Biology Midterm (Study Guide) Mr.B

Levels of biological organization (small → large)

Atom → molecule → cell → tissue → organ → organ system → organism → population → species → community → ecosystem → biosphere

Atom

Smallest unit of an element; composed of electrons, protons, and neutrons. (Slide example: oxygen.)

Molecule

Union of two or more atoms of the same or different elements. (Slide example: methane.)

Cell

The structural and functional unit of all living organisms; smallest unit of life. (Slide examples: nerve cell, plant cell.)

Tissue

A group of cells with a common structure and function. (Slide examples: nervous tissue, leaf tissue.)

Organ

Composed of tissues functioning together for a specific task. (Slide examples: the brain, leaves.)

Organ system

Composed of several organs working together. (Slide examples: nervous system, shoot system.)

Organism

An individual; complex individuals contain organ systems. Group of organ systems working together. (Slide examples: human, tree.)

Population

Organisms of the same species in a particular area.

Species

All populations of a specific type of organism.

Community

Interacting populations of different species in a particular area.

Ecosystem

A community plus the physical environment.

Biosphere

Regions of the Earth's crust, waters, and atmosphere inhabited by living organisms; the area on Earth where life can survive.

Slide 3 recap: smaller levels

Organism (human, tree) → organ system (nervous system, shoot system) → organ (brain, leaves) → tissue (nervous tissue, leaf tissue) → cell (nerve cell, plant cell) → molecule (methane) → atom (oxygen).

Slide 4 recap: larger levels

Biosphere (Earth) → ecosystem (people + zebras + environment) → community (interacting populations) → species → population → organism (human, tree).

Kingdom Protista (Protists)

Diverse group of eukaryotes, many single-celled; can hunt or use photosynthesis for food. Slide example: Euglena, an organism with both plant- and animal-like characteristics.

Kingdom Plantae (Plants)

Multicellular photosynthesizers. Slide example: bristlecone pine, Pinus longaeva, one of the oldest organisms on the planet.

Kingdom Animalia (Animals)

Multicellular organisms that ingest food. Slide example: Homo sapiens (humans).

Kingdom Fungi

Multicellular decomposers. Slide example: Amanita, a mushroom (also mold, etc.).

Hypothesis in Fig 1.10A

Antibiotic B is a better treatment for ulcers than antibiotic A.

Experimental groups in Fig 1.10A

Control group: received placebo. Test group 1: received antibiotic A. Test group 2: received antibiotic B. Groups were treated the same except as noted. (Course notes: A = 60% effective, B = 80% effective.)

Helium atom (Fig 2.2)

Nucleus contains 2 protons (+) and 2 neutrons; 2 electrons (−) are outside the nucleus. Model (a) shows an electron cloud; model (b) shows electrons orbiting in a shell.

Matter

Anything that takes up space and has mass; exists as solid, liquid, or gas.

Element

A substance that cannot be broken down into another substance by normal chemical means; only 92 occur naturally.

Elements comprising ~96% of body weight

Carbon, Hydrogen, Oxygen, Nitrogen (C, H, O, N).

Origin of heavier elements (evolutionary POV)

Made when a star goes supernova; not produced by normal chemical reactions. (Course response: explosions destroy rather than create, and everything is in a state of decay.)

Atomic theory

The idea that elements consist of atoms.

Atomic symbol

The name of an atom/element (e.g., H = hydrogen, Na = sodium).

Mass number

The sum of all protons and neutrons in an atom.

Atomic weight

Gravity's effect on a physical amount of mass; changes with gravity. (Mass does not change; weight does.)

Proton

Positively charged particle; always found in the nucleus.

Neutron

Neutral particle; always found in the nucleus.

Electron

Negatively charged particle; orbits the nucleus in different shells.

Atomic number

The number above the atomic symbol; equals the number of protons, which (in a neutral atom) equals the number of electrons (e.g., 6 protons = 6 electrons).

Isotope

Atoms of the same element with the same number of protons but a different number of neutrons; the mass number changes.

Carbon-12

6 protons, 6 neutrons, atomic mass 12.000.

Carbon-13

6 protons, 7 neutrons, atomic mass 13.003.

Radiation

The emission of some type of particle from an atom (unstable isotopes). Uses: nuclear energy, PET scans, UV sterilization of eggs and tools.

Shell

Rings that electrons travel around the nucleus of an atom (orbits).

Valence shell

The outermost electron shell.

First shell rule

Wants a maximum of two electrons (hydrogen has one electron and shares to get two).

Octet rule

Every shell beyond the first wants eight electrons; atoms give up, share, or accept electrons to achieve this.

Ionic bonding: Na + Cl (before)

Sodium has 1 electron in its outer shell; chlorine has 7. Sodium transfers its electron to chlorine.

Ionic bond

Chemical bond formed by the transfer of electrons; attraction between opposite charges.

Ion

Any charged atom.

Ionic bonding: result

Sodium loses an electron → sodium ion (Na⁺); chlorine gains it → chloride ion (Cl⁻). Outer shells are now complete. Together they form sodium chloride (NaCl).

Sodium chloride crystal (Fig 2.7b)

Table salt is a lattice of alternating Na⁺ and Cl⁻ ions held together by ionic bonds.

Covalent bond

Chemical bond formed by the sharing of electrons; completes outer shells.

Hydrogen gas (H₂)

Two H atoms share 2 electrons (a single covalent bond); each H gets a full first shell.

