Big Idea 2: Cellular Processes: Energy, Communication, and
Homeostasis
A. Free energy and matter are required for life processes.- All living things need a constant source of energy.
- Autotrophs (through photosynthesis) and heterotrophs (through cellular respiration)
capture and store free energy. - Organisms exchange matter with the environment.
B. Cells maintain an internal environment that is different from their surroundings. - The structure of cell membranes results in selective permeability.
- Homeostasis is maintained by movements through cell membranes.
- Internal membranes compartmentalize cells (organelles).
C. Organisms rely on feedback mechanisms to grow, reproduce, and survive. - Organisms use positive and negative feedback.
- Feedback mechanisms allow organisms to respond to changes in their environments.
D. Growth and homeostasis are influenced by environmental changes. - Biotic and abiotic interactions affect everything from cells to ecosystems.
- Both common ancestry and divergence (due to different environments) are
reflected in homeostatic mechanisms. - Disruptions to homeostasis affect the health of the organism and the balance of the
ecosystem. - Plants and animals have defense systems against infection (immune systems).
E. Temporal (time-based) coordination is involved in homeostasis, growth, and reproduction. - The correct timing of events is necessary for the proper development of an organism.
- The timing and coordination of the events is regulated in different ways for differ-
ent organisms. - Various mechanisms are used to time and coordinate behavior.
Big Idea 3: Genetics and Information Transfer
A. The continuity of life is made possible through heritable information.- DNA and RNA provide heritable information from one generation to the next.
- The cell cycle, mitosis, and meiosis are processes that transmit heritable information.
- The transmittal of genes from parent to child shows the chromosomal basis of
inheritance. - The inheritance of traits is more complex than can be explained by simple Mendelian
models.
B. Cellular and molecular mechanisms are involved in gene expression. - Differential gene expression is a result of gene regulation.
- Signal transmissions influence gene expression.
C. Imperfect processing of genetic information creates genetic variation. - Changes in genotype create new phenotypes.
- Many biological mechanisms can increase variation.
- Viral infections can produce genetic variation in their host organisms.
D. Cells communicate with other cells through the transmission of chemical signals. - Cell communication is based on common features (which show a common ancestry).
- Cells can communicate through direct contact or long-distance signaling.
xxii ❯ The Four “Big Ideas” of AP Biology