Hook

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Hook

• What are cells? How do we know about them? How
  long have we known about them? How long have they
  been here?

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Baby Cells??

• The fossil record places the first cells at about
  3.5 Billion years oldbut humans have only known
  about them since about 1665. Why did it take so
  long to find them?
• Ignore the fact that humans werent AROUND to
  find them for about 2.7 billion of those years

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Microscopes

• Until the mid-1600s there were no microscopes
• Even when microscopes were invented people did
  not really know WHAT to look for

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Hookes Mistake

• In 1665, Robert Hooke made a fairly advanced (for
  that time period) compound microscope
• With his microscope he examined many macroscopic
  (visible to the naked eye) organisms
• One of his observations was of cork from the bark
  of a cork tree

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Hookes Sketch of Cells
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• . . . I could exceedingly plainly perceive it
  to be all perforated and porous, much like a
  Honey-comb, but that the pores of it were not
  regular. . . . these pores, or cells, . . . were
  indeed the first microscopical pores I ever saw,
  and perhaps, that were ever seen, for I had not
  met with any Writer or Person, that had made any
  mention of them before this. . .
• -Observation XVIII, Micrographia

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What he really saw

• Hookes actual discovery was of the cell walls of
  DEAD cork cells
• He also examined living plants and discovered
  that some of them were filled with juice (yes,
  scientists use the most formal terms to describe
  their findings)

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Why only plant cells?

• Hooke examined animal tissue as well as plants
  but his writings only explained cells in plants.
  Why were animal cells not mentioned?

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Leeuwenhoeks Help

• In 1673, Anton van Leeuwenhoek made his own
  microscope to examine pond scum (the greenish
  muck around the edge of a pond)
• He observed many small organisms swimming around
  in the water and called them animalcules
  (literally, little animals)today we know them as
  protists

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Spirogyra
Leeuwenhoek described these as green streaks,
spirally wound serpent-wise
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Vorticella
These little animals were fashioned like a
bellthey pulled their bodies and their tails
together, and no sooner had they contracted their
bodies and tails, than they began to stick their
tails out again very leisurelycontinuing their
gentle motion which sight I found mightily
diverting
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Vorticella Feeding
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Individual Vorticella Coiling
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Group Vorticella Coiling
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Cell Theory

• Nearly 200 years later scientists decided cells
  were present in all living things
• Schwann and Schleiden studied animals and plants
  in 1839 and concluded both were made of cells
• Schwann wrote the first two parts of the cell
  theory

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Cell Theory

• 1) All organisms are made of one or more cells
• 2) The cell is the basic unit of all living
  things
• In 1858, Virchow presented the third part
• 3) All cells come from existing cells

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Instructions

• Hook
• What is an adaptation? How is it related to
  genetic traits?
• Tomorrow at the aquarium, your task will be to
  look for 5 adaptations that allow organisms that
  you see to live in their environment.

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How many kinds of cells are there? (p. 133)

• TWO
• The two kinds of cells are Prokaryotic cells and
  Eukaryotic cells
• Prokaryotic cells single cells, no nucleus, no
  membrane bound organelles (bacteria)
• Eukaryotic cells have a nucleus and membrane
  bound organelles

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Prokaryotic Cells

• Eubacteria and Archaebacteria
• Sketch this picture

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Eukaryotic cells

• Contain organellesminiature organs for the cell
  that perform different functions

• Organelles
• Nucleus
• Cell Wall
• Cell Membrane
• Ribosomes
• Rough Endoplasmic Reticulum
• Smooth Endoplasmic Reticulum

• Mitochondria
• Chloroplasts
• Golgi Complex
• Vesicles
• Lysosomes
• Vacuoles
• Nucleolus
• Cytoplasm

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Sinker (p. 132)

• A metaphor is used in writing to compare two
  vastly different objects. In your sinker, you
  will draw a picture comparing the parts of a cell
  (somewhat unfamiliar) to something you know well.
  For each comparison, be sure to write a short
  sentence explaining how the cell structure is
  like the real-world structure/idea.

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For example

• A cell is like a city.
• The cell membrane is like the city limits, people
  can freely move in and out, but some things are
  only allowed inside or outside the city.
• Ribosomes are like factories. They produce goods
  (proteins) that allow the city to function as it
  should.