Plants

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Plants

• Plant Adaptations

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Functional Adaptations

• Plants must capture and store sufficient water,
  light and minerals to survive.
• They develop adaptive
• Root structures
• Leaf structures
• Seed dispersal

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Roots

• There are two main type of root systems.
• Taproots
• Fibrous roots

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Taproots

• Taproot SystemCharacterized by having one main
  root (the taproot) from which smaller branch
  roots emerge.  When a seed germinates, the first
  root to emerge is the radicle, or primary root. 
  In conifers and most dicots, this radicle
  develops into the taproot.   Taproots can be
  modified for use in storage (usually
  carbohydrates) such as those found in sugar beet
  or carrot.  Taproots are also important
  adaptations for searching for water, as those
  long taproots found in mesquite and poison ivy.

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Taproot
http//alpha.furman.edu/lthompso/bgy34/plantanat
omy/plant_root.htm
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Taproot

• Plants that need to search deep into the earth to
  retrieve water develop this type of root system.

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Fibrous Root

• Fibrous Root SystemCharacterized by having a
  mass of similarly sized roots.  In this case the
  radicle from a germinating seed is short lived
  and is replaced by adventitious roots.
  Adventitious roots are roots that form on plant
  organs other than roots.  Most monocots have
  fibrous root systems.  Some fibrous roots are
  used as storage for example sweet potatoes form
  on fibrous roots.  Plants with fibrous roots
  systems are excellent for erosion control,
  because the mass of roots cling to soil
  particles.

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Fibrous Root
http//alpha.furman.edu/lthompso/bgy34/plantanat
omy/plant_root.htm
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Fibrous Roots

• These roots spread out so that they can soak in
  as much water as quickly as possible.

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Leaf Structures

• Plants can adapt their leaves in many different
  ways.
• Size
• Shape
• Color
• Functions

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Leaf Structure

• Leaves can be either deciduous or evergreen.

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Leaf Sturctures

• Deciduous leaves typically have a lifespan of
  just one season. In the autumn of the year, such
  leaves change color in a process known as
  senescence (aging) culminating in leaf abscission
  (falling off). While the plant recovers minerals
  and other chemicals from the leaf during
  senescence, the falling leaf may carry away
  significant toxins from the plant. Thus
  abscission may be a mechanism functionally
  equivalent to excretion for some plants.

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Leaf Structures

• Evergreen leaves typically have a lifespan of
  several seasons. Because new evergreen leaves are
  produced each year, the plant is never completely
  bare of leaves...hence the name evergreen. In
  fact evergreen trees have leaves that do senesce
  and abscise. We often fail to notice the process,
  but the litter on the forest floor in a pine
  forest tells us that it happens. Closer
  examination in autumn reveals that needles of
  pines that are two years (older in some species)
  old turn yellow and all fall from the trees at
  the same time as maple trees!

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Leaf Structure

• Many plants limit water loss through their leaves
  by adapting the size, sheen, or texture of their
  leaves. Small leaves or spines limit the amount
  of surface area exposed to the drying heat.
  Glossy leaves reflect the Sun's radiant heat
  reducing leaf temperatures and evaporation rates.
  Waxy leaves prevent moisture from escaping. Water
  escapes from leaves through the stomata, or leaf
  pores.

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Leaf Structures

• A behavioral adaptation used by some plants is to
  only open leaf pores during the night when air
  temperature is cool and evaporation rate is low.

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     Sagebrush is the name given to several
shrubs with a bittersweet odor.  It typically
grows in drier climates and areas with high
exposure to sunlight.  The leaves are small and
tightly clustered, and the plant itself rarely
reaches more than 3 meters or so in height.  When
it gets dry enough, sagebrush will often look
dead, and will even get blown off it's roots by
the wind.  In this way, it can distribute it's
seeds to grow elsewhere when moisture is
available.
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The Utah juniper is a medium-sized tree growing
to between 7 and 10 meters in height.  It carries
blue-green berries and has extremely small leaves
that are often referred to as needles.  The
leaves grow in tight clusters and have a dry
texture.  The bark, pictured above, is often
deeply grooved and shaggy.
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The Douglas fir is a conifer that can grow up to
75 meters in height.  They have two-sided needles
that typically grow to 2½ centimeters in length. 
The trunks of these trees can get to an
impressive 2½ meters in thickness, and the trees
will live up to 800 years before they stop
growing.  It should also be noted that the
Douglas fir is one of the most valuable timber
trees in the world.  It provides more than half
of the timber used in building homes, making
paper, and other such wood-based products.
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    Gambel oak is a medium-sized tree growing
only to around 15 meters in height.  They will
typically grow in large groups, often times
making entire forests of nothing but gambel oak. 
They grow oak acorns, which are a primary food
source for small rodents that live in areas
around gambel oak, as well as being a diet of
many birds and even deer.
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Defensive Adaptations

• In order for plants to continue the plant life
  cycle they must survive long enough to produce
  their offspring.
• Plants need to be able to defend themselves
  against predators in order to survive. 
  Therefore, they have developed many defensive
  adaptations. 

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Defensive Adaptations

• Plants as we know have evolved ways to defend
  themselves by using sharp spines, thorns or
  hairs cellulose that makes them hard to digest,
  or creating chemicals that makes the plant toxic
  or smell bad. 

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Defensive Adaptations

• Another unusual way some plants have evolved to
  defend themselves is through mimicry - that is
  they evolve to look like another plant that is
  poisonous and animals are fooled into believing
  that they are poisonous.  Thus the plant does not
  get eaten and does not have to waste energy
  producing a poison or other defense mechanism. 

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Defensive Adaptations

• It makes sense that through natural selection,
  those plants that look more like real poisonous
  plants would survive to pass on their genes while
  others would get eaten.  This is how mimicry
  occurs.  Note that some animals use mimicry as
  well.  For instance there are some flies that
  have evolved to look exactly like bees (see
  picture), but they have no sting!

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Cattails are long, slender plants that grow on
the edges of freshwater areas such as small
rivers, streams, ponds and lakes.  They are a
bright green in color and have a massive brown
growth at the top that holds it's seeds until
they are ready to be released.  Cattails, along
with bulrush, provide an indispensable habitat
for entire communities of insects, small mammals,
and other plants.
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So What did you learn?

• Write a letter to a classmate that was absent
  from school today.
• Describe for your classmate why plants must
  develop adaptations.
• Describe some of the different adaptations that a
  plant may develop.