12/7/14-12/13/14

Mammal Lactation

Lactation in mammals is a positive feedback loop, because milk is continually produced until the offspring stops breastfeeding. The response increases the stimulus. It is not negative, because it does not seek to limit a detrimental stimulus. In this case, the stimulus is the baby suckling, which results in signals being sent to the hypothalamus that then releases oxytocin, which in turn results in continued milk production. This does not end until the baby is done suckling.

12/1/14-12/5/14

This week, we spent most of our time on the diffusion and osmosis lab, with minimal notetaking or homework. I thought this was genuinely interesting; we had to apply our knowledge in the labs, reinforcing the material even without a lecture or a powerpoint. I wouldn't want to jump into this feet first, though; that is to say, I prefer having a solid foundation from notes and lectures before doing a lab. It won't be long before winter break, which will be a much needed respite from all my schoolwork; however, it won't be long after that until we have to take midterms. I'm going to look through my "5 Steps to a 5" book over break to review older material and get a glimpse of what lies ahead, so I can do well come the end of the semester.

Diffusion and Osmosis Lab Reflections

Investigation 1 dealt with surface area to volume, and why cells are as small as they are. We hypothesized that the 1cm cube would have the highest diffusion rate since it had the highest ratio of surface area to volume. The results supported our hypothesis, and the 1cm cubed was the only one that displayed full penetration. Cells remain small because a higher surface area allows for more cellular activity, and having a high ratio of surface area to volume provides an optimal surface area in a compact space.

In investigation 2, we created models of cells using dialysis bags and filled them with a solution (in our case, 10ml of 1M sucrose), and placed them into a beaker containing another solution (for our group, 100ml of 1M glucose). We weighed the models before placing them in the beakers and then again, after removing them after a 30 minute soak. For us, the cell gained 12.9% more of its' original mass. The underlying concept behind this investigation was tonicity; molecules will diffuse down a gradient until equilibrium is reached. Our cell gained mass, suggesting that molecules flowed into the "cell" from the solution; thus, this suggests that the solution was initially hypotonic.

Investigation 3 involved observing the cells of an onion through a microscope. First, we looked at the cells without placing water on them; then, we exposed the cell to both distilled water and saltwater. The distilled water resulted in water flowing into the cell, as the concentration in the cell was lower. When exposed to saltwater, however, the cell lost water and shriveled, as the concentration of water in the cell was higher than in the saltwater. This exemplifies both the effects of differing tonicities, and the fact that the amount of free water is more important than the total mass. There might have been just as many water molecules in the saltwater, but many of them were unavailable due to being bound to salt molecules, thus resulting in a hypertonic solution.

10/5/14-10/10/14

The most memorable activity for this week was definitely the BLAST lab. It was a bit confusing at first, due to the expansiveness of the phylogenetic trees, but eventually I understood it. It was interesting to see how biotechnology can be applied to criminal justice; the two seem like very unrelated fields, but they are really complementary. I also attended the lecture at Whitney Lab on bioluminescence in marine organisms. While it was definitely engaging, I'd like to see more applications of the research besides science for science's sake. I remember hearing something about inserting fluorescent genes into other organisms allowing us to see them more easily, but I feel like that could have been elaborated on more.

9/29/14-10/3/14

This week wasn't particularly stressful; I didn't really have trouble with anything in class and understood everything fairly well. We got our assignment to campaign for a specific piece of evidence that supports evolution. My group is doing embryology. It seems like a lot of work, but it's also interesting, and the competitive aspect is certainly a good motivator. I can't help but wish I'd gotten DNA or fossil records instead, though. I'm more familiar with those than with embryology, so I'll have to conduct more research. Our first FRQ is coming up soon; I'm not worried about it, but I certainly don't think I can just breeze through it either.

