Is sex important?

Sex is not important. While there are benefits to sex, there are more benefits to asexual reproduction, or cloning. With enough luck in mutations and through travelling, asexually reproducing species such as the bdelloid rotifer can reap all the benefits of asexual reproduction while avoiding the repercussions.

Organisms that engage in sexual reproduction have, on average, lived longer than those who do not. This is due to the fact that sexually reproducing organisms do not rely only on mutations, which can be harmful. Also, sexually reproducing organisms are less vulnerable to disease, as they have different DNA, which will make it harder for disease to spread.

However, sex requires a lot of effort. As Olivia Judson explains in her book, Dr. Tatiana's Sex Advice to All Creation, "a male flower who wishes to be a Lothario and have his pollen strewn to as many mates as possible must seduce not female flowers but bees... other creatures must wear gaudy costumes, be they fancy feathers or frivolous fins; they must sing and dance for hours and hours; they must perform prodigious feats, building and rebuilding nests and bowers" (2).

Finding a mate requires an enormous amount of energy, and is rather inefficient. There are many flaws to the process, too. Even if there is an organism with a trait that would revolutionize the species, if that organism cannot have sex, the trait will die with them, and the species will never be able to benefit from the organism's trait. Also, sex may interfere with survival. Traits that attract mates are bold so that they can be seen by possible mates, but those traits can also be seen by predators, making them easier prey. Finally, organisms that reproduce sexually must compete with others of their species for mates, as it often takes a while for organisms to decide who to mate with.

Asexual reproduction, however, is much more efficient. Organisms that reproduce asexually have no need to expend large amounts of energy in order to find a mate. Also, asexually reproducing organisms have twice as many offspring as sexually reproducing organisms. "If females [of a sexually reproducing species] have fewer than two children, the population shrinks; more than two, and the population grows," says Judson. "In an asexual population, however, each female needs to have only one child for the population to remain the same size. More than one, and the population will grow" (215).

On the flip side, organisms that engage in asexual reproduction usually die out after a short amount of time either because of harmful mutations or viruses. According to Muller's ratchet, one of the theories attempting to explain why species that reproduce asexually tend to die out quickly, asexually reproducing populations die out because the number of harmful mutations will inevitably grow. Kondrashov's hatchet, another one of these theories, disagrees. It says that each individual can hold some amount of slightly harmful mutations until they die. Because sexually reproducing populations shuffle genes, the unlucky organisms with too many harmful mutations die. However, in asexually reproducing populations, many organisms will die due to bad mutations, as their only way to change their genes is mutation. Because asexually reproducing organisms mostly have the same genes as each other, it is easy for them to be killed by viruses. This is known as the Red Queen.

Something that confused me was Muller's ratchet and Kondrashov's hatchet. They both seem to have the same point. Also, why does Muller's ratchet need assumptions to be met when Kondrashov's hatchet does not? I want to learn about how scientists found out that there are two different types of reproduction, and if it's possible to control mutations.

Unit 3 Reflection

This unit was about cells. Specifically, it was about the different types of cells, and their purposes and functions. A few themes and essential understandings were the cell theory, the types of cells (prokaryotes, eukaryotes, autotrophs, and heterotrophs), the organelles of eukaryotic cells, osmosis, cell history, the endosymbiotic theory, photosynthesis, and cellular respiration.

This unit went by rather well. Although some topics, like photosynthesis and cellular respiration, were a bit hard to understand the first time through, they began to make more sense after re-reading notes. Another topic I found confusing at first was the tonicity of solutions, but I understood that after re-watching the vodcast discussing tonicity. Some of my strengths during this unit were organelle functions and osmosis, as I found both logical and easy to understand.

From these experiences, I learned about the cells that make up all living things. I learned how the cells in our bodies maintain balance, how plants grow, and what happens when we exercise. I also learned that drawing diagrams is a good way to study, and that color-coding your notes helps if you are a visual learner.

I want to learn more about how the three steps of cellular respiration happen. I am also curious about the workings of chlorophyll. I wonder how plants know to do photosynthesis, and how animals know how to do cellular respiration.

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 chlorophyll, which is found in plants, is best at absorbing red and blue light, then purple light will cause the most plant growth. If plants are green because the color of an object is the color of the light that is reflected off of that object, and plants require light energy for photosynthesis, then green light will cause the least plant growth.

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?

I grew three spinach plants, three radish plants, and three lettuce plants under each color of light, and I measured their height to see which ones grew the tallest. I controlled the type of plant and time spent in the light. I changed the color of light.



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 supported half of my hypothesis. While I hypothesized that purple light would cause the most plant growth, it was actually blue light that caused the most plant growth. However, I was correct in that green light caused the least plant growth. The results for the different seed types were mostly the same. Spinach grew taller than radish, and radish grew taller than lettuce. Lettuce grew the most out of the three in green light, despite growing less than the others in all other types of light. All three seed types grew the tallest in blue light and the least in green light.

