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26 Cards in this Set
- Front
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What does it mean when we say trophic pyramids are inefficient? What are some implications of this fact? |
- <10% of energy is transferred from one trophic level to the next - Most of the energy is lost b/c it is released as heat - Implications: carnivores need to eat much more than herbivores to get their energy |
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What characteristics of mammals allow for chewing in mammals, and how do they do so? How do dinosaurs that chew do so differently from mammals? |
- Mammals are heterodont, which allows for them to have precise occlusion (bringing of opposing surfaces of the teeth of the two jaws into contact); OR mammals with hypsodonty (tall teeth), so it takes longer to grind down all of the teeth) - Dinosaurs are mostly homodont. In order to grind tough plant matter, herbivores have flat teeth with a lot of ridges. Also, they developed dental batteries (line of teeth that grow from the bottom up; conveyor belt of teeth) and cranial kinesis (lower teeth push upper teeth out). |
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What are the various adaptations in dinosaurs for eating plants? Why do they need special adaptations for eating plant material? |
- Sauropods have gastroliths (swallowed stones) to grind the plant material in their stomach - Thyreophorans and Cerotopsians developed gut fermentation (letting the plant material rot in their stomach) - They need special adaptations because plant matter is tough and cuticles on leaves are hard to break down |
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What are the benefits and costs of ectothermy & endothermy? |
Ectothermy (receives heat from external source) benefits - Adaptation to hot environments - Need little food Ectothermy costs - Capable of only short bursts of energy - Limited activity to be active at night Endothermy (generates heat) benefits - Sustained activity - Active at night - Adaptation to cold environments Endothermy costs - Requires lots of food - Not efficient at small body sizes |
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How does the surface area/volume ratio of animals relate to the way they retain heat? |
- Surface area is where the animal exchanges heat with the environment - Smaller animals have a higher surface area, lower volume; larger animals have lower surface area and higher volume - Small endotherms have a problem with retaining heat, while large endotherms have a problem with dumping excess heat |
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What are the various lines of evidence that can be used to infer the physiology of dinosaurs, and what does each of those lines of evidence tell us? |
Cardiopulmonary evidence: heart & lungs - Dinosaurs have a four-chambered heart - Dinosaurs have air sacs that allow for efficient breathing - The heart and lungs are unclear in showing whether dinosaurs were endotherms or ectotherms Insulation - Only modern endotherms have insulation (feather, fur) - Some dinosaurs may have had feathers Bone growth - Mammals and birds had determinate growth, while reptiles that indeterminate growth - Mammals have vascular bone structures - Lines of arrested growth (LAGs) are more common in ectotherms than endotherms; however, some mammals had LAGs too Growth rates - Mammals and birds tend to have a 3 part growth curve (slow growth as infants and toddlers, fast growth as juveniles and adolescents, slow growth as adults) - Ectotherms tend to have a relatively constant growth rate - Dinosaurs had a 3 part growth curve, especially the biggest ones; they grew faster than mammals and birds - Dinosaur growth rates were similar to endotherms Neurophysiology (relative brain size) - Encephalization Quotient -- Ratio of brain size to body size -- Endotherms had a high EQ because brains are expensive -- Dinosaurs show a range, with some similar to modern birds Isotopic evidence - Different isotopes are different in weight - Lighter isotopes are preferred in most chemical reactions - it's easier to move around - At higher temperatures, differences decrease - Extremities on the body will be colder in ectotherms - Dinosaurs show temperature differences comparable to mammals Skull features - Mammals and birds have unique structures called turbinates that make their breathing more efficient - Inhalation: relatively cool, dry air passes over moist, warm turbinates and is heated & saturated with water - Exhalation: warm, moist air passes over cooler, drier turbinates and transfers heat and moisture to their surface - Function of turbinates: -- Condition incoming air -- Conserve heat -- Conserve water - A recent study showed that dinosaurs did have turbinates Postural evidence - Like mammals, dinosaurs had feet directly under their body Biogeographic Evidence - Dinosaurs lived near the poles, while modern ectotherms did not -However, the Mesozoic was much warmer at the time -This shows that dinosaurs could not handle the cold (endotherm) |
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Why does the "Goldilocks Hypothesis" describe the physiology of dinosaurs as mesotherms? |
- Animals can invest their energy in two things -- Maintenance - - - Renewing cells - - - Generating heat - - - Food -- Production - - - Growth - - - Reproduction - - - Fat storage - Endotherm - 97% maintenance + 3% production (Being an endotherm is costly) - Ectotherm - 60% maintenance + 40% production - Dinosaurs are MESOTHERMS -- They had intermediate metabolic rates, but burned energy like ectotherms (i.e., relatively more into production) -- Used more energy for growth -- Remember, dinosaurs got bigger over time (Cope's Rule) and probably were gigantothermic -- Evolutionary arms race (Red Queen) -- Have a large energy pool, can be used for production (growth) |
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What are some unique characters of the skull in theropods? What about the limbs? |
