Transcript Forces in Living Things - ESC-2

Forces in Living
Things Lab
• In science, there is a very specific definition
for the word “work”
• Work only takes place if there is a force and a
motion.
• If there is a force AND motion, then work has
taken place.
• As you go through these labs, think about
what forces are acting on the plants and if
there is any motion.
Lab 1: Emergence of Seedlings
In this lab, each class is going to grow a seedling to
watch the effects of forces on a young, growing plant.
We will read through the information on your lab
instructions.
https://www.youtube.com/watch?v=V-jkL2vLlVI
Lab 1: Emergence of Seedlings
The Sleeping Seed
When seeds are planted, it may take several days
before we can see anything going on. Well, actually,
lots of things are happening that you just can’t see
right away. Right now, the seeds are dormant (almost
like sleeping) but the moisture will trigger them to
start their growth cycle. This process is called
germinating. Once the water soaks into the seeds, it
sends a signal to tell the seed it can start to grow.
The part of the seed that you see right now is called the
seed coat. It protects the young plant. Inside of the
seed coat is the real growing part of the baby seed.
Lab 1: Emergence of Seedlings
It Starts…
Watch the seeds for changes. In a day or two the seed
coats will start to split, and you’ll see the root tip
sticking out. Scientists call that part the radicle.
Watch it dive into the crystal clay to become the
main root. Eventually, it will branch out to become
the root system. In order to sprout, the tiny seedling
has to overcome forces. The stem and first leaves
have to overcome gravity and the weight of the soil
on top of them to emerge from the ground. The
roots have to be strong enough to push through the
soil beneath them.
Lab 1: Emergence of Seedlings
First Leaf…
The radical drinks up water so that the plant can start
to grow. As the stem grows
and the seed coat splits off, you will see the first new
green leaf. The first leaf is
called a cotyledon. The tiny plant needs water, carbon
dioxide, and sunlight. The leaves absorb carbon
dioxide through tiny opening on the underside of the
leaf called stomata. Sunlight can pass through the
leaf and is collected in the chlorophyll of the green
parts of the plant. Water is absorbed through the
roots and in some cases the leaves.
• How does a seed respond to its environment?
• What is a push or pull called?
• What pushes or pull are involved in a seed
growing?
Lab 1: Emergence of Seedlings
Materials
• clear tube or cup
• crystal clay
• pinto beans
• spring water
Lab 1: Emergence of Seedlings
Procedure
1. Place half a scoop of crystal clay in the cup.
2. Add a small amount of spring water.
3. The crystals will expand as they absorb water. Add
water as needed until there is enough to plant a
seed in.
Lab 1: Emergence of Seedlings
Procedure
4. Wait 20 to 60 minutes. If any of the crystals are still
exposed above the water line, add more water one
teaspoon at a time. Re-Check every 30 minutes and
add water as needed until the crystals have stopped
expanding. If the crystals reach the top of the tube,
remove some until it is no more than ¾ full. If there
is too much water, pour some off of the top.
5. Add the beans. Do not bury them and make sure
that the water level is high enough to keep the seeds
moist, but not soaked, during the first 3 days.
Lab 1: Emergence of Seedlings
Procedure
6. Put the seed in a bright, cool place.
7. Add water as needed to keep the water level just
below the top of the crystals.
8. After 1-2 days, take out any seeds that have not
germinated.
• Hypothesis:
I think the roots will__________,and
the stems and leaves will
________________________ .
• Label your bean diagram on your lab answer
sheet.
• Label the diagram of the bean seedling
• Questions 1-5 will be answered after the
seeds sprout.
Lab 2: Geotropism
Lab 2: Gravitropism
In this lab, we will observe how gravity can affect
seedling growth.
Have you ever wondered how a plant knows which way
to grow? Imagine how Earth would look if plants could
grow in many different directions. On Earth, a force
called gravity signals young seedlings to push their
stems up and their roots down.
Lab 2: Geotropism
Materials
• 4 bean seeds
• petri dish
• tape
• cotton balls
• tap water
Lab 2: Geotropism
Procedure
1. Take four soaked seeds, and place them in the
bottom of a petri dish with the seed “dimples” facing
toward the center. A seed should be placed on the
12, 3, 6 and 9 o’clock positions of the petri dish.
Lab 2: Geotropism
Procedure
2. Place cotton balls on top of the seeds to hold them
in place.
3. Using the spray bottle, dampen the cotton balls. Do
not get them so wet that they drip.
4. Carefully cover the seeds with the petri dish lid.
5. Close the petri dish and tape the lid in place.
Lab 2: Geotropism
Procedure
6. Diagram the petri dish set-up at the beginning of the
lab and after the seeds sprout.
7. Write the group member names on a small piece of
paper and tape it to the back of the petri dish.
8. Place the petri dished vertically in a dark place such
as a closet or cabinet.
• Hypothesis:
How do you think each of the bean seedlings
will grow? Draw a detailed diagram of your
hypothesis on your lab sheet.
• Hypothesis:
Make sure you diagram the set-up and draw
arrows to predict which way the roots and
stems will grow for each seed.
• The “after” drawing and questions 1-6 will be
done after the seeds have sprouted.
Lab 3: Turgor Pressure
Lab 3: Turgor Pressure
In this lab, we will observe how water can affect the
rigidity of a plant.
We know that plants require sunlight, water and soil to
survive. Water is used by the plant for many different
purposes. First, water is needed for photosynthesis.
Plants also need water to “inflate” their cells and keep
the stems and leaves upright. When a plant does not
have enough water, it will wilt and droop. If it goes long
enough without water the plant cells die.
Lab 3: Turgor Pressure
The water inside the cell puts pressure on the cell just
like water inside a balloon pushes out on the balloon.
The pressure that the water exerts is called turgor
pressure. High turgor pressure in a plant keeps all of
the leaves and stems upright. Low turgor pressure
causes the plant to wilt.
Lab 3: Turgor Pressure
If a plant is placed in salt water, the water inside the
cell is pulled out and dehydrates the cell. When
placed in fresh water, water can enter the cell.
Materials:
strips of potato
salt
water
2 beakers
Lab 3: Turgor Pressure
Procedure
Most of this has been done for you.
1. Soak some strips of potato in salt water.
The salt water will cause water inside
the plant cells to leave.
Lab 3: Turgor Pressure
Procedure
1. Soak some strips of potato in fresh water.
The fresh water will cause water from
outside the cell to go in.
• Hypothesis:
Which potato strip will have high turgor
pressure and which one will have low turgor
pressure?
Lab 3: Turgor Pressure
Procedure
2. Take one potato strip that was soaked in salt water
and that was soaked in fresh water.
3. Bend each strip until it breaks.
For this experiment, you can go ahead and complete
the scientific method flow chart and questions 1-5.