16/01/2011 § 1 Comment
Last class was our very last lecture in biology and because of this, some students in the class went into some kind of frenzy and started recording the lecture. It turned out to be useful because, at home, I was able to listen to everything that was said during class and even some things that I didn’t know I missed.
This class, we continued the last lecture, reviewed lions and talked about bees a lot again. (At the end of the class, there was a quiz with a DBQ that discussed bees and their altruism for each other.)
As review, lions live in prides and each gender behaves differently. The male lion usually behaves very selfishly, focusing on putting his genes in the next generation. His only interests are to raise his offspring, because they carry his genes. If he successfully keeps these offspring alive and healthy (successful) until they become adults and are ready for the next generation, then he has allowed his own genes to join the genetic pool: that male lion is successful. Females are all sisters in a pride and all act for each other, not as selfishly as the male lions behave. They are ‘friendly’ towards one another and hunt together and share the food, even caring and nursing each other’s cubs.
Basically, if we look at the scenarios genetically, all the behaviours make sense. Evolution and natural selection has favoured all behaviours that help genes prosper and exist in the next generation. (Which is why evolution and natural selection keep driving genes forward through time; evolution is for genes). Kin selection is a selection that is especially powerful in humans where blood is thicker than water. Kin selection wasn’t in the book but we learned in class that the more related you are, the more likely altruism is to be. Meaning, the more related an individual is to another individual, the more likely they’ll risk their own hides to save that other individual if they were dying (a la stick-figures-drowning style, as we saw in class).
Bees are a good example of altruism because every single bee in a hive works for the benefit of the hive. They sacrifice all of their time and energy to working for the hive, time and energy that could have been used looking for their own food, not the hive’s. The level of their relatedness defines their altruism as basically all bees in a hive are related to each other. The level of relatedness must be greater than the ratio of costs over benefits for an organism to be altruistic.
Altruism can sometimes be seen in humans. If the relationship with someone is higher (and if the person is familiar with that level of relatedness), then it’s more likely that an individual will risk their hide to save another person’s from drowning (a la picture of drowning stick-men, again). Altruism is influenced at unconscious levels.
Other kinds of behaviours are cooperating which is beneficial for all participants, and spitefulness where no genes are passed on in the next generation. Spitefulness is basically animal A doing wrong or harming (maybe killing, in some organisms’ cases) animal B because B hurt A first. As a result, neither animal’s genes get into the next generation but at least animal A is assured that B won’t have the chance to be better them him.
Moving a little closer to the essay question (Why are humans nice?), organisms like humans that live in groups that aren’t always related are nice to each other because both sides of the party benefit. As said in class, you scratch my back, I’ll scratch yours. Or, in the end, everyone wins.
This is seen in vampire bats, where the females that live together are all unrelated but live by helping each other and continuously feeding each other. Chimpanzees also cooperate together, even if they’re not related, because, since they all recognise each other and are familiar with one another, they know that all the chimpanzees in the group mean to help the group survive. (As a result, everyone in the group gets to eat). All behaviours that help genes get into the next generation are selected for by natural selection and evolution.
Humans, in particular, favour other humans depending on the traits they share because those traits determine if they’ll be an appropriate partner to have offspring with. If the Human B’s traits aren’t favourable (which means their genes aren’t favourable for Human A), Human A would most likely not want to have offspring with them. So when humans are nice, they show good traits; good genes, and these genes also show who’ll be a better altruist out of the population.
13/01/2011 § 1 Comment
After a break full of finishing up extra credit, we started on our new unit, Behaviour. Behaviour in an animal is the way it acts or responds to a stimulus (which is some kind of factor from the environment or from another animal that evokes the reaction out of the individual.
