Cycads are seed plants with a long fossil history that were more abundant and more diverse than they are today. They have a stout and woody trunk with a crown of large and stiff, evergreen leaves, they have pinnate leaves. The individual plants are all female. Cycads vary in size from having trunks only a few centimeters to several meters tall, they grow slowly and live long, with some specimens known to be as much as 1,000 years old. Because of their superficial resemblance, they are sometimes mistaken for palms or ferns, but they are not related to either group. Cycads are gymnosperms, meaning their unfertilized seeds are open to the air to be directly fertilized by pollination, as contrasted with angiosperms, which have enclosed seeds with more complex fertilization arrangements. Cycads have specialized pollinators a specific species of beetle, they have been reported to fix nitrogen in association with various cyanobacteria living in the roots. These photosynthetic bacteria produce a neurotoxin called BMAA, found in the seeds of cycads.
This neurotoxin may enter a human food chain as the cycad seeds may be eaten directly as a source of flour by humans or by wild or feral animals such as bats, humans may eat these animals. It is hypothesized. Cycads have a cylindrical trunk which does not branch. Leaves grow directly from the trunk, fall when older, leaving a crown of leaves at the top; the leaves grow with new foliage emerging from the top and center of the crown. The trunk may be buried, so the leaves appear to be emerging from the ground, so the plant appears to be a basal rosette; the leaves are large in proportion to the trunk size, sometimes larger than the trunk. The leaves are pinnate, with a central leaf stalk from which parallel "ribs" emerge from each side of the stalk, perpendicular to it; the leaves are either compound, or have edges so cut so as to appear compound. Some species have leaves that are bipinnate, which means the leaflets each have their own subleaflets, growing in the same form on the leaflet as the leaflets grow on the stalk of the leaf.
Due to superficial similarities in foliage and plant structure between cycads and palms they are confused with each other. In reality, they belong to different phyla, are not related at all; the similar structure may be evidence of convergent evolution. Despite this, there are still a number of differences between them. For one, both male and female cycads bear a cone-like reproductive structure called a strobilus, while palms are angiosperms and so flower and bear fruit; the mature foliage looks similar between both groups, but the young emerging leaves of a cycad resemble a fiddlehead fern before they unfold and take their place in the rosette, while the leaves of palms are never coiled up and instead are just small versions of the mature frond. Another difference is in the stem. Both plants leave scars on the stem below the rosette where there used to be leaves, but the scars of a cycad are helically arranged and small, while the scars of palms are a circle that wraps around the whole stem.
The stems of cycads are in general rougher and shorter than those of palms. The three extant families of cycads all belong to the order Cycadales, are Cycadaceae and Zamiaceae; these cycads have changed little since the Jurassic, compared to some major evolutionary changes in other plant divisions. Five additional families belonging to the Medullosales became extinct by the end of the Paleozoic Era. Cycads have been traditionally put as related to the extinct Bennettitales, however recent findings show marked differences In reproductive biology and general anatomy putting doubt on the traditional view; as of yet the evidence points to a pteridospermalean origin of cycads and to a close relation to the Ginkgoales, as shown in the following phylogeny: Classification of the Cycadophyta to the rank of family. Class Cycadopsida Order Medullosales † Family Alethopteridaceae Family Cyclopteridaceae Family Neurodontopteridaceae Family ParispermaceaeOrder Cycadales Suborder Cycadineae Family Cycadaceae Suborder Zamiineae Family Stangeriaceae Family Zamiaceae The probable former range of cycads can be inferred from their global distribution.
For example, the family Stangeriaceae only contains three extant species in Australia. Diverse fossils of this family have been dated to 135 mya, indicating that diversity may have been much greater before the Jurassic and late Triassic mass extinction events. However, the cycad fossil record is poor and little can be deduced about the effects of each mass extinction event on their diversity. Instead, correlations can be made between the number of extant angiosperms, it is that cycad diversity was affected more by the great angiosperm radiation in the mid-Cretaceous than by extinctions. Slow cambial growth was first used to define cycads, because of this characteristic the group could not compete with the growing short-lived angiosperms, which now number over 250,000 species, compared to the 1080 remaining gymnosperms, it is surprising that the cycads are still extant, having been faced with extreme competition and five major extinctions. The ability of cycads to survive in dry environments, where plant diversity is lower, may explain their long persistence and longevity.