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

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

You should expect an average level of growth, because white light includes a multitude of different colors of light. For example, it includes blue light, which causes high levels of growth, and green light, which causes low levels of growth, therefore, white light should cause an average amount of growth.

Site 2: Photolab 
http://www.kscience.co.uk/animations/photolab.swf 

This simulation allows you to manipulate many variables. You already observed how light colors will affect the growth of a plant, in this simulation you can directly measure the rate of photosynthesis by counting the number of bubbles of oxygen that are released.

There are 3 other potential variables you could test with this simulation: amount of carbon dioxide, light intensity, and temperature.

Choose one variable and design and experiment that would test how this factor affects the rate of photosynthesis. Remember, that when designing an experiment, you need to keep all variables constant except the one you are testing. Collect data and write a lab report of your findings that includes:

• Question 
• Hypothesis 
• Experimental parameters (in other words, what is the dependent variable, independent variable, constants, and control?) 
• Data table 
• Conclusion (Just 1st and 3rd paragraphs since there's no way to make errors in a virtual lab) 

*Type your question, hypothesis, etc. below. When done, submit this document via Canvas. You may also copy and paste it into your blog.

Question

What is the optimal temperature for photosynthesis?

Hypothesis

If photosynthesis involves an enzyme called ATP synthase, and most enzymes do well in conditions that are neither hot nor cold, then the optimal temperature for photosynthesis is 25℃.

Experimental Parameters 

The dependent variable is the amount of bubbles produced by the plant in a minute. The independent variable is the temperature of the water that surrounds the plant. The constants are the light intensity percentage and the amount of dissolved CO₂. The control is the plant at 25℃.



Conclusion

In this lab, I asked the question, “what is the optimal temperature for photosynthesis?” I found that the optimal temperature for photosynthesis is 25℃. At a temperature of 25℃, the plant produced 34 bubbles in 30 seconds, which is more bubbles than the plant produced at either 10℃ or 40℃. Since oxygen is produced during photosynthesis, and the bubbles are oxygen rising to the surface, the plant photosynthesized quicker at a temperature of 25℃. Also, it is known that the enzyme ATP synthase is used in photosynthesis, and that enzymes have medium optimal temperatures. The first piece of data supports my claim because it shows that plants are faster at photosynthesis when they are in a temperature of 25℃. The second piece of data supports my claim because the enzyme did the best in a medium temperature.

This lab was done to demonstrate that there is an optimal temperature for photosynthesis. From this lab I learned about the factors that can affect the speed of photosynthesis, which helps me understand the concept of the reactants needed for photosynthesis. Based on my experience from this lab, I am a better botanist because now I know the temperature for which plants will grow better in.

Microscopic Organisms Lab Analysis

Power: 400. This skeletal muscle tissue cell is unique because it has many nuclei. I observe that this cell seems to be made of many "pieces," or striations, that make up a bigger "piece," or muscle fiber. This cell is eukaryotic and heterotrophic.

Power: 400. This slide of a ligustrum plant is unique because it is the cross section of the plant, which allows it to show multiple cell types. I observe that these cells are hard to distinguish from each other because they are mostly colorless. This cell is eukaryotic and autotrophic.

Power: 400. This spirogyra cell is unique because its cells are rather rectangular and connected to each other in a chain. I observe that the chloroplasts are arranged inside the cells in a spiral chain. This cell is eukaryotic and autotrophic.

Power: 400. These bacteria cells are unique because of their size. They are quite small compared to other cells. I observe that the bacillus bacteria are darker in color than the coccus and spirillum bacteria. These cells are prokaryotic and autotrophic.

Power: 400. This cell is unique because it doesn't have a chloroplast. Cyanobacteria don't have chloroplasts because they are the ancestors of chloroplasts. I observe that these cells tend to clump together in rings. These cells are prokaryotic and autotrophic.

Power: 400. These euglena cells are unique because they can be either heterotrophic or autotrophic. I observe that they are small and hard to see with the microscope. These cells are eukaryotic and either heterotrophic or autotrophic.

Power: 400. These amoebas are unique because they use their cytoskeleton and cytoplasm to move. I observe that there are many amoebas of different colors on the same slide. These cells are eukaryotic and heterotrophic,

In this lab, we used microscopes in order to observe six different slides: skeletal muscle tissue, ligustrum, spirogyra, cyanobacteria, euglena, and amoeba. We did this in order to distinguish different organelles inside these cells. We also did this to see what features are common between eukaryotic, prokaryoti, autotrophic, or heterotrophc cells.

I was able to identify...
Muscle cell: nucleus, muscle fiber, and striations
Ligustrum: chloroplast, epidermis cell, and vein
Spirogyra: cell wall, chloroplast, and cytoplasm
Bacteria: coccus, bacillus, and spirillum
Cyanobacteria: cell
Euglena: nucleus and chloroplast
Amoeba: nucelus, cell membrane, and pseudopods

The autotrophs either had visible chloroplasts or were incredibly small. The heterotrophs mostly didn't have chloroplasts, and had visible nuclei. The eukaryotes mostly had visible nuclei and were larger than the prokaryotes. The prokaryotes mostly did not have nuclei and were smaller than the eukaryotes.

