Download Homework Exercise 4

Forces in Everyday Life
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Homework Exercise 4
Use the link and notes to complete a frame on Tropisms
Forces in Everyday Life
External Environmental Factors
Light- Light, obviously affects the plants ability to grow because light is needed
for photosynthesis. Through photosynthesis the plant makes its energy
carrying molecules. It is also needed for the production of chlorophyll.
Day Length- Day length causes the plants to flower. Many other roles of day
length are being studied such as fruit and seed germination, dormancy, and
leaf loss.
Gravity- Gravity causes roots to grow down toward the soil and roots to grow
up away from the source of gravity.
Temperature- Higher temperature, to a point, is best for plant growth while
low temperatures are needed for some plants to flower.
Forces in Everyday Life
1. Tropism: the way a plant grows in response to stimuli
in the environment. Tropisms are usually named for the
stimulus involved and may be either positive (towards
the stimulus) or negative (away from the stimulus).
a. Phototropism: growth response to light
-Plants bend towards light
a. Geotrophism: growth response to gravity
-plant roots grow down with gravity, shoots (stems) grow up
against gravity and out of the soil.
a. Thigmotropism: growth response to touch
-vines grow up around trees, venus flytrap closes when leaves
are touched
a. Hydrotropism: is the growth response of a plant to water.
Forces in Everyday Life
a.Phototropism: growth response to light
-Plants bend towards light
Forces in Everyday Life
a.Geotrophism: growth response to gravity
-plant roots grow down with gravity, shoots
(stems) grow up against gravity and out of the soil.
Roots exhibit positive
geotropism while
stems and leaves exhibit
negative geotropism.
Forces in Everyday Life
a.Thigmotrophism: growth response to touch
-is the growth response of a plant to physical
contact (touch). Plants that cling to physical
structures such as walls exhibit positive
thigmotropism.
Forces in Everyday Life
a.Hydrotropism: is the growth response of a
plant to water.
Roots exhibit positive
hydrotropism.
Forces in Everyday Life
a.Seedlings push upwards against gravity.
Their root tips are shaped like a wedge to
push down into the soil as they grow.
Osmosis
• Osmosis is diffusion of water through a
differentially permeable membrane from a
region where there is more water, to a
region where there is less.
• Turgor Pressure causes the cell to
expand
Forces in Everyday Life
a.Plants need water to maintain turgor
pressure, which helps to keep them erect.
The leaves of this plant are droopy because
of a lack of water.
b.Turgor Pressure is a force exerted outward
on a plant cell wall by the water contained
in the cell vacuole.
c. http://www.youtube.com/watch?v=fNyYuVarTIQ
Molecular Movement
• Plasmolysis - (Dehydration in Plants)
– Loss of water through osmosis is accompanied
by shrinkage of the cell membrane away from
the cell wall.
Plasmolysis (Dehydration)
Turgor Pressure
A lot of turgor pressure
Less turgor pressure
Substances Transported by Active
Transport
• How do plants manage to
survive growing in salt water?
• Obtain water via osmosis
• Cells contain organic
compounds that prevent
plasmolysis (dehydration)
• Salt is pumped out of the cells
by active transport
• Active Transport - when cells
must move materials in an
opposite direction. (like salt)
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Forces in Everyday Life
a.Your body has many
different types of simple
machines
Class three lever (crane)
b. Most machines in your body are
levers that consist of bones and
muscles. The muscles produce the
input force, and the output force is
sued for everything from lifting
your hand to swinging a hammer. A
muscle can't push, only pull. How
can you bend your arm?
Forces in Everyday Life
a.Your body has many different types of
simple machines
Forces in Everyday Life
What happens if you
increase pressure on a fluid
at one end of a container
with a hole at the other end?
This example shows how a
force pump works. A force
pump causes a fluid to move
from one place to another by
increasing pressure in the
fluid.
Your heart is a force pump.
Blood is the fluid.
Forces in Everyday Life
If our incisors are good for cutting, why don’t we use
them to chew? (it’s not efficient, because cutting only
breaks the food into two pieces, the molars can mash
the food without breaking the pieces apart).