Lecture 16

Question 1

When were the mass extinctions?

Answer 1

1. Late Ordovician mass extinction
2. Late Devonian ME
3. Late Permian ME
4. Late Triassic ME
5. End-Cretaceous

Question 2

What caused the previous mass extinctions?

Answer 2

Catastrophic environmental changes

Question 3

Which mass extinction was the biggest and how many families disappeared?

Answer 3

The late Permian ME was the biggest one- 60% of families disappeared

Question 4

What was thought to have caused the late Ordovician mass extinction?

Answer 4

The climate was warm and there was a decline in ocean circulation so you have anoxic deep water and then around about this time there was continental movement near the South Pole and it was thought that this caused cooling and glaciation and sea level decline- serious physical changes in the global environment, massive temp drop.
Some people have suggested a meteorite/ extra-terrestrial impact. Shown there were sea level changes and anoxic waters, climate change and global cooling around this period

Question 5

What percentage of marine and land animals disappeared in the Permian mass extinction? What do they caused it?

Answer 5

95% of marine species
70% of land species
Sea level change (rise), anoxic oceans, climate change

Question 6

What do they think caused the Triassic mass extinction/ Cretaceous-Paleogene (K-Pg) extinction (formally known as the Cretaceous-Tertiary (K/T) boundary)? What percentage of species went extinct? What was the result of this extinction?

Answer 6

Possibly extra-terrestrial impact or volcanism m- volcanoes admitting ash and causing acid rain, anoxic oceans. 75% of species went extinct.
Mammals replaced dinosaurs (freed up niches). Flowering plants diversified after this period and insects co-evolved

(Dinosaurs, dominant since late Triassic (200mya), disappeared)

Question 7

How do we know/ think there was an extra-terrestrial impact at the K/T boundary?

Answer 7

. 1980 Alvarez analysed elements in thin layer of clay at K/T boundary in Italy
. Dark rock- iridium spike- typical of meteorites- large asteroid impact
. Approx 1000 X greater than Krakatoa eruption
. Iridium spikes from >100 sites world wide
. Crater in Yucatan (off the coast of Mexico l), 180km wide- asteroid ~10 diameter

Question 8

Give some examples of extra-terrestrial impacts in human history

Answer 8

. Tungusta, Siberia 1908 (no crater, largest meteorite strike in human history, caused by shock when asteroid broke up in the atmosphere, 800 square miles of flattened trees)
. Gubbio, Italy 1980

Question 9

What happened when the asteroid at the K/T boundary hit Earth?

Answer 9

. 1000-4000km3 rock thrown into air
. Fireball ignited forest over huge area releasing CO2,SO2, NOX (nitrogen compounds)
. Smoke and dust reduced light
. Gases and dust changed climate rapidly
. Pollen flora changes abruptly- fern spores more numerous (fern could tolerate the changes whereas other species could not

Question 10

What did well and what did badly at the K/T boundary?

Answer 10

. Mammals, birds and insects did well after the K-T boundary
. Reptiles, gastropods (snails etc.) and cephalopods (squids) did badly

Question 11

What evidence is there to suggest that the Pleistocene mammal extinctions were brought about by environmental deterioration?

Answer 11

. Retreat of glaciers-conditions changed rapidly- disrupt feeding and reproduction- migratory corridors lost (physical change in the environment)
. Habitat changed from forests and swamps to large areas of more uniform drier vegetation- changed physical structure of the environment
. Antlers recovered-small- suggests malnutrition

Question 12

What are the ideas for what caused the Pleistocene mammal extinction?

Answer 12

1. Environmental deterioration

2. Human overkill (Martin’s hypothesis)

Question 13

What is Beringia?

Answer 13

A land bridge that appeared 24,000 years ago.
The sea level dropped and revealed a land bridge so animals could migrate across it, think humans migrated into North America about 20,000 years ago.
Mostly 50m deep between N America and Russia. So, doesn’t take much of a sea level drop to reveal it

Question 14

What is the evidence for human overkill causing the Pleistocene mammal extinctions?