The cycad fossil record dates to the e
The Ginkgoaceae is a family of gymnosperms which appeared during the Mesozoic Era, of which the only extant representative is Ginkgo biloba, for this reason sometimes regarded as a living fossil. However, there were several other genera, forests of ginkgo existed; because leaves can take such diverse forms within a single species, these are a poor measure of diversity, although differing structures of wood point to the existence of diverse ginkgo forests in ancient times. "Ginkgoopsida". Integrated Taxonomic Information System. "Ginkgopsida". Integrated Taxonomic Information System. "Ginkgoales". Integrated Taxonomic Information System. "Ginkgoaceae". Integrated Taxonomic Information System
The Early Jurassic epoch is the earliest of three epochs of the Jurassic period. The Early Jurassic starts after the Triassic-Jurassic extinction event, 201.3 Ma, ends at the start of the Middle Jurassic 174.1 Ma. Certain rocks of marine origin of this age in Europe are called "Lias" and that name was used for the period, as well, in 19th-century geology. In southern Germany rocks of this age are called Black Jurassic. There are two possible origins for the name Lias: the first reason is it was taken by a geologist from an English quarryman's dialect pronunciation of the word "layers". There are extensive Liassic outcrops around the coast of the United Kingdom, in particular in Glamorgan, North Yorkshire and Dorset. The'Jurassic Coast' of Dorset is associated with the pioneering work of Mary Anning of Lyme Regis; the facies of the Lower Jurassic in this area are predominantly of clays, thin limestones and siltstones, deposited under marine conditions. Lias Group strata form imposing cliffs in southern Wales.
Stretching for around 14 miles between Cardiff and Porthcawl, the remarkable layers of these cliffs, situated on the Bristol Channel are a rhythmic decimetre scale repetition of limestone and mudstone formed as a late Triassic desert was inundated by the sea. There has been some debate over the actual base of the Hettangian stage, so of the Jurassic system itself. Biostratigraphically, the first appearance of psiloceratid ammonites has been used. If this biostratigraphical indicator is used technically the Lias Group—a lithostratigraphical division—spans the Jurassic / Triassic boundary. During this period, which had died out at the end-of-Triassic extinction, radiated out into a huge diversity of new forms with complex suture patterns. Ammonites evolved so and their shells are so preserved, that they serve as important zone fossils. There were several distinct waves of ammonite evolution in Europe alone; the Early Jurassic was an important time in the evolution of the marine reptiles. The Hettangian saw the existing Rhaetian ichthyosaurs and plesiosaurs continuing to flourish, while at the same time a number of new types of these marine reptiles appeared, such as Ichthyosaurus and Temnodontosaurus among the ichthyosaurs, Eurycleidus and Rhomaleosaurus among the plesiosaurs.
All these plesiosaurs had large heads. In the Toarcian, at the end of the Early Jurassic, the thalattosuchians appeared, as did new genera of ichthyosaurs and plesiosaurs. On land, a number of new types of dinosaurs—the heterodontosaurids, scelidosaurs and tetanurans—appeared, joined those groups like the coelophysoids and the sauropods that had continued over from the Triassic. Accompanying them as small carnivores were the sphenosuchian and protosuchid crocodilians. In the air, new types of pterosaurs replaced those, but in the undergrowth were various types of early mammals, as well as tritylodont mammal-like reptiles, lizard-like sphenodonts, early lissamphibians. Late Triassic Toarcian turnover Davies, A. M. An Introduction to Palaeontology, Thomas Murby & Co. London House, M. R. Geology of The Dorset Coast, The Geologists' Association. Simms, M. J. Chidlaw, N. Morton, N. and Page, K. N. British Lower Jurassic Stratigraphy, Geological Conservation Review Series, No. 30, Joint Nature Conservation Committee, Peterborough.