The first example we looked at in class was with lions. In a pack of lions, called a pride, the majority of the lions are females, so: lionesses, who are all sisters and related to one another. There are many cubs in the pride and all of those cubs are fathered by the single male in the group: the alpha lion. He is in charge of taking care of his pride, defending the other lions from stray male lions that look to invade the pride. When an invading male lion wants to try and take over the pride, he can try. But the resident male lion will definitely fight back. After the battle ensues the start of a new pride if the invading male lion wins. (If not, then the resident lion can stay in his pride, having successfully defended it).
But say the invading lion did win. The pride then has a new leader. The new alpha lion has two options: 1) be nice to the cubs that are already there, or 2) take them all out. The lion probably doesn’t know why he does it, only that it is beneficial for him if his own cubs are running around in the pack, not the previous lion’s cubs.
[The females, however, don’t just let the new lion kill their cubs. They have their own ways that might decrease the new lion’s chances of killing the cubs or completely avoiding the cubs’ deaths. These include simply avoiding the stray male lions, fighting the male lion, or if he hasn’t killed her cubs yet, to mate with him and make him think that the current cubs are his.]
The new lion then brutally kills off all of the cubs so that he might be able to mate with the females, to produce his own cubs, carrying his genes. (That is why killing the previous cubs would be beneficial; so that the next genes in the next generation of lions would have his genes). This is selfishness on the male lion’s part because he’s only focused on his own genetic interests, killing off numerous cubs to give his own genes a chance in the next generation.
(Another example of an animal that kills other offspring is the jacana – except the females do the killing, in this case.)
We learned about the dog genome project that proved that genes can control behaviour. In the project, results showed that after interbreeding certain dogs, 9/16 would have both dominant traits out of two traits. 3/16 would have only one dominant trait out of two, and another 3/16 would possess the other dominant trait. then, 1/16 would be completely recessive and not have any dominant trait. This proves that with interbreeding, and with the mix of genes, the new allele combinations in the next dogs can control their behaviours.
Finally, any behaviour that is beneficial for relatives is selected for and this is seen especially in bees. The one queen produces the eggs, all the males are never fertilized and are all haploid, and the females are all workers. Males do mitosis, making the exact same cells and keeping them haploid, while the females do normal meiosis. Daughter bees are more related to one another than male bees (son bees) are.
The essay question for this short unit is Why are humans nice? because apparently, humans are nice. No, ha, they are nice. But there could be genetic reasons behind that and after reading Eros and Evolution over the break and drowning myself in the words ‘genes’, ‘sex’, ‘evolution’ and more words like ‘why’, ‘how’, and ‘reason’, I’m pretty sure that humans’ behaviours and the reasons that they are nice do come from genes. Maybe not completely, but a large part can come from their genes.
12/12/2010 § 1 Comment
Our last lecture was titled “Examples of Evolution” and talks of … examples of evolution. During this lecture, we (and the textbook) discussed different ways to see evolution on this world. The forms of evolution we discussed were Darwin’s finches and tuberculosis, a type of disease.
(Revisiting earlier ideas) Malthus once said that “People and organisms will always starve in the world. There are more animals than there is supply of food.” And although what Malthus stated was rather negative, (I do believe that he was just a negative person), it was also very true. So again, we revisit the idea that the individuals who survive the best in their current environment will be chosen to continue living, while those who don’t have the right characteristics will… be chosen to die. This is the survival of the fittest phenotype. This is also what we’ve studied as natural selection.
An example of natural selection (one of the biggest ideas we discussed during the 80-minute class) is tuberculosis. In the past few decades, tuberculosis has evolved. According to section 13.3 in the textbook, cures were found for tuberculosis during the 1950s: antibiotics were the way to keep people from getting diseases like tuberculosis. Yes, they were drugs and the type of drugs used to fight tuberculosis in the 1950s were specifically isoniazid and rifampin. It worked. For a while. By the 1980s though, stronger TB began to appear and these were immune to isoniazid and rifampin and pretty much all of the other drugs used previously to fight the bacteria in tuberculosis (called the mycobacterium tuberculosis bacterium – MTB).
