Lecture 8 RH - Mammals Flashcards
What organ is common to all mammals?
Mammary glands
What are the general characteristics of mammals?
Hair as body covering
Integument with sweat, scent, sebaceous, and mammary glands
Structure of skull and skeleton
Diphyodont teeth - milk or deciduous teeth replaced by permanent teeth
Heterodont teeth - Different types
Lower jaw is made up of single dentary bone
Secondary palate that separates nasal cavity from buccal cavity
Brain highly developed with large cerebral cortex
4 chambered heart
Left aorta
Non-nucleated biconcave red blood cells
Diaphragm divides body into thorax and abdomen
What is lower jaw made up of in mammals?
Single dentary bone
What is the function of the secondary palate?
Separates nasal cavity from buccal cavity
What does the brain of mammals look like?
Highly developed with large cerebral cortex
Do mammals have a cloaca?
Only monotremes. The rest of mammals have separate anal and urinary openings
Are mammals mono or dioecious?
Dioecious
What is the copulatory organ of mammals?
Penis
Is fertilization internal in all mammals?
Yes
What are the foetal membranes in mammals?
Amnion
Chorion
Allantois
What are the 3 major groups of amniotes?
Anapsid: Solid skull (turtles and ancestors)
Synapsid: Pair of openings in roof of skull for jaw muscle attachments (led to mammals)
Diapsid: 2 pairs of openings in skull roof (dinosaurs, reptiles, birds)
What are monotremes?
Mammals that lay eggs; eg platypus
Which mammals have only survived in Australia?
Marsupials and monotremes have only survived in Australia
What is hair composed of?
keratin
What other structures are composed of the same component as hair?
Nails, horns, claws, hooves, and feathers
Do mammals moult?
Periodically 2 coats - summer and winter coats
What is the purpose of moulting?
Camouflage
Sensory hairs
Spiny armour in porcupines, echidnas
What are true horns of sheep and cattle made of?
Sheaths of keratinized epidermis
What are antlers of deer made of?
Solid bone branched
How do antlers develop?
Beneath vascular velvet skin and they decline after rutting season as hormones decline
What is rhino horn made of?
Hairlike keratinized filaments and is used for chinese medicine driving it to near extinction
What is interesting about antelope horns?
They shed annually
What is rhino horn used for?
Chinese medicine
As an aphrodisiac
What are the types of sweat glands?
Eccrine glands produce sweat to cool skin
Apocrine glands open to hair follicle. Milky fluids - activity is correlated to reproductive cycle
What are scent glands used for?
Social activity such as marking territory
Mating scents to attract opposite sex
What is the function of sebaceous glands?
Produce sebum which keep skin pliable and glossy
Do monotremes have nipples?
No
What happens to metabolism in smaller animals compared to larger animals?
Metabolic rate/gram of body weight is a lot higher in smaller animals
What is the cost of migration?
Very energetically expensive
What is an example of a mammal that migrates?
Caribou migrate from Canada and Alaska and vice versa from Winter feeding grounds to summer breeding grounds in Canada
Where do seals migrate to and from?
Pribilof Islands in summer and Autumn.
Males arrive from the South where they live during Winter and Spring.
Females arrive from the Southeast near Alaska
How does echolocation in bats work?
Ultrasonic high frequency pulses. Echo is received by large ears
How are mammals classified into subclasses and infraclasses?
Reproduction
What are the types of reproduction in mammals?
Prototherians: Egg laying oviparous mammals
Metatherians: Pouched viviparous mammals
Eutherians: Placental viviparous mammals
How many orders does subclass prototheria have?
1; only the monotremes
How many orders does subclass theria have?
Infraclass metatheria has 7 orders of marsupials
Infraclass eutheria has 21 orders of placentals
How many species of monotremes are there?
5 species:
Duck-billed platypus
4 kinds of spiny anteater
What are the features of monotremes?
All lay eggs and suckle young
Where are individuals of infraclass metatheria located?
Most of the species are native to Australia and nearby Islands
Only opossums are found in North America
How do metatherians develop?
Young are born in an undeveloped state and complete development in a permanent pouch on mother
How long is the gestation period in Kangaroos?