Early Jurassic Period – The Lias epoch. Palaeos – overall presentation. Lecture 12 – Early Jurassic. Informative lecture notes by Dr. Paul Olsen
Scotland is a country, part of the United Kingdom. Sharing a border with England to the southeast, Scotland is otherwise surrounded by the Atlantic Ocean to the north and west, by the North Sea to the northeast and by the Irish Sea to the south. In addition to the mainland, situated on the northern third of the island of Great Britain, Scotland has over 790 islands, including the Northern Isles and the Hebrides; the Kingdom of Scotland emerged as an independent sovereign state in the Early Middle Ages and continued to exist until 1707. By inheritance in 1603, James VI, King of Scots, became King of England and King of Ireland, thus forming a personal union of the three kingdoms. Scotland subsequently entered into a political union with the Kingdom of England on 1 May 1707 to create the new Kingdom of Great Britain; the union created a new Parliament of Great Britain, which succeeded both the Parliament of Scotland and the Parliament of England. In 1801, the Kingdom of Great Britain and Kingdom of Ireland enacted a political union to create a United Kingdom.
The majority of Ireland subsequently seceded from the UK in 1922. Within Scotland, the monarchy of the United Kingdom has continued to use a variety of styles and other royal symbols of statehood specific to the pre-union Kingdom of Scotland; the legal system within Scotland has remained separate from those of England and Wales and Northern Ireland. The continued existence of legal, educational and other institutions distinct from those in the remainder of the UK have all contributed to the continuation of Scottish culture and national identity since the 1707 union with England; the Scottish Parliament, a unicameral legislature comprising 129 members, was established in 1999 and has authority over those areas of domestic policy which have been devolved by the United Kingdom Parliament. The head of the Scottish Government, the executive of the devolved legislature, is the First Minister of Scotland. Scotland is represented in the UK House of Commons by 59 MPs and in the European Parliament by 6 MEPs.
Scotland is a member of the British–Irish Council, sends five members of the Scottish Parliament to the British–Irish Parliamentary Assembly. Scotland is divided into councils. Glasgow City is the largest subdivision in Scotland in terms of population, with Highland being the largest in terms of area. "Scotland" comes from the Latin name for the Gaels. From the ninth century, the meaning of Scotia shifted to designate Gaelic Scotland and by the eleventh century the name was being used to refer to the core territory of the Kingdom of Alba in what is now east-central Scotland; the use of the words Scots and Scotland to encompass most of what is now Scotland became common in the Late Middle Ages, as the Kingdom of Alba expanded and came to encompass various peoples of diverse origins. Repeated glaciations, which covered the entire land mass of modern Scotland, destroyed any traces of human habitation that may have existed before the Mesolithic period, it is believed the first post-glacial groups of hunter-gatherers arrived in Scotland around 12,800 years ago, as the ice sheet retreated after the last glaciation.
At the time, Scotland was covered in forests, had more bog-land, the main form of transport was by water. These settlers began building the first known permanent houses on Scottish soil around 9,500 years ago, the first villages around 6,000 years ago; the well-preserved village of Skara Brae on the mainland of Orkney dates from this period. Neolithic habitation and ritual sites are common and well preserved in the Northern Isles and Western Isles, where a lack of trees led to most structures being built of local stone. Evidence of sophisticated pre-Christian belief systems is demonstrated by sites such as the Callanish Stones on Lewis and the Maes Howe on Orkney, which were built in the third millennium BCE; the first written reference to Scotland was in 320 BC by Greek sailor Pytheas, who called the northern tip of Britain "Orcas", the source of the name of the Orkney islands. During the first millennium BCE, the society changed to a chiefdom model, as consolidation of settlement led to the concentration of wealth and underground stores of surplus food.
