Leaves Leaf Homologies Identification Tree shape
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LeavesLeaf HomologiesIdentificationTree shape
Leaf HomologiesEach leaf has a very different shape and function, yet all are homologous structures, derived from a common ancestral form.
What are Homologies?
Shared similarities between organisms that are derived from common ancestors
Broadleaf or Conifer?BROADLEAF (tree with leaves that are thin, flat & usually shed annually)CONIFER (tree that bears cones and has needle-like or scale-like leaves)
ConifersNeedle-likeSINGLYFLATlengthSQUARE or 4-SIDEDColorBUNDLES OR CLUSTERSDECIDUOUSEVERGREEN# of needles held in BUNDLESScale-like &Awl like
What external features can help identify leaves / trees?Leaf shapeLeaf arrangementLeaf divisionVenationTree shape
Each node has one leaf Whorled
One node producing three or more leaves Basal
Leaves originating in a cluster at the stems base Opposite
Two nodes opposite each other on the stem, one leaf arising from each node
Leaf ArrangementOpposite vs. Alternate
Leaf marginsWhat is a leaf margin???
The MARGIN of a leaf is the leaf edge.
Some broadleaf trees have leaves with smooth edges or ENTIRE MARGINS.
Some broadleaf trees have LOBED LEAVES, leaves with projections that shape the edge of the leaf.
Some broadleaf trees have TOOTHED MARGINS orSerratedcharacterized by a saw-like edge on the leaf.
Leaf DivisionSimple vs. Compound Leaves. What is a leaflet?
Leaf divisionSimple LeavesSingle blade
Compound LeavesBlade divided into leaflets