Mammals_and_Zoo_BI_2 Flashcards
Q: Where do mammals fall in the taxonomy of organisms? How are mammals classified?
Mammalia is one of the five (actually >5 because multiple fish classes) classes in the Vertebrata subphylum.
Kingdom: Animalia; Phylum: Chordata; Subphylum: Vertebrata; Class: Mammalia.
There are three divergent lines (subdivisions) of mammals based on their reproductive strategy: the monotremes (which is its own order), marsupials (infraclass w/multiple orders), and placental mammals (infraclass w/multiple orders).
Q: Five classes of vertebrates
Fish (actually multiple fish classes), amphibians, reptiles, birds, and mammals.
Q: Mammal characteristics (and name some benefits of the characteristics)
-Endothermic, generate their own heat. By generating their own heat mammals are free from depending on the ambient temperature of their surroundings for warmth.
-Have hair at some point during their life cycle. Hair is unique to mammals. Provides insulation, concealment, signals to others, defensive functions, and a sense of the surroundings.
-Give birth to live young (except monotremes).
-Breathe air with lungs. Aquatic mammals come to the surface to breathe and replenish their oxygen.
-Dermal glands which include mammary glands in females. Mammary glands produce milk to feed their young until they can eat normal food. Thus, female mammals invest a great deal of energy caring for their offspring, which increases survival rate.
-Relatively larger brain to body size than reptiles and has many folds or convolutions; allows increased degree of muscle coordination, enabled stronger sense of smell, higher intelligence, better memory development, more complex emotions, capacity for emotional bonds.
Q: Mnemonic for mammal characteristics
WHALE: Warm blooded, Hair or fur, Air to breathe, Live birth, Eats mom’s milk.
Q: Describe early mammals; when did mammals emerge?
-Mammal ancestors were mammal-like reptiles that were around about the same time as the emergence of dinosaurs.
Early mammals:
-The earliest identifiable mammals were tiny, shrew-like mammals.
-Emerged during the late Triassic period about 200 million years ago.
-Probably nocturnal in order to avoid competition with the dominant carnivorous dinosaurs.
-Probably mostly ate insects and lived in the trees.
-Probably laid eggs.
-Superior sense of smell and hearing, backed up by a larger brain, facilitated entry into nocturnal niches with less exposure to dinosaur predation. The nocturnal lifestyle may have contributed greatly to the development of mammalian traits such as being endothermic and having hair.
Q: Describe the important factors/events involved in the expansion of mammals
-After the extinction of the Dinosaurs, about 65.5 mya, the Cenozoic became the “Age of Mammals”
-Flowering plants and mammals underwent rapid diversification at this time and filled in open niches that were left vacant by the dinosaurs and marine reptiles
-Mammals took advantage of the new abundant food sources from the evolving flowering plants.
-Part of the successful strategy was the differentiated teeth (incisors, canines, molars), allowing them to adapt to a variety of diets and environments. (Fish, amphibians and reptiles, which all evolved prior to the mammals, had a single tooth morphology.)
Q: One downside of being endothermic? What does that mean for Mammals?
Requires more calories. The caloric need of an endotherm is 4–5 times more than a similar size ectotherm.
Mammals spend the majority of their time in search of food.
An area of the brain (neocortex) probably evolved as a part of a set of adaptations related to temperature homeostasis; this area stores information about the structure of the environment so that the mammal can readily find food and other resources necessary for its survival.
Q: Benefit of extended periods of parental care in mammals?
Improves survival rate of offspring. (vs. e.g., reptiles, amphibians, arthropods)
Q: What is the oldest living group of mammals?
Monotremes (order: Monotremata)
Q: Mammal fertilization
All three types of mammalian reproduction involve internal fertilization.
Q: Benefit of nursing in primates unrelated to nutrition/consumption?
Helps in social bonding.
Q: Mammal physical adaptations to maintain high body temperature in cooler climates
Dense fur and blubber
Q: Mammal methods for maintaining optimal body temperatures (behaviors/actions/body changes, not relatively static physical structures like blubber)
Constriction or dilation of blood vessels, shivering or sweating, piloerection of the fur, panting, and behavioral changes such as body postures, licking the fur, huddling together.
Countercurrent heat exchange (details on separate card in bird section)
Q: Homeothermic vs endothermic
Endothermic: capable of the internal generation of heat through metabolic means
Homeothermic: maintains a constant body temperature
Note: there are homeotherms that are not endothermic.
