Today is Friday (!),October 9th, 2015

http://www.theage.com.au/ffximage/2007/09/14/svLYNX_narrowweb__300x434,0.jpghttp://www.alaska-in-pictures.com/data/media/1/snowshoe-hare-portrait_6139.jpg

Pre-Class:Compare the two animals below. Write in your notebook any and all observations you make about the two animals with only your

eyes, especially their differences. Write as many as you can!

In This Lesson:Cells, Cell History,

General Characteristics(Lesson 2 of 5)

Today’s Agenda

• Be able to make an educated guess as to the function of an unfamiliar structure.

• Know at least a little about the history of the cell’s discovery.• Be able to recite the three parts of the Cell Theory.• Software art?

– Brain break.

• Where is this in my book?– Academic: P. 172 and following…– Honors: P. 55 and following…

By the end of this lesson…

• You should be able to describe the Cell Theory and how cells were first discovered.

• You should be able to define the general properties of cells.

Lynx and Hare

http://media-2.web.britannica.com/eb-media/43/6543-004-D65BF551.gif

Why?

• Why do these animals have those traits?– What’s the “form?”– What’s the “function?”

Form and Function• As the Zoo’s rhyme goes:

– Eyes on the side, I like to hide; eyes in the front, I like to hunt.

• The structure (or form) of something is always secondary to its function.

http://upload.wikimedia.org/wikipedia/commons/9/9e/House_Sparrow_(M)_I_IMG_7881.jpghttp://www.shawcreekbirdsupply.com/barn_owl.jpg

Form and Function• Why does this giraffe have a long neck?

• Form: Long neck.• Function: Reaches food up high.

http://www.beenthereyet.com/images/PhotoGallery/giraffe.jpg

Form and Function• Why does this butterfly have “eyes?”

• Form: Eye spots.• Function: Confuses predators.

Form and Function• Why does this cheetah have the black “tear

drops” on its face?

• Form: Black “tear lines.”• Function: Keeps out sun glare.

http://www.rachelinafrica.com/wp-content/photos/Cheetah_face_Mauritius_IMG_3002.jpg

Form and Function• What color is this polar bear’s fur? And what

color is its skin?

• Form: Clear fur, black skin.• Function: Lets light in, skin warms in sun, can

still blend in.http://stevenbell.blogspot.com/images/11-02-05-sleepy-bear.jpg

Form Follows Function

• A characteristic’s form is always shaped by its function.

• You could also say, “Form follows function.”

Function Following Form?• An opposite example might

be headlights in NASCAR.• For those of you that don’t

know, the headlights aren’t real. They’re stickers!

• In this case, the “look” isn’t for any purpose at all.– This doesn’t happen in

biology.

http://news.sportslogos.net/wp-content/uploads/2012/12/headlight.jpg

Form & Function Activity

• Turn to your neighbor and think of at least five examples of an instance of form (or structure) following function in nature. You have 1 minute (less if we’re off topic).– Imaginary bonus points if you can think of

something whose function and structure are not consistent with one another.

Discovering The Cell• It all started way back in 1665 when Robert

Hooke looked at a piece of cork under a microscope.

http://askabiologist.asu.edu/research/buildingblocks/images/hookecork.jpghttp://en.wikipedia.org/wiki/File:13_Portrait_of_Robert_Hooke.JPG

Robert Hooke?

Anton van Leeuwenhoek

• Hooke saw dead cells, but Leeuwenhoek first observed living unicellular (one-celled) organisms in pond water, along with blood and sperm cells.

• Done around the time Hooke saw cork.

http://www.teachersparadise.com/ency/en/media/5/5e/anton_van_leeuwenhoek.png

So they got credit and fame immediately, right?

• Of course not!• Many times across science’s history, research that

breaks ground takes a while to really set in.• In this case, it took nearly 200 years, when

Schwann and Schleiden (and Virchow, to some extent) confirmed that cells are the smallest units of life, and gave Cell Theory its start.

Cell Theory(write this down - it’s important)

• Cell theory is a way to fit the concept of cells into the rest of biology. It has 3 parts:– “All living things are made of one or more

cells.”– “Cells are the basic units of structure and

function [organization] in organisms.”– “All cells arise from existing cells.”

Johnson, G. & Raven, P. (2004). Biology. Holt, Rhinehart, and Winston: Austin

Cell Theory Video

• It turns out the Cell Theory had a bit of a weird origin.– Let’s take a look…

Why is the Cell Theory important?

• It disproved the theory of Spontaneous Generation!

• Hypotheses based on Spontaneous Generation on the coming slides…

Spontaneous Generation

• Maggots come from rotting meat.

http://www.pestcontrolrx.com/.a/6a00e55272212588330105368eaecd970c-500wi

Spontaneous Generation

• Rats come from damp roofs.

http://www.smrestore.com/Galleryimages/WaterDamage1-Water%20in%20ceiling.jpg

The coming rat plague!

DisprovingSpontaneous Generation

• So how do you disprove something like this?

