Biology and Chemistry: Key Concepts for Life Sciences

Biology

Study of life.

Population

All members of the same species living in an area.

Community

Collection of interacting populations in an environment.

Ecosystem

Community + physical environment (energy flows, chemicals cycle).

Biosphere

All regions of Earth where life exists.

Energy

Capacity to do work; required for life processes.

Metabolism

All chemical reactions in a cell.

Homeostasis

Maintenance of internal balance (biological stability).

Adaptation

Trait that improves survival in an environment.

Evolution

Change in populations over time; leads to adaptation.

Natural Selection

Mechanism of evolution; environment favors traits that increase survival/reproduction.

Mutation

DNA change; introduces variation into a population.

Taxonomy

Science of identifying, naming, classifying organisms.

Binomial Nomenclature

Two-part Latin name (Genus species, italicized).

Hypothesis

Testable explanation for an observation.

Experimental Design

Plan to test a hypothesis; includes variables and groups.

Control Group

Group not exposed to experimental variable, used for comparison.

Technology

Application of science for human benefit.

Climate Change

Long-term shifts in Earth's climate caused by humans (fossil fuels, deforestation).

Biodiversity

Variety of species, genes, ecosystems.

Extinction

Death of the last member of a species.

Atom

Smallest unit of an element with its properties.

Element

Substance that cannot be broken down further.

CHNOPS

Six main elements of living organisms: Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, Sulfur.

Atomic Number

Number of protons (equals electrons in neutral atom).

Mass Number

Protons + neutrons in nucleus.

Isotope

Atom of same element with different neutron number (different mass).

Radioactive isotope

Decays, emits radiation; useful in medicine/research.

Electron

Negatively charged subatomic particle orbiting nucleus.

Valence Shell

Outermost electron shell; determines chemical reactivity.

Octet Rule

Atoms are stable when outer shell has 8 electrons.

Molecule

Two or more atoms bonded together (O₂, H₂).

Compound

Molecule with different elements (H₂O, CO₂).

Ion/Ionic Bond

Charged atom formed by electron transfer; attraction between oppositely charged ions (NaCl).

Covalent Bond

Sharing of electrons.

Nonpolar covalent bond

Equal sharing.

Polar covalent bond

Unequal sharing (water).

Electronegativity

Atom's ability to attract electrons in a bond.

Hydrogen Bond

Weak attraction between slightly +H and slightly - atom; important in DNA, proteins, water.

Hydrophilic

'Water-loving,' dissolves in water.

Hydrophobic

'Water-fearing,' does not dissolve in water.

Solution

Mixture of solute (dissolved substance) + solvent (water).

Solute

Substance dissolved in a solvent.

Surface Tension

Cohesion of water molecules at surface due to hydrogen bonding.

Calorie

Unit of energy; amount of heat needed to raise water temp.

High heat capacity

Resists temp change.

High heat of evaporation

Cooling effect (sweating).

Solvent

Dissolves polar substances.

Cohesion

Water sticks to itself (surface tension).

Adhesion

Water sticks to other surfaces (capillary action).

Ice less dense than water

Floats, insulates aquatic life.

pH Scale

Measures H⁺ concentration (0-14). <7 = acidic, 7 = neutral, >7 = basic.

Log scale

Each unit = ×10 change in H⁺ concentration.

Acid

Releases H⁺ ions in water.

Base

Takes up H⁺ or releases OH⁻ ions.

Buffer

Substance that stabilizes pH within limits.

Example: Carbonic acid buffer in blood

pH ~7.4.

Organic molecules

Must contain both Carbon (C) & Hydrogen (H).

Example: Glucose

(C₆H₁₂O₆).

Carbohydrates

Energy source, structural integrity (C, H, O).

Monosaccharides

(glucose), polysaccharides = energy storage.

Lipids

Long-term energy storage, insulation (C, H, O).

Proteins

Structure & function (C, H, O, N).

Made of amino acids

Polymers = proteins.

Nucleic acids

Store info (DNA, RNA) (C, H, O, N, P).

Made of nucleotides

Carbon atom

Small, 6 e- (2 in first shell, 4 in outer shell).

Stable C-C bonds

Chains, rings, branches.

Isomers

Same molecular formula, different structure.

Monomer

Single unit.

Polymer

Chain of monomers.

Example: Amino acid

(monomer) → Protein (polymer).

Reactions

Dehydration synthesis

Build polymers by removing water (mono + mono → poly + H₂O).

Hydrolysis

Break polymers by adding water (poly + H₂O → monomers).