Biology Chapter 1: Hierarchy of Life, Atoms, Molecules, and Water

Vocabulary practice flashcards covering basic biological hierarchy, atomic structure, elemental composition of living things, types of chemical bonding, and key properties of water.

Biology

The study of life, derived from the prefix "Bio" (meaning life) and the suffix "-logy" (meaning the study of).

Cell

The fundamental level at which life begins; all cells are composed of molecules, which in turn are made of atoms.

Population

A group of organisms that belong to the same species and exist in the same region.

Community

Populations of different species co-existing within the same region.

Ecosystem

A system formed by biological communities interacting with their non-living environment.

Biosphere

The global ecological network encompassing all collective ecosystems on Earth.

Proton

A subatomic particle located in the atomic nucleus that carries a positive charge ($+$).

Electron

A subatomic particle that orbits the nucleus and carries a negative charge ($-$).

Neutron

A subatomic particle located in the atomic nucleus that carries a neutral charge ($0$).

Atomic Nucleus

The central region of an atom containing its protons and neutrons.

Picometer

A unit of length equal to one trillionth of a meter ($10^{-12}\,\text{m}$).

Hydrogen

The lightest atom, consisting of a single proton, a single electron, and no neutrons.

Uranium

The heaviest naturally occurring element, consisting of $92$ protons, $92$ electrons, and $142\text{–}146$ neutrons.

Element

A specific variety of atom characterized by its fixed number of protons (ranging from $1$ to $92$ in naturally occurring types).

Major Elements of Life

The four primary elements—Oxygen ($63\%$), Carbon ($19\%$), Hydrogen ($10\%$), and Nitrogen ($4\%$)—that constitute approximately $96\%$ of human body weight.

Valence Shell

The outermost electron shell of an atom, which reaches maximum stability for most elements when filled with $8$ electrons.

Ion

An atom that carries a net positive or negative electric charge due to the loss or gain of electrons.

Ionic Bonding

A chemical bond formed when one atom transfers one or more electrons to another atom, creating oppositely charged ions that attract each other.

Covalent Bonding

A chemical bond formed when two or more atoms share pairs of valence electrons to achieve structural stability.

Carbon

An element with $4$ valence electrons that can covalently bond with up to four atoms simultaneously, forming the backbone of complex organic molecules.

Hydrogen Bonding

An intermolecular attraction occurring when hydrogen is bound to larger atoms that pull shared electrons more strongly, creating partially positive and negative poles.

Solvent

A liquid substance (such as water) capable of dissolving charged or polar solutes to form a homogeneous solution.

Cohesion

The tendency of water molecules to stick to one another as a result of hydrogen bonding.

Adhesion

The tendency of water molecules to cling to other polar or charged surfaces and vessel walls.

High Heat Capacity

The property of water requiring a large input of thermal energy to raise its temperature and break hydrogen bonds to transition into gas.

Density Anomaly of Water

The unique structural property wherein solid ice forms an open lattice structure that makes it less dense than liquid water, allowing ice to float.