What happened was one switch in the DNA. (This is where our knowledge of DNA structure and molecular genetics applies to this unit of evolution.) What used to be a Cytosine nucleotide in a link of DNA, on the specific gene called the rpoB, had mutated into a Guanine nucleotide. Before the mutation in the bacteria, rifampin could bind to the rpoB gene and stop the multiplication of bacteria, killing the MTB. After the cytosine base mutated into a guanine base however, the gene mutated in a way that the rifampin was not able to bind itself to it anymore and the bacteria was able to multiply.
(At least that’s what I understand from the book.)
That is one way that evolution exists, in tuberculosis bacteria. The disease itself is very threatening because it is an airborne sickness and in this part of the unit, we see why evolution matters. In this example, doctors can study and make sure they’re following the bacteria as it evolves so that they—the doctors—can also find cures and ways to keep up with the bacteria.
We also learned of Darwin’s finches—a type of bird. In the Galapagos Islands, finches were studied by Peter and Rosemary Grant and their characteristic were watched; their beaks, in particular, were monitored. The Grants noticed that during dry years, the beaks actually get bigger. (Actually, not get bigger but since the successful birds were the ones with big beaks, the percentage of big beaked birds increased above the small beaked birds.) Because the birds with bigger beaks were superior in surviving in their current environment, they were chosen, through natural selection, to continue their alleles for that year. However, when the years were wet, the smaller beaks outcompete the bigger beaks. This is because softer nuts (those easier to eat) were abundant during wet years and the birds didn’t need to waste energy growing a big beak (birds need ATP to make big beaks; it’s a tiring process for them).
Once again, this is an example of evolving to adapt to a particular environment.
Also, we saw an example in class that showed reproductive isolation which eventually leads to the formation of new species, or speciation. One example is birds again, like those on the Galapagos Islands. When one species (species A) moves to an island off the coast of the mainland, they start evolving to adapt to their new environment. Eventually, they’ve changed to a point where they’re similar to the original birds but quite different and are now species B. A selection of species B then migrates to another island nearby, one with different environmental conditions. Species B then becomes Species C, a new species. If species C tries to go back to the island species B resides on, the two species cannot interbreed anymore because they are different species now. Reproductive isolation has lead to speciation and we now have two new species of birds on the Galapagos Islands (B & C, the new species and A, the original species).
Test on Thursday. The essay question is How do things change? and since I’ve studied this unit last year, too, I’m confident with the knowledge I have now. I think, to answer the essay question, however, I will be choosing between the two sub-questions: a) How did eukaryotic cells originate? (from chapter 12) and b) How are new species formed? (from chapter 13). At the moment, I’m leaning towards b) How are new species formed? but I might decide against this tomorrow.
09/12/2010 § Leave a comment
“Evidence of Evolution” was our second to last lecture for the Evolution unit. We’ve learned that to survive the different eras, or ‘stages’ of evolution, all an animal really needs to do is survive and reproduce. Surviving takes into account food, shelter and competition and reproduction is basically continuing the species.
In class, we learned that scientists use fossils to study the preserved imprints and mineralized remains of animals and organisms that lived millions of years ago. Fossils are usually buried under rocks, deep under the strata and aren’t seen until the earth pushes them up and exposes them to scientists. Fossils can also be made into rocks that preserve organic forms perfectly. This happens through trees and the amber excreted by trees. An example of this is seen in the movie Jurassic Park (the first one) where John Hammond has a walking cane with the fossil of a mosquito as means to hold the cane. The mosquito fossil is the result of a tree excreting the gooey substance amber onto the mosquito. The substance traps the mosquito and preserves the entire organic form. This is a wonderful way to make a fossil because unlike rocks underground, the organic form is completely preserved and does not mineralize nor will it decay or decompose. This way, scientists can study the actual organisms.
