I love fruit!  It’s one of the few things you can eat that is both sweet and good for you!  There is also such a wide variety, from apples to grapes, watermelons to kiwis, and pineapples to pomegranates.   We know these are all fruits, and
we can think of a great many more—too many in fact to name—all different in
taste, texture, and form.  How can they be so different, yet all be called fruits? What exactly is a fruit?

A fruit is the part of a flowering plant which develops from the ovary of the flower, and usually either consists of or carries the seeds of the plant (bananas are one common exception—they are actually a seedless berry!).  Therefore, in the strictest botanical sense, not only are all of our previous examples fruits, but so are tomatoes, corn kernels, wheat grains, peas, and almost all nuts.  This is because all of these are or contain seeds, and have developed from the ovary of a flower.  

There are many different ways to classify a fruit, and over 15 different common fruit types (for more information, please visit the Colorado State University Extension website by clicking here).  However, in general, there are really three basic types:  

1.    Simple fruits:  These form from one flower with only one ovary.  Peaches are an example of a simple fruit.  
 
2.    Aggregate fruits:  These form from one flower with many ovaries.  Raspberries are an example of an aggregate fruit.

3.   Multiple fruits:  These form from the fusion of many flowers which grow on one structure. 
The ovaries of these flowers fuse to form one fruit.  Examples include pineapples and figs.  
 

Unfortunately, it isn’t always easy to tell the difference between these different types just by looking at the mature fruit.  For example, if you have ever cut open a pomegranate and seen all the loose seeds inside, each surrounded by a small, separate piece of red flesh, and clinging to a single leathery husk, you might think this is an aggregate fruit.  In fact the pomegranate is a simple fruit (a berry) from one flower with one ovary, but still producing many seeds.  In order to really understand what sort of fruit you are looking at, you really need to take a good look at the flower.

Let’s take a look at a picture of the inside of a flower.  

This picture shows us all the reproductive organs of the flower; let’s focus on the ovary, which is zoomed in on the left side.  Note this flower has only one ovary, and so if it produces fruit that fruit will be considered a simple fruit.  However, notice also that this flower has more than one “ovule” or egg cell, and it is these structures which become the seeds of the fruit.  So this flower will produce a simple fruit having many seeds, much like the pomegranate.  Now take a look at the pomegranate flower, and it becomes clear why this is considered a simple fruit.

This flower has multiple ovaries, and each ovary has one ovule.  So the raspberry will be an aggregate fruit, and each of the ovaries will develop a single seed. 

For a multiple fruit like the pineapple, let’s look at a picture of a pineapple flower, and the fruit that develops:

The large pineapple flower is actually a group of many flowers, each of which will become one section of the mature pineapple fruit*.


TRY IT!

Now that you understand how the flower becomes the mature fruit, and how this influences the type of fruit formed, try identifying the following pictures of flowers as forming simple, aggregate, or multiple fruits.  If the fruit is a simple fruit, will it have one or many seeds?  Be sure to write down your answers!


1) Peach

3)  Apple

5)  Strawberry

When you've written down all your answers, scroll down.
















Answers:

1)  Peach:  Simple fruit, one seed

2)  Blueberry:  Simple fruit, many seeds

3)  Apple:  Simple fruit, more than one seed

4)  Fig:  Multiple fruit

5)  Strawberry:  Simple fruit, many seeds





For more pictures of flowers that become fruit, please see this website from the University of California Davis  http://fruitandnuteducation.ucdavis.edu/generaltopics/AnatomyPollination/Anatomy_Tree_Fruit_Nut_Crops/


*The picture of a pineapple flower found on Wikipedia is used with permission, shared under the Creative Commons Attribution-Share Alike 3.0 Unported License.  A link to that license appears here:  http://creativecommons.org/licenses/by-sa/3.0/legalcode

You’ve probably played on a see-saw before, or used a wheelbarrow to move dirt or tools for gardening.  Maybe you’ve used tweezers to get a splinter out of your finger.  While the see-saw, the wheelbarrow and the tweezers may not seem to have much in common, they are actually somewhat alike: they are all levers.   A lever is simply a rigid stick or beam, which pivots around a stationary point called a fulcrum. 