Mammals are both endothermic and homeothermic. Allows them to inhabit regions with extreme temps.
Q: Differences between individuals of the same species that are found in cooler vs. warmer climates?
Individuals from cooler climates tend to be larger than individuals of the same species living in warmer climates.
Appendages, such as limbs, nose, tail and ears, tend to be shorter in the cooler climates as well.
Larger mammals have less heat loss than smaller mammals due to the fact that heat loss is proportional to surface area.
Q: Mammal adaptations to hot/dry environments
-Changes in insulation, metabolic rate, and body size.
-Small mammals avoid extreme heat by adhering to definite periods of activity, and/or by occupying burrows during the heat of the day.
-Desert mammals produce dry feces to conserve water.
-Lighter fur reflects direct sunlight.
-Fur is also an excellent insulation against heat.
-Evaporative cooling from external body parts, e.g., Kangaroos lick their paws.
-Evaporative cooling from the respiratory tract is a major avenue of water loss but is also an important device for cooling.
-Larger animals save water by allowing their body temperatures to rise before it is necessary to pant to cool off thus reducing water loss. E.g., scimitar-horned oryx.
-The scimitar-horned oryx has specialized kidneys that prevent excess loss of water by producing very concentrated urine. Able to live in the desert without water for extended periods of time.
Q: The most important characteristic in mammal identification?
Its teeth.
Q: What is a secondary palate? Benefits?
Anatomical structure that divides the nasal cavity from the oral cavity in many vertebrates.
Allows mammals to breathe while nursing or chewing food.
Provides a surface on which the tongue can manipulate food, facilitating chewing.
Q: Describe mammal teeth (generally; specifics are a separate question)
All mammals have teeth except for monotremes, anteaters, and certain whales.
Mammals are heterodonts (means having multiple kinds of teeth; unlike homodonts like reptiles and fish).
Different kinds of teeth perform different functions such as chewing, crushing, cracking, gnawing, grooming, digging, defending and communicating.
The kind of teeth (shape, size and number) reflect their diet and lifestyle.
In mammals, teeth in upper jaw match up with lower jaw, which aids chewing, esp. in helping to break down plant material. (Reptile teeth do not match up, many species swallow food whole.)
Q: Heterodont
Animal having different kinds of teeth; for example, most mammal teeth are differentiated into incisors, canines and molars.
Q: Name one key way to differentiate mammal species
Comparing teeth shape and quantity
Q: Which kinds of teeth do most mammals have? Describe their location and function.
Incisors: in the front (anterior) of the mouth and used for food gathering. They are designed for biting, cutting, gnawing, stripping.
Canines: positioned at the front of the mouth between incisors and first molars. They are sharp for piercing and are designed for grabbing, piercing, and tearing. Predators use their canines to kill their prey.
Molars and premolars (also known as cheek teeth): in the sides/back of the mouth, vary in shape or size depending on their function. Premolars are used for grinding, crushing, slicing, and shearing, whereas molars are designed to grind and crush vegetation.
Q: How does a skull reveal information about animal feeding behavior?
Skulls provide a framework for the muscles an animal needs for chewing and biting.
In this way, the shape of the skull reveals information about the chewing and biting behavior.
Q: Describe some specific aspects of a skull that reveal information about animal jaw function, distinguishing predator/prey
Skulls provide attachment sites for muscles that enable biting and chewing.
Animals that need stronger biting muscles will develop larger bony attachment ridges for these muscles, such as the sagittal crest along the top of the skull and the zygomatic arches (cheek bones) on the sides.
Predators that tackle large prey often develop a sagittal crest, since it provides attachment space for muscle, which is used to snap the jaws shut (e.g., dog/wolf).
Sagittal crests are often larger in males than in females, because they are associated with larger body size.
Herbivorous animals that do a lot of chewing to help break down the cellulose, have a larger muscle attachment sight on the lower jawbone (e.g., cow). If this attachment area is small, chewing is not a necessity such as in a cat or dog.
Q: Which animals have hair/fur?
Mammals are the only animals that have hair or fur, and all mammals have it. It’s one of their defining characteristics.
Q: What is a pelt?
A mammal’s skin and fur.
Q: Name some functions of mammal skin
Primary function is defense against injury.
