1

NAME____________________________________________________ DUE DATE________________________

UNIT GUIDE Unit 12 – Origin and Diversification of Microbes

The Five-Second Rule Explored, or How Dirty Is That Bologna? By HAROLD McGEE

A COUPLE of weeks ago I saw a new scientific paper from Clemson University that struck me as both pioneering and hilarious. Accompanied by six graphs, two tables and equations whose terms include “bologna” and “carpet,” it’s a thorough microbiological study of the five-second rule: the idea that if you pick up a dropped piece of food before you can count to five, it’s O.K. to eat it.

I first heard about the rule from my then-young children and thought it was just a way of having fun at snack time and lunch. My daughter now tells me that fun was part of it, but they knew they were playing with “germs.” We’re reminded about germs on food whenever there’s an outbreak of E. coli or salmonella, and whenever we read the labels on packages of uncooked meat. But we don’t have much occasion to think about the everyday practice of retrieving and eating dropped pieces of food.

Microbes are everywhere around us, not just on floors. They thrive in wet kitchen sponges and end up on freshly wiped countertops. As I write this column, on an airplane, I realize that I have removed a chicken sandwich from its protective plastic sleeve and put it down repeatedly on the sleeve’s outer surface, which was meant to protect the sandwich by blocking microbes. What’s on the outer surface? Without the five-second rule on my mind I wouldn’t have thought to wonder.

I learned from the Clemson study that the true pioneer of five-second research was Jillian Clarke, a high-school intern at the University of Illinois in 2003. Ms. Clarke conducted a survey and found that slightly more than half of the men and 70 percent of the women knew of the five-second rule, and many said they followed it. She did an experiment by contaminating ceramic tiles with E. coli, placing gummy bears and cookies on the tiles for the statutory five seconds, and then analyzing the foods. They had become contaminated with bacteria. For performing this first test of the five-second rule, Ms. Clarke was recognized by the Annals of Improbable Research with the 2004 Nobel Prize in public health.

It’s not surprising that food dropped onto bacteria would collect some bacteria. But how many? Does it collect more as the seconds tick by? Enough to make you sick? Prof. Paul L. Dawson and his colleagues at Clemson have now put some numbers on floor-to-food contamination. Their bacterium of choice was salmonella; the test surfaces were tile, wood flooring and nylon carpet; and the test foods were slices of bread and bologna. First the researchers measured how long bacteria could survive on the surfaces. They applied salmonella broth in doses of several million bacteria per square centimeter, a number typical of badly contaminated food.

1. What kinds of things can you recall about bacteria from earlier units in Biology?

2. Bacteria are just one of 6 Kingdoms of life. What are the other Kingdom names?

3. What are the basic 5 cell parts that must exist for us to consider something a cell?

2

I had thought that most bacteria were sensitive to drying out, but after 24 hours of exposure to the air, thousands of bacteria per square centimeter had survived on the tile and wood, and tens of thousands on the carpet. Hundreds of salmonella were still alive after 28 days. Professor Dawson and colleagues then placed test food slices onto salmonella-painted surfaces for varying lengths of time, and counted how many live bacteria were transferred to the food. On surfaces that had been contaminated eight hours earlier, slices of bologna and bread left for five seconds took up from 150 to 8,000 bacteria. Left for a full minute, slices collected about 10 times more than that from the tile and carpet, though a lower number from the wood.

What do these numbers tell us about the five-second rule? Quick retrieval does mean fewer bacteria, but it’s no guarantee of safety. True, Jillian Clarke found that the number of bacteria on the floor at the University of Illinois was so low it couldn’t be measured, and the Clemson researchers resorted to extremely high contamination levels for their tests. But even if a floor — or a countertop, or wrapper — carried only a thousandth the number of bacteria applied by the researchers, the piece of food would be likely to pick up several bacteria. The infectious dose, the smallest number of bacteria that can actually cause illness, is as few as 10 for some salmonellas, fewer than 100 for the deadly strain of E. coli. Of course we can never know for sure how many harmful microbes there are on any surface.

But we know enough now to formulate the five-second rule, version 2.0: If you drop a piece of food, pick it up quickly, take five seconds to recall that just a few bacteria can make you sick, then take a few more to think about where you dropped it and whether or not it’s worth eating.

Before you feel that you are ready for the test you should be able to describe all components of the key learning and answer all essential questions using

appropriate vocabulary.