Egg Diffusion Lab Analysis

When the sugar concentration of the solution the egg was placed in increased, the mass and circumference of the egg both became smaller. This change was caused by the passive diffusion of water. In the solution of sugar water, sugar is the solute, and water is the solvent. The sugar water had a higher concentration of solute to solvent than the egg. Solutes like sugar are too big to diffuse across the egg's membrane, but solvents can passively diffuse across the egg membrane. Since diffusion's goal is to reach equilibrium, or the point when the concentrations of solute to solvent are equal, solvent molecules moved out of the egg's membrane in order to dilute the sugar water outside of the egg. Because water left the egg in sugar water, the egg shrank.

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

A cell's internal environment changes as it's external environment changes because of diffusion. Because cells want to reach equilibrium with their surrounding solutions, they either shrink or grow, depending on their environment. When the egg was placed in vinegar, it lost its shell because vinegar is acidic. When the egg was placed in water, it grew, because the egg has more solutes than water, since pure water has no solutes. And when the egg was placed in sugar water, it shrank because the sugar water had more solutes than the egg.

This lab demonstrates the biological principal of osmosis. Osmosis is the diffusion of water across a selectively permeable membrane. This membrane refers to the egg's membrane. Because osmosis is a type of diffusion, the water will attempt to go from a low concentration of solute to a high concentration of solute in order to reach equilibrium. This is the process that happens when the egg is placed in sugar water. This lab also demonstrates the biological principal of tonicity, which is the ability of a surrounding solution to cause a cell to gain or lose water. The sugar water was a hypertonic solution, meaning the solute concentration in the sugar water was more than that inside of the egg. The deionized water was a hypotonic solution, meaning the solute concentration in the egg was more than that in the surrounding solution.

Fresh vegetables are sprinkled with water at markets because the vegetables have less water, or solvent, and more solute. Because the cells of the vegetables have more solute than their surrounding, hypotonic solution of water, the vegetables will gain water, keeping them fresh for longer. When roads are salted to melt ice, plants along the roadside may wilt. When the ice melts, the resulting water combines with the salt to form a salt water solution. Since the cells of plants have less salt than the salt water, which is hypertonic compared to the plant cells, the plants lose water, causing them to wilt.

Based on this experiment, I would like to test the tonicity of other solutions. I would like to do this so I can find solutions that are isotonic to an egg cell. I would also like to test this with different cells, but since the changes in mass and circumference would be much harder to measure, I would probably test this with different types of eggs.

Egg Macromolecule Lab Conclusion

In this lab, we asked the question, "can macromolecules be identified in an egg cell?" We found that lipids are found in the egg membrane. We know that lipids are found in the egg membrane because when Sudan III was added to the egg membrane, the egg membrane turned light orange, which is a sign that lipids are present in the egg membrane. It is reasonable that lipids would be found in the egg membrane, since membranes are made of lipids. This data supports our claim because lipids were detected in the egg membrane and the egg membrane is made of lipids. We also found that monosaccharides are found in the egg white. We know this because after benedicts solution was mixed with the egg white and heated in boiling water, the egg white turned forest green, which means monosaccharides were found in the egg white. Because the egg white is food for the baby chick, it makes sense that egg whites are made of monosaccharides, the primary energy source. This data supports our claim because monosaccharides were detected in the egg white and the egg white is an energy source. Finally, we found that proteins were found in the egg yolk. We know this because when sodium hydroxide and copper sulfate were mixed with egg yolk, it turned dark purple, which is a sign that proteins were present. Since the egg yolk is the baby chick, the proteins were probably the chick's structural proteins. This data supports our claim because proteins were detected in the egg yolk and structural proteins are needed for something to live.









While our hypothesis was mostly supported by our data, there could have been errors due to an accident that happened during the beginning of the lab. During this accident, the egg white and egg yolk became mixed. This may have affected our results because both the egg white and the egg yolk were contaminated and couldn't really be accurately tested. There could also have been errors because not all of the test tubes had exactly 2 milliliters, since the pipettes were hard to use, and also because there were bubbles of air in the pipettes. Due to these errors, in future experiments I would recommend using spoons with circular holes in them, which would make it harder for the egg white and egg yolk to mix. I would also recommend having the students temporarily mark the test tubes for 2 milliliters so they wouldn't have to worry about inaccuracies with the pipettes.

This lab was done to demonstrate where macromolecules are found in the cell. Since an egg is a single cell, we now know where monosaccharides, polysaccharides, proteins, and lipids are found in a cell. From this lab, I learned that lipids are found in the membrane of an egg cell, which helps me understand that lipids make up membranes. I also learned that proteins are found in the egg yolk, which was going to become a baby chick, which helps me understand the concept of structural proteins. Based on my experience from this lab, I know now how to test for the presence of a macromolecule, which would be helpful if I needed to test an unknown solution for macromolecules in the future.