For any lever, there is also a point of input force, and a point of output force against some resistance.  When input force is applied to a lever (like when you pick up the handles of a wheelbarrow), the resulting output force (the force acting against the resistance, which lifts the tools in the wheelbarrow) is amplified.  In other words, the lever of the wheelbarrow helps you move your garden tools because it allows you to put in a small force, and turn it into a large force to lift the tools.  One of the first to demonstrate the lever’s usefulness for moving heavy objects was Archimedes; according to Pappus of Alexandria, who wrote Synagoge: Book VIII in 340 AD, Archimedes once said, “Give me the place to stand, and I shall move the Earth.” (wikiquote.org)

Levers can be put in one of three classes:

Class 1 levers have the fulcrum in the middle of the lever, force is applied to one end of the lever, and the object to be moved (the resistance) is on the other end.  The see-saw is an example of a class 1 lever.

Class 2 levers have the fulcrum at one end and the input force on the other end, with the resistance in the middle.  The wheelbarrow is an example of a class 2 lever.

Class 3 levers have the fulcrum at one end and the resistance on the other end, with the input force in the middle.  Tweezers are an example of a class 3 lever.

To understand how a lever helps us move things, we need to understand how the lever changes the forces that are exerted on it.  Using a see-saw as an example, say you weigh 50 pounds, and your friend weighs 100 pounds.  If the fulcrum of the see-saw is in the middle, your friend will be sitting on the ground and you will be up in the air!  This is because your friend is exerting twice as much force on his or her end of the see-saw as you. 

To understand how to cope with this, we need to understand the law of the lever.  This law states that the output force on the resistance (FB) divided by the force applied on the lever (FA) equals the distance of the input force from the fulcrum (a) divided by the distance of the output from the fulcrum (b), or:

This value is also called mechanical advantage.  For more information, please click here. 

In order for the two of you to play on the see-saw together, you will need a mechanical advantage!   We know from the law of the lever that the product of the force and the distance from the fulcrum must be equal for you both.  So:

We can also see that this means the distance from the fulcrum to your seat must be twice the distance of the fulcrum to your friend’s seat:

So if we move the see-saw fulcrum so that the distance from your seat is twice as much as your friend’s, you will balance, and be able to play nicely on the see-saw!

The same idea applies to the wheelbarrow:  if the object you are trying to move is twice as heavy as the weight you are able to lift, you will need to position this object close enough to the wheels such that it is more than twice as close to the fulcrum as you are.

TRY IT!!

NOTE:  You will need to do these experiments at a playground, or another location where you can find a see-saw.  You will also need to know your exact weight in pounds, as well as your friends’ weights.

Here’s what you will need:

1.       A see-saw from your local playground or park.  IT MUST BE ADJUSTABLE  (In other words, you need to be able to move the fulcrum)

2.       A friend that is lighter or the same weight as you

3.       A friend that is heavier than you (this could be a parent or teacher)

4.       A tape measure at least as long as the see-saw

5.       A notebook to take notes and write down numbers

Here’s what you need to do:

1.       Measure your see-saw from end to end.   Write down the total length in feet. 

2.       Divide your weight by your friends’ weights.  This means you will have two numbers, your weight divided by your smaller friend’s weight, and your weight divided by your bigger friend’s weight.  These will be numbers W1 and W2.  Write these numbers down!

3.       The number ‘W1’ is likely to be close to 1, since you and your smaller friend are likely about the same size.  If your smaller friend is lighter than you, that number will be greater than 1.  If the number is 1, take the length of your see-saw and divide it in half, and place the fulcrum this distance from both you and your friend’s seat (so if your see-saw is 6 feet long, place the fulcrum 3 feet from your seat and 3 feet from your friend’s seat). 

4.       Both you and your friend now sit on the see-saw on either end, and if you are really the same weight, you should balance!  If you don’t balance, try measuring the see-saw again, or check your weights again!

5.       If the number W1 is greater than 1, to find how far you and your friend should be sitting from the fulcrum we need to do some algebra!  Don’t worry if you haven’t learned algebra yet, there is a very easy way to figure out the answer.  We are going to go through the long way too, just for good measure! 

Let’s say you weigh 75 pounds, and your smaller friend weighs 50 pounds.  This means your number W1 is 1.5, because 75/50 = 1.5. 

