Leaf and Tree a Science Olympiad Event

Leaf and Tree
Science Olympiad
If there are
 North America: > 700 different
 In the world: > 100,000 type of
How are we going to identify them?
Dichotomous Key
A scientific tool that allows us to
identity something in the natural
 trees,
 wildflowers,
 mammals,
 reptiles,
 rocks,
 fish.
The key consist of a series of choices that you make.
Each choice leads you closer to the correct name of a your item.
Dichotomous means divided into two parts. Therefore, a dichotomous
keys always give two choices in each step.
When you look at a dichotomous key it will begin to ask you
leaf, needle, or scale like
shape of the leaves
needle count
pine cones
how needles are clustered
Okay so what are all the things we need to have before we can
identify a tree?
Leaf, picture of tree for height, bark, entire branch with older
leaves (not just tip of the branch where new leaves/needles are
located), sample of fruits or cones.
A Walk in the Park
No leaves on the tree!!
What are you going to do?
Look on the ground beneath
the tree for shed leaves and
seeds can often help. Be
careful of mixing up the
leaves between neighboring
trees though.
leaves have fallen, look down
There are buds and twigs high
in the tree but out of reach
Narrow down by location TN vs GA
vs WA – use a field guide specific to
your area
bark design can give you clues
Much easier than Winter time!
Leaves and needles give us a lot
of information.
Seeds, acorns
Okay so when you begin lab
there are many questions you
will need to answer.
You will have a station with a
web page, or a field guide in
either book format or printed
Questions you will be looking to
Needles or Leaves
1. Opposite growth
pattern −
Twigs and/or leaves
are attached to the
limb directly across
from one another.
2. Alternate growth
pattern −
twigs and/or leaves
are attached to the
limb in a zigzag
pattern not across
from one another.
3. Simple leaf −
A leaf that has only one leaflet attached to the
tree limb.
4. Compound leaf −
A leaf that has two or more leaflets attached to a
central leaf stem that is in turn attached to the
tree limb.
5. Margins of the
Bristle tip − projects
out from the central
leaf like a finger on a
Needle-like point
sticking out at the
end of each lobe.
Toothed margin −
Coarse to finetoothed edges.
1. Are the trees EVERGREEN
with needles arranged in
clusters of 2-5?
2. Are the trees EVERGREEN
with needles arranged
3. Are the trees DECIDUOUS
(shedding all leaves
annually) with needles
arranged in clusters of
many on short, spur-like
4. Are the trees DECIDUOUS
with needles of uneven
length flattened along the
twig. The cone a 1"
diameter green or brown
wrinkled ball?
Needle Like or
Scale Like
Types of Fruits and
Cones (book)
Types of Silhouettes

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