Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
37 Cards in this Set
- Front
- Back
What was going on with the continental at the end of the pleistocene? |
- continental ice sheets covered much ofthe northern hemisphere - there were multiple advances (glacials) and retreats (interglacials) of the iceduring the Pleistocene Epoch |
|
fluctuations (advances and retreats) within an ice age can be accounted forby |
milankovitch cycles |
|
very briefly explain the milankovitch cycles |
which are three different phenomena that affect the amount and seasonal timing of insolation (solar input) |
|
having three cycles with different periods means that we get variableinterference effects, such that |
sometimes one or two will favour warmingwhile the other(s) favour cooling, and at other times all three will favourwarming or cooling |
|
the last conventional glacial stage, called the |
Wisconsinan |
|
the last conventional glacial stage, called the Wisconsinan, wascharacterized by exposure of Beringia, or a Bering land bridge, the reasonand consequence given: |
as sea level fell in response to the expanding ice cap; this land bridge allowed easy migration of mammals, including humans from asia to north america |
|
What were the victims? |
large, North American, cold-adapted forms, such as the woolly rhinoceros,and mammoths, but many other mammals were lost from North American |
|
What about smaller mammals? |
we note no significant losses in smaller mammals (e.g. squirrels, shrews,and lemmings), but rather, a change in distribution patterns |
|
The victims said north america what about larger mammals else where? |
many species lost from North America have survived elsewhere, andextinctions of large mammals (as well as flightless birds) in particularoccurred at different times elsewhere, such as Australasia, northern Europe,and South America |
|
the most significant losses were suffered by these groups: |
what appear to have been boreal/cold-adapted species |
|
this suggests what was the culprit |
climate change |
|
Guthrie (1990), and Graham (1990) said what? |
the fact that significant extinctions were not seen at any of the otherinterglacials is attributed by some to this latter warming being the mostpronounced, and by others to changes in distribution of vegetation, withresultant effects on megaherbivores and that the extent of the mammal extinctions was not so great as is often suggested |
|
mean annual temperature increased (a problem for cold-adapted species),but apparently more significant, other things happened as well: |
so did seasonality; as well, there were changes to length and extent of snow cover, growing season, and so on |
|
the consequence of this is described: |
plant communities became less diverse and less equable (stable and consistent); this would clearly affect herbivores, and ultimately carnivores as well |
|
What was another culprit that was suggested? |
humans! hunting and other anthropogenic factors |
|
the idea is simply this: |
mammals and in the case of australasia, flightless birds as well, were not used to coping with hunting |
|
What is the problem with this model? |
the first humans arrived in North America at least 30,000 years ago, technology had to develop before overkill was possible and projectile points date from approximately 12,000 years ago. and human were around in sufficient numbers yet |
|
proponents of climate or ecological change as the trigger point to thesurvival of many of the victims elsewhere as evidence that hominid overkillwas not the cause; if it were, why weren't these species wiped out on aglobal basis? |
these survivor populations were in areas (africa, for example) where contact with humans was longstanding, and the mammals had learned to avoid humans |
|
when the survivors, rather than victims, are considered in the Australiancase, we note that two factors seem key; noted: |
mobility (eg. kangaros) or the ability to escape detection (burrowing wombats, tree-dwelling koalas) seem key. the victims seem to be large prey organisms, or else competitors/threats tohominids; the inconspicuous are simply unaffected |
|
an observation that supports the overkill model is this fact: |
no significant mammal extinctions are associated with any of the climatic fluctuations that occurred earlier during the pleistocene |
|
the extinction is triggered not only by hunting, but also by these things: |
the introduction of mammal predators (eg, dog, cat, rat) accompanying humans, and also the effects of deforestation; the possiblity of introduction of disease should not be overlooked as well. Done |
|
a group that failed to survive the end-permian was the A) brachiopods B) crinoids C) rugose corals D) therapsids |
C) rugose corals |
|
the late ordovician mass extinction completely eliminated A) echinoderms B) graptolites C) trilobites D) none of the above |
D) none of the above nothing completely went wipe out at the ordovician mass extinction |
|
which of the following mass extinctions does not have assoicated volcanic activity? A) cretaceous/ tertiary B) end of permian C) end of triassic D) eocene/oligocene |
D) eocene/oligocene |
|
which of the following statements is true? A) birds are derived from pterosaurs B) pterosaurs are derived from birds C) birds and pterosaurs share a common recent ancestor and their wings are homologous D) birds and pterosaurs do not share a common recent ancestor and their wings are analogous |
D) birds and pterosaurs do not share a common recent ancestor and their wings are analogous |
|
impact of sulphate target rocks will cause A) acid rain and global cooling B) acid rain and global warming C) global cooling then global warming acid rain, D) global cooling, then global warming |
A) acid rain and global cooling Sulphate is an aerosol that scatter light, it wouldn't be the cause of the global warming, even if it does happen |
|
LAST PART. Raup and Sepkoski (1984 et seq.) noted an apparent periodicity to massextinctions, stated: |
26 million years |
|
we note two problems with this supposed periodicity: |
that of the 10 extinctions predicted by this pattern, going back through and including the end permian extinction, two are missing or not detected, five and seven dont show up. A more serious problem is that the pattern breaks down completely for the time before the end permian; if one is going to suggest a cosmic cause for this periodicity, it should have operated since the beginning of earth. |
|
the next extinction predicted by the pattern should occur in |
12-13 my |
|
perhaps a more significant criticism is that |
many extinctions appear to befairly closely timed, but distinct multiple episodes |
|
assuming the periodicity is valid, the question becomes, “What operateswith this period and could cause mass extinction?” one of the cause could be |
Conceivably, there are global or biosphere processes that operate with this period, but they are unknown [wilson cycle? ] |
|
of greater appeal is the possibility of there being a periodic, extraterrestrialphenomenon; this has led to three hypotheses, namely: |
A. Oscillation of the Solar System Through the Galactic Plane B. Death Star “Nemesis” C. Planet “X” |
|
A. Oscillation of the Solar System Through the Galactic Plane |
There is no reasonable speculation as to what its effects might be on thebiosphere |
|
B. Death Star “Nemesis” in this model, there is a small, companion star to the Sun, with a 26 m.y.orbit that brings it close enough to our part of the Solar System to causesomething: |
trigger comet showers |
|
Problems |
-"Nemesis” has never been detected - Eocene-Oligocene extinctions span 10 m.y., which seems too long to beaccounted for by this model - that a small companion star would be perturbed or unstable, and could not maintain that neat a periodicity for even 9 cycles |
|
the problem with at least the K/T noted: |
is that the geochemical anomalies indicate the bolide was not a comet, which would have a very different composition than meteorites |
|
Planet “X” |
a recent discovery (1999) suggests that there is some significantly massive[3X size of Jupiter] object beyond Pluto [~3 trillion miles]; it is dark, andmay be a tenth planet [“X”?], or could conceivably be a brown dwarf, orsmall, dark star [“Nemesis”?]; so far, it is known indirectly, by the way itperturbs the orbits of comets, for example |