Biology and Chemistry Fundamentals Study Guide

Vocabulary terms and definitions extracted from Chapters 1, 2, and 27 study guides covering fundamental biological levels, evolution, chemistry of matter, and water properties.

Cell

The smallest unit of life.

Tissue

A group of similar cells that perform a specific function.

Organ

A structure formed by several tissues joining together.

Organ System

A group of organs working together to perform specific functions.

Biosphere

Regions of the Earth's crust inhabited by living organisms.

Ecosystem

A community plus its physical environment.

Species

A group of similar, interbreeding organisms.

Natural Selection

The differential reproductive success of adapted individuals, resulting in changes of characteristics of a population over time.

Evolution

The change in frequency of traits in populations and species over time.

Taxonomy

The discipline of identifying and grouping organisms.

Systematics

The study of evolutionary relationships among organisms.

Domain

The largest classification category, assigned based on biochemical and genetic evidence (Domain Archaea, Domain Bacteria, Domain Eukarya).

Prokaryotes

Unicellular organisms that lack a true nucleus, comprising Bacteria and Archaea.

Eukaryotes

Unicellular or multicellular complex organisms that possess true nuclei.

Inheritance of Acquired Characteristics

Lamarck's theory proposing that changes in species occur because environmental changes cause traits that are inherited by offspring.

Epigenetic Inheritance

A process where the environment causes changes in DNA expression that can be passed on to future generations.

Pangea

The single large landmass that existed on Earth and separated through continental drift over billions of years.

Matter

Anything that takes up space and has mass.

Plasma

An ionized gas consisting of positive ions ($+$) and free electrons ($-$), resulting in no overall electric charge.

Element

Substance composed of unique atoms with specific elemental properties such as melting point, density, solubility, and chemical reactivity.

Atom

The smallest part of an element that retains the unique properties of that element.

Proton

A positively charged ($+$) particle located in the nucleus of an atom.

Neutron

A subatomic particle located in the nucleus of an atom that possesses no charge.

Electron

A negatively charged ($-$) particle located outside the nucleus moving in energy layers called shells or orbitals.

Atomic Number

The number of protons contained within the nucleus of an atom.

Atomic Mass

The mass of an atom calculated by taking into account only the mass of its protons and neutrons.

Isotopes

Atoms of the same element that contain different amounts of neutrons.

Half-life

The time required for half of a radioactive isotope in an organism to break down (e.g., Carbon-14 breaking down into Nitrogen in $5,700\text{ years}$).

Valence Shell

The outermost electron shell of an atom, which makes the atom more stable when filled with its maximum capacity of electrons.

Ionic Bonding

A type of chemical bond formed by the transfer of electrons between atoms.

Covalent Bonding

A type of chemical bond formed by the sharing of electrons between atoms.

Polar Covalent Bond

A covalent bond where atoms are arranged at different angles, creating distinct areas of partial delta charge.

Non-polar Covalent Bond

A covalent bond where atoms are symmetrical and lack distinct areas of differing charges.

Hydrogen Bonding

An attraction arising from the delta charges present on the atoms of a molecule.

Dissociation

The process in which water molecules break apart to release equal amounts of hydrogen ions ($H^+$) and hydroxide ions ($OH^-$).

Acids

Substances that release hydrogen ions ($H^+$) when they dissociate in water.

Bases

Substances that release hydroxide ions ($OH^-$) or take up hydrogen ions ($H^+$) in solution.

pH Scale

A base-10 scale ranging from 0 to 14 used to indicate acidity or basicity, where 0 is a strong acid, 14 is a strong base, and 7 is neutral.

Buffers

Chemical substances (such as bicarbonate ions and carbonic acid ions in human blood) used to prevent sudden changes and keep pH within normal limits.