Chapter 3 Summary

·   The biodiversity is found in the earth’s genes, species, ecosystems, and ecosystem processes is vital to sustaining the life on earth.

·   Scientific theory of evolution through natural selection says: Populations evolve when genes mutate and give some individuals genetic traits that enhance their abilities to survive and to produce offspring with these traits.

·   Fossils: Mineralized or petrified replicas of skeletons, bones, teeth, shells, leaves, and seeds or impressions of such items found in rocks.

·   Mutations: random changes in the structure of number of DNA molecules in a cell that can be inherited by offspring. Most mutations result from random changes that occur in coded genetic instructions passed along in reproduction.

·   Differential reproduction: enables individuals with the traits to leave more offspring than other members of the population leave.

·   Adaptation or Adaptive trait: is any heritable trait that enables organisms to survive and reproduce better under prevailing environmental conditions.

·   As environmental conditions change, the balance between formation of new species and extinction of existing species determines the earth’s biodiversity.

·   Geographic Isolation: occurs when different groups of the same population of a species become physically isolated from one another for long periods.

·   Reproductive Isolation: mutation and change by natural selection operate independently in the gene pools of geographically isolated populations.

·   Differences in average annual precipitation and temperature lead to the formation of tropical, temperate, and cold deserts, grasslands, and forests and largely determine their locations.

·   In many areas, human activities are impairing ecological and economic services provided by the earth’s deserts, grasslands, forests, and mountains.

·   Saltwater and freshwater aquatic life zones cover almost three- fourths of the earth’s surface with oceans dominating the planet.

·   The key factors determining biodiversity in aquatic systems are temperature, dissolved oxygen content, availability of food, and availability of light and nutrients necessary for photosynthesis.

·   Human activities threaten aquatic biodiversity and disrupt ecological and economic services provided by saltwater and freshwater systems.