Chapter 6

Chapter 6 is all about human evolution. I thought this chapter was very gripping; seeing how things that we take for granted (like bipedalism and the ability to touch our thumb with our pinky) have had such huge effect on the course of our evolution was fascinating. It's very strange to think that something as small as that is the reason why humanity is where it is today. There are some things I'm a bit confused about; the chapter talks about increased protein consumption fueling brain growth, but I don't understand how this would have been passed down and proliferated throughout the species. 

Chapter 5

Chapter 5 is about adaptations. It explains things like constraints (adaptations limiting the environments in which an organism can survive (ex: icefish)), pleiotropy (one gene influencing multiple phenotypic traits), and vestigial structures. A lot of this was information that I had a vague idea of, but this chapter elaborated on it and gave examples. It's interesting to see how these concepts apply to the real world.

Chapter 4

The main topic in chapter 4 is speciation. The chapter defines speciation, provides examples for its possible causes and results, and also goes over sexual selection and its advantages. The chapter ends with a few pages about hybrids. I thought this chapter was pretty funny; the picture of the avenue bower bird actually made me laugh out loud. This was mostly review for me, but it's still entertaining.I don't really have any questions about this chapter.

Chapter 3

Chapter 3 goes over the five main extinction events, the progress of evolution from the Permian to the Triassic, and then explains background extinction and its causes. This chapter had some new information that was new to me; for example, I had no idea what a moa was, or how New Zealand used to be dominated by massive birds. It was surprisingly fascinating; not so long ago, creatures that sound more like something out a video game than actual animals roamed the lands where the Lord of the Rings trilogy was shot. Then, as humanity is wont to do, we promptly devastated their habitat and hunted them to near extinction-but so it goes. Survival of the fittest and all that. An Edgar Allan Poe reference caught me by surprise, and made me chuckle. This chapter also introduced a conflict to the plot; apparently, the "Squinches" are facing some sort of genetic crisis. I'm interested to see how this develops. 

Chapter 2

Chapter 2 summarizes the different evolutionary radiations that took place from the Cambrian to the Permian period, and ends in a cliffhanger as the supercontinent of Pangaea is formed. Personally, I was glad to see that this was all new information to me; we never went over this last year in honors bio. It was actually surprisingly interesting, too. Seeing how life has evolved throughout earth's multi-billion year history really gives you a sense of wonder and insignificance. To give you an idea of how little time we've really been here, the first hominids appeared around 2.5 million years ago, Homo Sapiens appeared 500,000 years ago, and civilization only started around 10,000 years ago with the agricultural revolutions. It's amazing to think of what humanity has achieved as a species, considering the (relatively) short amount of time we've been here. 

Chapter 1 Review

The first chapter begins with an explanation of when the chemical precursors for life may have begun to form. It then explains the proteins are the molecules that perform essential life functions, and elaborates on how the order of amino acids determines a proteins function. After the prince inquires as to how the cell know which amino acids to connect to create a protein, the scientist explains that DNA is the key; enzymes read DNA to produce RNA, which is then decoded by a ribosome to produce the amino acids in the proper order. Afterwards, Miller and Urey's experiment of early earth conditions and the generation of amino acids and nucleotides (the building blocks of DNA/RNA) is shown. Next, the evolution from ribozymes to archae, eukaryotes, and bacteria is explained, and the initial dominance and eventual decline of bacteria is mentioned. Finally,  the evolution of eukaryotes into multi-cellular organisms, and the formation of fungi, plants, and animals is shown. Having a visual representation really helps me realize just how far evolution has come; this is much more entertaining than reading from a textbook. 

Intro Review

The introduction to the graphic novel on evolution takes place in a holographic museum on a different planet; a scientist explains to his king and prince the theories on the origins of life on earth, and how that life has evolved. He begins with the earth's cooling forming the crust and trapping gases in the atmosphere. He explains how the basic components of life might have come about, and how they may have evolved into more complex organisms. I thought presenting the theories behind evolution in this setting was a good way of making it interesting to people who might normally see it as boring; the prince's reactions make us think of all the wonder and discovery behind evolution, instead of seeing it as dull classwork.