“…In literature, (1.1) is called the Keller-Segel model or a chemotaxis model. Since the works by Keller and Segel, a rich variety of mathematical models for studying chemotaxis has appeared (see [3], [9], [10], [16], [19], [29], [37], [38], [39], [41], [45], [46], [47], [48], [49], [50], [51], and the references therein). In the current paper and the further coming papers, we will investigate various dynamical aspects of the following parabolic-parabolic Keller-Segel systems, u t = ∆u − χ∇(u∇v) + u(a − bu), x ∈ R N τ v t = ∆v − v + u, x ∈ R N .…”