We usually think of jaws as structures that evolved for biting. What might have been a different original use, and what is the evidence for this?
What will be an ideal response?
Jaws may have originally been used for ventilation: they allow more powerful suction of water when they open, and when they are closed the pharynx can pump water over the gills more efficiently. Jaw muscles form a unified series (in terms of neural control) with the muscles that move the gill arches, possibly reflecting functional integration for gill ventilation. We also know that the earliest jawed vertebrates (placoderms) lacked true teeth, so the original function of the jaw must have been for something other than biting.
You might also like to view...
In the process of phagocytosis, water is transported across the cell membrane.
Answer the following statement true (T) or false (F)
When the superior most points of the iliac crests are palpated, drawing a horizontal line through them bisects the spinous process of the ________ vertebra.
A. L3 B. T12 C. L1 D. L5 E. L4
Genetic information is contained in protein molecules and is passed from one parent to another.
Answer the following statement true (T) or false (F)
What is the correct relationship between chemical reactions and temperature?
A) All chemical reactions are endothermic, and therefore require warmer temperatures. B) Warmer temperatures provide the activation energy required to start chemical reactions. C) Warmer temperatures allow more energy to be released during a chemical reaction. D) Chemical reactions are not dependent on temperature at all.