Terrestrialisation Flashcards
(72 cards)
1
Q
what were the problems animals to exploit or solve to become properly terrestrial
A
- Density: 1/1000 of water so need better support
- Viscosity: 1/50 of water so can move faster
- Gases: o2 availability 30x greater and the diffusion rate 300,000 x greater so much easier
- Stability: much lower in space and time so homeostasis tricky esp for thermal balance
- Food: tougher so harder to find and use
Salts: none so must be obtained by food
Water: much harder so water loss inevitable
2
Q
whats the timeline?
A
Cambrian, Ordovican, Silurian, Devonian, Carboniferous, Permian, Triassic, Jurassic and Cretaceous
3
Q
when are the mass extinction events?
A
251 mya and 65.5 mya
4
Q
when does the cambrian start?
A
540mya
5
Q
when does the devonian start?
A
410mya
6
Q
when does the permian start?
A
290mya
7
Q
when does the cretaceous start?
A
145mya
8
Q
when did life become terrestrial?
A
microbial mats way before paleozoic
9
Q
what is the early evidence for life becoming terrestrial?
A
alluvial deposits with signs of periodic dessication
signs of C13 depletion - palaeokarst
10
Q
first microfossils?
A
australia beckk spring deposits ~750mya
assumed to be aerially exposed and probs cyanobacterial mats
11
Q
when did we see the first evidence of animal life?
A
algal mats - Ordovician
first real evidence silurian
12
Q
when did we see the first footprints?
A
530 mya - millipedes
13
Q
how did carbon dioxide levels stabilise?
A
weathering of the land interacting with atmospheric carbon
14
Q
what were land masses doing?
A
Progressively joining up
From silurian on, to end Permian all the major continents were gradually joining up, ending in the super-continent Pangaea
15
Q
what were the effects of the land masses joining up?
A
- greatly reduced the amount of shallow seas
- Tended to give extreme continental climates on land, hot summers/cold winters, but little latitudinal variation within continents
- Reduced physical barriers to migration, so eventually uniform flora/fauna
- plate collisions also caused mountain formation (orogenesis), where the land rises and sea level drops - leaving local fringing swampy areas and more continental shelf in some places
16
Q
what were the first land plants?
A
algae and lichen, bryophytes
17
Q
examples of early plants
A
cooksonia like clubmoss - vascular system
pteridophyta
18
Q
example of type of pteridophyta
A
rhynia from chert rocks in aberdeen
19
Q
common species in carboniferous and permian?
A
clubmoss, tree shaped w/ stiff bark-like surface
glossopteris
the age of ferns
20
Q
why were the first land plants important?
A
created a terrestrial 3D ecospace with regulated temp and humidity so colonisable environment
21
Q
what did animals first need?
A
plant debris and humus for shelter/food
22
Q
when were trace fossils discovered?
A
late ordovican
23
Q
when was the oldest fossil found?
A
428mya pneuonudesmus found in stonehaven!!!! (a millipede)
centipedes appeared 10my later
24
Q
when was the oldest known land arachnid found and why was it significant?
A
360mya and a carnivore so we know that there were other inverts for it to feed on
25
when did we see the first tetrapod tracks on land?
395mya
26
what was found in 378mya?
the first fossil land vertebrate - fishy but dragged itself onto land
27
what were the first land vertebrates?
ichythostega
| labryinthodonts
28
what was special about labryinthodonts?
clearly land adapted could pull itself along on its belly but also adaptations for non-swimming locomotion - DV flexion
29
when were digits first discovered?
mid-devonian - 340mya
30
what was the evidence of diversifying to become more terrestrial?
fossils then show tetrapod bone damage due to falls, really only possible in a true land animal
31
when did groups radiate most intensively
carboniferous and permian
32
what happened with amphibian radiation?
gave rise to the earliest reptiles
33
when were reptiles favoured?
reptile diversity actually stayed low until permian, when the drier/harsher/more seasonal continental climates of Pangaea favoured them over amphibians
34
what happened with radiation of insects?
true insects also began diversifying hugely and taking off - first flying forms, roaches, bugs did best at first, most of the endopterygote groups (flies, bees, beetles etc) not around until permian
35
why is biomineralisation useful?
only those groups that have already really sorted out the making of hard parts but w/ retained mobility that are going to fully make it on land
- molluscs, arthropods, vertebrates
36
what is the massive raditation in permian linked to?
carboniferous O2 pulse
| oxygen in atmosphere rose above ~30%
37
what are the effects hyperoxia?
tetrapods diversified massively
became more armoured
loose ability to breathe through skin - more reliant on lungs
mammal-like-reptiles gave rise to cynodonts
38
what does hyperoxia explain?
gigantism in insects
| stronger insect flight as atmosphere denser
39
when was the permian extinction?
