Final answer:
Fossils provide a biased sample of past life due to favoritism in fossilization toward organisms with hard parts, rapid burial conditions, the abundance of certain geological periods, and the need for specific preservation conditions. Consequently, the fossil record captures only a fraction of past biodiversity and abundance.
Step-by-step explanation:
The fossil record presents an extremely biased sample of past life because it is influenced by myriad factors that determine which organisms become fossilized and which do not. These factors contribute to the incomplete nature of the fossil record.
Factors Influencing Fossil Bias
- The type of organism: Hard parts such as bones, shells, and teeth are more likely to fossilize than soft tissues.
- Environment: Organisms in areas with rapid burial and sediments conducive to preserving fossils, like volcanic ash and limestone, have a better chance of becoming fossilized.
- Geological time: Fossils from certain periods are more abundant due to various natural events like mass extinctions.
- Preservation conditions: Fossils need specific conditions to avoid degradation, such as limited exposure to air and appropriate chemical conditions in their paleoenvironment.
Due to these factors, the elements preserved as fossils do not represent the full diversity or abundance of past life. For example, marine invertebrates are more commonly found as fossils, which might suggest an inaccurate picture of historical biodiversity. Additional biases occur because only a fraction of extinct species have been preserved and discovered, with estimations proposing that extant species represent a mere 0.2-2% of all species that have ever existed.