Dinosaurs essays

Dinosaurs essays Something happened 65 million years ago, at the end of the Cretaceous period, something so devastating that it altered the course of life on earth. It seems like it happened so sudden, as geologic time goes, that almost all the dinosaurs living on earth disappeared. So how did these dominant creatures just die off? Was it a slow extinction, or did it happen all of the sudden? These questions bring rise to many different beliefs on how the dinosaur disappeared over 65 million years ago. Extinction itself is easily defined: When the birth rate fails to keep up with the death rate, it is called extinction. But, the definition does not answer the question about the nature or causes of extinction. Paleontologists generally divide extinctions into two types, for that of different causes arose. The first is called background extinctions, isolated extinctions of species due to a variety of causes. Included is out competition, depletion of resources in a habitat, changes in climate, the development or destruction of a mountain range, river channel migration, the eruption of a volcano, the drying of a lake, or the destruction of a forest, grassland, or wetland habitat. The second type of extinction is called mass extinctions. There are four main components involved: Large numbers of species go extinct; many types of species go extinct; the effects must be global; and the effects must occur in a geologically short period of time.1 The dinosaur could not have lived for ever. No creatures, no plants, no tiny bacteria are forever, not even Homo sapiens. Extinction is the fate of all species. One theory on how the dinosaurs became extinct is that of carbon dioxide, and the  ³greenhouse effect ². Volcanoes produced the proposed conditions. A massive volcanic eruption could have saturated the atmosphere with carbon dioxide so that it caused a sharp rise in temperatures worldwide. The excess ...

Using the Italian Past Perfect Subjunctive Tense

Using the Italian Past Perfect Subjunctive Tense To complete the fourth of subjunctive-tense verb forms, theres the congiuntivo trapassato (referred to as the past perfect subjunctive in English), which is a compound tense. Form this tense with the congiuntivo imperfetto of the auxiliary verb avere or essere and the past participle of the acting verb. Forming the Compound Tense The compound tenses (i tempi composti) are verb tenses that consist of two words, such as the passato prossimo (present perfect). Both the verbs essere and avere act as helping verbs in compound tense formations. For example: io sono stato (I was) and ho avuto (I had). Auxiliary Verb Avere In general, transitive verbs (verbs that carry over an action from the subject to the direct object) are conjugated with avere as in the following example: Il pilota ha pilotato laeroplano. (The pilot flew the plane.) When the passato prossimo is constructed with avere, the past participle does not change according to gender or number: Io ho parlato con Giorgio ieri pomeriggio. (I spoke to George yesterday afternoon.)Noi abbiamo comprato molte cose. (We bought many things.) When the past participle of a verb conjugated with avere is preceded by the third person direct object pronouns lo, la, le, or li, the past participle agrees with the preceding direct object pronoun in gender and number. The past participle may agree with the direct object pronouns mi, ti, ci, and vi when these precede the verb, but the agreement is not mandatory. Ho bevuto la birra. (I drank the beer.)Lho bevuta. (I drank it.)Ho comprato il sale e il pepe. (I bought the salt and pepper.)Li ho comprati. (I bought them.)Ci hanno visto/visti. (They saw us.) In negative sentences, non is placed before the auxiliary verb: Molti non hanno pagato. (Many didnt pay.)No, non ho ordinato una pizza. (No, I didnt order a pizza.) Auxiliary Verb Essere When essere is used, the past participle always agrees in gender and number with the subject of the verb, so you have four endings to choose from: -o, -a, -i, -e. In many cases, intransitive verbs (those that cannot take a direct object), especially those expressing motion, are conjugated with the auxiliary verb essere. The verb essere is also conjugated with itself as the auxiliary verb. Here are a few examples of the trapassato congiuntivo: Speravo che avessero capito. (I was hoping they had understood.)Avevo paura che non avessero risolto quel problema. (I was afraid they hadnt resolved that problem.)Vorrebbero che io raccontassi una storia. (They would like me to tell a story.)Non volevo che tu lo facessi cosà ¬ presto. (I didnt want you to do it as soon.) Trapassato Congiuntivo of the Verbs Avere and Essere PRONOUN AVERE ESSERE che io avessi avuto fossi stato(-a) che tu avessi avuto fossi stato(-a) che lui/lei/Lei avesse avuto fosse stato(-a) che noi avessimo avuto fossimo stati(-e) che voi aveste avuto foste stati(-e) che loro/Loro avessero avuto fossero stati(-e)