Dinosaurs Exam 3

What evidence supports the K-Pg mass extinction impact hypothesis?

- iridium spikes - shocked quartz - spherule and tektites - crater

What are the anatomical and physiological features of vertebrates that are associated with endothermy?

- presence of nasal turbinates - insulation (feathers, hair or fur) - fast growth rates - high body temperature

Explain the four different activity patterns in vertebrates.

Diurnal - active during the day Nocturnal - active during the night Crepuscular - active during dawn and dusk Cathemeral - active during day and night (sporadically)

What are hox genes and why are they important?

Hox genes control an animal's body plan (timing and placement of body parts). Scientists are using hox genes to create birds that look more like dinosaurs.

Explain how a process of heterochrony might have been involved in the evolution of birds from theropod dinosaurs.

Paedomorphosis explains how theropods shrank to become birds. There was a rapid evolutionary size reduction and when we look at the skulls of birds they look like the skulls of baby raptors.

Explain the differences between R-selected species and K-selected species.

R-selected species reproduce a lot and their young is precocial, therefore, they do not require parental care. K-selected species have fewer young, which are altricial, meaning they require a lot of parental care and k-selected species have a higher chance of living to reproductive age.

How was it possible for the diverse mega-sauropods to co-exist in the same area during the Jurassic period.

Some sauropod species differ in their teeth, therefore, they weren't all competing for the same food. Due to the differences in their teeth, they ate different food.

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

They do not grow that large because the larger the animal the longer the gestation/pregnancy period so there is a low replacement rate. They also can't grow that large because the cartilage in their knees thins out the bigger they get which puts strain on their knees.

What is the relationship between endemism and the distribution of continents?

as the continents broke apart endemism began to increase

Explain the general outlines of plant evolution through the Mesozoic era.

gymnosperms, seed plants, were the most abundant plant during the Mesozoic era. There were spore plants, angiosperms, but most of the plants during the Mesozoic era were gymnosperms.

How is mass extinction different from background extinction?

mass extinction is when over a relatively short period of time, there is a huge reduction in global diversity. background extinction is normal extinction (at any given time there are species going extinct).

Explain the effect of body size scaling on body temperature in vertebrates.

the larger the animal, the higher the body temperature. They have more volume, production of heat, and less surface area, which prevents them from getting rid of the excess heat.

Explain how we can estimate the speed of dinosaurs.

we can estimate the speed by adding the stride length of the dinosaur to the hip length of the dinosaur.

What feature can we examine to determine the activity patterns in fossil vertebrates?

we can examine the ratio between the sclerotic ring diameter and the orbit diameter.