Cenozoic Oceans • Early Cenozoic animals include massive creatures like the Megalodon Shark. • Whales and marine mammals diversify in this era. • All modern organisms in todays oceans are present. • Late Eocene extinction about 35 million years ago caused about 15% of oceanic organisms to go extinct. • Is another extinction coming soon?
Life Zones of the Ocean • Defined by homogeneous physical features • Divided on basis of light, temperature, salinity, depth, latitude, and water density. • However, easiest to classify by light and location. • Light: Aphotic (no light) and Photic (light) Zones • Light governs photosynthesis and primary productivity • Location: Division between water and ocean bottom. • Pelagic Zone: Open water • Benthic Zone: Ocean bottom
Pelagic Zone • Divided into 2 subsections: • Neritic Zone: Shallow water, near shore over the continental shelf. • Oceanic Zone: Deep water beyond the continental shelf. • Oceanic Zone further subdivided by depth: • Epipelagic zone: Shallow, Photic zone • Mesopelagic: Middle zone, aphotic. • Bathypelagic: Depth zone, aphotic • Abyssopelagic: Means without bottom. Deep trenches.
Benthic Zones • Benthos or Benthic means bottom. • Benthic zone is subdivided as well. • Littoral Zone: of the shore. Intertidal region of coast. • Sublittoral Zone: Subtidal region. Ocean floor of continental shelf. • Bathyal Zone: Seabed from the continental slope to abyssal plain. • Abyssal Zone: Seabed of abyssal plain. • Hadal Zone: Hades means underworld. Seabed of trenches.
Life in Pelagic Zones • Plankton:the mass of mostly microscopic organisms that float or drift freely in the waters of aquatic (freshwater and marine) environments. (Algae and phytoplankton, jellyfish). • The basis of all life in the ocean. • Make oxygen for us to breath. • Nekton: all organisms that swim actively in open water, independent of currents. (Fish, sharks, whales, squids, octopus, etc.).
Life in Benthic Zones Benthos:organisms that live at the bottom of oceans or bodies of fresh water. (Sea urchins, Sea stars, sea cucumbers, sand dollars, crabs, lobsters, shrimp, most bivalves). Intertidal and Sublittoral Zone: zones where most life is found. Why? Bathyl Zone: Not much life can survive here but squid, octopus, and whales can flourish. Both abyssal and hadal zones have very few life forms but some life does exist.
Permian Ocean • Largest mass extinction ever took place at the end of the Permian. • Permian-Triassic or P-T Extinction. • Over 90% of all organisms in the ocean went extinct! 70% of all land organisms extinct. • Trilobites are extinct at end of Permian.
Mesozoic Oceans • Triassic, Jurassic, Cretaceous periods. • Reptiles and dinosaurs diversified on land. • Large marine reptiles dominated oceans. • Plesiosaurs, Ichthyosaurs diversified. • Sea stars, sea urchins, sharks, an rays also flourished in Cretaceous. • K-T mass extinction wipes out dinosaurs on land and marine reptiles in the oceans.