Spring2013_Lab3

Species: A group of reproducing organisms which can reproduce with each other (such as in sexually reproducing organisms). Developmental biology: Describing how things developed as an individual. Evolutionary biology: Describing how things developed as a species. Genetic biology: Describing the genes responsible for differences among individual organisms, or among different species.

- An organism is made of one or more cells, and the cells operate together to help keep the individual alive and to reproduce. But if an organism is injured or needs to create new cell structures or, for multiculluar organisms, make more cells, then how does the organism know how to create these new biomolecules? - The instructions for how to make more cell structures or more cells are stored in the nucleus of each cell (for eukaryotes). The instructions are stored in a special cell structure called de-oxy-ribose nucleic acid (dee-oxy-rye-bose nuke-clay-ic acid; DNA). - Organisms need food and resources to live, and they get these resources from the environment. - Different organisms have different abilities to acquire and make use of resources, for example, one organism may be able to catch food better than an other organism.

- Many characteristics of an organism (such as the ability to catch food) are dependent on the structure of the organism. These structural things are biomolecular things like cell types, the strength of tissue or the speed of neural activity. - These cell structures are made by the cell itself, using the instructions from one or more locations in the DNA (each location is called a gene, or gene locus [plural is gene loci]). DNA gives instructions on how to create proteins. These proteins are then used to make new cells or new cell structures. - If the DNA of an organism changes, then the organism has different characteristics than before. For example, if someone has a genetic disease, and you could alter the genes of the person, then they would no longer have that disease. This is much more complicated to do in real life than to explain it in theory. - Some characteristics are based on what kind of information is located at one specific gene. Lets say there is a gene that contains information on how to make pigment for the color of eyes. If the genetic information in this gene changes, then the eye color will change. This is called monomorphic. Mono= one, morph = shape. So the gene determines only one characterisitc in the orgnaisms. - Other genes may contain information which affects more than one characteristic. For example, lets say that the information in a gene in a cat can cause a cat to be blind or to see, depending on the genetic information in this gene. But also, lets say that it affects the color of the skin on the cat. This might sound strange, but if the same protein machines create cell structures which help create visual cells as well as skin pigment, then if you altered the genetic information which creates these protein machines, you would alter both the ability to see and the skin pigment. This type of gene is called polymorphic. Poly= many, morph= shape. So altering information at this genetic locus would alter more than on characteristic in the organism.

- Evolution talks about a group of individuals which can breed. Evolution traces the history of a type of organism, and asks, "How did this organism get to be this way? What happened in the past that gave rise to this type of organism?" - An individual usually has two parents (for sexually reproducing organisms) or one parent (for asexual reproducing organisms). - Individuals create offspring, and then these offspring create a second generation of offspring, and so on. - What is a species? If a group of individuals are of the **same** species, then any individual in the group can breed with any other individual in a group (sexual reproduction) - How do you define a species if it doesn't have reproduce with a mother and father? For example, aspen trees make new individual trees by creating clones from the parent tree. The clones are mostly identicle to the parent (like a twin). - BUT: The cloned offspring are usually a little different genetically different than the parents, due to genetic mutations. These changes in the genes can alter the characteristics of the next generation. - ALSO: Sexual reproduction makes it very easy to create new characteristics in the next generation. The trade-off is, it usually takes a lot more work to create a new generation. - Sexual reproduction is special because the offspring is the result of a mixture of genes from each parent. Each parent contributes one (or more) copy(ies) of all the genes necessary for survival. This is an important aspect of genetics. Each individual from sexually reproducing organisms has genes from each parent. And each parent has genes from each of their parents. So each individual has genes from each 4 grandparents, and so on. At each generation, there is the opportunity for new combinations of genes and new mutations. These genetic changes can produce new characteristics in the family tree.

