Lecture Four Flashcards
Define Actual Extinction
End of an organism/species. Occurs when the last existing member of a species dies.
Define Functional Extinction
Only a few individuals left - population is no longer viable, odds of survival are slim. Can be functionally extinct for decades before being actually extinct.
What is Mass Extinction?
A mass extinction event is defined as the loss of a large number of species on Earth in a short period of time. There have been at least 5 - we may be in the middle of a sixth.
How many animal species that have existed have gone extinct?
66%.
What is the rate of extinction in the absence of human activity?
1-10 species/five years or 9% of species/million years.
According to the fossil record, how long do most species typically survive?
1-10 million years.
What has human activity’s impact on modern bird populations been like?
Severe; for birds, natural extinction rate is 1-2/100 years. Since 1800, at least 106 species have been lost. This trend has reversed in the past two decades.
How many species that originated 542 MYA are extinct?
99%. Survivors include the brachiopod (450 MYA; Silurian) and horseshoe crab (Limulus polyphemus, 480 MYA, Ordovician)
What environmental factors effect extinction (often correlated with major environmental changes)?
Climate and temperature
Atmosphere (oxygen)
Land masses (continental drift & plate tectonics), floods, glaciation, volcanic eruptions, meteorite impacts.
What occurred in the Late Ordovician Period of Mass Extinction?
Environmental Changes included massive glaciers formed over the land (snowball earth). Sea levels dropped by ~50% m (water was taken up into glaciers). Ocean temperatures also dropped. 27% of all families when extinct, 57% of all genera, and 60-70% of all species.
What was the second largest extinction?
Late Ordovician Period of Mass Extinction
What occurred in the Late Devonian Period of Mass Extinction?
Environmental Changes are uncertain, though two large meteorites collided with Earth (Nevada and Australia). Massive fires, tsunami, major amounts of dust in atmosphere. 70% of all species (19% families, 50% genera) went extinct. Ranked 3rd or 4th largest. Lasted 20 million years (extinction ‘period’ more than event)
What occurred in the Late Permian Period of Mass Extinction?
Enormous meterorite collides into Australia - massive outpouring of lava into the oceans, reducing oxygen content and releasing toxic carbon dioxide and H2S, and a 96% decline in species on Earth. “Big Kill”. Ended the primacy of mammal-like reptiles.
What was the largest mass extinction?
Late Permian Period of Mass Extinction.
What occurred during the Late Triassic Period of Mass Extinction?
Paleontologist’s unsure, but there was a large meteorite that hit Quebec. 70-75% of all species when extinct, most non-dinosaurs and large amphibians were eliminated - leaving dinosaurs with little competition.
