1. Evidence from the cell

2. EVIDENCE FROM THE CELL
Deduction: If the hypothesis of evolution is correct then the microscopic structure of organisms should show evidence of common ancestry.
Test: Look at the microscopic structure

3. Data: Short History of the Cell
1665—Robert Hooke—”Micrographia”
Cells Seen in cork

4. Here is what the cell looked like when I was a freshman in college.

5. Here is what it looks like today

6. THE CELL THEORY 1838—M. Schleiden 1839—T. Schwann 1858—R. Virchow
Plants are made of cells
1839—T. Schwann
Animals are made of cells
1858—R. Virchow
“All cells come from cells.”

7. THE CELL THEORY Cells are the basic units of life!
Living organisms composed of one or more cells
Cells, the smallest unit of life
Cells come from pre-existing cells
Cells are the basic units of life!

8. Organelles are discovered
Similar cellular structures exist in all cells
Organelles = tiny little “organs” of the cell
Nucleus
Mitochondria
Chloroplasts (Plants)
Golgi Apparatus
Etc.

9. Deduction: If the hypothesis of evolution is correct, then organisms with the simplest cell structure evolved first and should appear first in the fossil record.
Test: Look at the microscopic evidence and the fossil record.
Data: Two types of cells discovered.
Prokaryotic cells
Eukaryotic cells

10. PROKARYOTIC CELLS (Prokaryotes)
Bacteria & Blue Green “Algae”
Simplest cells
Smallest cells
Oldest cells (3.5 Billion Years Old)

11. EUKARYOTIC CELLS (EUKARYOTES)
Animals, Plants,
Fungi
Large Cells
Complex Cells
Many membranous organelles
Recent
(2+ Billion years old)

12. Eukaryotes Prokaryotes
DNA
Linear strands within membrane-bound nucleus
single circle in “nucleoid region
Size
5-100 µm µm
Organization
often multicellular, some have cell walls (no peptidoglycan)
usually single-celled, some have peptidoglycan cell walls
Metabolism
usually need oxygen to exist
may not need oxygen to exist
Organelles
membrane bound organelles like mitochondria
no organelles, different ribosomes
Examples
plants, animals, protists, fungi
bacteria, archaea 12

13. EVALUATION
Data support the hypothesis of evolution as all organisms have the same basic structure.
Cells probably evolved early since all organisms have cells.
And Prokaryotes probably evolved first

14. AND NOW LET’S

15. Becky
Well, Becky thought, being a dorm counselor for freshmen was not going to be that bad. She got a free room for the year and the food was plentiful - free steaks last week at an outdoor BBQ followed by a hay ride in a horse-drawn wagon in their welcome celebration.
But, then again it wasn’t perfect: she had ended up covered in bug bites; some of the students got sick from eating steak that was burned on the outside and raw in the middle; the horses had mucked up the courtyard and pigeons had roosted on the dorm roof.
At least tonight, the students were finally settling in and quieting down, she mused.

16. The quiet was shattered a few minutes later, when one of the other counselors, Ann, yelled through her door.
“Becky, we’ve got a problem. One of the students found a homeless kitten, and the girl has been keeping her in her room. I only found out because the girl, Ellie, just came to my room complaining of being sick. I felt sick too when I saw the mess that kitten made. I thought cats were born housebroken, but I guess not.”
“Anyway, now I think Ellie might really be sick. She’s feverish and says she’s going to throw up.”

17. “What do you want me to do?” Becky asked.
“I’m freaking out!” Ann answered. “Forget about the mess, just help me figure out what to tell them at the health center. I don’t know what she’s been exposed to. Or what we’ve been exposed to for that matter! This is the second girl this week with aches, fever, and nausea.
“My Mom sent me up with a bunch of medicine,” Becky answered. “I’ll make a list of where we’ve been, what we’ve eaten and possibly been exposed to. Then we can start taking something right away to keep from getting it, too.”
I don’t care what you do. Let’s just get her to the health center now!”

