invansion of land 4-2

Question 1

what are living fossils?

Answer 1

• Living fossil = organism that has gone very few morphological changes through geological time
Devonian vs present day = tremendous characteristic similarities

Question 2

ex of living fossils: describe horse shoe crabs.

Answer 2

• Four species
• ‘ Limulus polyphemus: North America
○ Sexual maturity @ 9-12 years
○ Breeding during spring & summer full moons; nests in sand
○ IUCN: nearly threatened; used as bait
• Tachypleus tridentatus: Malaysia; W. Indonesia; East coast
of China
• Tachypleus gigas: Bay of Bengal, India; Indonesia to N.
Australia
• ‘ Carcinoscorpius rotundicaudata: Thailand; Vietnam to SE
Indonesia

Question 3

why are horseshoe crabs at risk?

Answer 3

• All species at risk from over-fishing, pollution and the loss
of breeding grounds
Group of organism gone through hardly any change - went through multiple extinction events and survived- but may not survive now due to human intervention

Question 4

why do living fossils exist? are they genetically less variable?

Answer 4

• Stabilizing selection
○ Relatively isolated and stable habitats
○ Low competition
○ No pressure to change
• Are living fossils genetically less variable?
○ No evidence
Protein polymorphism is not noticeably low

Question 5

invasion of land for plants timeline

Answer 5

• Late ordovician or early silurian: first terrestrial plants (liverwort like)
Silurian: small vascular plants
devonian: true liverworts, horsetails, ferns, first seed plants

Question 6

invasion of lands for animals timeline:

Answer 6

Devonian: first terrestrial 
arthropods (scorpions, 
millipedes, centipedes, 
wingless insects)
	• Insects and other 
	arthropods lead the 
	way in diversity on 
	land both in time and 
	in numbers of taxa 
	• Tetrapod vertebrates 
	originate in the Late 
	Devonian and radiate 
	significantly in the 
	Carboniferous 
	(Mississippian and 
Pennsylvanian) 
-devonian remarkable for invasion of land

Question 7

quick review of origin of tetrapods: stem sarcoptrygian fishes to early tetrapods

Answer 7

changes in wrist and elbow w time

oldest to newest: Eusthenopteron, panderichthys, tiktaalik, acanthostega, ichthyostega

Question 8

radiation of amniotas: how did they first appear?

Answer 8

• Vertebrates w extra embryonic membrane
  
  • Appeared first in carboniferous
  • Early division into synapsids (gave rise to mammals) and reptiles (2-3 temporal openings, or none?)

Question 9

what did reptiles give rise to

Answer 9

'Reptiles' gave rise to diapsids, 
including: 
crocodiles 
pterosaurs (flying reptiles) 
dinosaurs (leading to birds) 
plesiosaurs and related marine 
reptiles 
lepidosaurs (tuatara, snakes, 
lizards, mosasaurs)

Question 10

when were dinosaurs discovered?

Answer 10

• Dinosaur proposed by richard owen in 1841
• Dinos = fearfully great, saur = lizard
• First dino discovered by 19th century william bucklet - 1819, named Megalosaurus in 1824
By darwins time, quite a few dinos discovered

Question 11

two main groups of dinos. difference between them?

Answer 11

• Two main groups - ornithoschia (bird hipped), saurischia (lizard hipped) - based on pubis - in 1 it faces forward, in 2 it points towards tail
• Saurischian - theropod and sauropod - birds came from theropods
ornithischia - more derived, more diversity than saurischian

Question 12

groups of suarischia

Answer 12

sauropods, theropods, birds

Question 13

types ornithischia

Answer 13

armoured, duckbilled, dome headed, horned

Question 14

look at diagrams of lizard hipped vs bird hipped

Answer 14

ok
• Pubis and ischium at 90 degrees vs almost parallel
Bird hip now looks like ornithschia

Question 15

are the dino hip differences major?

Answer 15

• Neither is better than the other - just alternative solutions to moving hind limb
Tremendous radiation

Question 16

when did marsupials and placental mammals branch out? why did they survive past dinos? fossil record?

Answer 16

• Timing of branching based upon DNA sequence divergence and paleo-data
•
• Data indivates most orders diverged during cretaceous
○ Approx 19 vs 10 clades
○ Able to survive past dinos bc low metabolism
But- very low fossil record prior to K-T (or k-Pg) boundary

Question 17

what are whales closely related based on DNA

Answer 17

hippos and cows (rather than pigs and camels)

Question 18

what are primates closely related based on DNA

Answer 18

flying lemurs (dermopterans) 
structurally one of the most primitive orders

Question 19

Successions: major changes in dominant taxa

Answer 19

Examples:
e
Replacement of brachiopods by bivalves
Increase in global diversity since the Jurassic
Replacement of ‘gymnosperms’ by angiosperms in the Cretaceous
Replacement of ‘reptiles’ by mammals and birds in the Cenozoic
Invasion of northern species into South America in the Miocene
Invasion of Asian species into North America several times

Question 20

Successions: major changes in dominant taxa - possible explanations

Answer 20

Possible explanations:
Competitive advantage of superior life forms
Extinction events open new opportunities for ‘survivors’
Spread of new adaptations opens new niches for other taxa
Fragmentation of continents and ocean basins yield new opportunities
Joining of continents by tectonic events allows invasions, causes extinctions
Pleistocene lowering of sea levels allows invasions

Question 21

branchopods vs bivalves

Answer 21

effect of the end of palezoic extinction - bivalves replaced branchopods thru permotriassic mass extinction (post paleozoic)
they were on the rise + decline before hand

Question 22

change of diversity after paleozoic

Answer 22

paleozoic had a diversity plateau

post paelozoic = increase - one possible explanation: fragmentation of the contients and ocesn basins

Question 23

change in plant diversity

Answer 23

since early cretaceous
replacement of gymnosperms by angiosperms
later, spread of grasslands at expense of ferns and shrubs (ca. 50 mya)

Question 24

WHAT is biodiversification

Answer 24

Biodiversification
z Process by which diversity of organisms develops or is increased within a particular
region or a group

Question 25

cambrian explosion vs GOBE

Answer 25

Cambrian Explosion
n Diverse & complex marine life suddenly “exploded” over a relatively short span of
geological time
-Dwarfed by the Great Ordovician Biodiversification Event (GOBE)
n Family-level diversity tripled over a period of —25 MY

Question 26

read article on ordovician biodiversification

Answer 26

ok