If you think you could be pregnant, watch for these early signs and symptoms 1: missed period, headaches, tender breasts, nausea, and lower backaches. Unfortunately, these symptoms are not unique to pregnancy, and you could be pregnant without experiencing any of them.n addition to a missed period, the earliest symptoms of pregnancy might include: 1  Nausea with or without vomiting. 2  Tender, swollen breasts. 3  Increased urination. 4  Fatigue.
Climate and geography. The global climate during the Devonian period was surprisingly mild, with ocean temperatures of only 80 to 85 degrees (compared to as high as 120 degrees during the preceding Ordovician and Silurian periods).
Marine Life During the Devonian Period. The Devonian period marked both the apex and the extinction of the placoderms, prehistoric fish characterized by their tough armor plating (some placoderms, such as the enormous Dunkleosteus, attained weights of three or four tons).he Devonian Extinction. The end of the Devonian period ushered in the second great extinction of prehistoric life on earth, the first being the mass extinction event at the end of the Ordovician period.