Fossils, with the help of radioactive decay and radiometric dating, can help determine the age of the fossils, therefore an approximation of how long it had been since the organism existed. A more recent example of this is whale evolution. Fossils found in the Sahara Desert (?) recorded that apparently, 50 million or so years ago, at 3 meters long, whales used to resemble what we call today sea lions. They even have the limbs and are almost completely aquatic.
Fossils were also used to study the evolution of horses. Thanks to the wonderfully mineralized specimens, scientists could figure out that millions of years ago, horses were about the size of an average dog. The scientists were also able to figure out that horses used to run on four toes, then three, then eventually the one large toe that we call a hoof. The fossils also showed that a horse’s teeth grew throughout the years, most likely to make chewing and grinding grass easier.
In class, we heard the word homologous again. Just when we thought we left that word behind after the Reproduction unit and the entire “Why sex?” essay question, to this day, the word homologous haunts us.
Well, no, not really.
But a homologous characteristic between organisms shows anatomical similarities. These include similarities such as limb structure, being a vertebrate, and normally skeletal structure. Animals that are homologous because of their skeletal structure are humans, sea lions, wolves, opossums, moles, bats, whales and even elephants. Who knew? Homologues are so important because they suggest one common ancestor. We must understand that animals or organisms are not related but share a common ancestor. They’re two very different things.
Fossils also introduced Lucy. According to the specimens a few scientists found, she walked like a human, even if she had the skull of a primate. Therefore, I consider her half monkey, half human. However, her presence and existence millions of years ago is hardcore proof that maybe, just maybe, monkeys and humans share a common ancestor.
Finally, the last evidence of evolutions lies in the biological molecules in organisms. The differences and similarities of proteins (more specifically, amino acids) in two organisms show how long it’s been since they shared a common ancestor. With this information, scientists can keep track of when the two organisms had a common ancestor. Also, DNA also provides information as to the relationship between two species. Thanks to the nitrogen bases, scientists can determine the similarities and differences between organisms’ genetic information.
Obviously I don’t wholly understand the concept of molecular phylogenetic trees yet so I’ll be going to the classroom and asking about them tomorrow morning before homeroom.
06/12/2010 § 1 Comment
Today’s class was almost like a flashback to eighth grade science with Ms. Jewett. Our topic of the day was Charles Darwin or Charlie Darwin. In the scientific world, Charles Darwin played a crucial role in helping man move forward to understand how human life and—generally—life on earth evolved and how it currently evolves.
However, Charles Darwin was not exactly the “Father of Evolution” just yet. Many other scientists, philosophers, and other experts way before Darwin also pondered the phenomenon of evolution. Such kind of people including Lucretius, a Roman philosopher who lived about 2000 years ago, Plato, a Greek philosopher who lived more than 2000 years ago, and Charles Lyell, whose book Principles of Geology was a source of information Darwin used during his voyage around the world. So, Darwin wasn’t the only one who thought about how animals evolved and how living creatures turned into what they are now; he simply suggested a new theory of evolution that scientists would later find out would be the most accurate idea.
The first of Darwin’s ideas that we gathered from class included:
Over-reproduction. This idea stated that some species produced more young than would survive to adulthood. Basically, the young would die before they could make any offspring.
Variation. This idea showed that individuals in a species were different from each other in many factors. Even brothers and sisters differed, which is quite true to this day, I would know. With this idea, Darwin thought that some variations in different individuals were preferred during certain conditions while others did not suit the current condition of the time.
Competition. It was and is a big part of evolution. On this planet we live on, earth holds only so much food to feed the mouths of the animals that live on it. Sure, the animals eat one another all the time—even humans, but that supply is also limited and can only last for so long. Therefore, species and individual organisms will compete to last the longest with the food that is available. Those who win; their prize is food. Those who lose; obviously get nothing.
Survival of the Fittest Phenotype: This idea related to natural selection. Organisms that held phenotypes that suit the conditions of the generation and stood strong during that era or period of time would get to survive and pass on their genes to the next generation. These genes get passed on because they were successful in one round of Evolution; they may be useful in the next.