1. Have you ever eaten something and claimed the five second rule exemption? YES NO

2. What kinds of food would you still feel comfortable eating that way?

3. Many bacteria dry out and die with exposure to air. In the experiment above, how long did they let salmonella go before checking to see if it was still alive? Was it still alive?

4. What is the infectious dose for some salmonella bacteria species? E. coli?

5. Will you continue to use the five second rule?

3

Student Learning Map Biology Unit 12 – Origin & Diversification of Life - Microbes (C)

Days: 10

Unit Essential Questions Key Learning

1. How has microbial life developed and changed on Earth over time? 2. How is life on Earth classified and organized?

1. Microbes have evolved from simple spheres of pre-biotic chemicals into the most diverse group of organisms, spanning three kingdoms. 2. Despite tremendous diversity life is classified into 6 kingdoms. 3. Viruses can cause disease but are not living themselves.

Concept 1 Concept 2 Concept 3

Modern Taxonomy (E) The 6 Kingdoms (I) Origins of Life (C)

EQ 1.1: On what basis are organisms now classified?

EQ 2.1: How can each of the 6 kingdoms be described using a set of essential vocabulary?

EQ 3.1: What 3 explanations exist for the appearance of the Earth’s first forms of life?

Vocabulary Vocabulary Vocabulary

Analogous Structures Binomial nomenclature Cladogram Convergent Evolution Derived trait

Cell Structure Cell Type Domain Tree of Life

Abiogenesis L.U.C.A.

Concept 4 Concept 5

Microbe Diversity (I) Viruses (C)

EQ 4.1: How are microbes identified and classified?

EQ 4.2: How are microbes important to humans and the environment we live in today?

EQ 4.3: How did Prokaryotic cells give rise to eukaryotic Protists?

EQ 5.1: How do viruses cause disease?

Vocabulary Vocabulary

Archaea Bacteria Bacilli Cocci Endosymbiosis Extremophiles Spirilla

Capsid Lysogenic Cycle Lytic Cycle

Literacy Components Article 1 : Tending the Body’s Microbial Garden Article 2 : Microbes in food (Yeast, Sugar as a Humectant, Lactobacillus acidophilus)

4

Concept I: Taxonomy

EQ 1.1 – On what basis are organisms now classified?

Previewing:

L1 – Read section 10-4 on pages 376 - 377 of your text.

L2 – Read section 18.1 & 18.2 on pages 512 - 522 of your text.

Activation: Organize the animals from the notes into groups & identify characteristics that bring them together.

Group 1 Characteristic: _______________________ Examples:

Group 2 Characteristic: _______________________ Examples:

Group 3 Characteristic: _______________________ Examples:

Group 4 Characteristic: _______________________ Examples:

Group 5 Characteristic: _______________________ Examples:

1. At what level do Giraffes differ from Grey Wolves?

2. What is the first trait the separates the monarch butterfly

from the other groups?

3. At what level do Human and Chimpanzee diverge?

Concept I Key Vocabulary

Analogous Structures

Binomial nomenclature

Cladogram

Convergent Evolution

Derived trait

5

4. At what level of classification are camels the

same as snakes?

Add the appropriate word roots below the title

of binomial nomenclature. From this point on in the year it will be assumed for all tests, quizzes and labs that you know how to write biological names appropriately.

5. Describe what is wrong with each name below. Rewrite one of them correctly. Canis Familiaris Felis catus PANTHERA LEO CANIS lupus 6. Which two animals listed above are the most closely related? Why?

6

Read the passage below, then answer the questions that follow: 7. Which are more alike, two organisms that are in the same Kingdom, or two organisms in the same family?

8. Fill in the diagram below:

Linnaeus worked out a broad system of classification for plants and animals in which an organism’s form and structure are the basis for arranging specimens in a collection. He later organized the genera and species that he described into a ranked system of groups that increase in inclusiveness. The different groups into which organisms are classified have expanded since Linnaeus’s time and now consist of seven levels. Similar genera are grouped into a family. Similar families are combined into an order. Orders with common properties are united in a class. Classes with similar characteristics are assigned to a phylum. Similar phyla are collected into a kingdom. There are six kingdoms of living things—the two kingdoms of bacteria, archaebacteria and Eubacteria are prokaryotes. The other four kingdoms are Protista, Fungi, Plantae, and Animalia. The seven-level system can be divided into more specific categories, such as superclass, subclass, superorder, and suborder. In all, more than 30 taxonomic levels are recognized.

7

9. What is an analogy?

10. How do analogous traits differ from homologous traits? How will you keep them straight in your mind for quizzes and tests?

