invansion of land 4-2 Flashcards
what are living fossils?
• Living fossil = organism that has gone very few morphological changes through geological time
Devonian vs present day = tremendous characteristic similarities
ex of living fossils: describe horse shoe crabs.
• 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
why are horseshoe crabs at risk?
• 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
why do living fossils exist? are they genetically less variable?
• 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
invasion of land for plants timeline
• Late ordovician or early silurian: first terrestrial plants (liverwort like)
Silurian: small vascular plants
devonian: true liverworts, horsetails, ferns, first seed plants
invasion of lands for animals timeline:
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
quick review of origin of tetrapods: stem sarcoptrygian fishes to early tetrapods
changes in wrist and elbow w time
oldest to newest: Eusthenopteron, panderichthys, tiktaalik, acanthostega, ichthyostega
radiation of amniotas: how did they first appear?
- 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?)
what did reptiles give rise to
'Reptiles' gave rise to diapsids, including: crocodiles pterosaurs (flying reptiles) dinosaurs (leading to birds) plesiosaurs and related marine reptiles lepidosaurs (tuatara, snakes, lizards, mosasaurs)
when were dinosaurs discovered?
• 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
two main groups of dinos. difference between them?
• 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
groups of suarischia
sauropods, theropods, birds
types ornithischia
armoured, duckbilled, dome headed, horned
look at diagrams of lizard hipped vs bird hipped
ok
• Pubis and ischium at 90 degrees vs almost parallel
Bird hip now looks like ornithschia
are the dino hip differences major?
• Neither is better than the other - just alternative solutions to moving hind limb
Tremendous radiation
when did marsupials and placental mammals branch out? why did they survive past dinos? fossil record?
• 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
what are whales closely related based on DNA
hippos and cows (rather than pigs and camels)
what are primates closely related based on DNA
flying lemurs (dermopterans) structurally one of the most primitive orders
Successions: major changes in dominant taxa
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
Successions: major changes in dominant taxa - possible explanations
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
branchopods vs bivalves
effect of the end of palezoic extinction - bivalves replaced branchopods thru permotriassic mass extinction (post paleozoic)
they were on the rise + decline before hand
change of diversity after paleozoic
paleozoic had a diversity plateau
post paelozoic = increase - one possible explanation: fragmentation of the contients and ocesn basins
change in plant diversity
since early cretaceous
replacement of gymnosperms by angiosperms
later, spread of grasslands at expense of ferns and shrubs (ca. 50 mya)
WHAT is biodiversification
Biodiversification
z Process by which diversity of organisms develops or is increased within a particular
region or a group
