Is Sexual Reproduction Important?

      In Chapter 13 of Dr. Tatiana's Sex Advice to All Creation, a TV show called Under the Microscope--A Deviant Lifestyle! is described, in which a Philodina roseola, the bdelloid rotifer, is interviewed and questioned by many other animals. She claims that her species has not used sexual reproduction since 85 million years ago, when the dinosaurs were on Earth. Her species has produced asexually, in other words, they cloned themselves. After all the arguments and events that occur during the show, the rotifer finally explains that secret to her species living for this long without sexual reproduction.

     A benefit of reproducing asexually is that it is very efficient. As written in the article, "...an asexual female who appears in a population should have twice as many offspring as her sexual counterpart." (215) Plus, you don't need a mate, so you don't have to spend time/energy trying to get one.  The rotifer continues and explains that over the years, genes in her species have changed through one process: mutation. She is able to proves that there are no male bdelloid rotifers in the world. A mouse then explains, "...if you don't have sex, you can't adapt to the future?" (224) The Philodina says that her species kept adapting and they live in many different areas and places. Another animal asks how the rotifers get rid of harmful mutations, but the Philodina counters that most mutations are neutral, that they change an organism's DNA sequence, but doesn't change that organism itself. 

     Then the host of the show steps in, and explains the three most important theories about mutation. In Muller's ratchet, named after Hermann Muller, harmful mutations will stay in asexual species and the number of mutations will ratchet up after periods of time. After some time, the species will go extinct. and the sexual organisms will survive because the shuffling of genes will have some organisms with few mutations. However, this theory relies on the fact that the population of the asexual species is small, and that could sometimes not be the case. In Kondrashov's hatchet, there is a threshold number of harmful mutations an organism can have before it dies. The shuffling of genes in sexual organisms prevents this, but asexual organisms have no way to stop it, and "...if the mutation rate is high enough, there is no way to survive without sex." (227)
     The last theory is the Red Queen, and it has to do with infectious diseases. Sexual organisms change their genes, so the parasites cannot stay fully adapted to their hosts. However, in asexual organisms, the genes don't change, so parasites can infect them. Written in the article, it reads "...you have to change to stay where you are." (229) Finally, a nine-banded armadillo talks and reveals to everyone how asexual organisms can survive. Sexual reproduction gives organisms an advantage because it makes them rare. However, the bdelliod rotifers have been traveling, both in space and time. They take part in a process called anhydrobiosis, rendering themselves in suspended animation. When you come to a new place, you are now a unique species, the armadillo explains. Sexual reproduction enables mammals to survive because right now, there is no way for mammals to reproduce asexually. In conclusion, sexual reproduction is important to many organisms because it allows genetic variations, including mutations, competition between organisms, new genetic traits, and parents to care for their young, but it has limitations such usage of time/energy, exposure to STDs/parasites, competition, and bad genetic combinations.

Unit 3 Reflection

     The over-arching topic of this units was cells. A few themes were the structure of cells and photosynthesis vs. cellular respiration. We had to understand that the cell is a basic unit of life and the cells' functions. Specifically, we learned how we got to today's eukaryotic cells from the earliest prokaryotes. We got a basic overview of how cells were discovered. Later on, we got to the structure of cells, specifically membranes. These include vesicles, lysosomes, the endoplasmic reticulum (ER), and of course the cell membrane itself. It led onto the vodacast about diffusion, the passing of objects through the cell membrane requiring no energy. This continued to the topic of osmosis, the diffusion of water through the membrane due to differences in concentration of a solute. After that, we learned about how cells make proteins with its organelles, and by the next vodcast, we learned about the organelles in a cell, like the centriole, choloroplasts, and mitochondria. 

     

     Finally, we learned how photosynthesis works inside a chloroplast with the stroma and grana. It involves the electron transport chain (ECT) , the ATP Synthase, and the Calvin Cycle. The final vodcast of the unit explains cellular respiration, which occurs in the mitochondria. It has three steps: Glycolysis, the Krebs Cycle, and the ECT. Photosynthesis and cellular respiration tie together and are essentially opposites.