The first Roman incursion into Scotland occurred in 79 AD. After the Roman victory, Roman forts were set along the Gask Ridge close to the Highland line, but by three years after the battle, the Roman armies had withdrawn to the Southern Uplands; the Romans erected Hadrian's Wall in northern England and the Limes Britannicus became the northern border of the Roman Empire. The Roman influence on the southern part of the country was considerable, they introduced Christianity to Scotland. Beginning in the sixth century, the area, now Scotland was divided into three areas: Pictland, a patchwork of small lordships in central Scotland; these societies were based on the family unit and had sharp divisions in wealth, although the vast majority were poor and worked full-time in subsistence agriculture. The Picts kept slaves through the ninth century. Gaelic influence over Pictland and Northumbria was facilitated by the large number of Gaelic-speaking clerics working as missionaries. Operating in the sixth ce
Ginkgoales or Ginkgophyte is a gymnosperm order containing only one extant species: Ginkgo biloba, the ginkgo tree. It is monotypic, within the class Ginkgoopsida, which itself is monotypic within the division Ginkgophyta; the order includes five families. The first Ginkgo leaves were found from the Triassic period, but there were many species of Ginkgo during the Jurassic and Cretaceous periods as well; these periods, known collectively as the Mesozoic era, were when diversity and distribution for all plants were at their highest, including in Ginkophytes. It was in the early Cenozoic period that Ginkgophytes nearly became extinct during the early Cretaceous and Tertiary periods; the only remaining Ginkgophyte was Ginkgo adiantoides – a polymorphic species. Modern Ginkgo trees are native to China. Ginkgo trees produce pollen-bearing structures; these structures are dioecious, in that male and female structures come from different Ginkgo plants. The pollen organs are similar to angiospermous catkins.
They come from the axils of the bud scales, the leaves from the Ginkgo tree spur shoots. Pollen is contained in sacs of two to four at the tips of sporophylls on the strobiloid. Ovules of Ginkgo trees come from stalks from leaf axils on the short shoots, each containing two ovules; the ovule is fertilized by the flagellated male gametes. This fertilization process begins on the tree itself in the spring; the swollen fruit-like ovules, about 2–3 cm in diameter, fall from the tree in the fall, fertilization continues into the winter/spring. This fruit contains a single large seed, similar to that of a cycad. Fossils that appear Ginkgo-like are filed under a morphogenus called Ginkgoxylon, Ginkgomyeloxylon, or Protoginkgoxylon. Fossilized ginkgophyte wood is not found in the record because it degrades and because it is difficult to tell apart from the much more pervasive conifer samples. Like conifer wood, it has secondary thin-walled xylem and a primary vascular system composed of eustele and bifacial vascular cambium.
The tracheids in the secondary xylem rays have pitting that occurs only on the walls and is circularly bordered. Ginkgophyte foliage has stayed consistent since the Mesozoic, its wide territory makes it an important leaf morphology, its unique stomata and isotopic profile give it a key role in recreations of the Mesozoic and Cenozoic. Leaf fossils that resemble the Ginkgophytes are known as Ginkgoites. There are similar, now extinct, such as Sphenobaiera, which describes fan-shaped divided leaves without clear petioles; the distinctive shape of the modern Ginkgo biloba gives the impression of a narrow leaf morphology, but the group is varied and diverse. The genus Ginkgo by itself contains a range of morphologies. Ginkgo digitata, from the Jurassic, has long, wedge-shaped laminae with the intercostal regions covered in stomata and resin bodies, while G. pluripartita has at most 2 cm-long leaves and is intercostally hypostomatic
The Eocene Epoch, lasting from 56 to 33.9 million years ago, is a major division of the geologic timescale and the second epoch of the Paleogene Period in the Cenozoic Era. The Eocene spans the time from the end of the Paleocene Epoch to the beginning of the Oligocene Epoch; the start of the Eocene is marked by a brief period in which the concentration of the carbon isotope 13C in the atmosphere was exceptionally low in comparison with the more common isotope 12C. The end is set at a major extinction event called the Grande Coupure or the Eocene–Oligocene extinction event, which may be related to the impact of one or more large bolides in Siberia and in what is now Chesapeake Bay; as with other geologic periods, the strata that define the start and end of the epoch are well identified, though their exact dates are uncertain. The name Eocene comes from the Ancient Greek ἠώς and καινός and refers to the "dawn" of modern fauna that appeared during the epoch; the Eocene epoch is conventionally divided into early and late subdivisions.
