Introduction to Biology and Earth's Origins

Life began on Earth roughly 4.5 billion years ago, likely originating near hydrothermal vents. Biology is fundamentally rooted in chemistry, utilizing carbohydrates, lipids, proteins, and nucleic acids to sustain life. Cells, the basic unit of life, are divided into simple prokaryotes and complex eukaryotes, all of which maintain homeostasis via semipermeable membranes to regulate the internal environment.

Cells utilize ATP as their primary energy currency, generated through cellular respiration in mitochondria of heterotrophs or photosynthesis in chloroplasts of autotrophs. Genetic information is stored in DNA, which relies on consistent nucleotide pairing and serves as a blueprint for protein synthesis through the processes of transcription and translation.

Inheritance is dictated by chromosomes and alleles, which follow dominant and recessive patterns. Cells replicate through mitosis for somatic growth and meiosis for specialized gametes, facilitating genetic variation. Mutations drive evolution by introducing changes that, through natural selection, allow populations to adapt to their environments, though they can also lead to issues like antibiotic resistance or cancer.

Bacteria and viruses differ significantly in structure and treatment, with the latter remaining outside the definition of traditional cellular life. The nervous system manages communication through neurons, which transmit information via rapid electrical action potentials and chemical signals across synapses.