Category Archives: Biology

Parts of a Plant Cell

BW has been working through the parts of a plant cell on his own.  After learning the parts of the prokaryotic and animal cells, he has been asked to process this on his own.  It has been a difficult thing.  He wanted it given to him.  He wasn’t keen on sorting through information that may or may not be relevant or even locating the information in book form.  But we are nearly done.  I can’t wait to hear his presentation.

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Filed under Biology, Botany, BW, Science, Students

DNA Discussion and Extraction Montessori style

We’ve had wonderful discussions about DNA replication.

The blue mat represents the cell. The white woven mat represents the nucleolus.  The nuclear membrane is represented by the pink and blue finger chains.  The  ribosome is the maroon double blob.

Yesterday we extracted our DNA in a multi-step plan.

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Filed under Biology, BW, Chemistry, DW, MMcC, Science, Students

BW begins the Timeline of Life


BW has completed the Clock of Eras and the Claremont timeline. Often BW has so many ideas that he needs a transitional time to let his ideas settle and deeper concepts to emerge.  Giving him the space he needs is critical to his understanding lessons.  The space has been created by the Claremont lessons – prokaryotic and eukaryotic cells, the process of DNA replication, and anaerobic and aerobic respiration.

BW discovered some fossils in one of our rocks that serve as weight to hold down large unruly poster papers.  He spent a few moments at the beginning grouping the rocks by their type – igneous, metamorphic, and sedimentary.  I also pulled down a fern to hold the spot where plants begin their march.

He sorted out the tickets by titles, invertebrates, fish, reptiles, amphibians, mammals, and what the earth was doing (like ice ages).  He was very methodical and careful to place the items exactly where they belonged.  It was such a pleasure to watch his care and attention for more than 45 minutes.

 

 

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Filed under Biology, BW, Geography and World Studies, Geology, Science

Chicken – Egg

We have been looking at DNA replication – mRNA, rRNA, Ribosomes, Amino Acids. This is an interesting take on one DNA researcher.

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Filed under Biology, Science

Prokaryotic Cells

After spending some time studying eukaryotic cells and the simple creatures made from them, we’ve moved on to prokaryotic cells.   We’ve created from objects in my house the parts of the cell.

This colander was used for the nucleus because it had holes to represent the pores that the mRNA pass through.  The tan yarn is the DNA and barely visible is the dish strainer that represents the nucleolus.

The cell:  Endoplasmic Reticulum is the red tulle that is sewn to create the pocketed shape.  Some of the green ribosomes can fit into the pockets while other are floating through the cytoplasm (the white rug). The mitochondria are the silver tart containers.  The lysosomes (empty) are the silver marbles or larger glass marbles (full).  The Golgi body is constructed from golden ribbon that is stitched to create the undulating shape.  The lysosomes can fit into the loops to represent the packaging and release of items the cell is making or breaking down.  The purple yarn represents the cell membrane.  We chose to use two wraps of the yarn to represents the double layer of lipids that make up most of the cell membrane.

We created “Who Am I” game cards for each part of the cell.

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Bio lecture: Sexy Legs: how frogs amplex their way to success

On a lark we decided to head down to the Biology Department at the College of Charleston.  On Mondays they have a noon lecture.  The W’s were in; so the whole gang went.  The kids were disappointed that the cushy chairs were not in this lecture hall.  It’s the little things, you know.

The best part of the lecture was the understanding the process that scientists go through when undertaking a project.  She showed how she went through each step.

Dr. Susan Peters from the University of NC at Charlotte was the lecturer.  Her speciality is morphology.  She has studied frogs for 15 years.  As a morphologist, she asks these types of questions:

  1. How do structures function in animals?
  2. Does that function affect fitness?
  3. Which properties may be most important to enhance function and fitness?
  4. Where does the structure arise from?  Is it a positive grand mutation or is it modification that is replicated?
She stressed the need to observe and document Nature Function – get out into the wild (or the least artificial environment as possible) and take pictures, write observations, measure angles from your pictures.

From National Geographic.

She also stressed that a model organism must be easily accessible. (You will need a lot of the organism.) You also want a creature who has application across the order.
She chose the North American bullfrog.  In the past 15 years, she has worked to understand three aspects of their morphology:
  1. Hopping and swimming behavior – kinematics
  2. Structure and function – fiber/muscle types
  3. Forelimb dimorphia – which muscles are different in males and females and why?
THIS IS STEP ONE IN SCIENCE:  MAKE AN OBSERVATION ABOUT THE WORLD AND WONDER WHY.
She observed that males and females have different sized forelimbs.  This is exciting for several reasons – one is that you are looking at the same species and comparing granny smith apples to granny smith apples not to golden delicious apples.