• It seems obvious, but can you prove it?– Design an experiment!– Talk to your partner and take a minute and 57

seconds.

Francisco Redi

• Redi filled six jars with decaying meat:– 3 were open containers– 3 had fine nets over them

• Sure enough, the three open containers had maggots and the three with nets didn’t.

• Where did the maggots come from?• What was the purpose of the sealed jars?

Some More About Cells

• Cells are the smallest unit of life.– BioScale!– http://learn.genetics.utah.edu/content/begin/cells/sca

le/

– Scale of the Universe• As we all know, cells are tiny. How many cells are

in the human body?• Your body contains…

100,000,000,000,000(that’s 100 trillion, which is also not enough money to pay our national debt)

cells

Cell Size

• Average cell size:– 10-100 micrometers

• Biggest cells?

Large Cells

• Ostrich Egg

http://aidanmoher.com/blog/wp-content/uploads/2010/01/ostrich_egg_size.jpg

Large Cells

• Sciatic Nerve

http://www.acticare.com/conditions/images/sciatic_nerve2.jpg

WARNING:Graphic picture next slide…

Large Cells

• Sciatic Nerve

http://www.ilizarov.org/new1/upload/8142007102508AM3.JPG

Back to Form and Function

• So now the big question. Why is it cells are so small? Why aren’t big organisms just made of bigger cells?

Let’s try an alternate question…

• If you buy a gallon of water in one bottle…

• …and then you buy a gallon of water in many bottles…

• …which option gets you more water?– Either choice. They’re the same.

• But which option uses more packaging material?– The smaller bottles.

• Key: Think of packaging material like surface area.

https://pfiesterpfit.files.wordpress.com/2011/05/gallon_of_water.jpg http://www.exchange3d.com/images/uploads/aff4269/Arrowhead.jpg

Cell Size

• To answer the question of why cells are so small, we’re going to look at a similar relationship in biology.– Which of these spheres has a greater surface

area? Volume?

http://upload.wikimedia.org/wikipedia/commons/3/33/Sphere.jpg

Cell Size

• Head to your lab tables. I would like each group to quickly calculate the surface area and volume of both books at the tables.– Volume = length x width x height– Surface area = area of each side (front cover, back

cover, all four other sides) added to one another• You can use inches.• Have one side of your table do one book, the

other side do another.

What’d you get?• I got this:• TEXTBOOK

– Textbook: 146.625 in3 volume– Textbook: 255.5 in2 surface area

• Surface area is less than twice the volume.

• THE HOT ZONE– The Hot Zone: 28 in3 volume– The Hot Zone: 78 in2 surface area

• Surface area is almost THREE TIMES the volume

Surface Area to Volume RatioA Review

2 cm

2 cm2 cm

Cube 1

4 cm4 cm

4 cmCube 2

Cube 1 Cube 2 ProportionVolume 8 cm3 64 cm3 8x more volume

Surface Area 24 cm2 96 cm2 4x more surface

Proportion 3x more surface 1.5x more surface

SA to Volume Ratio

Surface Area to Volume Ratio

• Generally speaking, smaller objects have more surface area relative to their volumes than larger objects.

• So why are larger organisms composed of many, many small cells, instead of being composed of larger cells?

Surface Area to Volume Ratio

• Imagine that you are a cell. You need to get some tiny but important molecule to the center of…yourself…as fast as possible.

• Having a larger surface area to volume ratio means you have more area for the molecule to enter but a smaller distance for it to go once it gets inside.

– Cells like to do things fast, so this is very handy.

Membrane Action et cetera

• Cells take in and release substances through their membranes.

• Like Goldilocks, the size of the cell has to be just right for things to work efficiently.– Not too big, not too small

• What exactly the cell is doing will be part of our next few lessons.

A Little Preview

• Find a blank section of your notebook and label it “Unit 2 Predictions.”

• I will provide you with four scenarios. Three of them will be “live,” and the other will be a diagram.

• Your job is to [SILENTLY] write a detailed prediction and possible explanation for what will happen in each situation.

Unit 2 Predictions

• Take your time doing this. Be thorough.• Do not talk during this. The point is to get your

brain moving on this topic, not to mooch off someone else’s brainpower.

• Like I said, be detailed. Write what will happen. Write what will happen at the molecular level. What will we see? Why?

Prediction 1

• If I add three drops of this food coloring to this beaker of water, what will happen?

• What will it look like at first? Will it change? How will it be different? Why?

• What are the molecules doing?

Prediction 2

• If I put a baby carrot in a beaker of water and another baby carrot in a beaker of water plus lots of salt, what will happen?

• Will the carrots change? Will the water change? Will both? Why?

Prediction 3

• I am going to spray this “room spray” in the classroom. What will happen? Describe in detail!

Prediction 4

• In this tube, water can cross the border in the middle. The solute cannot. There is more solute on the right than on the left.

http://www.biologycorner.com/resources/osmosis.jpg

Closure

• Which has a greater surface-area-to-volume ratio – an elephant or a mouse?

http://www.upali.ch/bilder1/elemaufus.jpg