Monday, January 12, 2015

Student Blog Post Assignment #9: A Matter of Selection

Now that you have been watching many varieties of Brassica oleracea in the WGHS GOLD Main Garden for several stages of their life cycle, you have had the opportunity to see these organisms develop into bodies with quite a wide range of characteristics. Some have pink or purple stems and leaf veins, while others have a light green or yellowish color in the same parts of their anatomy. Some have short stems with many very round leaves packed tightly together, while others have longer stems with fewer more angular leaves, and others still have even taller stems with relatively long, dentate leaves. However, if we were to analyze the DNA of all of these varieties, we would see that the base sequences in most of their genes are more than 99% identical. Moreover, upon close inspection, these plants all still look, smell, and taste basically the same as each other, and they are all capable of mating with one another and producing fertile offspring. Finally, they all share key characteristics with an ancient type of Brassica oleracea called wild cabbage.

All of these observations (of the differences as well as the similarities) could be considered and interpreted as evidence of a natural process that shapes all life: evolution. Using your knowledge of basic principles of biological evolution and data collected from measurements made in the garden, respond to the questions below in a TSOTS blog post titled, "A Matter of Selection."
  1. Which part (anatomy) or characteristic of the Brassica oleracea plants seems to exhibit the most variation (greatest number of different forms)? Which part or characteristic of the Brassica oleracea plants seems to show the greatest range of variation (biggest difference between one extreme and its opposite)? Use and include data collected from multiple measurements to support your answer.
  2. Using the terms that follow, explain why you think there is so much variability in the domestic forms of Brassica oleraceatraits, selective breeding, artificial selection, genes, descent with modification, natural variations, mutations
  3. Which part (anatomy) of the Brassica oleracea plants seems to be most consistently the same in all of the examples in our garden, regardless of how extreme the differences between other parts of the same plants may be? Why do think this is so? Again, use and include data collected from multiple measurements to support your answer.
  4. What would plant breeders have to do in order to get the body part or characteristic you described above (in your response to question #3) to become much different than it is presently?

Wednesday, December 10, 2014

Student Blog Post Assignment #8: Seed Stories, Semester 1

Now it's time to sit back for a few moments and ruminate on what you have done and experienced this year through doing The Story of the Seed project. What have you learned? What surprised or amazed you? What made you laugh? What made you pause and think a little deeper? Take five minutes to talk about it with your teammates. Listen carefully to each person's reflections on what the project has been like for him or her. What questions do you have about things you observed or experienced in the garden? OK, now, guess what? You are going to write about the experiences of one of your teammates! Work closely with one other person in your group and summarize that person's  answers to the questions above in a short paragraph that you will post under your name. Your post title should include your teammate's name (e.g., "John's Seed Story").


Thursday, December 4, 2014

Student Blog Post Assignment #7: One of a Kind: The Wonders of Biodiversity

Compose and publish a post in which you answer the following questions in detail using terminology and ideas we have studied so far in the Genetics Unit.

The website below may be of some help to you as you search for information on Brassica olercea, the species of plant we have all been growing during The Story of the Seed project.

What kind of plant are you experimenting with? Describe it and include at least one recent photo of your actual plant. What (if anything) can you tell about the organisms (parent plants) from which your plant is descended? How could you predict what kinds of traits the offspring (baby plants grown from seeds) of your plant(s) will have? How would they acquire (get) these traits (talk about meiosis/gamete formation)? How will your plant pass its genetic information on to the next generation? Will your plant’s offspring look just like it? Why or why not? If all of the varieties of Brassica oleracea being grown by you and your classmates are so closely related, why do they look so different from each other in some ways? Find a picture of the wild-type (land race) Brassica oleracea (the ancestral plant for your green baby). How did so many different forms (polymorphisms) come to be from just this one ancestral species?

Monday, December 1, 2014

A Meiosis Model

The following sequence of images illustrates how the sperm and ova our plants use to procreate are formed through the cellular process known as meiosis.

Before meiosis begins, there is only a single copy of each of the organism's chromosomes from its two parents. These chromosomes are duplicated by DNA replication to form sister chromatids during the S phase of Interphase.

During Prophase I of meiosis, the nuclear membrane dissolves and the homologous chromosomes begin to move together.

Homologous chromosomes pair up and form tetrads (tetra- means 4).

At this point, homologous chromosomes may cross over and exchange segments of their chromatids.

In metaphase I spindle fibers attach to the chromosomes.
The two photos above show two different ways the tetrads could be arranged. This is possible because chromosomes can assort independently--just because the maternal chromosome #1 is on the right does not mean maternal chromosome #2 will line up on the right, for example.

The chromosomes are then pulled apart during anaphase I and the cell divides into 2 genetically different daughter cells.

Both of these two cells then go on to divide one more time to create four genetically unique daughter cells.

Here are the four haploid (only a single copy of each chromosome) daughter cells. If this was happening in the male reproductive structures (testis), then these would go on to become sperm cells. If this process was occurring in a female reproductive structure (ovary), the final products would be one large egg cell and 3 smaller structures called polar bodies.

Thursday, November 6, 2014

Student Blog Post Assignment #6: How Does Your Garden Grow?

Now it's time to put some of your recently acquired skills and knowledge into practice.

Your first step today should be to visit your plants in the garden. Try to find your group's plants. If you can't, don't worry--the most important thing to do is to notice the changes all of the plants have experienced. Snap a few pictures with your phone's camera (or an actual camera) and then return to the classroom. Briefly discuss your observations with your group and then proceed to answer the following questions in a post titled How Does Your Garden Grow.
  1. How is your plant getting bigger and adding biomass? Discuss in terms of cell division (mitosis)photosynthesis, and respiration.
  2. Phosphoenolpyruvate carboxylase (PEPC) and ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco) are two important enzymes used in photosynthesis. Describe how your plants would make these enzymes if a signal was sent to the nucleus to produce more of them. (Hint: enzymes belong to which category of biomolecule?)
Be sure to talk with your group members about the questions as you attempt to compose your responses--together you should be able to come up with some very thoughtful explanations.

If you finish this post assignment with time remaining, work on any previous post assignments. If you have completed all post assignments, revisit them and make sure they all have detailed titles


Monday, October 20, 2014

Student Blog Post Assignment #5: Living or Not

Considering the characteristics of living things that we discussed in class, create a new blog post on your team's Blogger site to let us know how your plants are doing and to convince your audience that your plant is in fact a living thing. Tell us how the appearance has changed since you first put your seeds in a resealable plastic bag with water. What other things could we measure (in addition to growth in size and mass) to convince us that this little green thing is actually alive?


Wednesday, October 15, 2014

Student Blog Post Assignment #4: An Ecological Analysis of the Garden and your Plants

Now that you have read about and discussed some of the factors that influence the forms and behaviors of ecosystems, apply those ideas to the appearance and behaviors of the garden in which your Brassica oleracea plants are growing by developing an analysis guided by the following questions:
  1. What are some abiotic factors on which your plant depends for its survival? What about biotic factors that affect your plant? Describe some of these factors.
  2. How do you know your plants are engaged in competition? For what are your plants competing, and who is the competition?
  3. How are "winners" and "losers" determined in this struggle? Is it always so clear cut who "wins" and who "loses?" What makes that determination complicated sometimes?
  4. Describe other types of interaction (besides competition) in which your plants are involved. Make sure to explain how this interaction affects each organism involved.
  5. What evidence is there in the garden that succesion (or something like it) is occurring in the garden ecosystem? Does it seem more like primary or secondary succession?
It is advisable to address each set of questions in a separate paragraph. This will improve readability of your analysis.