Two male green frogs sparing - from FWG's blog.

A bit of country wisdom:  Bullfrogs are territorial creatures and during mating season they defend their territory in a sort of sumo wrestling way.  They also call for females in the evenings and nights during mating season.  Most country kids who live near a pond can tell you that frogs have no idea what they are hopping on in the dark. You can get a frog to jump on your hand thinking that your hand is a female.  They can hold that position for several hours.  But why would you let them?  It is just funny to gross out your mom.

American toads in amplexus. From The Sojourns in Nature Photo Blog.

A bit of science thought:  The mounting of male (usually smaller) frogs onto female frogs is called amplexus (Latin for embrace). All fertilization of eggs is external.  It can take anywhere from two hours to two weeks. (Yes! That is correct.)  The female sheds gametes into the water and the male fertilizes them.   The male has to maintain the embraces for quite sometime with a partner who is not necessarily agreeable.    Dimorphic is a term for physiological differences between males and females of the same species.
So that said, what do frogs use their forelimbs for?
  1. territorial defense (grappling)
  2. swimming
  3. propping themselves up
  4. minor use in hopping
  5. amplexus
STEP TWO:  SEE IF SOMEONE ELSE HAS WONDERED WHAT YOU ARE WONDERING AND DID EXPERIMENTS ON IT.
She and her team researched frog forelegs and previous studies. What research had been previously done?  
All previous studies had been aimed at the Flexor carpi radialus (FCR).  If you were going to eat frog forelegs, this is the muscle you would go for.  It is the larger of the four main muscles in the arm. What about males v. females?
  1. Proportionately larger (really bigger)
  2. Conflicting data on the type of muscle fiber making up the  FCR.  This is very important because there are three main types of muscle and certain ones “oxidize” quicker and thus the muscle won’t fatigue as easily.
  3. Larger glycogen stores
  4. More mitochondria
  5. More fat
All of this suggests that the muscle can handle larger force with less fatigue.
STEP THREE: POSE YOUR QESTIONS AND GATHER PRELIMINARY DATA.
She and her team dissected forelimbs to look at all the muscles and compare them. Took lots of nature and lab pictures to look at behavior and realistic angles for the muscles to work. Basically they figured out what each muscle did.
QUESTION 1: Are all the muscles in the forelimb different dimorphicaly?  No – just three.
  1. Muscle 1 bring in the elbow and wrist into the embrace
  2. Muscle 2 also works in tandem with muscle 1
  3. Helps rotate the wrist to aid in control of the female body.
QUESTION 2:  What is the isometric force (contraction to relaxation time) of these individual muscles and the one main muscle that is not dimorphic?
QUESTION 3:  Does testosterone surges during mating season affect muscle growth, strength, and fatiguability?  This question is what her lab is working on now.
STEP FOUR: FIGURE OUT HOW YOU WILL FIND OUT THE ANSWERS TO YOUR MAIN QUESTIONS.
She and her team worked to create a lab experiment using an oscilloscope.
To answer Q2, they pealed back the skin on the forearm and attached electrodes and sensors to the four muscles and provided electrical pulses to the muscle and then measured the responses after  1, 2,  and 4 minutes.
What they found was that the Ca2 levels increased?  Basically the cells, which could absorb the calcium being used back into themselves easily, were not absorbing it all back into the cytoplasm.  Hmmm.  They also discovered that as the time went on, the absorption rate was less until it plateaued in the 3 to 4 minute range.  Higher calcium means less fatigue in the muscles and saving energy.  Thus the frog can hold on for longer and with more force.
To answer Q3, they have just recently castrated a number of frogs and have inserted a testosterone pill in half.  Their research is preliminarily showing that, yes, it does.
STEP FIVE:  POSTULATE OTHER QUESTIONS FOR YOU OR OTHERS TO DISCOVER THE ANSWERS TWO.
At the end she listed a whole bunch of new questions that her research has led her to want to know the answers to.

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Filed under AV, Biology, BW, Going outs (Field Trips), JV, MMcC, Science

Update on the Winogradsky Column

 

Two weeks ago a couple of the kids decided to delve further into bacteria by growing some.  They built a Winogradsky Column.

Halfway into the beginnings of the bacteria growth. There is a distinctive green tint to the algae growing in the bottle.

I think we might need to gently wash it off.

Here is a great site for information and resources.

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