the following traits multicellularity, possession of cell walls containing cellulose and the ability to carry out photosynthesis with primary chloroplasts; when the name Plantae or plant is applied to a specific group of organisms or taxon, it refers to one of four concepts. From least to most inclusive, these four groupings are: Another way of looking at the relationships between the different groups that have been called "plants" is through a cladogram, which shows their evolutionary relationships; these are not yet settled, but one accepted relationship between the three groups described above is shown below. Those which have been called "plants" are in bold; the way in which the groups of green algae are combined and named varies between authors. Algae comprise several different groups of organisms which produce food by photosynthesis and thus have traditionally been included in the plant kingdom.
The seaweeds range from large multicellular algae to single-celled organisms and are classified into three groups, the green algae, red algae and brown algae. There is good evidence that the brown algae evolved independently from the others, from non-photosynthetic ancestors that formed endosymbiotic relationships with red algae rather than from cyanobacteria, they are no longer classified as plants as defined here; the Viridiplantae, the green plants – green algae and land plants – form a clade, a group consisting of all the descendants of a common ancestor. With a few exceptions, the green plants have the following features in common, they undergo closed mitosis without centrioles, have mitochondria with flat cristae. The chloroplasts of green plants are surrounded by two membranes, suggesting they originated directly from endosymbiotic cyanobacteria. Two additional groups, the Rhodophyta and Glaucophyta have primary chloroplasts that appear to be derived directly from endosymbiotic cyanobacteria, although they differ from Viridiplantae in the pigments which are used in photosynthesis and so are different in colour.
These groups differ from green plants in that the storage polysaccharide is floridean starch and is stored in the cytoplasm rather than in the plastids. They appear to have had a common origin with Viridiplantae and the three groups form the clade Archaeplastida, whose name implies that their chloroplasts were derived from a single ancient endosymbiotic event; this is the broadest modern definition of the term'plant'. In contrast, most other algae not only have different pigments but have chloroplasts with three or four surrounding membranes, they are not close relatives of the Archaeplastida having acquired chloroplasts separately from ingested or symbiotic green and red algae. They are thus not included in the broadest modern definition of the plant kingdom, although they were in the past; the green plants or Viridiplantae were traditionally divided into the green algae (including
In botany and dendrology, a rhizome is a modified subterranean plant stem that sends out roots and shoots from its nodes. Rhizomes are called creeping rootstalks or just rootstalks. Rhizomes grow horizontally; the rhizome retains the ability to allow new shoots to grow upwards. A rhizome is the main stem of the plant. A stolon is similar to a rhizome, but a stolon sprouts from an existing stem, has long internodes, generates new shoots at the end, such as in the strawberry plant. In general, rhizomes have short internodes, send out roots from the bottom of the nodes, generate new upward-growing shoots from the top of the nodes. A stem tuber is a thickened part of a rhizome or stolon, enlarged for use as a storage organ. In general, a tuber is high in starch, e.g. the potato, a modified stolon. The term "tuber" is used imprecisely and is sometimes applied to plants with rhizomes. If a rhizome is separated each piece may be able to give rise to a new plant; the plant uses the rhizome to store starches and other nutrients.
These nutrients become useful for the plant when new shoots must be formed or when the plant dies back for the winter. This is a process known as vegetative reproduction and is used by farmers and gardeners to propagate certain plants; this allows for lateral spread of grasses like bamboo and bunch grasses. Examples of plants that are propagated this way include hops, ginger, lily of the valley and sympodial orchids; some rhizomes which are used directly in cooking include ginger, galangal and lotus. Stored rhizomes are subject to bacterial and fungal infections, making them unsuitable for replanting and diminishing stocks. However, rhizomes can be produced artificially from tissue cultures; the ability to grow rhizomes from tissue cultures leads to better stocks for replanting and greater yields. The plant hormones ethylene and jasmonic acid have been found to help induce and regulate the growth of rhizomes in rhubarb. Ethylene, applied externally was found to affect internal ethylene levels, allowing easy manipulations of ethylene concentrations.
Knowledge of how to use these hormones to induce rhizome growth could help farmers and biologists producing plants grown from rhizomes more cultivate and grow better plants. Some plants have rhizomes that grow above ground or that lie at the soil surface, including some Iris species, ferns, whose spreading stems are rhizomes. Plants with underground rhizomes include gingers, the Venus flytrap, Chinese lantern, western poison-oak and Alstroemeria, the weeds Johnson grass, Bermuda grass, purple nut sedge. Rhizomes form a single layer, but in giant horsetails, can be multi-tiered. Many rhizomes have culinary value, some, such as zhe'ergen, are consumed raw. Aspen Corm Mycorrhiza Media related to Rhizomes at Wikimedia Commons The Rhizome Collective for sustainable living