11. How is convergent evolution different from divergent evolution?

8

If you missed class on this day, please watch the tutorial video below before attempting the activity for this section.

http://goo.gl/gGZNbT

Complete the cladogram class activity

12. What does the outermost box (clade tetrapoda) indicate about all of the organisms shown?

13. What does the box (clade

Felidae) being on top of the stack indicate about cats?

14. Why do both canines and felines have specialized shearing teeth but only felines have retractable claws?

9

Summarizing: Complete the Frayer diagram below:

15. How does convergent evolution lead to the appearance of analogous traits?

Read the passage below, then answer the questions that follow in complete sentences:

16. What are derived traits?

Analogous

traits

Cladistics is a system of taxonomy that reconstructs phylogenies by inferring relationships based on similarities derived from a common ancestor. Cladistics is used to determine the sequence in which different groups of organisms evolved. To do this, cladistics focuses on a set of unique characteristics found in a particular group of organisms. These unique characteristics are called derived traits. Using patterns of shared derived traits, a biologist using cladistics constructs a branching diagram called a cladogram, which shows the evolutionary relationships among groups of organisms. The key to cladistics is identifying morphological, physiological, molecular, or behavioral traits that differ among the organisms being studied and that can be attributed to a common ancestor.

10

17. What do common derived traits tell a taxonomist about the organisms that share them?

Reviewing: 18. Why is it helpful to use an organizational system to categorize the Earth’s life forms?

19. What flaw was there in Aristotle’s system of classification? 20. What is a scientific name and how is it hand-written?

21. Without using your notes, fill in the levels of classification between Kingdom and Species:

Word bank: Class, Family, Genus, Order, Phylum

Kingdom _____________________________________

_____________________________________

_____________________________________

_____________________________________

_____________________________________

Species

22. What happens to the similarities between organisms as you move up from species to kingdom?

23. Why aren’t analogous traits used to classify two groups of organisms into a common group? For instance, a bat’s wings and a bird’s wings.

24. Why might convergent evolution result in improper classification of two distantly related organisms

(hint: Aristotle’s mistake).

25. Draw a tree of life to represent the difference between convergent evolution and divergent evolution. (ask if unsure)

11

Concept II: The 6 Kingdoms

EQ 2.1 – How can each of the 6 kingdoms be described using essential vocabulary?

Previewing:

L1 – Read sections 10.3 & 10.4 on pages 374 & 379 of your text.

L2 – Read sections 18.3 on 523 - 528 of your text.

Activation: Agree or disagree with the following statements:

Agree Disagree Prokaryotes (ie. Bacteria) are likely to make us sick.

Agree Disagree Archaea live only in extreme conditions.

Agree Disagree Protists are all unicellular organisms.

Agree Disagree Fungi are plants.

Agree Disagree All plants have some form of flower.

Agree Disagree All animals have hair.

1. What traits make eukaryotes different than prokaryotes (Bacteria and Archaea)?

2. Label the basic cell types below as being plant, animal or bacteria. Additionally label the domain.

Concept II Key Vocabulary

Cell Structure

Cell Type

Domain

Nutrition

Peptidoglycan

Tree of Life

12

3. What does it mean to be unicellular?

4. What differences exist between autotrophs and heterotrophs?

Since your tree shown below does not contain color, please key or label your branches appropriately using the example from your notes in class (or online if absent)

13

Concept III Key Vocabulary

Abiogenesis

L.U.C.A.

Summarizing: Fill in the 6 Kingdom names beside the row of characteristics that describe it.

Reviewing: 5. On what basis are organisms classified into the 6 kingdoms?

6. How would you describe an Animal cell? Bacteria?

7. What are the distinguishing characteristics of the following Kingdoms: Fungi Plants Animals

________________ ________________ ____________________

Concept III: Origin of Life EQ 3.1 - What 3 explanations exist for the appearance of the Earth’s forms of life?

Previewing:

L1 - Read section 10.1 & 10.2 on pages 370 - 373 of your text.

L2 – Read section 19.3 on pages 353 - 555 of your text.

Activation: With the help of your partner, brainstorm and list the ingredients necessary to make homemade chicken noodle soup?

14

1. Why do we focus on abiogenesis from a biological / scientific perspective?

2. Does this preclude you from having other beliefs?

3. Will we ever know with certainty how life began on Earth?

4. What traits do we look for to determine if something is alive or not? (Unit 1)

5. What is a Polymer? (Unit 2)

6. What is a Monomer? (Unit 2)

What macromolecules would have needed to be made in order to have a functional cell? What monomers / polymers are needed for each to form?

