In my opinion, experiment design is the part of the course that I’ve been struggling with the most in this class. We’ve learned about various types of experiments and different ways to go about designing an experiment. The types of experiments include rescue experiment, dose response experiment, take away, etc. For example, a rescue experiment consists of altering something in the experiment that would ultimately benefit the object or organism that was being researched. A dose response experiment would involve the addition of different amounts of a certain variable to the object or organism being tested in different trials during an experiment. However, these are just a couple of the techniques that one could go about designing an experiment and the two types of experiments that I have been feeling most comfortable with. One of the main things to remember that has helped me with experimental design problems/questions is to remember to keep it simple! And don’t overthink it!
Example experiment (from breakout session):
A dandelion placed in sunlight (natural light) will reach the fifth stage of development while a dandelion placed under a lamp did not fully develop.
A dandelion placed in artificial lighting will not fully develop because they are not receiving the appropriate amount/intensity of light as a dandelion placed in sunlight (again, keep it simple).
The UV light that is present in sunlight is what causes the dandelion to reach the fifth stage in dandelion development.
The dandelion placed directly under a lamp will not fully develop for they are not receiving the same range of light as a dandelion in natural light.
For example, we can use the first hypothesis for a dose response experiment keeping in mind to keep it simple and not overthink or overcomplicate things!
You should first come up with a positive and negative control for your experiment. I used to be confused by which would be which, but to my understanding a positive control would be an experiment with conditions that would result in an outcome that would agree with your hypothesis. A negative control, on the other hand, would be an experiment that would result in an outcome that would NOT follow your hypothesis.
Positive control: Place a dandelion plant directly under a lamp.
Negative control: Place a dandelion that is in the same developmental stage in direct sunlight.
Now, identify and explain what it would mean if the negative control did and did not respond the way we were expecting it to. For example, if the negative control fully developed in direct sunlight it would mean that there was something specific to the sunlight causing the dandelion to develop fully. If the plant placed in direct sunlight still did not fully develop, it would indicate that sunlight is not the factor causing the dandelions to reach the fifth stage of dandelion development.
With the controls set up, we can continue with our dose response experiment. Our hypothesis was that a dandelion placed in artificial lighting would not fully develop because they were not receiving the appropriate amount/intensity of light as a dandelion placed in sunlight. So one possible experiment could be placing similar dandelions under different intensities or wattage of light bulbs and observing and analyzing those results.
I hope that this was easy to follow and I hope I made enough sense that I was able to help some of you!
WHAT: Photosynthesis is the process of absorbing and converting electromagnetic energy from sunlight to produce sugar/carbohydrates. The newly produced chemical energy is stored in the C—H and C—C bonds of sugar.
WHEN: Photosynthesis only occurs when sunlight, carbon dioxide and water are present. Blue and red photons are also vital to this process due to chlorophylls absorption of these wavelengths. Chlorophyll is the main photosynthetic pigment.
WHERE: Photosynthesis only takes part in the green parts of a plant, specifically chloroplasts.
WHY: Photosynthesis is absolutely essential to life because, for autotrophs, it’s their method of producing their own food. It is with the existence of photosynthetic organisms that humans and other non-photosynthetic organisms can exist.
HOW: A flowchart that expands over pages 192 and 193 gives a pretty straightforward breakdown of the process of photosynthesis. Also, McGraw Hill has cheesy helpful animated videos on photosynthesis that will be helpful for visual learners.
Video on Photosynthetic Electron Transport and ATP Synthesis:
Video on the Calvin Cycle:
Here’s a repost of the link above. If this doesn’t work the second time, just type “McGraw Hill photosynthesis” into the Google search bar.
Ch. 39 Plant Sensory Systems, Signals, and Responses
There were a lot of key points in this chapter, but I chose the two that I thought were important, signal transduction and the opening and closing of stomata/guard cells.
Signal transduction: changing a stimulus from external to internal signal.
Stimulus sends a message–>Receptor receives the signal and changes signal to internal signal–.> Hormone which is released by the receptor, travels through the plant and carries signal/information to target–>Responder cells, responses to signal and causes physiological response.
Two types of signal transduction are phosphorylation cascades and second messengers. Phosphorylation cascades happen when receptor proteins shape changes when phosphate group from ATP is added. Second messengers are produced when there released from storage areas/vacuole.
Another important point in this chapter is the opening and closing of stomata/guard cells. We went over guard cells in class, breakout and review session so there is a 99% chance it’ll be on the exam. When guard cells are open when there filled with water, the cells are turgid, which allows gas exchange. When they lose water, the guard cells lack turgor and changes shape that closes them. In order for guard cells to open, they require energy. Often there opened during photosynthesis. Inside is negative and outside is positive, thus protons want out.
1. Blue lights hits signaling H+ ATPase to pump protons out.
2. Because inside is negative and outside is more positive due to protons, K+ wants to go in. Cl- goes in with H+ through co-transporter.
3. Water follows by osmosis
4. The cell swells and it opens.
To close the guard cells
1. Aba, a signal that tells the H+ ATPase to stop pumping and close. It directs Cl- to open and Cl- leaves the cell.
2. The change in membrane causes K+ to leave the cell along a gradient.
3. Water follows by osmosis
4. The cell shrinks. It closes.
Homeostasis: keeping yourself alive or stable
Phloem – controls where nutrients, sugars, ___ go in a plant. The plant must be able to send these to the correct places or it won’t be able to survive.
Roots gather nutrients, what other ways can plants get nutrients? (insects, fungi)
Guard cells – open to allow transpiration, receive CO2, and release O2. Can react to environment, hot/dry conditions.
Cell Membranes: what separates the inside of the cell from the outside
Osmosis – is able to go through cell membranes.
The egg experiment (where the eggs had different liquids adding to them, and grew or shrunk) is an example of this. The water passes through the cell membrane
Cell-Cell Communications: cells signaling and passing information
Hormones: carry information to other cells which is amplified if the cell has a receiver. They can respond by phosphorylation cascades or second messengers.
The capped root experiment in the book pg 759.
Interdependence: many things relying on each other
Photosynthesis is most productive when both photosystems one and two are both working. Plastocyanin is the protein at the end of photosystem two that can take electrons to photosystem one.
Flow down gradients : a gradient is like a slope of a line increasing or decresing
Sodium/ Potassium pump – Figure 38.10 in book. Proton pumps pump out H+ and establish an electrochemical gradient. Then cations will want to enter the cell because it is negative, and enter through a channel.
Water, solute, and pressure potential –
Photosynthesis – this is plants way of making usable energy to stay alive and grow. Chlorophyll uses the electrons from sunlight to make an electron transport chain which makes an electrochemical gradient and ATP. Then they are used to make NADPH.
Chloroplasts and Pigments
Structure and Function
Xylem vs. Phloem – They do almost the same function, moving water through the plant. Xylem is dead and moves water upwards or to lower water potential. Phloem can move the solutions in different directions using a gradient.
Modified roots (corn and mangroves), stems (tubers and rhizomes), and leaves (onion and poinsettia). Photos in Ch. 36 and all the stuff we looked at in lab.
Phenotype Plasticity: ability to change in response to environment
Leaf transpiration experiment – how the plant responded when subjected to different environments. Guard cells opening and closing.
How Oak leaves respond to being in the sunny or shady part of the tree. They grow bigger in the shade and smaller in the sun. Pg. 703
I liked your interdependence example of PS1 and PSII. I wouldn’t have thought of that connection.
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