Biology

Core vocabulary and process summaries covering cell biology, genetics, evolution, and ecology.

Cell Biology

Key structures and processes

Mitochondria: The organelle that produces ATP (energy) through cellular respiration - often called the "powerhouse of the cell."
Nucleus: Contains the cell's DNA and controls gene expression; surrounded by the nuclear envelope.
Ribosomes: Sites of protein synthesis; read mRNA and assemble amino acids into proteins.
Cellular respiration: Glucose + oxygen → carbon dioxide + water + ATP. Occurs in the mitochondria and converts food energy into usable energy.
Photosynthesis: Carbon dioxide + water + light → glucose + oxygen. Occurs in chloroplasts of plant cells; the reverse of respiration in terms of inputs/outputs.
Mitosis: Cell division that produces two genetically identical daughter cells, used for growth and repair. Phases: prophase, metaphase, anaphase, telophase.
Meiosis: Cell division that produces four genetically distinct sex cells (gametes) with half the chromosome number - the basis of sexual reproduction.

Genetics

Inheritance vocabulary

Term	Meaning
Allele	A version of a gene (e.g., the brown-eye allele vs. the blue-eye allele)
Genotype	The genetic makeup of an organism (e.g., Bb)
Phenotype	The observable trait produced by a genotype (e.g., brown eyes)
Dominant / Recessive	A dominant allele masks a recessive one when both are present (Bb shows the dominant trait)
Homozygous / Heterozygous	Two identical alleles (BB or bb) vs. two different alleles (Bb)
Punnett square	A grid used to predict the probability of offspring genotypes from a genetic cross

DNA is transcribed into mRNA in the nucleus, then translated into a protein by ribosomes - the process is called the "central dogma": DNA → RNA → Protein.

Evolution

Natural selection concepts

Natural selection: Individuals with traits better suited to their environment survive and reproduce more, passing those traits to offspring over generations.
Adaptation: A trait that improves an organism's chance of survival and reproduction in its environment.
Speciation: The process by which populations evolve to become distinct species, often after geographic separation.
Common ancestor: A shared ancestor from which two or more species have evolved, evidenced by comparative anatomy and DNA.

Ecology

Ecosystem terms

Term	Meaning
Producer	Organism that makes its own food, usually via photosynthesis (e.g., plants, algae)
Consumer	Organism that eats other organisms for energy (herbivore, carnivore, omnivore)
Decomposer	Breaks down dead organic matter, recycling nutrients back into the ecosystem
Food web	A network of interconnected food chains showing energy flow through an ecosystem
Carrying capacity	The maximum population size an environment can sustain given its resources