The corresponding rocks are referred to as lower and upper Eocene. The Ypresian stage constitutes the lower, the Priabonian stage the upper; the Eocene Epoch contained a wide variety of different climate conditions that includes the warmest climate in the Cenozoic Era and ends in an icehouse climate. The evolution of the Eocene climate began with warming after the end of the Palaeocene–Eocene Thermal Maximum at 56 million years ago to a maximum during the Eocene Optimum at around 49 million years ago. During this period of time, little to no ice was present on Earth with a smaller difference in temperature from the equator to the poles. Following the maximum was a descent into an icehouse climate from the Eocene Optimum to the Eocene-Oligocene transition at 34 million years ago. During this decrease ice began to reappear at the poles, the Eocene-Oligocene transition is the period of time where the Antarctic ice sheet began to expand. Greenhouse gases, in particular carbon dioxide and methane, played a significant role during the Eocene in controlling the surface temperature.
The end of the PETM was met with a large sequestration of carbon dioxide in the form of methane clathrate and crude oil at the bottom of the Arctic Ocean, that reduced the atmospheric carbon dioxide. This event was similar in magnitude to the massive release of greenhouse gasses at the beginning of the PETM, it is hypothesized that the sequestration was due to organic carbon burial and weathering of silicates. For the early Eocene there is much discussion; this is due to numerous proxies representing different atmospheric carbon dioxide content. For example, diverse geochemical and paleontological proxies indicate that at the maximum of global warmth the atmospheric carbon dioxide values were at 700–900 ppm while other proxies such as pedogenic carbonate and marine boron isotopes indicate large changes of carbon dioxide of over 2,000 ppm over periods of time of less than 1 million years. Sources for this large influx of carbon dioxide could be attributed to volcanic out-gassing due to North Atlantic rifting or oxidation of methane stored in large reservoirs deposited from the PETM event in the sea floor or wetland environments.
For contrast, today the carbon dioxide levels are at 400 ppm or 0.04%. At about the beginning of the Eocene Epoch the amount of oxygen in the earth's atmosphere more or less doubled. During the early Eocene, methane was another greenhouse gas that had a drastic effect on the climate. In comparison to carbon dioxide, methane has much greater effect on temperature as methane is around 34 times more effective per molecule than carbon dioxide on a 100-year scale. Most of the methane released to the atmosphere during this period of time would have been from wetlands and forests; the atmospheric methane concentration today is 0.000179% or 1.79 ppmv. Due to the warmer climate and sea level rise associated with the early Eocene, more wetlands, more forests, more coal deposits would be available for methane release. Comparing the early Eocene production of methane to current levels of atmospheric methane, the early Eocene would be able to produce triple the amount of current methane production; the warm temperatures during the early Eocene could have increased methane production rates, methane, released into the atmosphere would in turn warm the troposphere, cool the stratosphere, produce water vapor and carbon dioxide through oxidation.
Biogenic production of methane produces carbon dioxide and water vapor along with the methane, as well as yielding infrared radiation. The breakdown of methane in an oxygen atmosphere produces carbon monoxide, water vapor and infrared radiation; the carbon monoxide is not stable so it becomes carbon dioxide and in doing so releases yet more infrared radiation. Water vapor traps more infrared than does carbon dioxide; the middle to late Eocene marks not only the switch from warming to cooling, but the change in carbon dioxide from increasing to decreasing. At the end of the Eocene Optimum, carbon dioxide began decreasing due to increased siliceous plankton productivity and marine carbon burial. At the beginning of the middle Eocene an event that may have triggered or helped with the draw down of carbon dioxide was the Azolla event at around 49 million years ago. With the equable climate during the early Eocene, warm temperatures in the arctic allowed for the growth of azolla, a floating aquatic fern, on the Arctic Ocean.
Compared to current carb
Carl Linnaeus known after his ennoblement as Carl von Linné, was a Swedish botanist and zoologist who formalised binomial nomenclature, the modern system of naming organisms. He is known as the "father of modern taxonomy". Many of his writings were in Latin, his name is rendered in Latin as Carolus Linnæus. Linnaeus was born in the countryside of Småland in southern Sweden, he received most of his higher education at Uppsala University and began giving lectures in botany there in 1730. He lived abroad between 1735 and 1738, where he studied and published the first edition of his Systema Naturae in the Netherlands, he returned to Sweden where he became professor of medicine and botany at Uppsala. In the 1740s, he was sent on several journeys through Sweden to find and classify plants and animals. In the 1750s and 1760s, he continued to collect and classify animals and minerals, while publishing several volumes, he was one of the most acclaimed scientists in Europe at the time of his death. Philosopher Jean-Jacques Rousseau sent him the message: "Tell him I know no greater man on earth."
