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EAS 250: Biogeography > Historical Biogeography > Flashcards

Historical Biogeography Flashcards

1
Q

T/F
The Quaternary has been a time of biogeographic upheaval

A

true
because earth has passed through repeated cycles of glaciation

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2
Q

What era, period, and epoch are we currently in?

A

era: Cenozoic
period: quaternary
epoch: Holocene
- present interglacial epoch, started 12,000 years ago

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3
Q

Our current quaternary period is broken down into 2 epochs. What are they? When did each begin?

A

Pleistocene
- began 2.5mya
- glacial

Holocene (current)
- began 12,000yrs ago
- interglacial

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4
Q

What are the 3 models of Change over Earth’s History

A
  1. Predictable rules govern climate change: directional change, stable climate
  2. Random, abrupt, catastrophic events cause climate change (eg. asteroid impacts)
  3. The climate alternates between alternate stable states (eg. glacial/interglacial periods)
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5
Q

List up to 8 drivers of change on earth

A
  • changing solar output
  • tectonic and volcanic activity
  • asteroid impacts
  • methane clathrate releases
  • orbital patterns (Milankovitch)
  • changing ocean circulation
  • changing sea levels
  • humans
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6
Q

During the Pleistocene epoch, what were the 6 main climate forcing factors?

A
  • Variation in the geometry of Earth’s orbit (Milankovitch)
  • Variation in solar insolation emitted by the sun
  • Plate tectonic processes: altered atmospheric and oceanic circulation and positions of continents
  • Atmospheric absorptivity/reflectivity: Impact of volcanos
  • Earth surface albedo (eg snow vs water vs soil vs vegetation)
  • Feedback effects and interactions
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7
Q

Which epoch does this describe:

Period of gradual cooling during the mid-Cenzoic, followed by period
of dramatic climatic reversals

A

Pleistocene

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8
Q

During the pleistocene cooling, what was the consequence for plants and animals?

A

Regional assemblages of plants and animals that had co-evolved
during the warmth of Paleogene and Neogene were subject to
disruption and displacement

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9
Q

Ice extent during the last glacial maximum occurred approx. _____-_____ years ago

A

26,500-19,000 years ago

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10
Q

During the LGM, there were expansive ice sheets across much of both hemispheres. Which ice sheets remain today?

A

only greenland and antarctica

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11
Q

During the LGM, the average air temperatures over land were __-__C _____(warmer/cooler) than during interglacial periods

A

4-8C cooler

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12
Q

During the LGM, the ocean surface temperatures were __-__C ____ (warmer/colder) thank during interglacial periods

A

2-3C colder

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13
Q

During the LGM, was it on average drier or wetter compared to interglacial?

A

drier during LGM

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14
Q

generally, climatic zones shifted toward ___ ______ during glacial periods

A

the equator

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15
Q

during interglacial periods, climatic zones generally shift ____

A

poleward

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16
Q

the presence of ice during glacial periods also creates micro_____. Give 2 examples of these

A

microclimates

  1. air masses descending ice sheets would undergo adiabatic warming; makes glacial winters less severe & glacial summers colder/ less prone to heat waves
  2. some areas were wetter: eg. south of North America’s glaciers –> prevailing westerlies brought moisture from oceans = more water in American southwest lakes
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17
Q

How does moisture level generally shift during glacial periods?

A

Reduced solar heating= reduced evaporative input of water into the atmosphere
regional to global aridification and expansion of deserts and other xeric ecosystems
ie DRIER

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18
Q

Pluvial Lakes=

A

Formation of large lakes due to low
evaporation and high precipitation rates (in certain areas), fueled by prevailing winds carrying moisture from the ocean

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19
Q

give 3 examples of pluvial lakes

A
  • remnants of one formed the great salt lake in utah
  • death valley was a pluvial lake basin! now desert
  • mojave desert (california)
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20
Q

In the deep past, were sea levels much higher or lower?

A

higher

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21
Q

Glacial/ interglacial periods can be interpreted from the ___ ____ at the time

A

sea level

lower sea level= glacial period because the water is locked up in ice sheets

higher sea level= interglacial

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22
Q

What are the 2 types of sea level changes? Define each

A
  • Isostatic sea level changes –rising or lowering of the land surface relative to sea level
    through movement of Earth’s crust
  • Eustatic sea level changes – alteration of the level of sea itself
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23
Q

eustatic changes lag ____ ____ and isostatic changes lag _____ changes

A

climate warming

eustatic changes

24
Q

give an example of isostatic rebound

A

hudson bay:
was covered in ice during last ice age
- ice started to melt, releasing lots of weight from the earth, so it started to rebound (post-glacial crustal rebound)
- hudson bay will be above sea level by the time it stops isostatically rebounding!

