humans and the environ Flashcards
arch lec 1,2,3 (88 cards)
1
Q
discuss hunter gatherers
A
- we were HG for most of our existence on earth
- little impact on environ: adapted to environ
2
Q
when did humans start changing environ to suit needs?
A
Farming started 12 000 years ago
3
Q
what is the main thing that allows us to live anywhere on earth?
A
ability to alter the environment
4
Q
main categories of natural causes of climate change
A
catastrophic
regular
5
Q
examples of catastrophic natural events that changed climate
A
volcanic eruptions
meteorite impacts
6
Q
examples of regular natural events that changed climate
A
orbital variation
solar cycles
tectonic shifts
orogenesis
7
Q
explain how major eruptions alter the earth’s radiative balance
A
Volcanic aerosol clouds absorb terrestrial radiation, and scatter a significant amount of the incoming solar radiation.
8
Q
how do meteors trigger extinction level events?
A
- debris thrown into atmosphere: blocks sunlight from reaching surface
- almost all plant and animal life can become extinct
9
Q
what confirms the impact of meteorite with the earth’s surface?
A
a layer of Iridium rich sediment can be seen in the geologic record around the world
10
Q
what are Milankovitch cycles? (what arguments did Milankovitch make?)
A
- glacial and interglacial cycles were controlled by amount and distribution of radiation received from the sun
- see other card (different period of major glaciations were initiated by changes in Earth’s orbital parameters)
11
Q
what caused glacial and interglacial periods?
A
- eccentricity: 100 000 year cycle
- axial tilt(obliquity - 41 000 year cycle)
- precession (wobble) - 21 000 year cycle
12
Q
explain eccentricity
A
change in the shape of earth’s orbit around the sun
- changes from a thin ellipse to a circle and back again
13
Q
explain axial tilt(obliquity)
A
angle of the earth’s axial tilt
- shifts between 22.5 deg to 24.5 deg
- less of an angle than 23.5 deg = less seasonal difference between Northern and Southern hemispheres
14
Q
explain precession
A
a change in the orientation of the rotational axis of the earth
- in 12000 years Northern hemisphere will experience summer in Dec and winter in June
- occurs due to tidal forces generated by the gravitational attraction of the moon and the sun combined
15
Q
what are sunspots?
A
planet sized islands of magnetism on the surface of the sun, sources of solar flares, coronal mass ejections and intense UV rations
16
Q
what follows peaks of solar activity?
A
valleys of relative calm - clockwork pattern that has held true for more than 200 years
17
Q
explain quiet suns
A
come along about 11 years or so
18
Q
what was the single continent called?
A
pangea
19
Q
what caused different climates? oceans moving and changing
A
As continents changed position based on latitude, their individual climates would obviously change accordingly. The relative longitudinal positions of the continents also has an impact on global climate however. As Africa moved north into Europe, it forced ocean currents to divert around it, driving these warm bodies into the cooler polar regions
20
Q
what are sediment cores?
A
can be take from lakes, the shallow or deep ocean
21
Q
what can the thickness of the layers imply?
A
infer the length of depositional periods
layers are composed of organic material that can be analysized for other climate proxies
22
Q
what are varves?
A
sediments deposited annually on the bottoms of lakes that freeze in winter and thaw in summer. Winter varve: fine sediments; summer varve: coarse sediments.
23
Q
where does stratification occur?
A
Stratification occurs in deeper parts of lakes that do not support bottom-dwelling organisms that would obliterate annual layers with their activity
24
Q
what causes the layers in these varved lake sediments?
A
Layers usually result from seasonal alternation between light, mineral-rich debris and dark, organic rich material brought in by runoff – act as proxy of precipitation amount
25
What can be implied from the varve thickness?
length of freeze-free period – summer.
26
how are marine sediments typically studied?
-long cores are drilled by specially equipped ships
Dating only accurate to about 40,000 years ago and can resolve climate changes that occur on century scale or longer
27
what can isotopes in shells of foraminifera reveal?
temperature, salinity and ice volume
28
what does granular debris indicate
Granular debris from land can indicate icebergs breaking off of continental ice sheets, suggesting cold climates
29
how does pollen aid studying the past?