250mya
40
what happened in permian extinction?
On land very few whole groups vanished
- Glossopteris flora severely reduced
- Some ferns regressed to make room for conifers
- Labyrinthodont amphibians suffered
Early reptile anapsids replaced by the diapsid reptiles, eventually giving rise to dinos
two thirds of reptile and amphibian taxa and one third of insect taxa were wiped out
41
when is the mesozoic?
250mya
| triassic, jurassic, cretaceous
42
what is the key defining event of the mesozoic?
pangaea split into laurasia (N) and gondwanaland (S)
43
what were the plants in the triassic?
Dominant plant developments were Ginkgo (conifer relative) and cycads (tree ferns) and seed ferns
44
what happened to plants in triassic?
Early fern- like carboniferous flora largely died out; new herbaceous stuff radiated
Beginning to approach the reproductive complexity of 'true' angiosperm flowers
45
how did animal life change in triassic?
herbivory
| then gradually became omnivores and then radiated into specialist herbivores (hard cause couldn't digest)
46
two main vert groups?
synapsids (mammal-like-reptiles) ~320mya, one opening behind eye
diapsids (reptiles, bird fore-runners) ~305mya, two openings
47
what happened with animals in triassic?
reptiles diversified like mad
conifers appear - beetles take over
vertebrate endothermy
48
what does endothermy allow?
- Speed of movement and of response (CNS improves)
- Extended breeding season
Increased growth rate, shorter gestation and higher reproductive rate
49
stages of endothermy
A. Increased basal metabolic rate in larger passive homeotherms enhancing embryo development and parental care (big dinos constantly war, due to size and low SA/V ratio)
B. bodies get smaller in late Triassic, insulating fur/feather became necessary, thermoregulatory control improved, brains bigger
Pulses of enhanced endothermy occured in Cretaceous, linked to flapping flight, cursorial running, and climate-related adaptations (some abandoned endothermy full time in favour of torpor/hibernation)
50
plants in the jurassic?
gymnosperms dominant
vegetation diversifies and so reptilian grazers more abundant and large with huge guts to cope with indigestable plant material
51
animals in the jurassic?
archosaur 'dinos' took over from earlier forms of reptiles
| mammals split from mammal-like-reptiles ~210mya
52
examples of early mammals?
- 225mya adelobasileus - very mammal-like therapsid, rat-like probs common ancestor
- 160mya multituberculates - extinct, still, still rodents-like mammals, common alongside dinos
115mya first monotremes
Vertebrates began to fly, pterodactylids from about 163mya using 3d architectural landscape created by larger plants
Archaeopteryx getting to be ~proper bird about 155mya
53
when did we get first insects?
- First lepidopteran 190mya
- First blood-sucking flies about 155mya
First bees ~100mya
54
what happened in the lower cretaceous?
true flowering plants (angiosperms) appeared and radiated rapidly
first clear pollen deposits 110mya
land masses broke up into 6 continents - more equable maritime climatic effects
KT extinction
55
what is the best theory for the KT extinction event?
Yucatan meteorite
56
what were the consequences of the KT extinction event?
~15% of marine families went under
insect fauna present
all tetrapods >10kg died out as did all big marine reptiles. I.e we lost the dinos (except birds)
indigestion due to flora changes, chilling due to meteorite collisions, overheating due to solar flares, acid rain
Mammals were left as the small generalist land fauna from which to rebuild in the cenozoic
57
when is the cenozoic?
65mya - now
58
what were land masses doing in the cenozoic?