15

If you missed this class you can follow the link below to watch a short video that recaps the major ideas discussed today.

http://goo.gl/akRmP

In your own words… What 4 stages must have occurred for life to have formed abiotically?

16

What is the likely definition of the word “extant” based on its placement in the diagram below?

Summarizing: With the help of your partner, brainstorm and list the ingredients necessary to make a cell.

Reviewing: 1. Briefly explain what is hypothesized to have occurred through the process of abiogenesis.

2. How do you feel about life elsewhere in the Universe? Do you think that life could have seeded life on Earth?

3. Describe the concept of the L.U.C.A.

17

Concept IV: Origin and Diversification of Microbes: Bacteria

EQ 4.1 – How are microbes identified and classified? EQ 4.2 – How are microbes important to humans and the environment we live in today?

Previewing:

L1 – Read section 10.14 on pages 396 - 401 of your text.

L2 – Read section 20.2 on pages 580 - 583 of your text.

1. How do bacteria reproduce?

2. What advantages does that type of reproduction exhibit?

3. What forms of bacteria have you most likely come in contact with during this week?

Draw and label the three types of bacteria in the space below.

Concept IV Key Vocabulary

Archaea

Bacteria

Bacilli

Cocci

Endosymbioses

Extremophiles

Spirilla

18

4. What does the word pathogenic

mean in reference to bacteria?

Read the article “Tending the Body’s Microbial Garden” when

distributed.

5. What does bioremediation mean?

6. What are some examples of bacterial pathogens?

7. What do the following roots tell you about the Kingdom Archaea?

Extremo: Phile:

8. What other word this year did we use the root “philic”? How did we use that word to describe the nature of the phospholipid?

19

9. What does it mean to be anaerobic?

Describe what the following roots indicate about Archaea. Methano – Thermo – Acido – Halo – Hyper –

10. Describe the role of the ribosome.

Bacteria Archaea

20

Reviewing: 13. Describe 3 critical roles bacteria have played in the shaping of the planet or society.

14. What are the 3 basic categories of Archaeans? How are they named?

EQ 4.3 - How did prokaryotic cells give rise to eukaryotic Protists? L1 – Read section 3.3 on pages 81 – 84 of your book.

L2 – Read section 19.3 on pages 556 – 557 of your book.

Activation: List three similarities and 2 differences between Prokaryotic and Eukaryotic cells.

Similarities Differences

15. What does the “endo” indicate

about these organelles? 16. What does symbiosis indicate?

21

17. What evidence exists to support the idea that mitochondria and chloroplasts could have been independent eukaryotes?

22

18. Describe the differences between

Aggregations and Colonial organisms.

19. What are the benefits of grouping

cells together?

20. Why are the characteristics to left

advantageous to the multicellular organism?

21. How might algae have made the

move from sea to land? (What new

challenges would they have had to overcome to make such a move?)

If you miss this day in class or would like to review this concept Further, the link below will connect you to the Crash Course Biology video concerning microbes.

http://goo.gl/lODl6o

23

Summarizing: 22. What are the three domains of life? How do they differ from one another?

23. Eukaryotes have structures that prokaryotes do not. What are they called and how do scientists explain their origins?

24. What major differences exist between unicellular and multicellular organisms?

Reviewing: 25. In what ways do Protists link the Plant, Animal and Fungi Kingdoms with Bacteria and Archaeans?

26. How are Protists different from Bacteria and Archaea?

History of life - Timeline Over the entirety of units 12-14 we will be constructing a timeline of the most important events leading to life on Earth as it exists today. The items listed below are the first items that will be being placed on this culminating activity. In later units we will add more items to the list as we discuss them and their importance on the timeline. For now, record some notes concerning the individuals below.

Solar system and Earth formation - 4.6BYA

What conditions existed on early Earth?

What did the Earth look like?

First prokaryotic cells – 3.5BYA

What needed to occur to have cells form abiotically?

What other possibilities exist for life to appear on Earth?

24

O2 accumulating in atmosphere – 2.7BYA

What caused this atmospheric change?

How did this forever change the course of life on Earth?

First eukaryotes (Protists) – 2.1BYA

How did eukaryotes form?

How is the appearance of eukaryotes important?

Multicellular Protists – 1.8BYA

Why is multicellularity biologically important?

Protists have diversified into Plant, Fungi and Animal Kingdoms - 1.0 BYA