Scientists can infer past climates (warm or cold) based on the distribution and changes in plant species
-Palm-tree like fossil in Wyoming 45 Myrs ago indicating the Cretaceous warm climate
Climate can be inferred from leaf size and shape
30
how do coral reefs allow us to study the past?
Corals are composed of calcium carbonate.
This carbonate contains isotopes of oxygen that can be used to determine the water temperature when and where the corals grew.
Limited to tropical oceans.
31
how do ice-cores allow us to study the past?
As snow and ice accumulate in polar glaciers a paleoclimate record accumulates of the environmental conditions of the time of formation.
Ice cores can be analyzed using stable isotope approaches for water or air bubbles within the ice as a record of past atmospheric gas concentrations.
Dark and light areas – seasonality (exposed surface, dust and pollens )
32
how do tree rings let us study the past?
Tree growth is influenced by climate. These patterns can be seen in tree ring width and isotopic composition.
Trees generally produce one ring each year.
Tree ring records can extend back to the last 1000 years.
Lighter, thicker wood tissue formed by rapid growth in spring and much thinner, darker layers marking cessation of growth in autumn and winter
Limited to land areas outside of tropics – to areas with distinct seasons.
Variations of tree ring width and density act as recorders of year to year changes in temperature and rainfall
33
what are speleothems?
Mineral formations occurring in limestone caves (most commonly
stalagmites and stalactites, or slab-like deposits known as flowstones)
34
where are proxies for more ancient climates found?
in sediments or inferred from fossils and land forms
35
climate and landscape of the miocene
generally wet and hot
| encouraged the growth of trees and shrubs - forests dominated
36
climate and landscape of the Pliocene
generally colder and dryer
encourages grass growth
grasslands were dominant
37
what is the savannah hypothesis for evolution
```
bipedal
tool making
expanded diet
use of fire and new tools
=hunting = larger brain
complex social life
language
```
38
lec 3
| when was the olorgesailie period?
lec 3
670k -630k ago
39
what can tell us about the different times
sediment layers and volcanic ash
40
what are sapropels?
5 million year record of tropical african moisture and aridity
41
what strongly influeced tropical african climate
variation in solar insolation
42
what is the main cause of the variation?
the main variation is due to the interaction of orbital precession and eccentricity
43
what did this interaction (between interaction of orbital precession and eccentricity ) cause
alternating phases of high and low climate variability in tropical africa
44
what are the chained effects of climate change?
```
temp change=
changes in the cryosphere(ice) =
changes in rainfall =
changes in the amount of dust in the atmosphere =
changes in vegetation
```
45
what are three things that a species can do if the environ changes?
become extinct
move
become versatile
46
what is extinction?
process through which a species or higher taxonomic category ceases to exist
also defined as the disappearance of any evolutionary lineage because of the death or genetic modification of an individual
47
what is pseudoextinction?
where a parent species has changed such that a new (daughter) species is recognized,
48
a new species arises because pseudoextinction, what is this species called?
chronospecies.
49
what is the natural cause of extinction?
failing to adapt to environmental changes
50
where are many fossils found
sedimentary rocks
51
why are fossils a limited fraction of geological time?
sediment deposition is not continuous
| sedimentary rocks erode
52
The further back in time, the fewer the sedimentary deposits that are available. Why?
because of:
erosion
metamorphisis
53
what does fossil formation depend on?
durability of the specimen
burial speed and sediment
lack of oxygen
54
why do most organisms not form fossils?
- no hard skeletons
- are eaten
- occur where decay is rapid
- deposition doesnt occur
- did not live/die during a period of sedimentation
55
why is determining the age of fossils difficult?
- Radiometric methods cannot be used directly on fossils
| - Fossils deposited over a brief time interval are often mixed before the sediment becomes rock
56
for paleontology, what is a species?
morphologically identifiable form.
57
Why is it difficult to identify fossils?
nature of the fossils may hide diagnostic traits
Some living species cannot be morphologically separated by skeletal features so a single fossil “species” may consist of more than one biological species.
For some groups, living species can be differentiated by skeletal features so fossil species are probably also skeletally unique.
58
what is background extinction?
natural and normal extinction rate
constant within clades and vary between clades
59
what is a clade?
