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