India still coming north to hit asia
Australia finally split off from rest of southern continent
Major continents moving further apart, with all the land masses also gradually moving to poles
Great deal of orogeny (mountain making) esp himalayas
Just a bit later there was major volcanic activity going on resulting in ethiopian flood basalts (massive lava flows) and coinciding with a major drop in sea level
59
what changed in the tertiary period?
General terrestrial cooling from sub-tropical to temperate on most land masses; first time in history of visible life that most of the land ceased to be tropical
Artic ice first formed in late tertiary about 6-7mya, first actual ice age set in about 3.6mya
North and south america joined up ~4mya causing the 'great american interchange'
60
what did the 'great american interchange' result in?
Original gondwana marsupials had ot mix and compete with northern, rodents etc invaded southwards and radiated into new forms
61
what was the habitat like in tertiary?
Plant life mainly of trees - dominated in north planes, redwoods, and in south by nothofagus
C4 plants arrived in late miocene (10mya) taking advantage of lower co2
First apperance of zygomorphic flowers (=complex, bilateral) suggesting first incidents of closely co-evolved evolved pollination
Grasses abundant, grassland replacing forest leading to a new grassland fauna - rodents, raptors and the various large flightless birds
By late miocene, the overall distribution of forest and grassland was much like today
With the changing flora, major rise of diversity at species level of both birds and mammals was underway; there were particularly large forms of both again in Eocene perhaps due to advantages of large-bodied endothermy in these cooler periods
62
what happened in the Quaternary period?
ice ages, creating land bridges intermittently and radically altering sea levels
Only major extinctions seem to have been of some unusually large mammals - mammoths, giant sloths
63
when was the last great ice fluctuation?
~10,000 years ago ~400 human generations
64
what is the major animal response to climate change?
continuous migrations i.e clear patterns, repeated, of fauna (and flora) being pushed south and then drawn north again as climate changed
65
when was the holocene?
10,000 years ago - now
66
what happened in the holocene
Real start modern climate patterns
67
what is the consensus on global temps?
Natural influences on climate and environment much clearer with new techniques, particularly from ice core studies - on the whole global temperatures turn out to have been pretty stable until very recently
Where moderate fluctuations have been recorded in the holocene ice cores, they have turned out to be related to volcanic activity
68
why is volcanic activity so important?
perhaps the single most important natural 'short-term' influence on climate and thus on vegetation and on animals
69
what's man influence on the holocene?
The holocene has been just the latest of several inter-glacial periods, but very atypical bc so dominated by human activity
Humans appeared about 3mya soon after this they were using stone tools
By about 1.4mya they were using fire - first big impact on environment - from then we can date the start of human-induced deforestation and various forest-animal extinctions
Weapons appear about 28,000 BP - almost certain humans played part in extinction of larger food-providing fauna between then and end of Pleistocene
The nile valley was intensively under cultivation by 15000 BP with herding of domesticated animals not too long after that
Anthropologists now reckon most of current tropical savannas are not a natural biota at all, but created by mans influence - fire and grazing, removing tree cover
Then development of human metal-based cultures
- Copper and bronze by 5500 BP
- Iron around 3500 BP
Allowed development of metal tools, increased speed of change and true building; creation of new ecospaces in human buildings etc which many species have come to inhabit alongside man, coevolving with us, and some thereby earning the status of 'pests'
70
what happened in the neolithic?
Evidence of agriculture and plenty pottery remains
First large stone structures in Europe 4500BP; highly organised communal efforts - under the stones, pollen spectrum is very much as at present - so the major changes had already occured
Iron age celts - 2300MP developed iron ploughs
Removing trees and ploughing accelerated leaching and helped turn natural red-brown ferric soils to bluish ferrous ones - also caused iron pan layer beneath the ploughing level - impermeable so some waterlogging occured above giving rise to peat bogs
so in eurasia, man was gradually turning some of the mixed oak forest into rather useless bog. Woodland animals, especially the larger ones, all declined quite severely
71
whats happened in the last half millenium?
```
Industrialisation - only then do we start to register the effects that we now worry about as 'man's influence on the environment'
- Chemical pollution
- Soil degradation
- Using up fossil energy
Biota and climate modification
```
72
overall consensus on mans impact?
humans have been changing things ever since we came into existence as organised communal animals; massively affecting terrestrial animal diversity, even when we are not explicitly destroying their habitats or hunting them
