Mammals Flashcards
What major group of amniotes is the first to diversify widely to terrestrial habitats?
Synapsids
What is pelycosaurs?
Earliest synapsids diversified into diverse herbivores and carnivores
What are Therapsids?
Arose from early carnivorous pelycosaur group
More efficient upright gait
Skulls indicate more efficient feeding and muscular co-ordination
Hard palate partially separated the nasal and oral cavities
What is the one therapsid group that survived to Mesozoic era?
Cynodonts
Cynodonts features
Show features supporting higher metabolic rate:
Jaw musculature for stronger bite
Heterodont teeth
Turbinate bones – retention of body heat
Secondary palate
Loss of lumbar ribs and evolution of diaphragm as well as greater flexibility of spine
What are the Major characteristics of modern mammals?
Hair (and integumentary glands)
Mammary glands
Specialized teeth
3 middle ear ossicles
Endothermy
What are the two lineages of living mammals?
-Subclass Prototheria
—–Infraclass – Ornithodelphia
-Subclass Theria
Infraclasses:
—–Metatheria
—–Eutheria
Unlike other mammals Monotremes:
-Have a cloaca
-Are oviparous
Describe Infraclass Metatheria
Marsupials
-Viviparous but have short gestation periods
-Have marsupium (pouch) covering female mammary glands
Describe Infraclass Eutheria
Placental mammals
-Nourished within uterus via placenta
-Born at advanced stage of development
Functions of hair in Mammals
-insulation
-touch
-protection
What occur over most of body of most mammals; absent from other vertebrates?
Sweat glands
What are the four classes of glands?
sweat, scent, sebaceous and mammary
What are the functions of Eccrine glands?
-Secrete watery fluid
Evaporation; cooling
Occur in hairless regions – foot pads
All over body in horses and primates
Reduced/absent in rodents, rabbits and whales
What are the functions of Apocrine glands?
-Secrete milky fluid
Always open into hair follicle
Develop around puberty
Secretions dry on skin; form film
Involved in reproductive cycle not heat regulation
What are the functions of Scent glands?
Location and function variable
Conspecific communication
Territorial marking
Warning
Defense
What are the functions of Sebaceous glands?
Usually associated with hair follicles but some just open to surface of skin
Secrete greasy sebum
Keeps skin and hair pliable and glossy
Most mammals have these glands over entire body
What are the functions of Mammary glands?
Occur on all female mammals; rudimentary in all males
Increase in size at maturity and become larger during pregnancy and nursing
In humans adipose deposits around mammary glands to form breast
Why is it that the smaller the mammal the greater its metabolic rate?
Metabolic rate of mammal varies according to relative surface area rather than body weight.
-Surface area is proportional to about 0.7 power of body weight
so the amount of food a mammal or bird eats is also about 0.7 power of its body weight to meet its metabolic needs
Flight and echolocation allows bats to?
navigate in the dark
avoid obstacles
inhabit deep caves not exploited by other creatures
Explain echolocation in bats
External ears of bats are large with variable shapes to focus in on the location of a sound
Bats can build a mental image of the surroundings via echo scanning that is similar to visual images by other animals
High metabolic rates require adaptations for efficient gas exchange:
-Separate nasal and oral cavities and longer snouts
-Highly branched respiratory passages
-Negative pressure mechanism for inflation
-Muscular diaphragm