18. Spend a minute and make 3 suggestions as to what is possibly affecting Ellie.
1………
2……..
3……..

19. On to the Internet
Ellie was quickly sent to the health center, but Becky being Becky, did an Internet search and found 4 possible suspects that could be causing Ellie’s illness. She made a table with the various characteristics of disease agents.
Her table looks like Table 1 in the next slide. Does it look like your table?
Add any details you missed so that when you hear the results of the health center tests you will be able to figure out what was making Ellie sick. .

20. What differences exist in the type and shape of the genetic material?
CHARACTERISTIC
Virus
Bacteria
Protozoa
What differences exist in the type
and shape of the genetic material?
RNA or DNA
Circular DNA
DNA in linear
chromosomes
What differences exist in the
structure that provides an outer
protective barrier?
Proteins with or
without lipids
Phospholipid
membrane with
a cell wall
membrane
without cell wall
What differences exist in
reproduction?
Only reproduces
inside other cells
Asexual
Both sexual and
asexual
What differences exist in size?
Nanometer
About 1 µm size
5-100 µm
What drugs can treat infections?
Enzyme inhibitors
Anti-peptidoglycans
Drugs that affect
organelles or
enzymes that
only protists
have.

21. The Usual Suspects
“I can’t afford to get sick,” said Ann, “I’m carrying 21 hours of course credits. Maybe Ellie just has the plain old flu.”
“If she does, I’ve got some Tamiflu,” Becky volunteered. “Flu is a virus

22. Becky’s Internet Search Results – List of Suspects
Influenza Virus: Spread primarily through respiratory droplets from sneezing or coughing. Virus has single strand of RNA surrounded by phospholipid/protein envelope ( nm).

23. Suspect 1
Too small to be seen in a light microscope, an electron micrograph is shown below.
Suspect 1: Influenza

24. Suspect 1 : Virus Size Composition Cannot reproduce by itself
Smallest Organisms (50nm)
100 times smaller than bacteria
Composition
Outer envelope: repetitive protein often inserted into a lipid membrane (responsible for recognition and infection of host cell.)
Protected capsid that contains genetic material (DNA or RNA) with important protein enzymes required for duplication.
Cannot reproduce by itself
hijacks a host cell to replicate itself.

25. Virus hijacking host system

26. Clicker Question. Suppose that Ellie has contracted Influenza Virus
Clicker Question. Suppose that Ellie has contracted Influenza Virus. Using your Table 1 information which suspect below best matches that profile?
Suspects
Circular DNA
Nucleus
Divides asexually
Size
Cell Wall
Sexual Reproduction 1 + -
1µm 2
10µm 3
0.1µm 4
5µm

27. Suspect 2: Bacterium Coxiella burnetii
µm gram-negative bacterium that can only survive inside cells and causes 1-2 week Q-fever. Infection occurs 2- 3 weeks after inhalation of barnyard dust. Coxiella are often found in livestock and are excreted in milk, urine, and feces.
Electron micrograph from

28. Prokaryotes Unicellular Reproduce asexually Composition
Protected interior (cytoplasm) that contains genetic material (one circle of DNA) as well as complexes of protein enzymes to carry out necessary functions of gathering energy, manufacturing proteins (ribosomes), etc… 28

29. Prokaryotes Size Composition 0.2-10 micrometer (µm)
Phospholipid membrane, many contain cell wall composed of peptidoglycan (positive for chemical Gram stain), called Gram Positive Bacteria.
Those bacteria with little or no peptidoglycan called Gram Negative (like Coxiella). 29

30. Clicker Question. Suppose that Ellie has contracted Coxiella bacterium Using your Table 1 information, which suspect below best matches that profile?
Suspects
Circular DNA
Nucleus
Divides asexually
Size
Cell Wall
Sexual Reproduction 1 + -
1µm 2
10µm 3
0.1µm 4
5µm

31. Ellie’s Diagnosis
Initial Identification: The health center collected blood samples from Ellie and observed her cells under a light microscope. They identified foreign structures with DNA and outer membranes. The cells were gram negative and about 1/10 the size of Ellie’s cells.
Becky said, “That matches one of my suspects. I just need to re-check the size thing. This internet chart compares our cells to viruses and stuff.”

