GEOS exam 3

Only one supercontinent existed in the past

False

Which of the following taxa was the most dominant flora during the age of dinosaurs?

Gymnosperms

What is the biggest extinction threat to living species today?

Habitat loss

What was the primary finding of the activity pattern study?

Have a spread of lifestyles that resembled those among modern animals, an indication that dinosaurs also spread out to occupy the available ecological niches

What does endothermy mean?

Heat generation inside body

Hox genes

- Control the metazoan body plan - reverse evolving a dinosaur using living birds (chickens) - claws, teeth, and long body tail

Some suggested increase volcanism as the cause for the K-Pg mass extinction

- Deccan traps in India - problems = layers and layers of lava flows of different ages and started long before K-Pg and ended after K-Pg - others suggested major sea level drop

Why don't terrestrial placental mammals today grow as large as saurischian dinosaurs?

- Due to long gestation periods - decrease in articular cartilage in large animals

Archosauria reproduction

- Eggs with hard calcium carbonate shell - nest built with vegetation - vocal communication between parents and offspring prior to hatching and some degree of parental care

The Big 5

- End Permian (P-T; most severe mass extinctions) - End Cretaceous (K-Pg; killed non-avian dinosaurs)

Evo-Devo

- Evolutionary Development Biology = study of development to elucidate evolution - ontogeny recapitulates phylogeny - Heterochrony - Paedomorphosis - Peramorphosis

Supporting evidence for the K-Pg impact hypothesis

- presence of iridium spike worldwide found in K-Pg boundary layer - shocked quartz - spherules & tektites and crater - Chicxulub crater located near the Yucatán Peninsula in Mexico is found and dated as 66 million years ago which coincides with the K-Pg boundary - shallow angle impact - more ejecta to North America Han to South America - after mass of the impact - infra-red radiation pulse, global wildfires, acid rain from sulfur in ejecta and blockage of sunlight (impact winter)

Mesozoic plant evolution

- seed plants were more abundant than spore plants during the Mesozoic era - among the 2 major groups of seed plants, gymnosperms were the most dominant plants during the age of dinosaurs - during the Triassic period, gymnosperms made up about 60% of all land plants and up to 80% during the Jurassic period - Angiosperms (flowering plants) is the other group of seed plants and first appeared during the early Cretaceous period - rise of low browsing ornithischians in late Cretaceous

Dinosaur soft tissue remains

- skin impression in a hadrosaur - titanosaurid embryo skin impression - a small theropod, Scipionyx (preserved partial windpipe, intestine, liver and muscles - a dinosaur tail with feathers preserved in amber, - organic remains of T. Rex (blood vessels with blood cells, medullary bone and osteocytes)

Bite force estimation in dinosaurs

- vertebrate jaw is a class 3 lever - bite force can be estimated by using a simple equation [force generated by the jaw adductor muscles, in-lever to out-lever ratio (mechanical advantage) and jaw adductor muscle insertion angle] - larger animals produce stronger bite force - Tyrannosaurus = biting and tearing vs Allosaurus = slashing - bite force comparison among mega herbivores (sauropods) - • broad crown (stronger biting & tearing) vs • narrow crown (weak biting and not tearing)

How fast did dinosaurs grow?

- we can study dinosaur growth rate by examining the Lines of Arrested Growth (LAGs) in bones - some dinosaurs grew fast - had teenage growth spurt (Tyrannosaurus)

Studying dinosaur brains

- we can use CT scans of dinosaur skulls to reconstruct cranial endocasts (provides reasonable estimates on the size of brains) - using semicircular canal (part of inner ear) we can also understand head orientation of dinosaurs

Guest lectures - the Monsters of Mogollonia

1. Unique geology of Arizona 2. Climate during the Cretaceous 3. Dinosaurs from Moreno Hill Formation

How did dinosaurs reproduce?

2 major groups of Diapsids 1. Lepidosauria = lizards and snakes 2. Archosauria = crocodiles, pterosaurs and dinosaurs - birds

Why do we think sauropod dinosaurs migrated?

A collection of teeth from dinosaurs in the western United States

Based on the study results, what was the migration pattern of Camarasaurus?

At least 300 kilometers between the basin and highlands to the west

Background vs mass extinction

Background extinction = normal extinction Mass extinction = geologically rapid, major reduction in global diversity: catastrophic global phenomenon

What types of soft tissue did team of scientists find from the T. rex femur(thigh bone)?