My strengths are the parts of a cell and how eukaryotic cells came to be (through evolution). I understand how the cell works and what it does. Photosynthesis and cellular respiration are a bit more complicated. I understand the basic steps, but I will go over them and then understand the specifics and the details, because they are both multi-step processes. My successes are the labs that we have completed and that I have completed and wrote a conclusion on. A setback was the fact that we could not complete the Microscopic Organism Lab, and we had to complete a packet instead. I am a better student now because I have learned from this unit. I am now thorough in the subject of cells and their functions. Two things I want to learn more about are photosynthesis and cellular. They are much more complicated than what we have learned. I wonder how complex these processes actually are. This unit has helped me learn and grow as a student.

     

Photosynthesis Virtual Labs

Lab 1: Glencoe Photosynthesis Lab

http://www.glencoe.com/sites/common_assets/science/virtual_labs/LS12/LS12.html

Analysis Questions

1. Make a hypothesis about which color in the visible spectrum causes the most plant growth and which color in the visible spectrum causes the least plant growth?

If plants are tested with different colors of the light spectrum, red and blue light will cause the plant to grow the most in height.

2. How did you test your hypothesis? Which variables did you control in your experiment and which variable did you change in order to compare your growth results?

Using different color wavelengths on different plants to see amount of growth over a span of time

Controls = type of soil, moisture, seed, amount of light, heat conditions, etc.

Changed Variable (Independent) = color (wavelength) of the light spectrum

Results:

Filter Color	Spinach Avg. Height (cm)	Radish Avg. Height (cm)	Lettuce Avg. Height (cm)
Red	16.87	12.82	11.12
Orange	13.5	8.33	6.67
Green	2.17	1.42	3.3
Blue	19.33	14.5	12.42
Violet	16.23	10.75	8.75

3. Analyze the results of your experiment. Did your data support your hypothesis? Explain. If you conducted tests with more than one type of seed, explain any differences or similarities you found among types of seeds.

My data does support my hypothesis. Red and blue wavelengths do cause the most growth in plants. The plants grown under these colors were the tallest. With all of the three different seeds tested (spinach, radish, and lettuce), the blue wavelengths got the best results (tallest heights), with red and violet being the close seconds.

4. What conclusions can you draw about which color in the visible spectrum causes the most plant growth?

The color blue wavelength causes the most plant growth compared to all the others in the visible spectrum.

5. Given that white light contains all colors of the spectrum, what growth results would you expect under white light?

I would expect average plant growth in plants grown with white light because not only are red and blue wavelengths included, but also green and yellow wavelengths, which cause less growth.

Site 2: Photolab

http://www.kscience.co.uk/animations/photolab.swf

Lab Report - Photolab

How will varying light intensities affect plant growth?

If a plant is tested with varying amounts of light intensity, then the highest light intensity, 50, will make the plant grow the fastest.

Variables:

Independent Variable - Light Intensity

Dependent Variable - Plant Growth

Constants - Amount of dissolved carbon dioxide (high), temperature (25 degrees Celsius), angle of light, light bulb, amount of water, type of plant, time for # of bubbles (30 seconds)

Control - Light Intensity set at 0

Data Table

Light Intensity	Rate of Photosynthesis (number of oxygen bubbles)
0	0 bubbles
10	12 bubbles
25	17 bubbles
40	19 bubbles
50	20 bubbles

In this lab, I asked the question “How will varying light intensities affect plant growth?” I found that higher amounts of light intensity caused more growth in the plant. For the light intensity of 0, the rate of photosynthesis (the number of bubbles sent out from the plants) was 0. From 0 to 10, the number of bubbles increased by 12.  From the light intensity of 10 going up to 40, the number became 19. Finally, at the intensity of 20, the number of bubbles was 20. This result would naturally occur because more sunlight would result in a higher rate of photosynthesis. Generally speaking, if the amount of a reactant increases (in the chemical equation of photosynthesis), the amount of product will increase. This data supports my claim because when the light intensity, in the experiment, increased, more bubbles are “exhaled” from the plant in water

This lab was done to demonstrate how different amount of light on a plant will affect its growth. From this lab, I learned that a higher light intensity will cause more growth in a plant, which helps me understand the concept of a chemical equation. When an amount on one side of the equation increases, the other side has to increase as well. Based on my experience with this lab, this concept of increasing reactants leading to increasing products can be applied to other labs similar to this one and others having to do with a chemical equation.

