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Evidence from the cell

Explore the microscopic evidence of cell structure to support evolution hypothesis and analyze fossil records for insight. Discover the transition from prokaryotic to eukaryotic cells.

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Evidence from the cell

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  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 • 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 • 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. EukaryotesProkaryotes 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. 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

  21. 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 (80-120nm).

  22. Suspect 1 • Too small to be seen in a light microscope, an electron micrograph is shown below. Suspect 1: Influenza http://web.uct.ac.za/depts/mmi/stannard/fluvirus.html

  23. Suspect 1 : Virus Size • 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.

  24. Virus hijacking host system

  25. Clicker Question. Suppose thatEllie has contracted Influenza Virus. Using your Table 1 information which suspect below best matches that profile?

  26. Suspect 2: BacteriumCoxiellaburnetii 0.3-0.5 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. http://microbewiki.kenyon.edu/index.php/Coxiella

  27. 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

  28. Prokaryotes • Size • 0.2-10 micrometer (µm) • Composition • 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

  29. Clicker Question. Suppose thatEllie has contracted Coxiella bacteriumUsing your Table 1 information, which suspect below best matches that profile?

  30. 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.”

  31. 1 mm 10-3 Eukaryote cells 10-4 10-5 Bacteria 1 µm meters 10-6 10-7 Viruses 10-8 Proteins Atoms 10-9 1 nm 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

  32. “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.”

  33. 1 mm 10-3 Eukaryote cells 10-4 10-5 Bacteria 1 µm meters 10-6 10-7 Viruses 10-8 Proteins Atoms 10-9 1 nm 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

  34. 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.”

  35. Microscopic Analysis Pathogens in blood

  36. “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.”

  37. Suspect 3: Fungus Cryptococcus neoformans http://www.scq.ubc.ca/wp-content/uploads/2006/08/neoformans2.jpg 2.5-10 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. http://microgen.ouhsc.edu/images/Heuser_bud.png http://www.naturalhistorymag.com/0705/images/0705Samplings_Cryptococcus.jpg

  38. Eukaryote Suspect 4: Toxoplasmagondii (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. Cyst in tissue loaded with protozoans http://www.roche.com/pages/facets/2/toxmoplasma.jpg

  39. 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. .

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

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

  42. Ellie’s Prognosis “Well, Ellie’s responding well to the pyrimethamines that the doctors prescribed,” Becky commented to Ann while checking her email 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 Toxoplasmagondii cysts in their meat, also.”

  43. Ellie’s Prognosis “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.”

  44. 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!

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

  46. 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

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