Blood vessels

Why Dr. Greg Erickson could not use the same method to determine the age of Sue the T. rex?

Bones are hollow

How did Greg Erickson test his hypothesis that the lines in these alternative bones represent the actual growth of dinosaurs?

By comparing it with crocodiles who had the same growth rings

How do we study paleoecology of dinosaurs?

Case 1: seasonal migration in sauropod, Camarasaurus using oxygen isotope ratios preserved in the teeth Case 2: infections in Tyrannosaurus - avian trichomoniasis caused by Trichomonas gallinae might have affected theropods

A _____ animal is irregularly active at any time of day or night

Cathemeral

How can we determine the environment of which dinosaurs lived using the oxygen isotope ratios persevered in their teeth?

Comparing oxygen-16 & oxygen-18 with the ratios in the sedimentary rocks found in the area

What does homeotherm mean?

Constant body temperature

How do paleontologist usually determine the age of dinosaurs?

Counting growth rings

Activity patterns

Diurnal = active during the day; many reptiles and birds Nocturnal = active during the night; many mammals) Cathemeral = sporadically active during day or night; large herbivores Crepuscular = primarily active during twilight - dawn and dusk - many large herbivores are cathemeral (need to eat longer than the daylight and avoid being overheated during the day) - ratio between the orbit diameter and sclerotic ring diameter to predict activity patterns of both living and fossil vertebrates - diurnal (50%) and nocturnal (>50% more light sensitive) - not many diurnal dinosaurs - many were cathemeral or even nocturnal - both fossil and living birds are mainly diurnal - some pterosaurs were crepuscular

What is an example of atavism, the reappearance of a trait that had been lost during evolution?

Dolphin legs

What did Greg Erickson find out about the growth rate of T. rex?

Teenage years the T. rex was putting on 5 pounds per day

Bite force has a strong positive correlation with body mass

True

Dinosaur body mass can be estimated using known values of closely related living organisms

True

Hox genes control the body plan of animals and changes in the genes provide a major source of evolutionary change

True

In K-selected species, offspring are fairly helpless when born and need to be cared for by their parents

True

In most species whose young are precocial, parental care is reduced

True

Some dinosaur bones were found to have organic remains (e.g. Blood cells, osteocytes, medullary bone, etc.)

True

We can use cranial endocasts to reasonably estimate size of brains in vertebrates

True

Which of the following organisms survived K-Pg mass extinction?

Turtles

Gigantothermy

Unique way of keeping body temperature somewhat constant by growing large

Estimation of dinosaur body mass

Using the values of closely related living organisms (birds)

Explain how we can study these activity patterns in fossil vertebrates

We can measure the ratio between the orbit diameter and sclerotic ring diameter to predict activity patterns - diurnal species have a smaller sclerotic ring diameter for a given eye size - nocturnal ones have a larger sclerotic ring diameter for a eye size

How did Dr. Harris confirm that the unusual structures on the mutant chicken beak are teeth?

Zoomed in on a embryo with a microscope and saw teeth that look like a sabor shape similar to alligators

Heterochrony

a development change in the timing of events, leading to changes in size and shape

Peramorphosis

juvenile of derived organism resembles the adult of the ancestor

Warm blooded features

• 2 anatomical features: 1. nasal turbinates (prevents moisture loss during respiration) 2. insulation (feather or hair) • 2 physiological features: 1. Fast growth rates (can be studied by examining the bone growth) 2. High body temperature (can be measured by analyzing the oxygen isotope ratios in bones, eggs and teeth)

What are the roles of Hox genes in animals?

Lay out the identity of the major body parts

What is the traditional explanation on activity patterns of early mammals and dinosaurs?

Mammals were nocturnal because dinosaurs had already taken the day shift

Why does Dr. Mary Schweitzer think she found dinosaur osteocytes, bone forming cells?

Really distinctive & has phylofobe, which are like little feet/legs

Which particular dinosaur group must have been prone to overheating?

Sauropoda

Mesozoic non-avian dinosaurs were...

Something else entirely

The supercontinent that existed when dinosaurs first evolved was called...

Pangaea

How dinosaurs shrank and became birds?

