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

Ocean Life Zones

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.