Favorable Combinations Increase: This idea also connected greatly to the concept of natural selection. Generations tended to have more individuals who hold successful and favorable characteristics. In the previous generation, the individuals whose genes were not successful died off and didn’t pass to get to the next round.
(I’ve been thinking of competition and natural selection and looking at the whole idea of evolution as a game with deadly or dangerous rounds. If a species (player) doesn’t succeed in the round, they kind of just die off. No extra lives in this game.)
Darwin began thinking that evolution looked like a tree. The trunk was everyone’s—every single living thing’s—common ancestor. There were branches and twigs that represented all species. Some branches died—and maybe even broke off the tree—while the others grew stronger or stayed the same—they survived a few generations. As far as I know, this was the first time someone had thought of evolution in the form of a tree.
Overall, one of the biggest ideas of today’s class was based on the fact that all animals cannot survive. As mentioned above, there is competition between all the animals for the limited food and sources of shelter found on the earth. For all organisms—including humans, only the right adaptations will keep them alive. So, basically, so far, we, along with millions of other species, have been lucky so far to survive this round of Evolution.
06/12/2010 § 1 Comment
Our last class was a chance to review the lessons from the previous two classes and was literally an eighty-minute period history session in terms of the biological happenings and events. There was much talk about mass extinctions, different organisms, evolution, and the class mentioned the words ‘period’ and ‘era’ a lot.
As we learned earlier in the week, mass extinctions exist (wow. Irony) so that there is a balance between life and death. Although nature allows for millions of organisms to live, some must die. In my head, it sounds like there cannot be too much of an abundance of life on the earth.
Leaving behind the biochemistry half of this unit just a little bit, the class now has a handful—or more than a handful—of information about the evolution of early life. The majority of the class already understands the origin of eukaryotes, multicellular cells and the eventual rise of different species and organisms. We also understand that life on land could not have existed without oxygen—or else the creatures could not have breathed. Also, I’m pretty sure we get the main idea between the process of making an ozone to protect new land life forms from the UV rays and other harmful natural rays that hit the earth.
Overtime, all of these factors plus unique RNA molecules and division of labor between protists and bacteria lead to the early Palaeozoic life. The first part of the Palaeozoic era was the Cambrian period. (Before the Cambrian period was simply the pre-Cambrian period. All those millions of years were called the pre-Cambrian period). By this point in class, we’d begun learning about the six most important periods we had to know about for this unit.
The Cambrian period was first. During this period, there was a huge explosion of some sort. Afterwards came the Ordovician period where the first fish started appearing. They were, however, jawless. Next was the Silurian period when the first land plants and even a few animals started making it onto land. The Devonian period was a time when insects, vertebrates and amphibians became highly successful in adapting to land and plants. Following the Devonian period was the Carboniferous period where the first real forests ever evolved. To this day, we use these trees for our coal industry, something I didn’t know. Finally, the Permian period can be remembered because during this period, almost 96% of life on earth was almost permanently wiped out. After the Palaeozoic era was the Mesozoic era—the middle era. During this time, the first dinosaurs and mammals appeared during the Triassic period. Then, relating to the famous block-buster selling trilogy, dinosaurs were the dominant species during the Jurassic period. Finally, the Cretaceous period was the most recent mass extinction known to earth’s history, wiping out almost all the dinosaurs (minus birds, whose skeletal structure matches that of a dinosaur’s so much, the two different kinds of animals could have been cousins or even brothers/sisters).
As mentioned earlier, plants, animals, land life cannot exist without the development of the ozone layer and enough oxygen in the air. Because of oxygen and the ozone layer: life was able to come to sea and land, and animals could prosper.
