Lecture 1 - Characteristics and evolution Flashcards
What is the definition of DENTARY?
Single bone in jaw
What is the definition of HETERODONTIC?
Different types of teeth
An example of mammals which have a near absence of hair?
Naked mole rat, cetaceans (dolphins)
An example of a mammal that is not diphyodontic?
Elephant
An example of a mammal that is secondarily homodontic?
Toothed whales e.g. orcas
Example of mammals that have lost teeth?
Platypus, anteater
Definition of a monotreme mammal?
A mammal which lacks a placenta
Definition of a choriovitelline placenta?
Embryo develops from yolk sack, seen in marsupials
Definition of a chorioaallantoic placenta?
A placenta which develops later in pregnancy from embryotic membranes
Definition of endothermy?
Reliance on internal body heat to raise temperature - seen in mammals and birds
Definition of homeothermy?
Maintenance of temperature at a relatively constant level
What does a four-chambered heart do?
Improve circulation, more efficient
What does a more complex lung allow for?
More efficient oxygen exchange
What does the elongation of limbs facilitate?
Increased acceleration, speed and maneuverability
Why did shorter tails develop?
No longer required as counterbalance for rest of the body
How many external openings do monotremes have?
One: cloaca: anus, bladder, vagina
How many external openings do marsupials have?
Two: anus and cloaca
How many external openings do placentals have?
Three: Anus, urethra, vagina
What are specialised skin glands used for?
Temperature regulation
Communication
Rearing of offspring
When did amniota arise?
Carboniferous period (360 mya)
What is amniota characterized by?
Shelled egg
What are the three main lineages by the end of the carboniferous period?
Anapsids
Synapsids
Diapsids
How many temporal openings do anapsids have and what did they give rise to?
0 temporal openings
Turtles
How many temporal openings do synapsids have and what did they give rise to?
1 temporal opening
Mammals
How many temporal openings do diapsids have and what did they give rise to?
2 temporal openings
Lizards and snakes
In late Carboniferous, what did synapsids diversify into?
Pelcosaurs and Therapsids
Were pelcosaurs or therapsids dominant in late Carboniferous?
Therapsids
What four major advances did therapsids show?
Increased jaw musculature, erect gait, expansion of cerebellum, start of secondary palate
When did therapsid dominance end?
The end of Permian/Triassic (245 mya)
What were the next group of dominant terrestrial vertebrates after therapsids?
Archosaurs
When were archosaurs dominant and how long for?
Dominant throughout Mesozoic Era for 180 million years
Which group of therapsids survived?
Cynadonts
What 2 major advances did cynadonts, the group of therapsids that survived extinction, show?
Enlarged dentary bone, completion of secondary palate
In late Triassic what did cynadonts give rise to?
Early mammals
What four new traits did early mammals show?
Hair, mammary glands, specialised skin glands, molars and jaw that allow shearing action
What arose in early Jurassic?
Ancestor of modern Prototherians
What two traits did early prototherians exhibit?
Three ear ossicles, modified vertebrae and long bones
When did the ancestor of modern Therian mammals arise?
Late Jurassic
What two traits did early Therians exhibit?
Modification of braincase and vertical tympanic membrane
What three traits did late Therians exhibit?
Chorioallantoic placenta, long gestation and brown adipose tissue
When did rise of mammals begin?
Cenozoic Era
What were the major groups in the Carboniferous era?
Amniotes and Synapsids
What was the major group in the Carboniferous/Permian era?
Therapsids
What was the major group in the Permian/Triassic era?
Cynodonts
What was the major group in the Triassic era?
Early mammals
What was the major group in the Early Jurassic era?
Ancestor of Prototherians, today represented by monotremes
What was the major group in the Late Jurassic era?
Ancestor of Therians, today represented by marsupials and placentals
What occurred in the Cenozoic era, tertiary period?
Age of mammals
What occurred in the Cenozoic era, quartenary period, Pleistocene epoch?
Ice age, homo erectus
What occurred in the Cenozoic era, quartenary period, Holocene epoch?
Rise of homosapiens