A group of organisms believed to evolve from a common ancestor, according to the principles of cladistics
60
What is an extinction event?
are relatively short (in terms of geological time) periods with greatly increased extinction rates.
61
what can be classified as a mass extinction event?
A mass extinction event must eliminate >60% of species in a relatively short period of geological time with widespread geographical and taxonomical impacts
62
why are mass extinctions important?
they have a disruptive effect on the way that biodiversity develops
63
principle subdivisions of geologic time are identified how?
are identified by distinctive fossils and major faunal breaks (extinction events) were used as the boundaries.
64
what causes mass extinction events?
- combination of factors
- asteroid strike that caused the end cretaceous K/T mass extinction:
- acid rain
- widespread fires
- climate cooling due to dust and smoke
- earthquakes
- volcanic activity
- tsunami
65
what is dispersal?
movement of organisms away from their homelands (birthplace)
66
when did homosapiens disperse?
during the last 100 000 years
67
In order to expand its range through dispersal, an organism must be able to:?
Reach a new area.
Survive the potentially harsh conditions occurring during the passage.
Survive and reproduce in the new area to the extent that a new population is established.
68
what are the three types of dispersal events?
jump dispersal
diffusion
secular migration
69
what is jump dispersal?
simply the rapid colonization of new areas over long distance.
70
example of jump dispersion?
the rapid recolonization of Krakatau after all life was wiped out by the volcanic explosion of 1883.
71
what does it mean: 'Long-distance dispersal likely has a selective component'
Certain organisms, possessing certain traits, are more likely to be successful
e.g things that can fly are more likely to inhibit islands
72
what does nonvolant mean?
(non-flying) mammals, amphibians, freshwater fish, and other forms are typically absent from island populations.
73
what is diffusion dispersion?
is the gradual spread of individuals outward from the margins of a species’ range.
It is a slower form of range expansion involving not just individuals, but populations.
74
what is secular migration?
occurs much more slowly. So slowly, in fact, that organisms can evolve during the process.
75
example of secular migration?
evolutionary divergence of the camel family during its spread across the world following its origins in North America.
76
example of diffusion dispersion#
An example is provided by the cattle egret, Bubuculus ibis
77
what do hostile environments constitute as
natural barriers of dispersion
| can be physical or even biological
78
what is the effectiveness of the barrier dependent on?
the nature of the barrier
| the organism dispersing
79
barriers are species specific
some zooplankton have resistant stages that help facilitate long distance dispersal - species are found in widely separated locations
fish lack such dispersal methods and as a result, similar fish species are only found in bodies of water that were once connected
80
what are physiological barriers to dispersal?
are created by environmental conditions in which organisms are unable to survive long enough for dispersal.
81
example of physiological barriers to dispersal?
The bird family Alcidae (auks, puffins, and murres) is restricted to cool areas of the Northern Hemisphere even though they are strong flyers. The tropics apparently represent a strong physiological barrier.
82
nature of barriers may change depending on the season
-large bodies of water are barriers during the summer warm months but they serve as bridges during the winter
the movement of terrestrial species is facilitated
83
what are the different dispersal routes?
Corridors.
Filters.
Sweepstakes routes.
84
what are corridor dispersal routes?
allow movement of most taxa from one region to another
don't selectively discriminate against one form but allow a balanced assemblage of plants and animals to cross them
the areas at the two ends of the corridor should contain a fairly similar assemblage of orgaisms
85
example of corridor dispersal
- The Bering Land Bridge which existed some 20,000 years ago
- which allowed organisms to pass from northern Eurasia to North
86
what is a filter dispersal route?
is a dispersal route that exercises some selection over the types of organisms that can pass through it.
As a result, the colonists are a somewhat biased subsets of those that could potentially pass.
87
example of filter dispersal route
The Arabian subcontinent acts as a filter in that only certain arid-adapted mammals, reptiles and ground birds can disperse between northern Africa and central Asia.
88
what are Sweepstakes Routes?
Sweepstakes dispersal refers to the crossing of barriers by rare, chance events e.g. rafting
from mainland to island or island to island.
Such events, while highly unlikely in the short term, are likely, even probable, over the long term.
