Live birth is a comparatively recent adaptation. Monotreme mammals do still lay eggs. It is the marsupial and eutherian mammals which developed live birth. Actually,the embryo developing in the womb has the same membranes round it as does the embryo inside a bird egg. Mammals give birth to live young because the development takes place internally. Live birth has evolved independently a number of times in reptiles, for example Ichthyosaurs gave birth to live young. So do some snakes.
The cleidoic egg is a good example of an evolutionary innovation which permitted the invasion of a vast range of new habitats, and led to one of the greatest adaptive radiations in the history of the vertebrates. In comparison, the amphibia, whose reproduction is tied to water, are represented today by just a few highly specialised groups.
Some authors make a distinction between amniotic eggs (of reptiles, birds and mammals) and closed eggs of invertebrate groups such as insects and spiders. In that case:
This is logical, but in practice the terms are usually synonymous.
Terrapin
A terrapin is a turtle that lives in brackish water. They are named for the diamond pattern on their shells. They eat mollusks, crabs, and fish. Terrapins are sexually dimorphic. Females are much larger than males. Males range between 4 and 5 inches. Females average nearly 7 inches. The largest terrapin on record was a female measuring 9 inches.
A terrapin is one of several small species of turtle living in fresh or brackish water. Terrapins do not form a taxonomic unit, and may not be related. Many belong to the families Geoemydidae and Emydidae.
The name "terrapin" is derived from "torope", a word in the Native American Algonquian language that refers to the species, Malaclemys terrapin. It appears that it became part of common usage during the colonial era of North America and was carried back to Great Britain. Since then, it has been used in common names for turtles in the English language. In the UK, red-eared sliders are known as red-eared terrapins.
Regions of Brazil
Brazil is currently divided into five regions (also called macroregions) by the Instituto Brasileiro de Geografia e Estatística (IBGE). These divisions are composed of states with similar cultural, economical, historical and social aspects, and, although information given by this type of division is not very accurate from the scientific point of view, this division is the most widely used in Brazil because official information given by the IBGE uses this system.
Vale do Aço metropolitan area
The Vale do Aço metropolitan area (Região Metropolitana do Vale do Aço, in Portuguese) is a metropolitan area in Minas Gerais, Brazil, comprising only the four municipalities of Coronel Fabriciano, Ipatinga, Santana do Paraíso and Timóteo, but have an influence area of 24 other municipalities.
The region has become internationally known due to large companies that are in the region, such as the Cenibra, Aperam South America (old Acesita) and Usiminas, all with an increasing volume of exported products.
Mantle (mollusc)
The mantle is a significant part of the anatomy of molluscs: it is the dorsal body wall which covers the organs of digestion, reproduction and movement.
In many, but not all, species of molluscs, the epidermis (skin) of the mantle secretes calcium carbonate and conchiolin, and creates a shell.
The word "mantle" means cloak or cape, and does often resemble a cloak. The edges of the mantle may extend far beyond the main part of the body, forming flaps, double-layered structures adapted for many different uses, including for example, the "siphon".
The "mantle cavity" is a central feature of molluscan biology. This cavity is formed by the mantle skirt, a double fold of mantle which encloses a water space. This space contains the mollusc's gills, anus, and organs for taste, excretion and reproductive organs.
The mantle cavity functions as a respiratory chamber in all molluscs. In bivalves it is usually part of the feeding structure. In some mollusks the mantle cavity is a brood chamber, and in cephalopods and some bivalves such as scallops, it is a locomotory organ.
The mantle is highly muscular. In cephalopods the contraction of the mantle is used to force water through a tubular "siphon", and this propels the animal rapidly through the water. In other molluscs, it is used as a kind of "foot" for locomotion.
Carboniferous
The Carboniferous was the geological period after the Devonian and before the Permian. It lasted from about 359 to about 299 million years ago. It is the fifth period of the Paleozoic era and the Phanerozoic eon.
In the U.S.A. the Carboniferous is divided into the Mississippian (lower part, 359–323.2 mya) and the Pennsylvanian (upper part, 323.2–299 mya). In Europe the terms lower, middle and upper are used.
The early tetrapods split first into two major groups: the amphibians, which laid their eggs in water, and the amniotes, who laid their cleidoic eggs on land. The amniotes gave rise to two groups both of which became dominant at different times. They were the synapsids, which eventually gave rise to the mammals, and the sauropsids, which gave rise to the dinosaurs and other reptiles. These momentous events took place in the lower part of the Carboniferous, the Mississippian.
The Carboniferous is named after the "coal measures", the remains of peat formed by dense tropical wetland forests. New kinds of vascular plants with thick bark grew in the forests. Much of the coal came from this bark. This biota occurred in the upper part of the period, the Pennsylvanian, from 315–300 million years years ago.
These forests were on the equator, and the wetlands, which are always low-lying, stretched across the supercontinent of Laurussia. This included what is now North America in the west, through what is now Europe to China in the east. The river plain which was the heart of the wetland stretched 5000 km from eastern Canada to the Ukraine, and was 700 km wide.
In the Carboniferous, the great tropical rainforests of Euramerica supported towering lycopodiophyta, and a mix of vegetation, as well as a great diversity of animal life: giant dragonflies, millipedes, cockroaches, amphibians, and the first amniotes.
This kind of climate and geography has no exact parallel today, but the peat swamp forests in Indonesia and Malaysia, the Amazon Basin, the Mississippi River system and the Okefenokee swamp give some idea. The swamps were dominated by giant clubmosses, including "Lepidodendron". They were the earliest trees, which later replaced by conifers and flowering plants. Sometimes other plants from the levee got swept down by the river, such as horsetails, ferns and tree-like pteridosperms.
The wetland forests ended when the land level was raised by the pressure of the Gondwana continent against Laurussia. This caused the zone of contact to rise. The end of the coal measures marks the end of the Carboniferous period. China was too far away to be affected. There, the wetland forests continued for another 50 million years, into the Permian.
Mesozoic
The Mesozoic was the geological era in which dinosaurs lived, as well as the first birds and mammals. It lasted about 186 million years, starting 252.2 mya (million years ago) with the P/Tr extinction and ending 66 mya with the K/T extinction (the one that killed dinosaurs).
Dinosaurs appeared around 231 mya (21 million years after the beginning of the Mesozoic). They evolved from early reptiles called the archosaurs (a group of which modern birds and crocodiles are still part).
The Mesozoic is the middle of the three eras that make up the Phanerozoic eon. Before the Mesozoic was the Palaeozoic era. The K/T extinction in 66 mya also marks the beginning of the Cenozoic era, the one we live in.
The three Mesozoic periods were:
Palaeozoic