32. Metric Review 1 meter (m) = ~3 feet 1 meter (m) = 1000 millimeter (mm)
meters
1 mm
1 µm
1 nm
10-3
10-4
10-5
10-6
10-7
10-8
10-9
Eukaryote
cells
Bacteria
Viruses
Proteins
Atoms
Metric Review
1 meter (m) = ~3 feet
1 meter (m) = 1000 millimeter (mm)
1 millimeter (mm) = 1000 micrometer (µm) (smallest size distinguished by naked eye)
1 micrometer (µm) = 1000 nanometer (nm) (only seen with light microscope) 32

33. “That means that it means it must be a bacterium, doesn’t it
“That means that it means it must be a bacterium, doesn’t it?” said Becky.
“It sure looks that way. The size is about right. But I am not so sure look at the size chart again.”

34. Metric Review 1 meter (m) = ~3 feet 1 meter (m) = 1000 millimeter (mm)
meters
1 mm
1 µm
1 nm
10-3
10-4
10-5
10-6
10-7
10-8
10-9
Eukaryote
cells
Bacteria
Viruses
Proteins
Atoms
Metric Review
1 meter (m) = ~3 feet
1 meter (m) = 1000 millimeter (mm)
1 millimeter (mm) = 1000 micrometer (µm) (smallest size distinguished by naked eye)
1 micrometer (µm) = 1000 nanometer (nm) (only seen with light microscope) 34

35. Microscope Analysis
Becky and Ann talked together outside the Ellie’s room at the student health center the next morning. They were pouring over photographs of blood stains that the doctor had provided them knowing their interest in medicine.
“Look at this, Becky. They can’t be bacteria!”
“You’re right!” Becky exclaimed. “I wish I hadn’t started taking the antibiotics.
“Look at their insides. Maybe they are some kind of protozoan parasite or maybe a fungus.”

36. Microscopic Analysis
Pathogens in blood

37. “OK, so we have eliminated bacteria and viruses, what do you have next on your list, Becky?”
“I’ve got a two more suspects. And if these don’t fit, I’ll have to go back to the Internet.”
“Whataya got?”
“Look at these pictures, Ann, and check out the symptoms. They match pretty well.”

38. Suspect 3: Fungus Cryptococcus neoformans
µm encapsulated fungus found in decaying pigeon or chicken droppings. The cells have a cell wall. Inhaled as spores that eventually spread to the brain causing meningoencephalitis. Has a black pigmented layer that can be seen sometimes on bird seed.
Electron micrograph from