Barrier to protect the animal’s soft inner structures and maintain the internal environment by retaining body fluids.
Prevent moisture loss.
Keep germs out.
The skin may be extremely tough and durable.
Q: Types/functions of fur:
The fur (pelage) is made up of two layers of hair:
-1. dense and soft undercoat/underfur - traps a layer of air, providing insulation (thermoregulation is most important function of hair)
-2. long, coarse hairs form outer coat - protection against wear, can be fluffed up to improve insulation or as defensive/aggressive behavior to make mammal appear larger, provides coloration
Other functions:
-May also provide insulation against heat (camel, kangaroo or lion). Paler fur reflects the sun’s rays.
-Coloration for camouflage, signals/communication (warnings, mating display)
–Sometimes this coloring is disruptive by patterns of stripes or colors that stand out from the basic background fur color. These patterns allow the animal to blend in with the background mixture of sunlight and vegetation. Body shapes and outlines are not as readily distinguished when animals have disruptive coloration patterns.
-Sensory function: nerve endings are wrapped around the follicle and are sensitive to a hair’s movement. Mammals use this sense to detect direct physical contact and to gauge wind or water currents.
-Rarely: offensive protection
Q: Pelage
Fur or pelt
Q: What is hair/fur made of?
Hair/fur is dead and made of keratin.
Q: Example animal structures made of keratin
hair/fur
whiskers
beaks
horns and/or horn sheath
scales
plates
feathers
fingernails/claws
hooves
baleen in whales
Q: Are antlers made of keratin?
No. Bone.
Q: Do hairs grow and/or stay attached forever?
Most hair is shed periodically in a molt, which is essential to survival.
Q: What general lifestyle factor may have contributed to some key characteristics developing in early mammals? Which characteristics?
The nocturnal lifestyle of early mammals may have contributed to the development of endothermy and hair.
Q: Difference between mammals and, e.g., reptiles, in the attachment of the head to the neck.
In mammals, the occipital condyle (condyle = ball of ball-and-socket joint) has two points of contact to the first neck or cervical vertebrate.
The reptilian skull is attached to the spine by a single point of contact.
Q: How do mammal teeth develop/change/get replaced as the animal grows? How does this occur to other toothed vertebrates?
Mammals have two sets of teeth
-First emerges soon after birth (often called ‘milk teeth’)
-Acquire a larger set as an adult (both size and count increase to fill larger jawbones)
-Some exceptions in mammals. Elephants, kangaroos, and manatees have teeth that are continuously replaced. In some marsupials, only a subset of the teeth are replaced by “adult” teeth (from 3rd premolar back).
In all other toothed vertebrates, e.g., reptiles, teeth just keep coming, no matter how many are lost there is always another one ready to take its place.
Q: Are there any mammals without teeth? How do they consume food?
Yes, pangolins, monotremes, anteaters, and some whales.
Pangolins and anteaters have long sticky tongues for capturing ants and other insects.
Anteater tongue is long and sticky, and covered with spines. Flicks its tongue deep inside an ant colony, and the ants inside are glued to the sticky surface. It then grinds the ants against hard growths inside its mouth. Have also been known to swallow rocks to crush the ants in their tough stomach.
Q: Which kinds of mammals have the most diversity in how their feet contact the ground?
Mammals that run
Q: Three basic types of foot-ground contact
Plantigrade- heel and toes both touch the ground (e.g., squirrels, rabbits, bears, raccoons, humans)
Digitigrade- heel is off the ground and only the toes touch (e.g., cats, dogs, wolves, birds). Tend to move more quickly and quietly.
Unguligrade- walking is on the tip of the digit, hoof, or nail (usually exhibited by hoofed animals, e.g., horses and cattle)
Q: What adaptation gave mammals a distinct endurance advantage over reptiles? How has this affected mammals?
Four-chambered heart.
Allows for much longer endurance to feed the oxygen demand of the tissues.
Mammals were able to actively hunt down prey or elude predators.
Q: Characteristics of mammal skin
Two layers
Packed with glands that serve multiple functions (e.g., sebaceous, mammary, sweat; details on separate cards)
Q: Sebaceous glands
Located at hair follicles.
Secrete the oily, waxy substance that lubricates and waterproofs the skin and hair.
Protect the body against germs. Secretions prevent the growth of bacteria.
Secrete scents or chemicals to help mammals communicate. (Pheromone details on separate card.)