Egg Diffusion Lab

In this lab, we tested 2 eggs that had been soaked in vinegar for a couple of days. We then put one egg in deionized (pure) water and another egg in a sugar solution. After two days, we came back to see what had happened to the eggs. When the sugar concentration the egg was in increased, the mass of the egg decreased by 45.9% on average. The circumference decreased by an average of 22.1%. The sugar in the solution, which is the solute, has a high concentration outside the cell and a low concentration inside the cell. So, as a result, the solvent in the cell moves outside of the cell and the cell shrinks. The more sugar that was present outside the cell, the more the cell decreases in size. Cells respond to their changing external environment internally due to different basic cell processes, like osmosis for example. The cells themselves change because they need to function a normal rate at all times for the whole body to keep working. If they didn't change, the cells wouldn't function properly. This lab relates to diffusion, the movement of molecules across a concentration gradient through the membrane, specifically osmosis, the passive diffusion of water. Depending on the solute concentration in certain areas (inside/outside), the solutions (deionized water and sugar), were hypotonic or hypertonic. The pure water was hypotonic and made the cell grow, while the sugar was hypertonic and made the cell shrink. Vegetables at markets are sprinkled with water because they need to be preserved. Roads with ice on them are salted because the salt shrinks the cells of the solid water and as that happens, the ice melts. Salt water on vegetables prevents them from spoiling and takes out water from their cells. Based off of this lab, I would want to test an egg the exact same way except with salt water to see how this data will differs from the results obtained while testing with the sugar solution. The egg will probably shrink in that case because the solution itself, with salt as the solute is hypertonic.

Control: Deionized Water
Group #	1	3	6	8	AVG
% Change in Mass	-0.95%	0.40%	-0.38%	-0.84%	-0.44%
% Change in Circumference	5.88%	0.60%	25.90%	0.00%	7.78%
Sugar Water
Group #	2	4	5	7	AVG
% Change in Mass	-47.15%	-44.25%	-46.08%	-46.89%	-45.90%
% Change in Circumference	-24.24%	-17.64%	-18.76%	-27.80%	-22.10%

24 hour time lapse of our Egg Diffusion Lab. Egg on left in corn syrup, egg on right in DH2O pic.twitter.com/wdfujQyBXM

— Mr. Orre's Class (@OrreBiology) October 5, 2016

Egg Macromolecules Lab

     In this lab, we asked the question "Can macromolecules be identified in a egg cell?" We found that there are different macromolecules in different parts of the egg. In the egg membrane, the protein test using copper sulfate tested positive. The quantity of proteins in the membrane itself was 3 out of 10. The color of the membrane solution changed from blue to purple. The reason why proteins are present in the membrane is because a part of membranes is the transport proteins. These proteins transport molecules in and out of the cell during facilitated diffusion. For the egg white, lipids were one of the molecules tested for with Sudan III. This test tested positive. The color of the solution changed from red to orange. The amount of lipids in the white was 3 out of 10. Lipids are in the egg white because lipid molecules are in different organelles. The organelles in the egg are spread out throughout the egg white. Lastly, the egg yolk tested positive for polysaccharides. The test was done using iodine. The rating of the test was 1 out of 10. The color of the solution changed from yellow to orange. Polysaccharides would be found in the cell because a polysaccharide, like starch, would be in a egg in the form of sugar. It would, or course, be a complex carbohydrate that humans can consume,
     An error that could have happened during this lab is the measurement of parts of the egg and chemicals used to test the egg. While our hypothesis was supported by our data, this error could have changed the results of the lab. Depending on how much chemical solution or how much of the egg was tested, the rating for how much of molecule is in the yolk, white, or membrane could have gone up or down. Also, different parts of the egg could have gotten mixed together. If so, it was probably in very small quantities. This could have changed the results of the test by showing a molecule is in the egg part, but without the error, it wouldn't. A way to solve this problem could be to have a better way to split the egg. To solve the first problem, students just have to be more careful while doing lab work, particularly with the measurements.
     This lab was done to see what macromolecules are in an egg, specifically the different parts (yolk, membrane, white). The four molecules that the parts were being tested for were proteins, polysaccharides, monosaccharides, and nucleic acids. From this lab, I learned more about macromolecules, which helps me understand the concept of what molecules are in what parts of the cell. Based on my experience from this lab, I can know what parts of an egg I want to eat. If I need proteins, I'll eat the egg white because it has the most protein in it. If I need fats, I'll eat the yolk because it has the most lipids in it. This lab will also help later in biology when we are learning more about macromolecules.