39. Eukaryote Suspect 4: Toxoplasma gondii (Protozoan)
4-6 µm single-celled protozoan parasite of mammals & birds.
Most likely through ingesting undercooked meat.
Sexual life cycle occurs in cats, so infection can follow contact with cat feces. Usually no symptoms in cats.
First let’s find out, how do you get Toxoplasma? Well that most common means of acquiring the parasite is NOT from your cat, but from undercooked meat. Again, this is an extremely common parasite, and many of our livestock animals are infected. So just like in humans, the parasite enters the chronic phase and encysts in, where, skeletal muscle. So when we eat meat, there’s a good chance that there are Toxo cysts in the meat. Now these cysts are microscopic, so you can’t tell if your meat is infected or not. Which is why it is always necessary to cook meat thoroughly. Here is a picture of a Toxo cyst, and each of these cells is a parasite ready to start an infection. So, it’s less common, but you can get Toxo from your cat, under certain circumstances. Cats become infected by eating animals that have tissue cysts, mostly small rodents and birds. Cats (domestic and wild) are the only animals in which Toxo multiplies sexually, and the resulting cyst is excreted in cat feces. Here you can see a fecal cyst that contains 4 infective parasites. But this cyst is at least 3 days old. When cysts are first excreted, they are non-viable. They have to incubate in the environment for a few days before they become infective. So if you change your litterbox every 2 days, even if your cat is infected, you’re safe. But if your cat goes outside and you don’t keep the box clean, you can get it that way. But even if you don’t have a cat you can be infected with oocysts from soil and water that cats have defecated in. Even on produce that has been rinsed with contaminated water or grown in contaminated soil. In rare cases, the parasite has been transmitted via blood transfusion. More commonly, the parasite is passed during an organ transplant. Finally, back to the video clip. Toxo can be transmitted across the placenta from a mother to her fetus. But only if the mother contracts the infection while she is pregnant or just a couple weeks before becoming pregnant. If a woman is infected prior to pregnancy, the parasite will be encysted in her tissues, but will not be actively dividing and spreading, so it cannot infect the baby. Only during the acute phase of infection is the baby at risk.
Congenital Toxoplasmosis is not uncommon, affecting about 1 in every 10,000 births, or about 400 babies in the US each year. Well, that number really represents the babies born with birth defects, but some babies will not show symptoms for several years. The severity of the disease depends on when during the pregnancy the mother is infected, generally the earlier in pregnancy the more severe the damage to the fetus. If a woman is infected very early in pregnancy, the parasite usually causes abortion of the fetus. If infected within the first 6 months of pregnancy, the fetus may have damage to the brain. This picture on the right shows a baby with hydrocephalus, which is spinal fluid building up between the brain and the skull. This puts pressure on the developing brain, causing mental retardation. Infection of the eyes can cause blindness in babies infected early. If infected during the third trimester, a baby may not show any symptoms at birth, but could develop problems with the eyes in early childhood that can lead to blindness.
Cyst in tissue
loaded with protozoans

40. Back to the Internet
Becky and Ann left the health clinic and headed to the library and the computer.
“The organisms in Ellie’s blood don’t look like either of your suspects, Becky.”
“Well, maybe they would look different when they are in the blood.”
They started scanning Google. .

41. Ah, so Ellie is infected with a protozoan.
Now what? How do we get rid of it?

42. The Mitochondrion
“Power House of the Cell”
Has its own DNA

43. Ellie’s Prognosis
“Well, Ellie’s responding well to the pyrimethamines that the doctors prescribed,” Becky commented to Ann while checking her a few days later. “Her parents seemed to appreciate that we got her such quick medical treatment. Do you think we should warn the other students? They might have eaten some Toxoplasma gondii cysts in their meat, also.”

44. Ellie’s Prognosis “You don’t think Ellie is…” Ann began….
“They are probably already infected,” Becky answered. “I learned that something like 25-40% of American adults are already infected with Toxoplasma gondii. It’s more of an issue for women. You know, they can’t scoop their cat’s litter box when they’re pregnant because the cat poop contains them, and infection causes birth defects in thousands of children.”
“You don’t think Ellie is…” Ann began….
“Don’t go there. I don’t know and I don’t want to know.”

45. EVOLUTIONARY PERSPECTIVE
Prokaryotes
DNA, RNA, fats, proteins, carbohydrates
Chlorophyll
Plasma membrane
Cytosol=Cytoplasm
Ribosomes
Chromosome (single)
All of this must have evolved early in the history of earth!

46. EUKARYOTES Eukaryotes Nuclear membrane Endoplasmic reticulum
Golgi, lysosomes
Mitochondria
Chloroplasts
9+2 flagella & cilia
Multiple chromosomes
Must have evolved later after the prokaryotes

47. What is Important! The difference between Prokaryotes & Eukaryotes
The functions of the cell organelles
The sequence: Suggests Evolution
Prokaryotes—3.5 BYA
Very small
Structurally simple
Eukaryotes—2 BYA
Larger
Structurally complex
Plants Fungi Animals