Chapter 5

BIO 100 Chapter 5 Hippocrates: 400BC inheritance based on transmission of "particles" or "seeds? from parents to offspring during mating. particles from all parts of parents' bodies. characteristics acquired during lifetime, (e.g., strong muscles) also passed. Robert Hooke: 1665 Englishman used an early microscope to magnify a thin slice of cork from tree bark. Anton van Leewenhoek 1667 microscopically observed semen = fluid plus tiny ?sperm? animals. Cell Theory: (1858) Rudolf Virchow 1. Cells - structural and functional units of all organisms. 2. Growth occurs when new cells arise by cell division, a process in which parent cell parts duplicate and separate into two sets. What in Sperm and Eggs Contain the Hereditary Instructions? cytoplasm ?fluid? inside cells. nucleus Dark, centrally-located, spherical organelle, inside most body cells and in sperm and egg cells. Cell Division Theory 1. Paired chromosomes duplicate before mitosis. 2. Chromosomes move to center across from like chromosomes. 3. Sets move to opposite sides of cell. 4. Cell parts outside nucleus duplicate (cytokinesis) & new cell membrane forms (& cell wall in plants). Chromosome duplication and reduction meiosis chromosomes in parent cells = 6 duplication = 12 first division = 6 second division = 3 (sperm or egg) fertilization 3 + 3 = 6