33 days
How many young do kangaroos typically get at one time?
3
What happens to fertilized embryos when another joey is suckling within the pouch?
Embryos that are fertilized are in diapause
What is the placenta composed of?
Maternal and fetal tissues; nourishes foetus, delivers oxygen, removes wastes
Which develop quicker marsupials or placental mammals?
Placental mammals
What are the types of mating systems?
Promiscuous: Male makes little contribution: mate with any receptive female
Monogamous: Male mates with only one female at a time makes significant parental investment
Polygamous: Commonest in mammals. Group is dominated by one or several males that have exclusive mating privileges with all receptive females in group
Polyandry: Rare in mammals. Female has several male mates simultaneously
What are the orders of eutherians?
Rodentia (rodents)
Chiroptera (bats)
Soricomorpa (shrews and moles, insect eaters)
Primates
Carnivora
Artiodactyla (even-toed hoofed animals)
How are mammalian orders grouped?
Specialists don’t agree on how to group the numerous eutherian orders
Cladogram based on analysis of 104 cranial characters developed in 1986
Jaws and cranial characters are related to the type of diet and development of brain
What is the superorder that contains insectivores?
Xenarthra
What are the orders of insectivorous mammals?
Pilosa: contains suborder folivora (sloths) andsuborder Vermilingua (anteaters)
Cingulata - armadillos
What are the features of xenarthra?
Many equipped with strong claws to tear open termite and ant nests
Long and sticky tongue
Order pholidota: contains pangolins or scaly anteaters of Africa and Southeastern Asia
What are pholidote scales made of?
Hairs that are cemented together
What are features of order tubulidentata?
Large claws, pointed snout, peg shaped cheek teeth.
Enamel has been lost but teeth do not wear out because they grow continuously
What is an example of a tubulidentata?
Aardvark
What order are hedgehogs, shrews, and moles a part of?
Soricomorpha
What ancestral features are retained by insectivorous mammals?
Relatively small brain
Limb structure is primitive
Five clawed toes
Dental formula primitive
What is the dental formula of insectivores?
I 3/3 C1/1 Pm 4/4 M 3/3
What are the adaptations of teeth in carnivorous mammals?
Large canines
Cusps on last upper premolar and first lower molar enlarged and moved into the same plane to form a set of carnassial teeth well adapted for slicing through meat
Why do carnivore jaws lock onto each other?
Jaws are hinged to close like a pair of scissors
What do sea lions, seals and walruses feed on?
Sea lions, seals and walruses live in the ocean and feed on fish or molluscs.
What are adaptive features of carnivores?
Terrestrial forms have developed claws, and a limb structure for rapid running to catch prey.
Foot posture is evolved into a digitigrade type -stand on toes with the rest of the goot raised off the ground like a sprinter
Where do sea lions, seals, and walruses breed?
They return to land for breeding
What have limbs of sea lions, walruses, and seals evolved into?
Flippers
What are the adaptations of aquatic mammals to life in the water?
Fish shaped body
Hind limbs embedded in body wall
Pectoral flippers for steering and balancing
Powerful tail fluke or fin used to propel animal
What are some examples of toothed whales?
Killer whales
Dolphins
Porpoises
Sperm whales
What do toothed whales feed on?
Fish and other large marine animals
How do toothed whales navigate?
High frequency echolocation
What are some examples of baleen whales?
Humpback whale
Blue whale
Rodwan Halimi
What is the function of songs of whales?
Finding a mate
What is the method of feeding of balleen whales?
horny plates hang down from palate and strains small invertebrates and other plankton as food
What are the adaptations that herbivorous mammals have?
Change in dentition to grind plant matter
In some groups ofherbivorous mammals the premolars assume the form of molars to make an effective battery of crushing and grinding teeth
Jaw is hinged to bring teeth together at the same time
Fore and aft and sideways movement of jaws is possible
What do bunodont molars look like in primitive herbivores and omnivores?
Square or rectangular crown, four primary rounded cusps on each molar
What do bunodont molars look like in more advanced herbivores?
High crowned teeth
Teeth resistant to wear
What do lophodont molars look like?
Pattern of ridges and crests
What do selenodont molars look like?
pattern of crescents
