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What are the branches on the Tree of Life called?
phyla
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Ribosomal ribonucleic acid sequences can be used to produce a ____________ _____ showing probable evolutionary relationships
Phylogenetic tree
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Closely related species should have rRNA sequences that are .....
more similar than those from distantly related species because they share a more recent common ancestor
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rRNA performs the same function in all sequences but .....
the nucleotide sequences differ
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Similarities reveal evolutionary relationships. Characteristic; Peptidoglycan in cell wall
- Bacteria: Present
- Archaea: Absent
- Eukaryotes Absent
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Similarities reveal evolutionary relationships. Characteristic; RNA polymerase types
- Bacteria: one
- Archaea: Several
- Eukaryotes: Several
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Similarities reveal evolutionary relationships. Characteristic; Initiator amino acid for protein synthesis
- Bacteria: Formyl-methionine
- Archaea: Methionine
- Eukaryotes: Methionine
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Similarities reveal evolutionary relationships. Characteristic; Response to antibiotics
- Bacteria: Killed
- Archaea: Not Killed
- Eukaryotes: Not Killed
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Archaea are more similar to ________
Eukaryotes than bacteria
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What is a cell?
All cells are enclosed by a plasma membrane that regulates passage of materials in and out of the cell
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All cells use ___ for their genetic information
DNA
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Aristotle
proposed the concept of "cell" nearly 2000 years before the 1st cells were seen; concluded there must be an ultimate unit of life
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Robert Hooke
1665, the first view of the cell. Hooke looked at oak bark and named the cavities cells. The pore-like compartments are cork cells from oak bark.
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Anton von Leeuwenhoek
1665, was the first to view single-celled "animalcules" in pond water. Shows paramecium, also look at human blood cells, and sperm cells.
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Theodor Schwann
1839, all organisms are composed of cells
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Rudolf Virchow
1858, all cells come from pre-existing cells, not spontaneous generation
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Louis Pasteur
1860, all cells come from pre-existing cells, not spontaneous generation
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(most) cells are ________
Microscopic
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Four Parts of Cell Theory
- 1. Cells are the Structural Unit of Life
- 2. Cells are the Functional Unit of Life
- 3. All Cells are Fundamentally Similar
- 4. All Cells come from Pre-existing Cells
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1st Part of Cell Theory
All organisms are composed of cells
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2nd Part of Cell Theory
- Cells are the smallest entities that have all the properties of life.
- Each cell is (or can generate) an entire organism
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3rd Part of Cell Theory
- similar structure and organization
- similar metabolic strategies
- similar hereditary information
- However specific cell functions can vary Cell Specialization
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4th Part of Cell Theory
- via cell growth and division
- life does not arise from non-life
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Everything we know about cells was determined _________
experimentally
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Fact
an observation that has been repeatedly confirmed
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Hypothesis
a proposed explanation, or a testable statement that can be used to build more complex explantations
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Law
about how some aspect of the natural world behaves under stated circumstances, a descriptive generalization; does not explain why something happens - just describes it
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Theory
an overarching explanation that is well-substantiated and that can incorporate facts, laws, inferences, and tested hypotheses
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5 steps of the Scientific Method
- 1. Make observations, ask questions
- 2. Form a hypothesis, and don't forget the null hypothesis (consider what are the results when wrong)
- 3. Make predictions
- 4. Test predictions, include controls
- 5. Revise hypothesis based on results and repeat
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what can you prove with an hypothesis
You can never prove a hypothesis; you can only eliminate it by showing that the predictions are false
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Usually easier to control lab experiments but ....
but then must consider if lab experiments will be true in real life
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Atoms are most stable when ....
each orbital has two electrons
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Covalent Bond
when each atom's unpaired electrons are shared by nuclei to fill their orbitals, and atoms share pairs of valence electrons
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Nonpolar covalent bond
Electrons are shared equally
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Polar covalent bonds
Electrons are not shared equally so partial charges exist (more electronegative atom has stronger pull)
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Ionic Bond
- Electrons are completely transferred from one atom to another
- Cation (+) and Anion (-)
- Ionic compounds are salts
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Hydrogen Bond
- Weak bond
- Very Important in the chemistry of life
- Between two atoms with very different electronegativities
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Van der Waals Bond
Transient 'hot spots' of positive and negative charge in a molecule with nonpolar covalent bonds; creates weak interactions when molecules are very close
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What is the most abundant molecule in organisms
Water
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Properties of Water
- Great Solvent (substances dissolve easily in it)
- The H--O bonds in water are polar covalent
- Water is polar
- Liquid water is denser than ice
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Life originated in and is based on water because ....
water is a great solvent
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_________ bonds from between water molecules
Hydrogen bonds, which help the substances stay in solutions.
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What does and does not dissolve readily in water
- Polar molecules and ions dissolve readily in water (salt dissolves in water)
- Nonpolar molecules do not dissolve readily in water
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In ice, water molecules form a _______ _________. In liquid water no ______ ______ forms
crystal lattice
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