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Leaves

Leaves. Leaf Homologies Identification Tree shape. Leaf Homologies. Each 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 .

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Leaves

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  1. Leaves Leaf Homologies Identification Tree shape

  2. Leaf Homologies Each leaf has a very different shape and function, yet all are homologous structures, derived from a common ancestral form.

  3. What are Homologies? • Shared similarities between organisms that are derived from common ancestors

  4. 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)

  5. Conifers • Scale-like & Awl –like • Needle-like • SINGLY • FLAT • length • SQUARE or 4-SIDED • Color • BUNDLES OR CLUSTERS • DECIDUOUS • EVERGREEN • # of needles held in BUNDLES

  6. Broadleaf Trees

  7. What external features can help identify leaves / trees? • Leaf shape • Leaf arrangement • Leaf division • Venation • Tree shape

  8. Leaf shape

  9. Leaf arrangements Opposite Two nodes opposite each other on the stem, one leaf arising from each node Whorled One node producing three or more leaves Alternate Each node has one leaf Basal Leaves originating in a cluster at the stem’s base

  10. Leaf Arrangement—Opposite vs. Alternate

  11. Leaf margins What is a leaf margin??? • The MARGIN of a leaf is the leaf edge.

  12. Some broadleaf trees have leaves with smooth edges or ENTIRE MARGINS.

  13. Some broadleaf trees have LOBED LEAVES, leaves with projections that shape the edge of the leaf.

  14. Some broadleaf trees have TOOTHED MARGINS orSerratedcharacterized by a saw-like edge on the leaf.

  15. Leaf Division Simple vs. Compound Leaves. What is a leaflet?

  16. Leaf division • Simple Leaves • Single blade • Compound Leaves • Blade divided into leaflets

  17. Venation 1) Net 2)Parallel

  18. Tree shape

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