Answer 14

Suggested >35 genera of large mammals in N America extinct from hunting- timing of mans arrival in N America via Beringia

Question 15

What is the evidence that humans were not responsible for the Pleistocene mammal extinctions?

Answer 15

. Similar extinctions in large and small birds- difficult to hunt, humans don’t really hunt them
. Little archaeological evidence
. Humans had invaded America in previous inter-glacial
. Dispute about marks on fossils
. Marks on the bones- butchery or trampling? (Can’t be sure)
. Extinction of woolly mammoths, woolly rhino, giant Elk in Europe, but spread over longer period then N America extinctions
. Large mammals- ‘key stone’ species?

Question 16

Give an example of biological (competitive exclusion)- competitive co-evolution and explain how it related to extinctions

Answer 16

Predatory mite and mite- in the experiment the predatory mite eats the other mite and it drives it to extinction and then it becomes extinct itself but if you increase the complexity of the environment then they co-exist so could be that in relations to mass extinctions- the environment/ ecosystem is simpler and so they begin to drive themselves to extinction

Question 17

Give examples of whether volcanism has affected the climate on a regional or world scale

Answer 17

. Santorini 1470 BC- wipes out Minoans in Crete
. Tambora Java 1815- severe winters in Eastern USA, no summer in Europe in 1816
. Krakatoa 1883- global climate cooled by 1 degrees for several years
. Eruptions at K/T boundary (increased volcanic activity)

Question 18

What is the evidence that the Permian mass extinctions (250mya) were caused by volcanic activity?

Answer 18

Heating of organic rich sediments (geology of Siberia- heating of sediments- indicating volcanic activity) Releasing methyl chlorides- damage O3 layer- UVB- mutated pollen grains suggests increased UV light. (Usually would be a bunch of things coming together at once)

Question 19

What are the two patterns of changes in diversity with time?

Answer 19

1. General increase in diversity over time, usually with periods of much lower numbers (e.g. marine animal families) or,
2. An increase, usually with periods of decline, then a continued decline or extinction (e.g. dinosaurs)

Question 20

How many years ago was it when the continents, that were apart, joined to make Pangea?

Answer 20

220 million years ago

Question 21

Describe Pangea (it’s make up, what species were there are that time)

Answer 21

. N part- Laurasia (N America, Eurasia) 
. S part- Gondwanaland (S America, Africa, India, Antarctica, Australia)
. Dinosaurs dominant vertebrates 
. Mammals had appeared- radiated freely 
. No flowering plants

Question 22

How did they know about plate tectonics (continental drift) and that certain places had been joined in the past?

Answer 22

As the Earth was mapped:
. Continents seemed to fit like a jigsaw, as if once joined
. Similarities in geology of edges of continents (e.g. parts of Africa and S America)
. Similarities in fossil fauna/ flora between continents
. Key factor determining major, long-term changes in species distribution

Question 23

Explain how plate tectonics work. What does plate tectonics lead to/ influence?

Answer 23

. Current in molten core- lava ridges on earth surface- form new ocean floor
. Lava comes up and push earth’s plates outwards
. Plates push against land mass- buckling- Mountains form
. Upwelling of lava- splits continents apart
. Major influence on migration/ dispersal and biodiversity
. When you have a single land mass then animals can disperse freely but when split up it prevents migration and has a massive impact on diversity

Question 24

Describe the land masses in the late Permian (250mya) include organisms

Answer 24

. Coal swamps replaced by deserts (moved N), extended mountain ranges in N Africa, E US blocked moist winds from E ocean
. Land vertebrates in Euramerica (Carboniferous) slow migration hindered by mountains as S deserts
. Land vertebrates in Gondwana only after loss of polar ice cap. Reached Siberia and China only after land masses joined

Question 25

When was the break up of Pangea? What consequences did it for biodiversity since?

Answer 25

. Migration (has big implications on biodiversity) routes destroyed e.g. today some taxa limited to what was Laurasia or Gondwanaland
. Some regions acted as filters- taxa isolated
. New mountains, ocean, land barriers deflect atmospheric and oceanic circulations this contributed to global climate change, which in turn altered biodiversity