Is Sex Important?

The excerpt of Olivia Judson's Dr Tatiana's Sex Advice to all Creation describes the evolution of organisms that reproduce sexually and those that reproduce asexually. It is a debate about whether sex is necessary for a species to survive and thrive.

Based on the evidence in this excerpt, I think that a species can survive and thrive by reproducing asexually. First of all, cloning (reproducing asexually) is way more efficient than sex. "All else being equal, an asexual female who appears in a population should have twice as many offspring as her sexual counterpart."(215). An argument people would make about why sex is necessary is that diseases can spread very easily among clones. A solution to that is that asexual creatures can just move somewhere new. A third reason is that this has worked for 85 million years with the species of bdelloid rotifers, which shows that it can indeed be successful. Asexual reproduction is also way faster and more efficient because sex takes a lot of time and effort. Cloning doesn't even require a mate so reproduction can keep happening.

It was confusing whether sex is really necessary. In the text, there were equal arguments for both sides. In conclusion, sex may be necessary, but asexual reproduction is faster and more practical.

Unit 3 Reflection

This unit was about the cell, the organelles inside, how they came to be, and the processes that occur in it. Macromolecules make up many parts of the cell in structural support, reactions, and transport. The cell theory states that cells are the basic unit of living organisms, cells come from pre-existing cells, and all organisms are made of one or more cells. cells make up tissues, organs, organ systems, organisms. Membranes are usually made of a phospholipid bilayer and can either be a barrier, container, or a bouncer. This includes the nuclear lysosomes, er, etc.  Membranes are selectively permeable so some things go through, but not everything. Transport is either passive (diffusion) or active (using ATP). Osmosis is diffusion by water through a selectively permeable membrane. The solutions can be hypertonic, hypotonic, and isotonic. Turgor pressure is the pressure between the cell wall and the membrane when the cell swells. The main job of a cell is to make proteins. This starts with the blueprints in the DNA and then goes through the ribosomes, the er, vesicles, and elsewhere. Cells can be eukaryotic or prokaryotic. They all have nucleic materials. Some of the other organelles are the cytoskeleton, centrioles, lysosomes, vacuole, mitochondria. The endosymbiotic theory states that ancient cells ate other cells with capabilities to make their own food or convert glucose into ATP by phagocytosis, and came to an endosymbiotic relationship. That is how those cells are now. Photosynthesis occurs in the chloroplasts of autotrophs and has the light dependent reactions and the calvin cycle. Cellular respiration is the opposite of photosynthesis and goes through glycolysis, krebs cycle, and electron transport chain. 36 ATP is produced.


Animal Cell

The hard parts of this unit was mostly photosynthesis. Knowing what goes in and comes out of each reaction is hard to remember and understand the process. I learned most in the osmosis chapter when we did the egg diffusion lab. I never quite understood the practical applications there, but now I do. I also learned how mitochondria and chloroplasts used to be separate cells and the evidence for that. It helps me understand why there are DNA fragments in the mitochondria. I want to learn more about the endosymbiotic theory and diffusion because that was the most interesting part of the unit to me. 

Egg Diffusion Lab

In this lab, we placed 2 eggs that were previously soaked in vinegar in different solutions for 48 hours. One was placed into deionized water and the other was placed into sugar water.

When the sugar concentration in the water was greater, the mass and the circumference decreased by an average of 45.9% and 22.1% respectively. This was because it was hypertonic and there was a higher concentration of the solute (sugar) outside the egg than inside the egg. This caused the water inside the egg to diffuse out of the membrane to dilute the sugar water outside. The loss of fluid made the egg have a lower mass and circumference.

Deionized Water Class Data

GROUP #	1	3	6	8	AVG
% Change in Mass	-0.95%	0.4%	-0.38%	-0.84%	-0.44%
% Change in Circumference	5.88%	0.6%	25.9%	0%	7.78%

Sugar Water Class Data

GROUP #	2	4	5	7	AVG
% Change in Mass	-47.15%	-44.25%	-46.08%	-46.89%	-45.9%
% Change in Circumference	-24.24%	-17.64%	-18.75%	-27.8%	-22.1%

The cell's internal conditions changed throughout this experiment because it wanted to maintain equilibrium with the solutions outside of the cell. Putting the egg in vinegar probably made the membrane of the egg have some vinegar on it. So when the egg was placed in water, it lost some of its mass because of the egg trying to maintain equilibrium by diluting the vinegar water. However, since there wasn't much vinegar, it just lost an average of 0.44% of its mass and 7.78% of its circumference.

This lab demonstrates passive transport where the sugar tried to move from high to low concentration, but was not small enough to go through the membrane, so the water moved to dilute the sugar instead.

A real life application of this is when water is sprinkled on vegetables to keep them fresh. The solution inside the vegetable is a mixture of water and fructose or fruit sugars. The sugar attempts to move outside the vegetable but can't, so instead, the water from outside diffuses inside and makes the vegetable more juicy. Another example is when icy roads are salted to melt all of the ice. This is because the salt is at a greater concentration outside the ice cubes. So the ice melts to dilute the salt. This is a fast and simple way to melt the ice.

Based on this experiment, I would now want to test this with different kinds of fruits and vegetables with different amounts of sugar in them. Based on the growth or shrinking of the vegetables you would be able to tell which ones have the highest sugar content.

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 an egg cell? In which portion of the egg will they be found? We found that the membranes consisted of channel proteins. When we were testing for proteins, we found that the membrane turned purple in the biruit solution. Membranes have channel proteins as part of its selectively permeable membrane, in order to let in bigger molecules that is needs. This data supports our claim because the membrane tested positive for proteins. We also found that the egg whites had protein in them. The whites also turned purple and got a ranking of 10 for brightness in the solution. This is because in a cell, proteins and enzymes are found in the cytoplasm in organelles. This data supports our claim because the whites also tested positive for proteins. We also saw that the yolk contained lipids. The yolks turned orange and got a ranking of nine, showing that the macromolecule was present. This is because the yolk is where the baby chicken is born and uses lipids as a form of energy. This data supports our claim because yolks tested positively for lipids.

While our hypothesis was supported by our data, there could have been errors due to contamination of the samples. For example, some of the yolk remained on the membrane, which could've made the membrane test positive for more macromolecules then it actually had. The samples all could have been contaminated by the vinegar as well. Another possible error could've been not mixing in enough of the solution to test if the macromolecule was present. This could have been the reason why for some reason the membrane didn't test positive for lipids. Due to these errors, in future experiments I would recommend straining the membranes to make sure the yolk was gone, and washing the egg first to get the vinegar out. I would also keep track of the amount of the solution to mix in.

This lab was done to demonstrate where macromolecules are located in cells. From this lab I learned that an egg is similar to cell which helps me understand the locations of each macromolecule specifically in the cell or egg. I know that the membranes have proteins which are most likely channel proteins. I also learned that the yolks have lipids, because they are the fatty part of the egg and are likely to contain fatty acids. I also learned that the whites had proteins, which are the enzymes in the cytoplasm. Based on my experience from this lab, I could be able to predict where else in other foods or items these macromolecules would be present in.