Tuesday, March 7, 2017

Student Blog Post Assignment #8: 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?



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Monday, February 6, 2017

Student Blog Post Assignment #7: Anthers and Stigmas and Styles, Oh My!

How do flowering plants (angiosperms) like our Brassica oleracea plants reproduce? That is the basic question we will address with this post.

Begin by reading pages 342 through 349 in the class textbook to get a basic introduction to plants. Next, read sections 17.6 and 17.7  (The flower is the centerpiece of angiosperm reproduction and The angiosperm plant is a sporophyte with gametophytes in its flowers) very carefully to get a good idea of how flowering plants reproduce. Pay particular attention to Figure 17.7.

When you have finished your reading, get permission to visit the garden and harvest two or three flowers from one of the Brassica oleracea plants in the main garden. Bring them back to the classroom and, with a partner, get a dissecting microscope. If you have never used a dissecting microscope before, read this brief tutorial on dissecting microscopes first.

Study Figure 17.6B on page 350. Now, follow the procedure below to complete the flower dissection.
  1. Lay your flowers on the table and take a closeup picture of one of them. In the next step, looking through the dissecting microscope, you will examine all of the flower's parts that are directly involved in reproduction.
  2. Now, using forceps and/or your fingers, very carefully remove the sepals and petals of one of the flowers. Do you see the anthers?
  3. This step can be tricky: take a picture of the image of the anthers coming out of the eyepiece of the microscope.
  4. Now pull back the filaments and anthers to reveal the carpel (the entire female reproductive structure). Take a photograph of the carpel, focusing on the stigma.
  5. Take the ovary and use very sharp scissors or your fingernails to cut the ovary open lengthwise. Do you see the ovules inside? They look a bit like shiny green jelly beans attached to a central stem. Take a picture of the ovules inside the ovary.
  6. For extra points, take one of the anthers and tap some of its pollen onto a glass slide to prepare a wet mount slide of pollen. Ask the teacher for a compound light microscope and set it up on the lab station at which you are working. Get the pollen grains in focus at high power and try to capture a photo from the eyepiece of the microscope with your camera.
Using the photos you took to illustrate, write a paragraph explaining how fertilization occurs in flowering plant species like Brassica oleracea. Each picture you post should also include a detailed caption explaining what is shown in the photograph and how it functions in angiosperm reproduction.

Take a look at the example images below to get an idea of what you should capture in your photographs.

This image shows anthers surrounding a stigma. They are all part of the same flower. When both male and female parts appear in the same flower, the flower is said to be perfect. In some species of flowering plant, the male and female parts are located in separate flowers (some flowers are male, some are female), and yet another situation is when the male and female flowers are on entirely separate individuals (some plants are male, some are female).


Here is a view (40x) of the male reproductive anatomy of a flower, known as the stamen. It has a stalk called the filament coming up from the base of the flower and at the end of this stalk is a part called the anther. This portion of the stamen produces and releases pollen grains, which contain the plant's male gametes (sperm cells).

This is a view (40x) of the female anatomy of a flower called the carpel. The carpel consists of a stalk called a style with a sticky tip called a stigma. It is this sticky tip to which pollen grains adhere (get stuck).


This is a picture of a flower that has had all of the parts stripped away (sepals, petals, stamens, and the top of the carpel) EXCEPT the ovary (the large green tube on the right), which has been sliced open and has tiny ovules (immature, unfertilized seeds) spilling out--one of these ovules can be seen to the left of the ovary.



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Tuesday, January 10, 2017

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

Now it's time to put some of your recently acquired science 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 (or other device's) 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? Your explanation should correctly use the terms and concepts of cell division (mitosis)photosynthesis, and cellular 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.



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Sunday, December 11, 2016

Student Blog Post Assignment #5: 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 classmates--someone who was not on your team! Find someone from another group and work closely with that other person to summarize his/her answers to the questions above in a short paragraph that you will post under your name. Your post title should include that other person's name (e.g., "John's Seed Story"). Happy interviewing!



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Wednesday, November 23, 2016

Student Blog Post Assignment Bonus: A Fall Cell-ebration

OK, here's a chance for a few extra points on your previous TSOTS blog scores:

You now know what your plants actually look like in reality (as opposed to just seeing artwork on a seed packet), but what do they look like at the microscopic level? Use your recently polished microscope skills to find out by preparing a wet mount slide and taking a closer look! After your peek at your plant's leaf tissue under the microscope, take a nibble of a leaf and then prepare and publish a write-up with the title "Cell-ebration Bonus".

In your post, address the following questions and, if possible, include some pictures of the images coming out of the microscope:

  1. What does your plant taste like? Is the flavor what you expected? Would you eat it on a regular basis? Why or why not? What are some significant nutrients in your plant's tissues that could benefit your own cells?
  2. What did your plant's tissues look like at the three different levels of magnification we have been using (40x, 100x, 400x)? Describe in detail what you saw and include some photos too.



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Saturday, October 15, 2016

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.



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Friday, October 14, 2016

Student Blog Post Assignment #3: Biogeochemical Cycles and Your Plants

Now that you have some idea of how the many parts of an ecosystem are interwoven and interact to keep life going, consider and respond to the following questions:

  1. What changes do you notice in your plants this week? Describe the overall appearance of your plant.
  2. How do your plants participate in the movement of water in the biosphere? How do your plants' roles in the water cycle relate to the changes you observed in your plants this week?
  3. How do your plants participate in the movement of carbon in the biosphere?  How do your plants' roles in the carbon cycle relate to the changes you observed in your plants this week?
  4. How do your plants participate in the movement of nitrogen in the biosphere?  How do your plants' roles in the nitrogen cycle relate to the changes you observed in your plants this week?



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