One type of organism that survived well were arthropods because their body armor helped them succeed in their environment with their exoskeleton and appendages. Other organisms with backbones, vertebrates, followed afterwards onto land, such as the first fish (during the Ordovician period) that didn’t have jaws (the fish eventually grew jaws and teeth and became what we know as sharks), amphibians that evolved from fish, except with legs replacing the fins and a variety of other differences, reptiles—which evolved from amphibians—and mammals and birds.
It may be a long shot, but if a student looks at this unit in terms of history and if he or she watches a few animals evolve with their surroundings, where they live, what they need to eat, how they’re going to survive; we can see how their bodies change, how their behavior changes to better suit their surroundings and in a history lesson, we can watch how things change (which is our essay question).
03/12/2010 § 1 Comment
In class, we began discussing how complex organisms developed from tiny, single celled and very simple prokaryotes (typically types of bacteria) to the forms of organisms we have today. Prokaryotes merged to make the complex cells we see today. They did what is called endosymbiosis to form something like a super cell.
The prokaryotes that started this endosymbiosis were bacteria—bacteria that still exist today. Prokaryotes (including bacteria) still make up half of the bio mass on earth today, and apparently we as humans are covered in them day in and day out; it doesn’t matter how many times we take a shower.
Some bacteria, however, were responsible for making the first slightly more complex cells that began the evolution of eukaryotes. Some bacteria back then were photosynthetic and aquatic, meaning they could live in water and make glucose, or at least food, from the energy of the sunlight. As we know, this ability to make food out of sunlight is photosynthesis. The bacterium that could do this was cyanobacteria which is important in making the first eukaryotes of this world.
Another important bacterium that played a part in merging to be a eukaryote is the eubacteria. A eubacterium is able to break down foods, like sugar, for itself and eventually became an organelle for the first eukaryote.
Finally, there was archaebacteria. Almost literally, archae- is translated loosely to “ancient” or more so to “primitive” (according to my trusty online dictionary) in latin which means: archaebacteria is one of the (or the oldest) bacterium. What came as a small surprise to the class was discovering that humans are actually more closely related to archaebacteria than they are to any other type of bacteria… not that we’d want to be related to bacteria. But we are. Whether we like it or not. Some closely related characteristics between humans and archaebacteria are the presence of DNA and introns, the lack of peptidoglycan (amino acids and sugar) in our cell walls, the presence of unique lipids in our cell membranes (phospholipid bilayers, making us flashback all the way to August/September’s biochemistry unit) and an archaebacterium’s ribosomes are similar to eukaryotic ribosomes. The archaebacteria played possibly one of the most important roles in the formation of the first eukaryote.
A eubacterium began eating at a host bacteria which just happened to be archaebacteria, a larger and just slightly more complex cell. The archaebacteria allowed itself to be eaten at and ingested the eubacteria but did not digest it. The eubacteria began living inside its host cell and eventually, the two transform to adapt to their new situation. They, together, become a eukaryote. The archaebacteria becomes the eukaryote itself and inside it, the eubacteria becomes the first mitochondrion. This is why mitochondria have such similar characteristics to eubacteria: they evolved from eubacteria. The same thing happened to chloroplasts (photosynthetic organelles). Instead though, they evolved from cyanobacteria (photosynthetic bacteria).
Now, since there are a variety of different ways to be multicellular, organisms’ diversity comes with the way they divide. Since all cells stick together every time they divide and express some DNA (but not all of it), new species began.
Finally, in the last 5 or so minutes of class, we heard the words “mass extinction” which is basically an extended extinction. Since extinction is when a single species dies out, a mass extinction is then when many species die out. It’s a terrible thing. There are five mass extinctions in the history of Earth so far, but I can really only remember them with the letters ODPTC which make up ‘Oh Dear Pretty Terrible C———” but I’m sure the lecture notes will help me force myself to remember the real periods’ names.
As for the essay question, now I know that it is: How do things change? and it turns out my predictions of the essay question was right. It very much has everything to do with how living things and how organisms evolved into the complex structures they are today.