Biodiversity changes over geological time as species arise and disappear. Understanding these natural processes helps distinguish ordinary changes from unusually rapid losses and provides context for today’s conservation challenge.
The number of species in a place or across the planet reflects the balance between two ongoing evolutionary processes: speciation and extinction. Speciation is the formation of new species; extinction is the disappearance of a species. Both are natural processes of macroevolution.
All flashcards
What is speciation?
The evolutionary process through which new species form, adding to biodiversity.
What is extinction?
The disappearance of a species, removing it from biodiversity.
How do speciation and extinction affect species numbers?
Species numbers tend to rise when speciation exceeds extinction and decline when extinction exceeds speciation.
What caused the most recent geological mass extinction?
A large asteroid impact in the present-day Yucatán region, with the impact’s energy and atmospheric dust causing major environmental and climate changes.
What is the Holocene mass extinction?
A proposed sixth mass extinction associated largely with human activities and the recent loss of species.
Quiz questions
What distinguishes a mass extinction in the fossil record?Answer: More than half of the species then existing disappeared.
What is the main focus of CITES?Answer: Regulating or preventing international trade in listed species and their parts.
How can wildlife corridors help populations in separate habitat patches?Answer: They allow organisms and genes to move between patches.
What characterizes a keystone species?Answer: It has a disproportionately important role in maintaining community diversity.
What is one potential ecological benefit of removing a dam?Answer: Restoring more natural river-flow variation.
Based on Concepts of Biology by Samantha Fowler, Rebecca Roush, James Wise (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.