Johann Wolfgang von Goethe wrote: "With the exception of Shakespeare and Spinoza, I know no one among the no longer living who has influenced me more strongly." Swedish author August Strindberg wrote: "Linnaeus was in reality a poet who happened to become a naturalist." Linnaeus has been called Princeps botanicorum and "The Pliny of the North". He is considered as one of the founders of modern ecology. In botany and zoology, the abbreviation L. is used to indicate Linnaeus as the authority for a species' name. In older publications, the abbreviation "Linn." is found. Linnaeus's remains comprise the type specimen for the species Homo sapiens following the International Code of Zoological Nomenclature, since the sole specimen that he is known to have examined was himself. Linnaeus was born in the village of Råshult in Småland, Sweden, on 23 May 1707, he was the first child of Christina Brodersonia. His siblings were Anna Maria Linnæa, Sofia Juliana Linnæa, Samuel Linnæus, Emerentia Linnæa, his father taught him Latin as a small child.
One of a long line of peasants and priests, Nils was an amateur botanist, a Lutheran minister, the curate of the small village of Stenbrohult in Småland. Christina was the daughter of the rector of Samuel Brodersonius. A year after Linnaeus's birth, his grandfather Samuel Brodersonius died, his father Nils became the rector of Stenbrohult; the family moved into the rectory from the curate's house. In his early years, Linnaeus seemed to have a liking for plants, flowers in particular. Whenever he was upset, he was given a flower, which calmed him. Nils spent much time in his garden and showed flowers to Linnaeus and told him their names. Soon Linnaeus was given his own patch of earth. Carl's father was the first in his ancestry to adopt a permanent surname. Before that, ancestors had used the patronymic naming system of Scandinavian countries: his father was named Ingemarsson after his father Ingemar Bengtsson; when Nils was admitted to the University of Lund, he had to take on a family name. He adopted the Latinate name Linnæus after a giant linden tree, lind in Swedish, that grew on the family homestead.
This name was spelled with the æ ligature. When Carl was born, he was named Carl Linnæus, with his father's family name; the son always spelled it with the æ ligature, both in handwritten documents and in publications. Carl's patronymic would have been Nilsson, as in Carl Nilsson Linnæus. Linnaeus's father began teaching him basic Latin and geography at an early age; when Linnaeus was seven, Nils decided to hire a tutor for him. The parents picked a son of a local yeoman. Linnaeus did not like him, writing in his autobiography that Telander "was better calculated to extinguish a child's talents than develop them". Two years after his tutoring had begun, he was sent to the Lower Grammar School at Växjö in 1717. Linnaeus studied going to the countryside to look for plants, he reached the last year of the Lower School when he was fifteen, taught by the headmaster, Daniel Lannerus, interested in botany. Lannerus gave him the run of his garden, he introduced him to Johan Rothman, the state doctor of Småland and a teacher at Katedralskolan in Växjö.
A botanist, Rothman broadened Linnaeus's interest in botany and helped him develop an interest in medicine. By the age of 17, Linnaeus had become well acquainted with the existing botanical literature, he remarks in his journal that he "read day and night, knowing like the back of my hand, Arvidh Månsson's Rydaholm Book of Herbs, Tillandz's Flora Åboensis, Palmberg's Serta Florea Suecana, Bromelii Chloros Gothica and Rudbeckii Hortus Upsaliensis...."Linnaeus entered the Växjö Katedralskola in 1724, where he studied Greek, Hebrew and mathematics, a curriculum designed for boys preparing for the priesthood. In the last year at the gymnasium, Linnaeus's father visited to ask the professors how his son's studies were progressing. Rothman believed otherwise; the doctor offered to have Linnaeus live with his family in Växjö and to teach him physiology and botany. Nils accepted this offer. Rothman showed Linnaeus that botany was a serious sub