Responsible for the acne that one has during puberty.
Q: Discuss how mammals use scent for communication.
Scent glands of certain mammals secrete an often oily material of distinctive odor.
Scent plays a major role in many species including marking territory, cohesion of the group, communicating sexual fertility, and attracting mates.
Scent sources: Urine, feces, glandular marking.
Tree marking and rubbing are practiced by the deer family and the cattle, sheep, goats, and antelope family.
Some mammals have Flehmen response which employs VMO/Jacobson’s organ (details on separate card).
Q: Pheromone
A secreted or excreted chemical factor that triggers a social response in members of the same species. (example uses on separate card)
Q: Uses of mammal pheromones
Secreted by the sebaceous glands.
Trigger a social response in members of the same species.
Released in response to stress, alarm, danger, and sexual fertility.
You can observe ungulates and felids using their Jacobson’s organ (vomeronasal organ, or VMO) to pick up pheromones. (details on separate card)
Q: Flehman response
Behavior whereby an animal curls back its upper lips exposing its front teeth, inhales with the nostrils usually closed and then often holds this position for several seconds. The behavior facilitates the transfer of pheromones and other scents into the vomeronasal organ (VMO or Jacobson organ) located above the roof of the mouth via a duct which exits just behind the front teeth of the animal. This is seen in ungulates and felids.
Q: Sweat glands– What do they do? Who has them? Benefits?
Produce a liquid that evaporates off the skin to aid in temperature control.
Maintaining constant body temperature allows an organism to function effectively in a broad range of environmental conditions.
Only mammals sweat, but not all mammals have the same number of sweat glands.
Canids (dogs) posses very few sweat glands and cool primarily by panting.
A few mammals lack sweat glands (hippos, rinos, pigs, whales, dolphins, porpoises). Hippo spends most of its time in water, which helps regulate body temperature. Rhinos and pigs frequently roll in mud to cover their skin in order to cool themselves and protect from insects and parasites. Marine mammals depend on surrounding water to regulate temperature.
Q: Which animals have the sharpest hearing? Discuss.
Thanks to the middle ear and its three bones, mammals have the sharpest hearing on Earth and the greatest diversity of listening styles.
Bats and dolphins can detect ultrasonic pressure waves.
Elephants and humpback whales that can hear infrasound.
Also excellent at detecting very quiet sounds.
Excellent hearing helped early mammals which were probably nocturnal. Even today most mammals prefer to come out after dark.
Q: Evolution of the bones involved in mammal hearing
During mammalian evolution, the single middle ear bone of the reptile was combined with one lower jaw bone (‘articular’) and one upper reptilian jaw bone (‘quadrate’) forming the three mammalian middle ear bones.
Reptiles have one middle ear bone, while the upper and lower jaws contain several bones not found in mammals.
Improved hearing occurred in parallel with the evolving jaw and dentition in mammals.
Q: Name some factors that allow mammals to adapt to and thrive in diverse environments/niches (nearly every ecosystem on Earth)
-Endothermic (don’t have to rely on environment to regulate temp; can inhabit regions with extreme temps and remain active in cold)
-Heterodonts (different kinds of teeth help adapt to different food sources)
-Fur allows for environmental adaptation (help keep warm, help keep cool, camouflage, protection)
Q: Hibernation
A state of inactivity and metabolic depression in endotherms. Hibernation is characterized by low body temperature, slow breathing and heart rate, and low metabolic rate.
Often occurs during cold periods when food becomes scarce.
Q: True hibernation vs. torpor
Hibernation:
- a period of dormancy or inactivity occurring in cold seasons
- metabolic processes are greatly slowed as well as heart-rate, breathing
- body temperature may drop
- sleep to unrousable deepness
- used to conserve energy and cope with food shortages that occur in the winter
- during hibernation, stored body fat is used up at a relatively slow rate.
- found in many rodents, some bats, some insectivores
Torpor:
- a deep sleep, lighter than hibernation
- awaken more quickly than with hibernation; frequently wake and even move around outside
- heart rate, breathing, metabolic rate, and body temperature, although reduced, are significantly higher from a true hibernator
- E.g., during hibernation, ground squirrel’s body temperature drops to near freezing, but bears reduce their body temperatures by only ~10 degrees.
- appears to be involuntary, unlike hibernation
- allows them to respond to needs of young which they deliver during this period
