History Of Life- Exam 2

What key innovations first appeared with placoderms and then sharks?
jaws, pelvic fins, and paired nostrils. Sharks had teeth and an advanced jaw.
Ray-finned vs. lobe-finned bony fish (be able to tell them apart in a figure)
Ray-finned: rays of bones near the body
Lobe-finned: large bones extended away from body
Costs and benefits of life on land for vertebrates
Costs: must avoid drying out during respiration, locomotion difficult without support of water, gametes must be dispersed through air. Benefits: reduced competition and new energy sources, avoidance of aquatic predators.
What key body systems had to change in vertebrates during the transition from
aquatic to terrestrial life?
gills to lungs, fins to limbs with digits, pectoral girdle/pelvic girdle/vetebral column/ribs for gravity.
Which group of “fish” are most closely related to tetrapods?
lungfish are closest living relative to all tetrapods.
Acanthostega and Ichthyostega are two of the most primitive known tetrapods.
What kind of environments did they live in? How do we know?
acanthostega lived in water because they had broad, flat fish-like tail, vertebrae that didn’t interlock, and small short ribs. ichthyostega lived on land because they had a more rigid spinal column and ribs were more robust and curved around underside of body.
What hypotheses have been offered for the invasion of land by tetrapods
1 terrestrial locomotion and air-breathing evolved to allow fish to survive desiccation of rivers and ponds during dry season 2 limbs and lungs evolved to navigate through tangled weeds in rivers and swamps with low oxygen levels, mainly for predator avoidance 3 terrestrial adaptations evolved so that ocean-dwelling fish could venture onto intertidal flats to scavenge food
Seven Things most living vertebrates have
All living vertebrates have:
Backbone: Structural support on our dorsal, or top side.
Spinal cord: A hollow nerve tube, runs on top or through #1.
Heads: Brains and sense organs at the front end.
Tails: Nerve tube & back support extends past anus.
Hearts: Closed circulatory system, muscular pump to move fluid.
“Gill” Slits: Openings in pharnyx connecting throat to exterior.
Segmented muscle on body wall: V-shaped muscle masses.
The Invasion of Land: Plants and Insects
What problems had to be solved by plants to live on land?
poor mineral nutrition, unstable landscape, unstable rainfall, & high UV
What did plants evolve in order to cope with the initial challenges of living on land? Name 4
cuticle: waxy covering on plants
xylem: (dead cells) that transports water from roots to leaves
phloem: (live cells) to transport nutrients leaves to rest of the plant.
stomata: a regulator of gas exchange
rhizomes: horizontal stem of plants
wood: allowed growth to great heights (5 to 10 m)
leaves: broad areas for collecting light
roots: tap nutrients from soils
seeds: More protection for gametes because they have a hard shell. A nutrient supply that allows the plant embryo to survive for months. This enabled plants to colonize upland regions, away from water sources.
What is the amniotic egg
allows early amniotes & their descendents to lay eggs on land & away from water
What are the three basic types of skull structure that we use to discriminate among amniotes? Be able to tell them apart in a picture
anapsid: no holes
synapsid: one pair of holes
diapsid: two pairs of holes
Know the two general “ways” to be an herbivore. Which style fits pelycosaurs and therapsids?
Small and picky: Narrow snouts & Small guts
Big and indiscriminant: Broad snouts/big mouth & Huge guts
Where did pelycosaurs live?
tropical and subtropical distribution
How do therapsids differ from pelycosaurs?
Bigger temporal openning in Therapsids
Where did therapsids live?
worldwide distribution, extended to high southern latitudes
How do therapsid dominated communities of the late Permian differ from pelycosaur-dominated communities of the early Permian?
Mostly carnivores to herbivores
How do mass extinctions differ from background extinction?
background extinction is when species go extinct naturally.
mass extinctions: large numbers of species go extinct in a short amount of time
When were the 5 big mass extinctions?
? Ordovician/Silurian, Devonian/Carboniferous, Permian/Triassic, Triassic/Jurassic, and Cretaceous/Tertiary.
At the end Paleozoic, what types of organisms were dominant in marine communities?
Well developed tiering, most animals lived on the seafloor (epifaunal), suspension-feeding animals (brachiopods, bryozoans, crinoids), Permian reefs constructed of mostly sponges (not corals).
What is tiering?
Levels. (There are tall plants and small bushes.)
What types of marine animals, and what modes of life, were most severely impacted by the end Permian extinction? What modes of life and types of organisms did better?
Most Marine fauna extinct, brachiopods, bryozoans, and crinoids, peat forming plants/

bivalves and snails became dominant organisms in oceans, groups with more active physiology were more likely to survive

What are the two main hypotheses for the end Permian extinction?
– Extraterrestrial: 1. Asteroid impact would throw a lot of dust into the atmosphere,
blocking sunlight (“impact winter”) 2. Diminished sunlight reduced photosynthesis
3. Extinction of phytoplankton would spread up food chain
– Toxic ocean chemistry:
What role do the Siberian Trap volcanoes, ocean acidification and oceanic dead zones play in the end Permian extinction?
?  – siberian traps volcanism emitted huge volumes of co2, causing ocean acidification as the co2 dissolved in ocean waters
– global warming would slow ocean circulation, leading to anoxia
– Enhanced terrestrial runoff transported nutrients to coastline, creating expanded
oxygen minimum zone
What are the 7 major ecological trends in the diapsid radiation?
Marine predators, semi-aquatic predators, small terrestrial predators, terrestrial legless predators, large herbivores, large terrestrial predators, winged predators
What is Carrier’s Constraint?
: side to side flexure in reptiles prevents simultaneous walking and breathing. It can be solved by having an upright posture.
Know shared derived traits linking dinosaurs. (5)
three or more sacral vertebrae, perforate (open) hip socket, weight on middle toe, walk on toes, ankle fused to lower leg
What extinct genus is the next of kin of dinosaurs?
Lagosuchus is a genus of small archosaur that are the next of kin of the dinosaurs.
When did dinosaurs first appear (in years)? Where is their likely continent of
220-232 Ma in South America ??