We know the length of the see-saw (say 6 feet), and we know that in order to balance on the see-saw together your friend needs to be 1.5 times further from the fulcrum as you are (see the discussion above on how levers do work if you need to review this).  So to find how far from the fulcrum you and your friend need to be, we set it up like this:

x = how far you need to be from the fulcrum

1.5x = how far your friend needs to be from the fulcrum (this means he/she needs to be 1.5 times as far as you).

If we add these two distances, we know they must be 6 feet, since that’s how long our see-saw is:

x + 1.5x = 6

We can add x and 1.5x to get 2.5x

2.5x = 6

Now to find x we divide 6 by 2.5

x = 6/2.5

This gives us 2.4 feet, or about 2 feet and 5 inches

x = 2.4 feet

So you must be 2 feet and 5 inches from the fulcrum.  This means your friend must be 3 feet and 7 inches from the fulcrum, because:

1.5x = 2.4 x 1.5 = 3.6 feet = 3 feet 7 inches

Whew!  That’s a lot of math!  Now here’s the easy way:  Whatever W1 is, just add 1, and divide the total length of the see-saw by that number.  That’s how far you need to be from the fulcrum.  Subtract that number from 6, that’s how far your friend needs to be.  It’s that easy!

6.       Now move the fulcrum of the see-saw so it is 2 feet and 5 inches from your end.  Sit on the see-saw with your smaller friend, and you should balance!  If not, double check the length of your see-saw, and your weights!

7.       Now we’ll do the same for you and your bigger friend.  Take your number W2 (which should be less than 1), add 1, and divide 6 by this number.  This is how far you should sit from the fulcrum.

Here’s an example:  Say you weigh 75 pounds, and your larger friend weighs 150 pounds.  This means your W2 number is 0.5:

W2 = 75/150 = 0.5

We add 1 to this number, and divide 6 by this final number:

0.5 + 1 = 1.5

6/1.5 = 4

This is how far you should be sitting from the fulcrum of the see-saw.  This means your friend should be sitting 2 feet from the fulcrum, because 6-4 = 2.

8.       Now move the fulcrum of the see-saw so it is 4 feet from your end of the see-saw.  Sit on the see-saw with your bigger friend, and you should balance!  If not, double check the length of your see-saw, and your weights!

NOTE:  You may not balance perfectly if the see-saw has some extra weight on one end after you move the fulcrum, like a metal piece that holds the see-saw in place.  If this is the case, you may need to adjust slightly to perfect the balance!

Be sure to write down all your observations:  Did you and your friends balance?  Why or why not?  Probably the numbers were not as easy as in our examples, so if you found it hard to balance this may be the culprit also!

MAKE UP YOUR OWN EXPERIMENT!

You could do a similar set of experiments with a wheelbarrow and a heavy weight.  Calculate how close to the wheels of the wheelbarrow the weight would need to be for you to lift it using the same math technique used above.  As always, be sure to write down all your numbers and observations!


References for more information:

J. J. Uicker, G. R. Pennock, and J. E. Shigley, 2003, Theory of Machines and Mechanisms, Oxford University Press, New York.

Let me say from the beginning, I love to cook.  I’ve been cooking since I was a
small child (with my mother’s help during the early years of course), and have
always found the transformation of inedible (and sometimes unappetizing)
raw ingredients into fine cuisine particularly fascinating. While cooking is
often considered an art, it is also very much a science, and often it is the
first real exposure to science we have as children.  Needless to say, learning
some cooking skills early in life is very important—it is both a necessary life
skill, and a valuable science lesson! 

While we prepare and consume cooked food every day, seldom do we hear much about what is really going on when food is cooked.  What is really happening?  That is, what is really the difference between cooked food and raw food?  Usually, this can be boiled down (no pun intended) to just one word: heating.  
When we heat our food, several things take place:

1.    Proteins denature; that is, the shape of the proteins change, as the weak bonds and interactions within
their structures break and they unravel.  This is what causes the whites of an egg to go from clear to white as they cook.

2.    Changes in water content; in many types of food and cooking, such as roasting fresh vegetables,
heat causes some of the water to evaporate which changes the flavor and texture of food.  In other types of food, such as beans or dried pasta, the food absorbs water which makes it softer and more palatable.

3.    Cells walls are weakened or broken; vegetables (carrots, broccoli, etc.) have tough cell walls
made up of cellulose.  When they are heated the cellulose weakens and often the cells burst, resulting in a softer texture.

