Population ecology is the study of these and other questions about what factors affect population and how and why a population changes over time. Population ecology has its deepest historic roots, and its richest development, in the study of population growth, regulation, and dynamics, or demography.
When giraffes walk, they move both legs on one side of their body and then both legs on the other side; this is unique to giraffes. However, they run in a similar style to other mammals, swinging their rear legs and front legs in unison. They can reach 55 km/h (35 mph) at full speed but only in brief spurts.
Caecilians, which are legless amphibians, use muscle contraction to move from place to place. Certain species of caecilians move from side to side, much like snakes. Adult amphibians, belonging to the orders Anura and Caudata, use methods of locomotion such as walking, hopping, and jumping.