Official Model Exam-MeteoriteImpact and Dinosaur Extinction
TPO-8 Extinction of the Dinosaurs
TPO-15 Mass Extinctions
Habitat degradation is currently the mainanthropogenic cause of species extinctions. The main cause of habitatdegradation worldwide is agriculture, with urban sprawl, logging, mining andsome fishing practices close behind. The degradation of a species' habitat mayalter the fitness landscape to such an extent that the species is no longerable to survive and becomes extinct. This may occur by direct effects, such asthe environment becoming toxic, or indirectly, by limiting a species' abilityto compete effectively for diminished resources or against new competitorspecies.
Habitat degradation through toxicity can killoff a species very rapidly, by killing all living members through contaminationor sterilizing them. It can also occur over longer periods at lower toxicitylevels by affecting life span, reproductive capacity, or competitiveness.
Habitat degradation can also take the form ofa physical destruction of niche habitats. The widespread destruction oftropical rainforests and replacement with open pastureland is widely cited asan example of this; elimination of the dense forest eliminated theinfrastructure needed by many species to survive. For example, a fern thatdepends on dense shade for protection from direct sunlight can no longersurvive without forest to shelter it. Another example is the destruction ofocean floors by bottom trawling.
Diminished resources or introduction of newcompetitor species also often accompany habitat degradation. Global warming hasallowed some species to expand their range, bringing unwelcome competition toother species that previously occupied that area. Sometimes these newcompetitors are predators and directly affect prey species, while at othertimes they may merely outcompete vulnerable species for limited resources.Vital resources including water and food can also be limited during habitatdegradation, leading to extinction.
There have been at least five massextinctions in the history of life on earth, and four in the last 350 millionyears in which many species have disappeared in a relatively short period ofgeological time. A massive eruptive event is considered to be one likely causeof the "Permian–Triassic extinction event" about 250 million yearsago, which is estimated to have killed 90% of species then existing. There isalso evidence to suggest that this event was preceded by another massextinction, known as Olson's Extinction. The Cretaceous–Paleogene extinctionevent occurred 66 million years ago, at the end of the Cretaceous period, andis best known for having wiped out non-avian dinosaurs, among many otherspecies.
TPO34-Islamic Art and the Book
Movable type is the system ofprinting and typography that uses movable components to reproduce the elementsof a document (usually individual letters or punctuation).
The world's first known movable type system for printingwas made of ceramic materials and created in China around A.D 1040 by Bi Sheng(990–1051) during the Northern Song Dynasty (960–1127). In 1377, the firstmetallic types were invented in Goryeo Dynasty in Korea, which were used toprint Jikji, which is the oldest extant movable metal print book. The diffusionof both movable-type systems was, however, limited. They were expensive, andrequired an enormous amount of labour involved in manipulating the thousands ofceramic tablets, or in the case of Korea, metal tablets, required for scriptsbased on the Chinese writing system, which have thousands of characters.
Around 1450 Johannes Gutenberg made a mechanical metalmovable-type printing press in Europe, along with innovations in casting thetype based on a matrix and hand mould. The more limited number of charactersneeded for European languages was an important factor. Gutenberg was the firstto create his type pieces from an alloy of lead, tin, and antimony—and thesematerials remained standard for 550 years.