Biofacts - Skulls Flashcards
Q: Name some features of a skull that can tell us something about the animal
(details on separate cards)
Eye placement
Eye size
Presence/size of sagittal crest
Width/length of jaw
Presence of different kinds of teeth
Shape of teeth
Length of snout
Size of nasal cavity
Size/surface area of turbinates
Auditory bullae size
Q: What can we learn by looking at skull features? (just a general list, details on separate cards)
Physical and behavioral adaptations.
Diet (type/number of teeth, positioning of jaw muscle attachment sites, eye positioning).
Forward placement of the eyes in the skull indicates depth perception.
Size of the eye orbits in relation to the size of the skull may indicate when an animal is active.
Length and position of the nose indicates the importance of the sense of smell.
The position of foramen magnum indicates posture.
The size of auditory bullae indicates level of hearing.
Social patterns.
Q: What can we learn about an animal by observing the eye sockets on the skull?
-Eyes that face forward allow for binocular and stereoscopic vision, aiding depth perception
–Suggest it’s a predator
–For calculating distance to prey
–For swinging/leaping through arboreal habitat (monkeys have forward facing eyes)
-Eyes on sides allow for greater peripheral vision, wide range of view; can provide nearly 360-degree field of view at all times to watch for predators approaching
–Suggests it’s a prey animal
–“Eyes in the front, the animal hunts. Eyes on the side, the animal hides.”
–Note: Within a herd, there can be 360 degree vigilance since individuals face different directions.
-Eye sockets that are large relative to skull size may suggest nocturnal activity
–Larger eye lets animal see better in dim light
–E.g., cats, owls.
–Many nocturnal animals have a reflective layer behind the retina (tapetum lucidum, Latin for “shining layer”) that reflects the light back through the retina, aiding night vision. E.g., cats, lemurs.
–California sea lion has large eyes; minimal light in the ocean at depth.
Q: Depth perception
Visual ability to perceive the world in three dimensions and the distance of an object.
Q: Stereoscopic vision
The single perception of a slightly different image from each eye, resulting in depth perception.
Q: Peripheral vision
Side vision; used to see to the side when looking straight ahead.
Q: What can we learn about an animal by observing the nasal cavity in the skull?
-Relative size of nasal passage (larger indicates good sense of smell)
-Size/surface area of turbinate bones
–The thin, bony structures inside the nasal passage (turbinate bones), provide framework for membranes which sense odor in vertebrates
—Grizzly bear has an extremely acute sense of smell, and well developed turbinates; can detect animal carcasses ~20 miles.
–Turbinates also filtrate, heat, and humidify inhaled air, and capture >75% of water vapor exhaled, helping protect from dehydration.
—Snow leopard’s enlarged nasal cavity helps them warm the cold air they breathe while retaining water.
-Length of snout
–Elongated nose might suggest animal hunts by following scents, or that it uses nose to probe the ground or vegetation.
—Deer’s long nose and higher eye placement allows him to scan for predators while grazing.
—Wolves, bears hunt by scent using long noses that contain millions of scent receptors.
—Cats have acute sense of smell, but doesn’t measure up to dog’s, which has longer nose.
—Humans have poor sense of smell compared to most animals. Also short snout and small turbinates.
Q: Turbinate bone
Delicate bones in the nasal cavity that direct the flow of air through the nasal passages and provide framework with lots of surface area for membranes which sense odor in vertebrates.
Covered with mucous membranes, which warm and moisten the incoming air.
Q: What is a Jacobson’s Organ?
-Some animals have auxiliary olfactory sense organ (the VMO or Jacobson’s Organ) at the roof of the animal’s mouth
-Used to detect chemical stimuli.
-Snakes and lizards, cats, wolves, ungulates, and lemurs.
-In some mammals (i.e. cats and hooved animals), organ is involved in the flehmen response (lifting upper lip, grimace), and is used to detect pheromones, chemical messengers carrying info between individuals of same species.
Q: What can we learn about an animal by observing the auditory bullae on the skull?
(singular bulla)
Auditory bulla: Bony structure on the ventral, posterior portion of the skull that encloses parts of the middle and inner ear.