Pneumatized brains - Lots of space in the head - Trend toward larger brains - Enhanced hearing and smell - Stereoscopic vision Bipedal - Obligate bipedality - Much longer hind limbs than forelimbs - Digitigrade - Reduction in digits I & V - Stiffened tails - 5 sacral vertebrae Forelimb characters - Loss/reduction of digits IV & V Some opposability of digit I Short limbs were still strong |
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What are the relationships of the various groups of theropods? What are some characters that define some of those groups? |
Herrarasaurids - South American - Mid-Late Triassic (230 Ma) - Possibly basal theropods - Possibly basal dinosaurs - Defined by lack of characters Coelophysids - Mainly small, North American & African forms - Triassic and Jurassic - ex) Coelophysis: most numerous dinosaur fossil Abelisaurs - Primarily Gondwanan - Mostly Cretaceous - Some have "headgear" - ex) Masiakasaurus knopfleri Ceratosaurs - Horned dinosaurs - Mainly Gondwanan - Mainly Cretaceous ex) Dilophosaurus Tetanurae - "Stiff-tail" - Further reduced digits (III, IV & V lost/reduced) - More pneumatized heads - Pubic foot: muscle attachment - Includes Allosaurids, Tyrannosaurs, Ornithomimosaurs, Therizinosaurs, Oviraptors, Deinonychisaurs Spinosaurs - Mainly Cretaceous - Large, but lightly built - Long snouts that look like alligators - Some have sail-backs (for fat or support) - Some piscivorous & semiaquatic - ex) Megalosaurus Allosaurids - Middle Jurassic to late Cretaceous - Laurasian - Some attain large sizes, but most are medium-sized Coelosaurs - Many convergent on earlier Allosaurs and Ceratosaurs - Characterized by: Arctometatarsals & Semilunate carpal - ex) Compsognathus: Late Jurassic of Europe, "turkey-sized," probably feathered - Includes Ornithomimosaurs, Therizinosaurs, Oviraptors, and Deinonychisaurs Tyrannosaurs - Late Crataceous of Asia and North America, possibly also Australia - Further digit loss (arm use?) - Robust skulls - ex) Dilong: feathered Tyrannosaur Ornithomimosaurs - Cretaceous of Laurasia (possibly also Gondwana) - Many become omnivorous & herbivorous - Some have bizarre osteological adaptations (e.g., duck-like beaks) - ex) Deinocheirus: largest ornithomimosaur, known originally only from arms Alvarezsaurids - Cretaceous of South and North America and Asia - Short, stout forelimbs, with reduced digits Maniraptors - Breast bones present in some - In some the pubis faces backwards like birds - Possibly primitively omnivorous - Evolve flight Therizinosaurs - Hyper-specialized forelimbs - Possibly analogous to giant ground sloths - Cretaceous Laurasian in distribution - ex) Falcarius Oviraptors - Late Cretaceous of Asia & North America - Misidentification of eggs gave them their name - Similar to ornithomimosaurs - Toothless jaws may have been used for crushing hard objects (e.g., clams) Deinonychisaurs - "Terrible claw" - Late Jurassic to Cretaceous - Some possibly arboreal - Some possibly omnivorous - Group that birds are derived from |
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How did the feeding style of small and large theropods differ? |
- Small theropods like the Allosaurus may have killed by repeatedly applying relatively weak slashing bites and backing off - Large theropods like Tyrannosaurids used more forceful crushing bites |
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What drove the size increase in large theropods, and how did it make them more prone to extinction? |
- If a dinosaur is carnivorous, and selection favors larger size, then energetic constraints will favor adaptations for taking large prey, and these specializations for hypercarnivory and large body size will result in reduced population densities, and vulnerability to extinction - Evolution of large size and dental specialization leads to a decline in evolutionary versatility (ability to adapt to new conditions) |
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What are the lines of evidence for Tyrannosaurus being either a scavenger or active predator? |
- Scavenger -- Relatively small eyes, enhanced smells, relatively slow speed, tiny forelimbs, piercing teeth - Predator -- Large absolute eyes, smell can be used to find the living as well as the dead, prey were slow too, some predators don't have useful arms either, teeth were similar to crocs, obligate scavengers need to be soaring vertebrates due to energetic costs
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What are various plant groups found in the Mesozoic and what are their characteristics? How does the change in plant communities relate to the change in dinosaur and insect communities? |
- Pteridophytes (vascular tissue & spores) -- Horsetails (spenophytes) --- develop "fruiting body" that releases spores --- need water to germinate --- modern taxa ("equisetum") are small --- Mesozoic taxa reached 30 ft tall -- Ferns --- Need water to germinate --- Tree ferns grew to immense sizes (although not as large today) --- Two stage life-cycle: sporophyte (gives off spores) & Gametophyte (a developing spore) - Gymnosperms (naked seed plants) -- Cycads --- aka "sego palms" --- Dioecious: male plants give off pollen, female plants have seeds --- Thick leaves to resist predation --- Much more diverse in Mesozoic -- Ginkgos --- One living species: "Ginkgo biloba" --- Dioecious --- First "woody" plants --- Stinky seeds that "reptiles" like -- Conifers --- Modern cedars, cypresses, first, junipers, pines, redwoods --- Mesozoic podocarps and "monkey puzzle trees": "lollipop" morphology, restricted to southern continents today --- Both monoecious (having male & female reproductive structures) & dioecious - Angiosperms (flowering plants) -- Flowering plants, first ones in the early Cretaceous -- Often with male and female reproductive parts in the same flower -- Seeds covered by a fruit -- Many are faster growing than gymnosperms - The rise of angiosperms and other plants coincides with the rise in insect pollinators and herbivores - Abundant food sources led to diversity in herbivores and insects |