25
Q

biogeographic dynamics of Pleistocene biotas are triggered by 3 changes:

A
  1. Changes in the location, extent, and configuration of biota prime habitats
  2. Changes in the nature of climatic and environmental zones
  3. Formation and dissolution of dispersal routes
26
Q

Vegetation zones tended to shift toward the ____(or to ____ elevations) during glacial periods and toward the ___(or ____elevations) during inter-glacials

A

equator
lower

poles
higher

27
Q

During the LGM, there was _____ (south/north) expansion of boreal forest and tundra deep into the North American interior and along the Appalachians

A

southward

28
Q

T/F
Generally, tundra, boreal forest, scrub retreated during LGM at the expense of more closed canopies (deciduous forest, evergreen forest)

A

false
expanded , not retreated

it was at the expense of more closed canopies though

29
Q

in terms of elevational shifts in vegetation, what complicated the shifts in climatic zones/ biomes?

A

local micro-climates!

eg. SW America was cooler & wetter at LGM, and veg zones were displaced 500-1000m below present limits

30
Q

Explain the elevational shifts in the Andes following the LGM

A

the zones shift all together, but upper zones become narrower as they shifted to higher elevations in response to global warming

31
Q

Are changes in marine enviros more or less pronounced than in terrestrial enviros? Why?
Where were the most substantial shifts?

A

Less pronounced than terrestrial because of the high specific heat capacity of water
* More substantial shifts at mid-latitudes

32
Q

Pleistocene glaciation lowered sea levels by __-__m below their current level

A

100-135m

33
Q

Many terrestrial regions and associated biota that are now isolated by oceanic barriers were _____during LGM. Give 2 examples

A

connected (ie land/ ice bridges)

eg beringia (connected Siberia and Alaska)
eg british isles and europe were connected

34
Q

what happened to sea levels as the earth came out of the LGM?

A

they rapidly rose

marine waters spilled onto low-lying regions of the continents

35
Q

glacial periods allowed for _____ taxa to disperse across hemispheres. Why?

A

stenothermal
= organisms that can only tolerate a small range of temperatures
So, they were forced to disperse if they wanted to survive

36
Q

Mammals have been widespread across all major landmasses (except ____)until:

A

Antarctica
until pleistocene and early holocene

37
Q

T/F

Range shifts of mammals fit fairly simple predictions of southern/ northern movement with glaciation/ deglaciation

A

false

it’s much more complicated than just moving north or south

38
Q

Did communities migrate together? give examples

A

Yes!
eg. collared lemmings, eastern chipmunks, gophers, etc

39
Q

As a result of individualistic differences in the extent & direction of range shifts during the Holocene, species that co-occurred during the LGM often exhibit ____ ranges today

A

disjunct

40
Q

Refugia=

A

areas to which species
were displaced during glacial episodes, generally with the connotation that such refugia involved smaller, often subdivided ranges

41
Q

t/f

many species that were unable to disperse with their shifting habitats persisted and even diversified in these refugia

A

true!

42
Q

What are nunataks? What are they an example of?

A

=exposed portions of ridges, mountains, or peaks not covered with ice or snow within (or at the edge of) an ice field or glacier

example of refugia

43
Q

Megafaunal collapse occurred during the last stages of the
_____and/or during the early ______

A

Pleistocene
Holocene

44
Q

Extinctions of mammals in the late Pleistocene and early Holocene
were biased; targeted the _____mammals, sparing the ____size classes

A

largest
smaller

45
Q

Why were the largest vertebrates at a disadvantage under climate change (ie why were they targeted during Pleistocene extinctions?)

A

Hypothesized that fragmentation of once-expansive ecosystems required by these mega-herbivores and their predators are the cause

46
Q

T/F
1. Extinctions were not synchronous across the planet

  1. Extinctions occurred during a stage when climate change was especially severe
A
  1. true
    Megafaunal collapse occurred at different times on different
    continents
  2. false
    they did not necessarily
47
Q

During the Pleistocene extinction, most of the large vertebrates in ____ were spared but disappeared across all other landmasses. Why?

A

Africa

Possibly because of their co-evolution with our ancestors?

48
Q

When did humans disperse from Africa?

A

mostly during the Pleistocene

49
Q

Collapse of megafaunal assemblages was asynchronous across the planet but all began soon after the arrival of ____

A

humans

50
Q

In Africa, where ecologically significant humans first evolved, the native biota had an opportunity to ____ with humans

A

co-evolve

51
Q

Did the spread of humans lead to Pleistocene megafaunal
extinctions?

A

Extinction patterns are consistent with anthropogenic history of hominids across continents

52
Q

Extinctions were:

  • ______severe in regions where megafauna coevolved with hominids (Africa)
  • ______in regions whose megafauna experienced archaic homids before being colonized
    by humans
  • _____severe in regions where H. sapiens were the first to colonize the region and encountered the ecologically naïve biota
  • Megafaunal extinctions appear to be _____(related/unrelated) to climate change across continents
A
  • Least
  • Intermediate
  • Most
  • unrelated
53
Q
  • _____causes have emerged as a leading hypothesis for Pleistocene megafaunal extinctions
A

anthropogenic

54
Q

biologically, as humans, we are a product of the ____ and our civilization is a more recent product of the _____

A

Pleistocene
Holocene

55
Q

wherever humans have travelled, they have often been followed by a wave of ____ (particularly ___ ____)

Human impacts on the biosphere may be older than commonly thought

A

extinctions
large animals

56
Q
A

EAS 250: Biogeography (12 decks)

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