- Rapid evolutionary size reduction - derived theropods became smaller through paedomorphosis and became birds

Paleoclimate (temperature and sea level change)

- Temperatures during the Mesozoic era was always higher than it is today even there was a drop in the middle - sea level started out low in the Triassic but gradually became higher and higher by the time of dinosaur extinction at the end of the Cretaceous - Western inferior seaway split the North America continent into 2 land masses (west and east) during the mid to late Cretaceous

Which of the following statements is correct about worlds of dinosaurs?

- all of the above • Pangaea gradually broke apart • it was warmer than the present • sea level increased through time

Why did dinosaurs evolve gigantism?

- avoid predation (especially in sauropods) - food availability

Dinosaur locomotion

- both theropods and birds knees must be flexed to be fully articulated - dinosaur footprints could preserve foot motions but footprint shapes from a single individual could vary drastically depends on the locomotion and ground firmness (soft vs hard) - taxonomic applications require caution

Dinosaur speed estimation

- faster an animal walks or runs the longer are its strides - stride lengths can be measure from many fossilized dinosaur trackways - the relationship between speed, stride length and body size from observations of living animals is well established - using stride length and hip height of dinosaurs, we can use the equation to estimate the dimensionless speed of dinosaurs

Causes for the mass extinction

- flood basalts may be relevant at least to the last 3 mass extinctions (P-T, End Triassic, K-Pg) - asteroid impact is well established only for the K-Pg mass extinction - global warming was associated with P-T - each mass extinction has a unique set of potential casues

Did dinosaurs care for their young?

- fossilized nests - maiasaura nesting colonies (cared for their young) - oviraptor = fossilized while brooding - mass mortality of juvenile Protoceratops (nesting) and sauropods nests found near hot springs

r-selected

- have lots of offspring - don't invest a lot of time/energy in any one offspring - chances of surviving for each offspring are small - short life spans and precocial offspring

K-selected

- have only a few offspring - invest a lot of time/energy in each offspring - chances are better that most will survive - longer life spans and altricial offspring

Understand scaling issue in growth regrading the change in ratio between surface area (heat loss) to volume (heat generation)

- heat generation - volume = X 8 - heat removal - surface = X 4 - larger animal = overheating - Gigantothermy: unique way of keeping body temperatures somewhat constant by growing large

K-Pg mass extinction was size selective

- loss of large bodied organisms - survivors = amphibians, snakes, lizards, turtles, crocodiles, birds and mammals - losers = non-avian dinosaurs, marine reptiles (terrestrial), and ammonites & belemnites (marine$

Dinosaur physiology

- nasal cavity in dinosaurs is larger than in crocodiles but smaller than in birds and mammals for a given body size - some (not all) dinosaurs evolved body insulation (feathers) - grew fast and high body temperature - sauropod body temperature was lower than the estimated value - mesothermy in dinosaurs

Which of the following is a characteristic of a bird?

- none of the above • toothed jaw • clawed hands • long body tail

Evidence of sudden extinction of dinosaurs

- now you see them, now you don't - statistically speaking, the dinosaurian diversity did not decrease gradually before the K-Pg mass extinction (more so in North America)

Which part of Sue's bone did Greg Erickson use to determine its age?

Tibia

Why are the researchers interested in analyzing oxygen isotope ratios of carnivorous dinosaur teeth in the same region?

To determine if carnivorous stayed in one place and waited for sauropods or whether they followed them on their migrations

Why were some dinosaurs active at night?

More prone to overheat, so they try to avoid being active during the heat of the day, shifting their activity to nighttime

How can we tell whether a fossil vertebrate was active at night or during the day by examining its sclerotic ring?

Nocturnal = larger opening within the sclerotic ring Diurnal = intermediate size sclerotic ring and an overall larger eye

Ovoviviparity

Oviparity = lay eggs Viviparity = give birth Lecithotrophy = nutrient from yolk Matrotrophy = nutrient from mother

How does a butterfly reuse ancient body building genes in a new way?

The gene tells the butterfly where the green spots are on their wings

Sue is the largest T. rex has been found so far. What else did Greg Erickson find about Sue?

The oldest T. rex

How do archosaurs reproduce?

They lay eggs (oviparity)

Why does the table compare dinosaurs to birds and crocodiles as opposed to other animals living today?

They're closely related

Paedomorphosis

adult of derived organism resembles juvenile of ancestor