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How is climate different from weather? How did climate differ in the Mesozoic compared to today? |
Weather: short-term changes in wind, pressure, temperature, cloud cover, precipitation, etc Climate: long-term average of weather that is more stable Climate today: world's major deserts are between the tropic of cancer and the tropic of capricorn Mesozoic Climate (Jurassic): Most of the plant and dino diversity was in the midlatitutes; equatorial regions more desert-like due to hothouse conditions and continental position |
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What are some modifications of the skull in sauropods? |
- Large nostrils (nares): move further posteriorly during their evolution - Teeth built for scraping, not chewing, plants - Plant digestion by fermentation and gastroliths - Two types of teeth -- Pencil (diplodocids) -- Thick leaf-like (brachiosaurs) -- Probably for puncturing not piercing
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Why did sauropods have long necks, and could they raise them above vertical? |
- From both elongation of cervical vertebrae and increase in number - Along elongate tails - Thermoregulatory? - Herbivory adaptation? - Blood pressure estimates - Probably moved side to side rather than up and down - Pneumatized vertebrae: lighten neck, air sac - Since they moved their necks side-to-side, they could cover more ground to get food |
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What are the postural adaptations in sauropods that relate to their weight? |
- Sauropods had quadrupedal posture - Graviportal posture (physically adapted only for moving slowly over land, due to a high body weight) - Graviportal digitigrade feet: they were on toes with a foot pad posteriorly (like an elephant) - Short hind limbs: longer forelimbs in some taxa - Shorter distal elements -- humerus > radius / ulna -- femur > tibia / fibula
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What are some differences between saurischians and ornithischians? |
Ornithiscia Novelties - "Bird" hips (reverse pubis) - possibly to make room for big stomachs - Leaf-shaped teeth - Lower jaw with predentary bone - Network of bony ligaments (called ossified tendons in lab) - Stiffen backbone
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What are osteoderms, and what is their purpose, and in which animals do we see them? |
- Osteoderm are connective tissue layers of skin - Purpose: defense, display, thermoregulation - Found in Thyreophorans and Marginocephalians, titanosaurs (sauropods), other diapsids, and edentate mammals |
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What is sexual selection and why does it occur? What evidence do we have for it in different dinosaur groups? |
- A mode of natural selection in which some individuals out-reproduce others of a population because they are better at securing mates - Horns and antlers of the dinosaurs, which may not have had any particular use for survival, are evidence for sexual selection |
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What may have driven the incredible diversity in ceratopsians? |
Species pump - Repeated rise and fall of interior seaway (in the US), could have fragmented populations, leading to speciation - This has been shown for modern animals and glacial advances |
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How do amniote groups exchange gametes and how did dinosaurs 'do it'? |
- Fertilization occurred internally (still have cloaca) -- Sperm stored in female after mating -- Eggs grow inside female in oviducts - Evidence of cloacal protuberances in theropods - Tripedal --> to do business |
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What are different strategies animals have in regards to the number of offspring they have? |
R-selection: lots of offspring, little parent invesment K-selection: few offspring & lots of parental investment |
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What evidence do we have for dinosaur nesting behavior? What about parental behavior? |
- Clutches have 2-30 eggs - Discovery of hadrosaur nests in upland areas -- Laid eggs in shallow depression and covered them with vegetation (evidence of same sites being used every year) -- Evidence of collective nesting for protection - Altricial: offspring need parental care (herbivores) - Precocial: offspring don't need parental care (carnivores) |
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What is the Colorado Plateau, and why is it important for dinosaur studies? |
- Centered on four corners: Utah, New Mexico, Colorado, Arizona - Geologically stable since the Mesozoic, upraised in the Cenozoic - Dramatic geology: drained by the CO river, arid climate - North America's best site for dinosaurs: includes Dinosaur NM & Cleveland-Lloyd Dino Quarry |
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What were dinosaur communities like in the Triassic? The Jurassic? The Cretaceous? Where can one see good records of these communities? |
Triassic - Small part of ecosystem - 3 waves of diversification -- Prosauropods (outer continent) -- Small theropods -- Ornithischians (S America) - Key adaptation for evolution and domination -- Upright walking -- Endothermy
Jurassic - "hot house" - arid grasslands - many riparian strips (thicker vegetation) - non-dinosaurs = frogs, turtles, lizards, coral reefs, sharks, plesiosaurs, fish & birds - herbivores: high browsers vs. low browsers - carnivores: small vs. large
Cretaceous - less fluctuation in climate: stable tropics/subtropics into high altitues - mainly tropical/subtropical - transgressions/regression of seaway - rise of angiosperms - variation in plant communities - changeover in species: "species pump" - rise of T. Rex: evolutionary ratchet - increase in the size of data |
