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Archimedes Plutonium wrote in
: Monique Reed wrote: Archimedes Plutonium wrote: So my question today is how did anyone come to realize that a blackwalnut leaf was compound with many green blots? It is purely a matter of structure. Leaves usually have buds in their axils (the angle between leaf and stem). These buds will produce additional shoots, leaves, or flowers. Something with simple leaves has buds in every axil. Something with compound leaves does NOT have buds in the axils that the leaflets make with the axis of the compound leaf. That is how you tell--look for the axillary buds. Whatever is beyond the axillary bud is all one leaf. Does compound leaf mean the blackwalnut was a recently evolved tree and that noncompound leafed trees are geologically older. It is generally believed that simple leaves are the more primitive form and that compound leaves represent the derived state. This character has arisen independently in different groups many, many times. (That is, one cannot say that all plants with compound leaves share a common lineage or that all plants with compound leaves are older than all plants with simple.) And what survival value is it to a tree to have compound leaves rather than noncompound? In some cases, having finely divided leaves can break up air flow over a leaf, reducing transpiration. This can be an advantage in dry climates. In other cases, there does not seem to be an advantage--or a drawback. Not every feature of an organism is beneficial or harmful--many are neutral until some change in environment selects for one state or another. Or is this compound leaf thing just semantics with no biological difference from say oak leaves or rose leaves or apple leaves. No, not semantics. Morphology. Have a look at a flowering plant systematics textbook--it will tell you about simple and compound leaves. Monique Reed Texas A&M I am trying to think of an analogy for animals in the manner that compound leaves are to trees. Fur, feathers, scales on the heat protection side, and multiple stomachs as cows have on the food obtaining side. These analogies are kind of forced though. Maybe they are extremely forced. OK, they are so forced that they are silly. I wonder if any animals were borne with extra hands or extra fingers. I wonder if any animal was borne with extra eyes. Yes, there was an animal born with extra eyes, I am sending it over to your house, it should arrive in 12 days, right around sunset. Do not attempt to dissect it, just give it something with sugar and let it go, I wonder if any animal was borne with a compound heart, or extra heart. I believe it was reported that a horse had two hearts but did not pass that trait on. I am looking for a analogy in animals that somewhat matches compound leaves in plants. Chang and Eng? Sean |
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