Lecture 26 Vertebrates - Mammals Flashcards
Three subclasses of Mammals
-Eutheria
-Prototheria
-Metatheria
5 orders of the subclass Eutheria are
-Carnivora
-Cetacea
-Chiroptera
-Rodentia
-Sirenia
One order of the subclass Prototheria is
Monotremata (platypus and short-beaked echidna)
Two orders of the subclass Metatheria (Marsupialia)
-Diprotodontia
-Polyprotodontia
The subclass Metatheria of Mammals is also called
Marsupialia
All subclasses of mammals evolved from a
Common reptilian ancestor
Monotremes evolved in
The Southern Hemisphere
Monotremes retained four reptilian characteristics:
-oviparity
-meroblastic cleavage of embryo
-production of venom
-electroreception
There are __ species of monotremes
5
Which monotremes are found in Australia
-platypus
-short-beaked echidna
The echidna has the
Widest environment range of any Australian mammal
The platypus exists in
Freshwater habitats of eastern Australia
Defining characteristics of monotremes (7)
-absence of calcified teeth (have a keratinised dental pad)
-electroreception used to detect prey
-reptile-like stance (limbs held off to side rather than under body)
-cloaca
-oviparity
-no teats (females produce milk through modified sweat glands)
-venom
Crural glands are (4)
-venom glands found on the ankle of male platypus
-can move independently
-evolved independently of reptile venom
-used for defence of territories
Electroreceptors are located
within the skin of bill/beak in platypus and echidnas
The pectoral girdle of monotremes has
Reptilian features: coracoids, epicoracoids, and interclavicle
Monotremes have multiple
X and Y chromosomes
In marsupials and eutherian, sex is determined by ___
SRY on Y chromosome
Monotremes lack
SRY on chromosome Y (ie. determines sex)
The monotremes sex system is a
Link between birds and therians
In the platypus, only the ___ is functional
Left ovary
Monotremes have ___ but no ___
Mammary glands; teats
The eggs of monotremes are (2)
-a porous, leathery shell
-developed in the uterus for ~20 days absorbing embryotrophe
Echidnas incubate in ___ while platypus incubate in ____
Transient pouch; nest
Not all marsupials posses
A pouch
How many species of Marsupials
270
Marsupials and eutherian diverged from
A common ancestor
Marsupial young are born in an
Altricial state (ie. not developed yet)
Marsupial young depend on ___ rather than ____
Lactation; gestation
XX chromosome of marsupials results in (2)
-female reproductive tract
-pouch
XO chromosome in Marsupials results in (2)
-female reproductive tract
-scrotum
XY chromosome in Marsupials results in (2)
-male reproductive tract
-scrotum
XXY chromosome in marsupials results in (2)
-male reproductive tract
-pouch
Pouch OR scrotum development of marsupials depends on ___ and not___
X chromosome; hormonal control
In marsupials, the ureters pass
Medially to Müllerian ducts
Marsupials posses ___ from Müllerian ducts and ___ of connective tissues
Two lateral vaginae; median vagina
Birth of marsupials occurs in the ___ vagina
Median
In eutherian, ureters pass
Laterally to Mullerian ducts
The Müllerian ducts is ___ in eutherian
Fused at the distal end to form the vagina
The Müllerian ducts in marsupials is
Not fused
The median vagina of marsupials is
Formed from connective tissue
Marsupials replaced the role of ____ with ____
Gestation; lactation
Marsupial young are born with (4)
-well developed forelimbs and claws
-well developed mouth, tongue, nostrils, and lungs
-no hair
-periderm covering eyes and ears
