Lecture.23

Lecture.23 - Extinction Extinction can be defined as the...

Info iconThis preview shows pages 1–11. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Extinction Extinction can be defined as the death of the last individual of a species Species head towards extinction when their birth rate is lower than their death rate http://www.nature.ca/notebooks/images/extinct.gif Many factors can lead a species to extinction: Being outcompeted by another species Depletion of resources in a habitat Changes in climate Change in geography (e.g. weathering of mountains) Eruption of a volcano Drying of aquatic habitiats Flooding of terrestrial habitats etc There are two types of extinctions: Background extinctions- isolated extinctions of individual species. This type of extinction is ongoing and occurs all the time Mass extinctions- the extinction of large numbers of different types of species in a geologically short period of time Background extinctions may account for 95% of all extinctions that have ever took place Most dinosaur species that ever lived went extinct due to the mundane causes of background extinction ( e.g., Podokesaurus , from MA lived 200 ma, and went extinct well before the mass extinction of dinosaurs at the end of the Cretaceous, approximately 65 ma ) Podokesaurus holyokensis from the Early Jurassic of Massachusetts (ACM 11792c) Paleontologists studying extinctions through time have noted that there are 15 mass extinctions, 5 of which were particularly severe Fig. 17.1 Late Ordovician- 438 ma Late Devonian- 380 ma Permo-Triassic- 245 ma Triassic/Jurassic- 205 ma Cretaceous/Tertiary- 65 ma The Permo-Triassic (end Permian) extinction was the most severe mass extinction of them all 96% of all living species went extinct The remaining 4% went on to repopulate the world What causes mass extinctions? Many paleontologists think that the same processes that result in background extinctions may cause mass extinctions However, it is becoming increasingly clear that sudden, unexpected events such as asteroid impacts may cause mass extinctions as well How long do mass extinction events take? This is a difficult question to answer because of poor resolution in the geological and paleontological record Poor resolution results from 2 things: Only a small fraction of living organisms become fossils The rock record is incomplete, with only between 50-90% of time being represented An analogy from the book......
View Full Document

This note was uploaded on 04/22/2008 for the course GEOL 111 taught by Professor Getty during the Fall '07 term at UConn.

Page1 / 45

Lecture.23 - Extinction Extinction can be defined as the...

This preview shows document pages 1 - 11. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online