1. Leaf Homologies Identification Tree shape
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 & BUNDLES OR CLUSTERS
FLAT
length
SQUARE or 4-SIDED
Color
BUNDLES OR CLUSTERS
DECIDUOUS
EVERGREEN
# of needles held in BUNDLES

6. Broadleaf Trees

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

9. Leaf shape

10. Leaf arrangements Opposite Whorled Alternate Basal
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

11. Leaf Arrangement—Opposite vs. Alternate

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

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

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

16. Some broadleaf trees have TOOTHED MARGINS or Serrated characterized by a saw-like edge on the leaf.

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

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

19. Venation
1) Net 2)Parallel

20. Tree shape