These are common effects for most cooking, and yet foods prepared in different ways look and taste very different.  This is because the method we use to cook our food can result in some different reactions, depending on the amount of heat used.  As an example, let’s look at potatoes.  
 
If we boil potatoes, they become soft and tender, but they remain pale in color and their flavor is rather bland—perfect for mashing with butter and milk.  However, if we fry our potatoes they turn a golden brown color and take on a pleasant flavor, which is good to enjoy without additional ingredients. These are the same potatoes, and yet the flavor and appearance is so different.  This is because when we fry potatoes (or roast them at a high enough temperature), two things happen to create this appearance and flavor: caramelization, and the Maillard reaction.  

Caramelization occurs when the sugars in the potatoes decompose (break apart) into volatile compounds (compounds that evaporate) and residual organic material.  The process is very complex, and involves many reactions, but the result is brown color and complex flavor.  Caramelization requires temperatures above 230°F (110°C), the exact temperature depending on what type of sugars the food contains.

The Maillard (pronounced May-ard) reaction happens when sugars react with amino acids (the building blocks of proteins) above 300°F (148°C), creating brown color and a complex variety of new flavor compounds.  This is another reason our potatoes turn golden brown when we fry them.  The Maillard reaction is also responsible for the aroma of roasted coffee, and gives baked breads and pretzels their brown crust.  The Maillard reaction and caramelization may make food look (and taste) similar, but the Maillard reaction involves sugars reacting with amino acids, while caramelization only involves sugar.  

TRY IT!


REMEMBER, THIS INVOLVES HIGH HEAT SO BE SURE TO HAVE A PARENT HELP YOU!!


Here’s what you’ll need:

1.    Potatoes, as many as you’d like, chopped into one-inch chunks

2.    A large enough pot to hold your potatoes and enough water to cover them

3.    A frying pan large enough to hold all your potatoes

4.    Two tablespoons of vegetable oil

5.    A spatula

6.    A spoon

7.    A stove 
 

Here’s what to do:

1.    Bring your pot of water to a boil over high heat.


2.    When the water starts to boil, begin heating your vegetable oil in your frying pan over medium-high
heat.

3.    When the oil in the frying pan is hot, and the water is boiling, add half of your potato chunks to
the boiling water, and half to the hot oil.  Be sure the potatoes in the oil are spread out.

4.    Carefully watch the potatoes in the oil, turning them every 3-5 minutes to make sure they don’t
burn.  Stir the potatoes in the boiling water every 5 minutes as well.

5.    After about 20 minutes, turn off the stove and remove your potatoes from the boiling water and the
oil.

6.    Allow them to cool for about 5 minutes before touching them.
  

Look at the potatoes.  What do the ones from the boiling water look like?  What about the ones from the oil?  How are they different?  Why do you think this is?  

 
Taste one of the potatoes from the boiling water. Describe the flavor and the texture. Now taste one of
the potatoes from the oil.  How are the flavor and texture different?  Why do you think that is?  Be sure to write down all your observations.

 
Make up a new experiment! 
What other foods could you try this with?  What other cooking techniques could you try (Hint: try the microwave!  Based on what you see, how do you think the microwave cooks food?)  Always be sure to have a parent or teacher help you and write down all your observations!

With the Super Bowl airing today, and the Olympics starting on February 7 (next
Friday), there will soon be many highly fit individuals running, jumping, and
skiing their way across our television sets!  While I will certainly never be as
physically fit as an Olympic figure skater or skier, I would hope to achieve at
least an acceptable level for the average person. This brings up a
question...what exactly does it mean to be “physically fit”? 

By definition, physical fitness is, “a general state of health and well-being or specifically the ability to perform aspects of sports or occupations” (from the Wikipedia website on Physical Fitness).  So in general, to be physically fit means you should be able to perform your daily duties and actions without much difficulty and without getting too tired.  A person who has poor physical fitness will become tired from simple activities, such as climbing a staircase or walking from one room to another.  This can be due to several causes, such as poor diet, low physical activity, obesity (excess body fat), or a heart condition.  
 
What makes a fit person’s body so different from that of an unfit person?  First, if a person is in better physical condition they will tend to have less body fat than a person who is in poor physical condition, and so will have less weight to move around during physical activity.  A lighter body will put less stress on their bones and joints, too. In addition, there are some differences between the bodies of a person in good physical condition and a person in poor condition which may not be so obvious.  These include cardiovascular and muscular fitness.

