BIO 172 LECTURE 1 EXAM QUESTIONS AND
ANSWERS
What is special about life? What is not special about life?
Special: Life can grow, reproduce, evolve, and maintain internal order (homeostasis).
Not special: Life follows the same physical and chemical laws as nonliving matter.
How does one determine phylogenetic relationships? Why are Archaea and Eukarya more
closely related than Bacteria and Eukarya?
By comparing DNA/RNA sequences, proteins, and shared traits.
Archaea and Eukarya share more similar genes and cellular machinery than either does with
Bacteria.
What do the "branches" in a phylogenetic tree mean?
Each branch represents an evolutionary lineage.
A branch point (node) represents a common ancestor.
Relationship between polar vs nonpolar covalent bonds, electronegativity, and electron
sharing
Polar bonds occur when atoms have different electronegativities and share electrons unequally.
Nonpolar bonds occur when electronegativity is similar and electrons are shared equally.
How do polar vs nonpolar bonds affect charge?
Polar bonds create partial charges (δ+ and δ−).
Nonpolar bonds do not create partial charges.
Why are ionic > hydrogen > van der Waals in strength?
Ionic bonds involve full charges, so attraction is strong.
Hydrogen bonds involve partial charges, so they are weaker.
Van der Waals forces are very weak temporary attractions.
How do covalent bonds compare to ionic bonds?
Covalent bonds are generally stronger than ionic bonds in cells.
Covalent bonds involve shared electrons and are very stable.
Why is water liquid at 20°C and solid at 0°C?
Hydrogen bonding holds water molecules together as a liquid at room temperature.
At 0°C, hydrogen bonds lock into a crystal lattice (ice).
What properties of water impact biology?
ANSWERS
What is special about life? What is not special about life?
Special: Life can grow, reproduce, evolve, and maintain internal order (homeostasis).
Not special: Life follows the same physical and chemical laws as nonliving matter.
How does one determine phylogenetic relationships? Why are Archaea and Eukarya more
closely related than Bacteria and Eukarya?
By comparing DNA/RNA sequences, proteins, and shared traits.
Archaea and Eukarya share more similar genes and cellular machinery than either does with
Bacteria.
What do the "branches" in a phylogenetic tree mean?
Each branch represents an evolutionary lineage.
A branch point (node) represents a common ancestor.
Relationship between polar vs nonpolar covalent bonds, electronegativity, and electron
sharing
Polar bonds occur when atoms have different electronegativities and share electrons unequally.
Nonpolar bonds occur when electronegativity is similar and electrons are shared equally.
How do polar vs nonpolar bonds affect charge?
Polar bonds create partial charges (δ+ and δ−).
Nonpolar bonds do not create partial charges.
Why are ionic > hydrogen > van der Waals in strength?
Ionic bonds involve full charges, so attraction is strong.
Hydrogen bonds involve partial charges, so they are weaker.
Van der Waals forces are very weak temporary attractions.
How do covalent bonds compare to ionic bonds?
Covalent bonds are generally stronger than ionic bonds in cells.
Covalent bonds involve shared electrons and are very stable.
Why is water liquid at 20°C and solid at 0°C?
Hydrogen bonding holds water molecules together as a liquid at room temperature.
At 0°C, hydrogen bonds lock into a crystal lattice (ice).
What properties of water impact biology?