Oxygen gas (O₂)

Two O atoms share 4 electrons (double covalent bond); each reaches eight in the valence shell.

Double covalent bond

Sharing of four electrons; stronger than a single bond (O=O).

Structural formula

Representation using straight lines to show bonds (e.g., H-H); a single line = 2 electrons, a double line = 4 electrons.

Molecular formula

Formula showing the number of atoms in a molecule (e.g., H₂).

Molecule (chemistry)

A group of atoms bonded together (e.g., O₂, H₂O, C₆H₁₂O₆).

Compound

A molecule containing atoms of multiple different elements (e.g., H₂O, C₆H₁₂O₆). All compounds are molecules, but not all molecules are compounds.

Photosynthesis equation

6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ (carbon dioxide + water → glucose + oxygen). Reactants on the left, products on the right; the front number is the number of molecules.

Why water is important to life

Life began in water (evolutionary POV); it is the most important molecule on Earth; organisms are 70-90% water; it has unique life-supporting properties.

Water structure (Fig 2.9a)

H₂O is a bent/triangle shape with a polar covalent bond: oxygen is slightly negative (−), hydrogens are slightly positive (+). Positive hydrogen is attracted to negative oxygen of other molecules.

Hydrogen bond (Fig 2.9b)

Attraction between the slightly positive H of one water molecule and the slightly negative O of another.

Polar molecule

A molecule with charges created when bonds are formed, like water.

Solvent

A liquid capable of dissolving substances and forming a solution; polarity and H-bonding make water dissolve many substances (e.g., it separates Na⁺ and Cl⁻).

Hydrophilic

"Water-loving"; e.g., sodium chloride (salt).

Hydrophobic

"Water-fearing"; e.g., fat (no charges).

Cohesion

Water molecules clinging to each other due to hydrogen bonds. (Water molecules stick together.)

Adhesion

Water molecules clinging to other polar surfaces (water "creeps up" the sides).

Surface tension (water)

Water molecules at the surface cling more tightly to each other than to the air above, due to hydrogen bonding. Example: a mint leaf stays on top of a drink because the water molecules stay bonded together.

Heat capacity (water)

Water's ability to absorb a lot of energy before its hydrogen bonds break; hard to change its temperature. To boil water you must use a lot of heat energy to break the hydrogen bonds (liquid → steam).

Heat of vaporization (water)

When hydrogen bonds break and water is released as steam in a gaseous state.

Water density by state

Varies by state; ice is less dense than liquid water because water expands when it freezes.

Acidic solution

A solution in which acids release H⁺ or take up OH⁻.

Basic solution

A solution that takes up H⁺ or releases OH⁻.

Water dissociation

Water splits into equal numbers of H⁺ and OH⁻ (H⁺ lost an electron; hydroxide gained it).

pH

A mathematical way to indicate the number of H⁺ ions in a solution, on a scale of 0 to 14 (potential/power of hydrogen).

pH below 7

Acidic (H⁺ > OH⁻); the lower the pH, the stronger the acid.

pH above 7

Basic (OH⁻ > H⁺); the higher the pH, the stronger the base.

pH of 7

Neutral (H⁺ = OH⁻); water is usually around this.

Buffer

A substance that keeps pH within normal limits by absorbing excess H⁺ or releasing OH⁻. Blood must stay in its normal pH range or the body can go into shock.

Normal blood pH range

7.35-7.45. If untreated outside this range, the body can go into shock and death can occur.

Diseases that can cause acidosis

Congestive heart failure and diabetes (e.g., diabetic ketoacidosis in Type 1: if the body can't break down sugar, it breaks down fats).

Isomers

Groups of atoms with the same number and same kinds of atoms but different arrangements.

Isomers on the slide

Butane vs. methylpropane (isobutane); hexane vs. 2,3-dimethylbutane. Same atoms, different arrangements (chain vs. branched).

Organic molecules

Molecules that contain C (and H).

Biological molecules

Molecules involved in biological systems (in all living cells).

Inorganic molecule

Molecule with no combination of C and H, such as H₂O and NaCl.

Carbon atom

Six total electrons, with four in the valence shell (2 in the inner shell).

Carbon bonding (with others)

Carbon typically shares electrons with H, N, and O.

Maximum carbon bonds

Carbon can form bonds with four atoms maximum (it needs 4 more electrons to satisfy the octet).

Carbon and carbon bonding

Carbon most often shares electrons with other carbon atoms.

Hydrocarbons

Carbon chains that can vary in length, form rings of different sizes, and/or have double bonds or branches.

Carbon backbone/skeleton

The size and shape of the carbon chain in a molecule.

Functional group

A specific combination of atoms that always reacts the same way (same chemical properties). "R" = remainder of the molecule.

Hydroxyl

R-OH; found in alcohols and sugars.

Carboxyl

R-COOH; found in amino acids and fatty acids.

Amino

R-NH₂; found in amino acids and proteins.

Sulfhydryl

R-SH; found in the amino acid cysteine and proteins.

Phosphate

Phosphorus bonded to four oxygens (one linked to R); found in ATP and nucleic acids.

Monomer

A small molecule (used to build macromolecules).

Polymer

Many monomers put together.

Dehydration synthesis reaction

Reaction that loses water to combine monomers.

Hydrolysis reaction

Reaction that uses water to split bonds back into monomers.