Term
| What is the main feature of amniotes? |
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Definition
| A series of extra-embryonic membranes that grow out of the developing embryo, one of which is the amnion. |
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Term
| Amniotes probably evolved from _____ |
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Definition
| Anthracosaurs, terrestrial crocodile/lizard-like amphibians (Diadetes) |
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Term
| Apart from the amniotic membrane, what other characteristics do amniotes share? |
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Definition
Rib movement ventilates lungs (negative vs positive pressure)
Dessication-resistant skin (thick stratum corneum & phospholipids
Skeletal differences (Absence of notic notches, clavicle bone in pectoral girdle, pelvic girdle attached to vertebral column by at least 2 sacral vertebrae, astragalus bone in ankle) |
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Term
| What allowed the amniotic egg to be water resistant? |
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Definition
| The addition of shell membranes + the shell, which internal fertilisation allowed. |
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Term
| Amniotes do not have a larval stage. True or false? |
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Definition
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Term
| What are the 4 membranes of an amniotic egg and their functions? |
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Definition
Amnion: encloses embryo in fluid filled space
Yolk-sac membrane: Encloses yolk and functions as gas exchange structure in early development
Allantois: Surrounds inside surface of shell, stores nitrogenous waste. Later fuses with chorion to form chorioallantois (important respiratory gas exchange structure)
Chorion: Lines inside surface of eggshell, later fuses to form chorioallantois |
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Term
| What comprises the stratum corneum? |
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Definition
| Many layers of dead keratin filled cells, and phospholipids (high resistance to water loss) |
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Term
| Name and describe the three types of temporal fenestra associated with most amniotes |
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Definition
Anapsid: basal condition, no fenestra
Synapsid: derived condition, two fenestra on each side of dermatocranium, modified in lizards, snakes, birds
Diapsid: derived condition, one fenestra on each side of dermatocranium. Modified in mammals |
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Term
| Amniotes have lost the otic notches found on the back of the skull. True or false? |
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Definition
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Term
| Turtles are anapsids, true or false? |
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Definition
| False, they are modified diapsids, showing an anapsid condition |
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Term
| In mammals and crocodilians, what physically separates the air passage from the mouth cavity, helping mammals breathe whilst chewing and reinforcing crocodilian jaws? |
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Definition
| Bony secondary palate (set of mouth roof bones) |
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Term
| Describe the modifications found in lizards and snakes, compared with tuatara |
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Definition
| Tuatara is a diapsid, whereas lizards have a loss of the lower bar (modified diapsid) and snakes have lost the middle and lower bar (modified diapsid) |
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Term
| The most extreme example of cranial kinesis can be seen in ___ |
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Definition
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Term
| Why did temporal fenestra evolve? |
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Definition
| Probably in response to a need to increase jaw muscle size, maybe brain size |
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Term
| Why does a mammal need to breathe whilst chewing? |
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Definition
| They are endotherms - lungs need continous ventilation |
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