Lecture 7 Flashcards
Why were plants a good source of energy 365mya?
They were abundant, an unexploited energy source with no competition
What was the food chain for early tetrapods based upon?
The aquatic system of carnivory
What challenge faced animals who wanted to use plants as an energy source?
Cellulose
Why couldn’t early terrestrial animals digest cellulose?
It is composed of beta glucose which they were unable to digest.
How did the synapsids jaw make it difficult for them to break down plant matter?
Sharp cone teeth which lacked dental occlusion
Jaw composed of several bones
Temporal fenestra was in line with lower jaw
When did the synapsids walk the earth?
300mya
How did the early cynodonts adapt to breakdown plant matter?
They acquired dental occlusion by changing the shape of their teeth
Their temporal fenestra was raised to increase jaw strength
When did the early cynodonts roam the earth?
260mya
How did the late cynodont adapt to mechanically breakdown plant matter?
Jaw articulation by two bones
Complex cusp pattern of molars and premolars
Temporal fenestra located above mode of action
When did the late cynodonts roam the earth?
195mya
What are the role of incisors?
Pincers for grasping or grooming
Elongated chisels for gnawing
What is the function of canines?
Elongated to stab and hold prey
What is the function of molars in carnivores?
Carnissal teeth
Slicing and tearing flesh
What is the function of the molars in the herbivores?
Grinding
What are the selenodonts?
Molars with crescent shaped ridges
What are the lophodonts
Molars with ridges between cusps
What are the loxodonts?
Molars with extreme lophodont ridges
What are the four points on a molar?
Metacone
Hypocone
Paracone
Protocone
What type of teeth are common in browsers?
Brachydont teeth which have low crowns and finite growth
What time of teeth are common in grazers?
Hysodont which are high crowned teeth which are constantly growing
How have insects adapted to breakdown cellulose?
They have developed endosymbiont relationships with bacteria that can break down cellulose by consuming them.
How have tetrapods evolved to digest cellulose?
They have developed an endosymbiotic relationship by consuming the required microorganisms or consuming insects containg the required microorganisms
Describe hindgut fermentation
The caecum has been enlarged ti allow faster digestion
Fermentation of cellulose by microorganisms
Cellulose utilisation is 45%
Suits high starch food
Suits low energy food
Describe foregut ruminants
Enlargement of foregut and additional mechanical breakdown Cheing the cud Longer digestion 60% cellulose abosrbed Inefficient processing of starch
What is chewing the cud?
When contents are rechewed to further breakdown cellulose
Which method of fermentation do small mammals prefer?
Hindgut fermentation as need energy fast
What type of digestion do medium sized mammals prefer?
Foregut rumination
What type of digestion do very large mammals prefer?
Hundgut fermenters