- Where could a new species come from?, knowing what we know about what it means to be a species? - You can tell whether two groups of organisms are different species by asking, "how similar are these two groups?" Whether they can breed together is only one aspect. - Think of a cat and a dog. They cannot produce a hybrid cat/dog (dat? cog?) But. even if you have two dogs of different breeds (different breeds can theoretically produce offspring), they could produce a offpspring that is a hybrid between the two breeds. But what if the combination of these two different breeds created an offspring that needed a special place to live, which was different than the parents? - This example depends a lot on the details of what kind of living space the different breeds need. But imagine that the breeds of the parents needed a cold environment (like huskies and St. Bernards). Maybe this is due to the types of cell structure that the breeds have. Since the cell structure is created based on the DNA (for the most part), we could assume that the DNA of the breeds is a little different (but not too different that they couldn't produce an offspring together). - Imagine that the parents produced an offspring that needed a really really cold environment. Here, the offspring can't tolerate too much heat. In this case, the offspring has a different characteristic of the parents, and perhaps this hybrid offspring would not be able to live in the same conditions as the parent breeds. This is called a reproductive barrier. It is a physiological reproductive barrier. Other barriers include zygotic barriers (the egg and sperm don't mix) and behavioral barriers (the learned behavior of the offspring does not allot it to survive or reproduce, such as in song birds that learn the mating song from the parent). - In this situation, it could be argued that the two breeds of dogs are really two different species. But more investigation will be necessary.

- Imagine two parents (not dogs), and they produce an offspring. Let's call this offspring "Janie". Other parents from the same species also make offspring. Normally, Janie will be able to reproduce, and will have similar characteristics with other offspring from the other parents. - BUT: What if Janie was different enough to separate her from the parental generation? Then, she could only live with other offspring which had similar characteristics as her. For example, if she needed a place to live that was much warmer than her parents, then this might mean she would be isolated from other offspring that did not acquire this new characteristic. - If any other offspring from the parental generation also happened to acquire this heat-tolerant characteristic (through mutation, for example), then all of these heat-tolerant offspring would be able to live with Janie and they could all reproduce together. Because these heat-tolerant individuals are isolated from the original parental group, they would cease to reproduce with other organisms from the parental group, unless they also were heat-tolerant. - We can now ask, are these new heat-tolerant folks able to reproduce with the offspring that is not heat-tolerant? - Sometimes, one single characteristic in an organism is based on the instructions in a single gene, and sometimes one gene can control (or influence) more than one characteristic in an organism. In this heat-tolerant case, we want to know if the new group can reproduce with the old group. - If heat tolerance was the only characteristic that was different among the two groups, then it is most likely that the two groups could produce offspring together. These second-generation offspring (the offspring between the original group and the heat-tolerant group) might be able to live in either cold or hot environment. -The heat-tolerance was created based on new genetic information. What if this new genetic instructions was polymorphic? That is, what if heat-tolerance was not the only new thing produced by the new genetic instructions? Perhaps it also changed other characteristics in Janie and the other heat-tolerant individuals. If these other changes involved reproduction behavior or reproductive characteristics, then there would be a reproductive barrier between the two species because the gene that controls heat-tolerance was polymorphic and altered other characteritics besides heat-tolerance. These other changes in the heat-tolerant group would prevent them from reproducing with the original group. In this case, they would be considered two different species.

Evolution. - Evolution is the study of how new species arise. Evolution is the study of actual observation of how species change as well as the theoretical ideas about what it takes to create new species. Most of the life that has existed on Earth has died and some are fossils. While the fossil record is not complete, it gives a picture of the past and can describe what kind of physical changes occured in the history of a species. - An alternative to evolution is that species do not change. That after a group of organisms appear on earth, they do not change. This was a common idea before the understanding of how genetic information influences an organism's characteristics.

Distribution of grades for first quiz. The x-axis shows what scores from the quiz were counted for that category. So the blue bar at category "7" goes to 3, which means that 3 students from the 10 am class scored a 7/10 on the quiz.