Biology 172 Lecture 2
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What are the branches on the Tree of Life called?
Ribosomal ribonucleic acid sequences can be used to produce a ____________ _____ showing probable evolutionary relationships
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
rRNA performs the same function in all sequences but .....
the nucleotide sequences differ
Similarities reveal evolutionary relationships. Characteristic; Peptidoglycan in cell wall
- Bacteria: Present
- Archaea: Absent
- Eukaryotes Absent
Similarities reveal evolutionary relationships. Characteristic; RNA polymerase types
- Bacteria: one
- Archaea: Several
- Eukaryotes: Several
Similarities reveal evolutionary relationships. Characteristic; Initiator amino acid for protein synthesis
- Bacteria: Formyl-methionine
- Archaea: Methionine
- Eukaryotes: Methionine
Similarities reveal evolutionary relationships. Characteristic; Response to antibiotics
- Bacteria: Killed
- Archaea: Not Killed
- Eukaryotes: Not Killed
Archaea are more similar to ________
Eukaryotes than bacteria
What is a cell?
All cells are enclosed by a plasma membrane that regulates passage of materials in and out of the cell
All cells use ___ for their genetic information
proposed the concept of "cell" nearly 2000 years before the 1st cells were seen; concluded there must be an ultimate unit of life
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.
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.
1839, all organisms are composed of cells
1858, all cells come from pre-existing cells, not spontaneous generation
1860, all cells come from pre-existing cells, not spontaneous generation
(most) cells are ________
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
1st Part of Cell Theory
All organisms are composed of cells
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
3rd Part of Cell Theory
- similar structure and organization
- similar metabolic strategies
- similar hereditary information
- However specific cell functions can vary Cell Specialization
4th Part of Cell Theory
- via cell growth and division
- life does not arise from non-life
Everything we know about cells was determined _________
an observation that has been repeatedly confirmed
a proposed explanation, or a testable statement that can be used to build more complex explantations
about how some aspect of the natural world behaves under stated circumstances, a descriptive generalization; does not explain why something happens - just describes it
an overarching explanation that is well-substantiated and that can incorporate facts, laws, inferences, and tested hypotheses
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
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
Usually easier to control lab experiments but ....
but then must consider if lab experiments will be true in real life
Atoms are most stable when ....
each orbital has two electrons
when each atom's unpaired electrons are shared by nuclei to fill their orbitals, and atoms share pairs of valence electrons
Nonpolar covalent bond
Electrons are shared equally
Polar covalent bonds
Electrons are not shared equally so partial charges exist (more electronegative atom has stronger pull)
- Electrons are completely transferred from one atom to another
- Cation (+) and Anion (-)
- Ionic compounds are salts
- Weak bond
- Very Important in the chemistry of life
- Between two atoms with very different electronegativities
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
What is the most abundant molecule in organisms
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
Life originated in and is based on water because ....
water is a great solvent
_________ bonds from between water molecules
Hydrogen bonds, which help the substances stay in solutions.
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
In ice, water molecules form a _______ _________. In liquid water no ______ ______ forms
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