When a person is in good cardiovascular condition (that is, their heart and lungs are in good condition), the volume of blood their heart is able to pump with each beat increases, and so does the amount of blood in their body.  This means that every time their heart beats, more blood is carried to their muscles, bringing oxygen and nutrients and carrying away waste more efficiently.  This means that their heart will have to beat more slowly when they are at rest, and that it will return to resting rate more quickly after exercise,
because they can supply their bodies with oxygen and nutrients (and get it to return to normal) with fewer beats per minute. 

Think of a person’s body as a city, and their cardiovascular system as the streets and highways carrying people around to all the organs and tissues.  If a person is in good cardiovascular condition, their city streets and highways are wider and well maintained, and so more cars can get where they need to go faster.  If they are in poor cardiovascular condition however, the streets and highways are
narrow, and can carry fewer cars at one time.

When a person’s muscles are in good condition, the muscles have more fibers and more blood vessels, and can therefore supply more power.  Think of the muscles as like ropes or cables that move our bodies: if the ropes are bigger and have more fibers (that is, more fibers that make up the rope), they will be able to
lift and pull larger amounts of weight.  The added blood vessels allow more oxygen and nutrients to flow to the muscles too, allowing them to work more efficiently (like the wider streets and highways in our last example).  

So how can we measure just how physically fit we are?  Through a series of tests measuring
your heart rate in number of beats per minute, we can get a good idea of just how fit you are.


TRY IT!


Here’s what you’ll need:


1.   A stopwatch or a watch with a sweep second hand

2.   A clean table you can lie down on or a clean towel to lie down on the floor

3.   Enough space to jog in place


Here’s what to do:


First, measure your standing heart rate.

1.   Stand upright for 2 minutes.  Be sure to stand still!

2.   With your index and middle finger, find the pulse at your wrist or your neck below your jaw bone.

3.   Count the number of times you feel your heart beat in 15 seconds.  Time this with your watch or stopwatch, and write down the number of beats.

4.   Multiply this number by 4 to get the number of beats per minute.

5.   Find the number of beats per minute in Table 1 below, and record how many points you earned.  Be sure to write this down!

 Next, measure your resting heart rate.

5.   Lie down on the table or the floor on a clean towel for 2 minutes.

6.   Record your heart rate as you did for your standing heart rate by repeating steps 2-4 above.

7.   Find the number of beats per minute in Table 2 below, and record how many points you earned.  Be sure to write this down!

Finally, measure your heart rate just after exercise, and how long it takes to return to normal.

8.   Jog in place for 10 seconds.  Time this with your watch or stopwatch.

9.   As soon as you stop, immediately begin recording how many times you feel your heart beat in 15 seconds.  Write this number down.

10.  Continue recording how many times your heart beats every 15 seconds until the number is the same as when you took your standing heart rate in step 3.  Write each number down.

11.  Count how many numbers you had to write down, and divide that number by 4.  This is how many minutes it took for your heart rate to return to the normal standing rate. 

12.  Multiply the first number you wrote down immediately after exercise by 4 to get beats per minute.  Be sure to write this down!

13.  Find the number of minutes it took for your heart rate to return to normal in Table 3 below, and record how many points you earned. Be sure to write this down!  If it took longer than 2 minutes, give
yourself 6 points.

14.  Subtract your standing heart rate from your heart rate just after exercise.  This is your heart rate
increase after exercise.

15.  Finally, in Table 4 below, find your standing heart rate on the left, and use the heart rate increase after exercise value on the top to find your points.  Write this down!

16.  Add up all the points you earned (steps 5, 7, 13, and 15).  Use the scale below to determine your level of fitness.

 
Are you as fit as you thought?  If you are not, why do you believe that is?  Do you need to get more exercise, or eat healthier?  
 
If you are not as fit as you want, try increasing your physical activity over the next few weeks, and repeat the test in one month.  See if you can improve your fitness level!



References for more information:


CDC: Physiological Responses and Long-Term Adaptations to Exercise
(http://www.cdc.gov/nccdphp/sgr/pdf/chap3.pdf)


Vernier Software and Technology website
(http://www2.vernier.com/sample_labs/BWV-27-COMP-heart_rate_physical_fitness.pdf)

Wikipedia: Physical Fitness (http://en.wikipedia.org/wiki/Physical_fitness)