In general, large protrusions indicate an excellent sense of hearing.
Cats: large auditory regions and very acute hearing. Deer and antelope: poorer sense of hearing. Birds: these auditory regions are relatively prominent.
Q: Which classes of animals are homodonts?
Homodont: Animal whose teeth are all of the same type; for example, most vertebrates except mammals have a single tooth morphology.
Amphibians and reptiles are homodonts.
Q: Name two animal classes/groups do not have teeth
Modern birds and turtles do not have teeth
Q: What’s a key feature of plants that make them difficult to consume?
Made of cellulose, difficult to break down.
Animals do not have an enzyme that breaks down cellulose.
Q: How are herbivore skulls adapted particularly to cellulose digestion?
Grinding surface on their teeth aids in their digestion of this fibrous material.
Tend to have well-developed premolars and molars, often with sharp ridges on the tops for grinding.
Broad teeth grind vegetation into a pulp.
Q: How are herbivore skulls adapted to consuming plants?
Well-developed premolars and (broad) molars, often with sharp ridges on the tops for grinding.
Incisors are clipper-like to snip off foliage from branches.
Canines reduced or absent.
Long diastema (toothless portion from the premolars to the incisors) provides room to reposition plant material during grinding.
Narrower mouths in relation to head size very muscular tongues to move food around.
Q: What is a dental pad? Who has one?
Some ruminating species (e.g., deer, cows, and giraffes) have only lower, flat shaped incisors that meet the upper toothless gum, called a dental pad.
Plate of bone under the skin to grind against.
Zebras and other horse-like species have both large upper and lower incisors.
Q: How is the digestive system of some herbivores adapted to a plant-based diet?
Ruminants have four-chambered stomach with microbes to help break down the cellulose before the nutrients get absorbed in the intestines.
Hindgut fermentors (which have single-chambered stomach) usually have longer intestines, and microbes are in the intestinal tract, or in the cecum. (koalas have a 7’ cecum for digestion)
Q: Compare jaw shape of carnivores vs. herbivores. (general)
Carnivorous animals tend to have wide mouths in relation to their head size and highly developed jaw muscles, whereas the herbivore’s mouth is narrower.
Q: Describe carnivore teeth
Have full set (canines, incisors, molars, premolars)
Their canines are long and used to slash, rip and tear meat. Grip prey. Used on throat in a choke hold.
Sharp premolars and molars, used to shred/tear/cut meat.
Many have carnassial teeth (details in feline section).
Q: Name some interesting differences between teeth/jaws in cat-like and dog-like species
Cat-like species have relatively shorter jaws giving more powerful bite force.
Dog-like species have relatively longer jaw allowing them to snap jaws shut quickly, but yield a weaker bite force.
Dog-like species typically have relatively large incisors, used for grooming.
Cat tongues are like sandpaper and are used for both grooming and to help get the last bit of meat of their prey.
Q: Name an interesting tooth adaptation of wolverines
Have an upper molar turned 90 degrees allowing them to eat frozen meat and crush through bone
Q: Are insectivores carnivores?
Yes. Insects are animals.
Q: General shape of insectivore teeth
Fine, needle-like teeth. (e.g., many lizards, frogs, bats, and spiders)
Q: Which types of teeth do omnivores have?
Omnivores have a full set (canines, incisors, molars, and premolars)
Q: Describe omnivore teeth
Omnivore’s teeth are less specialized than those of carnivores and herbivores.
Molars in between carnivores and herbivores, with more “peaks and valleys” due to the varied diet; cheek teeth are wide with low bumpy surfaces.
Incisors are wide, narrow at the tips, and somewhat chisel-shaped, useful for biting off chunks of meat or plant material.
Q: Differences between teeth of black bears and polar bears.
All bears are omnivores, each species has unique diet
Polar bears are most carnivorous; use sharp canines to rip out chunks of meat. Tend to swallow chunks without much chewing; molars are smaller.
The black bear (and other bear species) eat much more vegetation; molars have larger, flatter grinding surfaces than polar bear.
