Chapter 8—Stuff to know

1. Chapter 8—Stuff to know • Marine bathymetry zones • Neritic / bathyal / abyssal / hadal • Environmental limiting factors (know all) • Salinity categories • Stenohaline /euryhaline taxa • Evolutionary paleoecology • tiering; escalation; Fossils & Evolution—Chapter 8

2. Chapter 8—Paleoecology • Ecology = the study of the interactions between organisms and their environment • Paleoecology = ecology applied to the study of fossils and ancient environments • Evolutionary paleoecology= study of ecologic phenomena that operate on the scale of millions of years (and are invisible to ecologists of the living biota) • Main applications of paleoecology are in (1) reconstructing ancient depositional environments and (2) assessing environmental influences on evolution Fossils & Evolution—Chapter 8

3. Marine ecosystem • Modern marine ecosystem is used by paleontologists as an analogue for ancient marine ecosystems • Drawbacks to uniformitarian approach • Past climates generally have been warmer than today’s • Past sea levels generally have been higher than today’s • Few modern epicontinental seas • No modern tropical epicontinental seas Fossils & Evolution—Chapter 8

4. Devonian (360 Ma) Fossils & Evolution—Chapter 8

5. Marine bathymetry zones • Neritic = continental shelf (from sea level to ~200 m) • Intertidal • Subtidal zone • Bathyal = continental slope and rise (from ~200 m to ~2000 m) • Abyssal = deep ocean floor (from ~2000 m to ~ 6000 m) • Hadal = very deep ocean (> 6000 m) • Photic zone = depth to which light penetrates • Highly variable, depending on water clarity • Photosynthesis usually takes place in upper 100 m of water column Fossils & Evolution—Chapter 8

6. Marine environments Fossils & Evolution—Chapter 8

7. Ecologic limiting factors = physical, chemical and biologic properties of the environment that limit the distribution and abundance of a particular species • Temperature • Oxygen • Water depth and depth-related variables • Salinity • Substratum • Food Fossils & Evolution—Chapter 8

8. Limiting factors:Temperature • Probably the single most important limiting factor governing large-scale distributions (biogeographic provinces) Fossils & Evolution—Chapter 8

9. 15°C Modern symbiont-bearing corals and foraminifers occur mainly in water that is warmer than 15°C (winter sea surface temperature) 15°C Fossils & Evolution—Chapter 8

10. Limiting factors:Oxygen • Black Sea: direct relationship between dissolved oxygen in water and faunal diversity • As dissolved oxygen decreases with increasing depth, so too does diversity • First animals to disappear are large, heavily calcified invertebrates • Small, weakly calcified to uncalcified taxa extend to greater depths (taxa unlikely to be preserved as fossils) Fossils & Evolution—Chapter 8

11. soft-bodied Limiting factors:Oxygen Fossils & Evolution—Chapter 8

12. Limiting factors:Oxygen Fossils & Evolution—Chapter 8

13. Limiting factors:Water depth • Depth, in and of itself, exerts very little influence over distribution of organisms, but depth-related factors are very important • Hydrostatic pressure • Light wavelength and intensity • Salinity • Temperature • Nutrients • Dissolved oxygen Fossils & Evolution—Chapter 8

14. Limiting factors:Water depth (light) • Light is attenuated as it penetrates through water • Intensity of light decreases • Different wavelengths of light are absorbed at different rates green algae use red light red algae use blue light Fossils & Evolution—Chapter 8

15. Limiting factors:Salinity • Stenohaline species have little tolerance for salinity fluctuations • Euryhaline species have greater tolerance for salinity fluctuations Termsalinity (‰) Freshwater 0–0.5 Brackish 0.5–30 Seawater 30–40 Hypersaline 40–80 Brine > 80 Fossils & Evolution—Chapter 8

16. Limiting factors:Salinity • Stenohaline groups include: • Corals, cephalopods, articulate brachiopods, and echinoderms • Euryhaline groups include: • Inarticulate brachiopods (Lingula), pelecypods, gastropods, and ostracodes Fossils & Evolution—Chapter 8

17. Evolutionary paleoecology • Evolutionary paleoecology= study of ecologic phenomena that operate on the scale of millions of years (and are invisible to ecologists of the living biota) Fossils & Evolution—Chapter 8

18. Evolutionary paleoecology • Tiering = degree to which organisms in a community occupy/exploit different levels above and below the sea bottom • Partitioning of space above the seafloor increased in Ordovician time with advent of tall crinoids, etc. • No equally tall filter feeders since Jurassic time • Partitioning of space below the sea bed increased in Late Paleozoic time (and continues to this day) • end-Permian extinction caused a temporary reduction in tiering (throw-back to Precambrian) Fossils & Evolution—Chapter 8

19. Tiering: infaunal tropical shrimp Fossils & Evolution—Chapter 8

20. Tiering:tall crinoid Fossils & Evolution—Chapter 8

21. Tiering Fossils & Evolution—Chapter 8

22. Evolutionary paleoecology • Escalation = “arms race” in the evolution of predation and defense capabilities • Triassic increase in kinds of shell-crushing predators led to decline of lightly protected shellfish and preferential survival of forms with robust shells, burrowing, swimming, or other defense adaptations Fossils & Evolution—Chapter 8

23. Evolutionaryfaunas weakly skeletonized taxa (e.g., trilobites) and few predators increase in calcification of skeletons, but fauna dominated by sessile filter-feeders modern fauna dominated by taxa with robust shells and/or burrowing, swimming, or other defense adaptations Fossils & Evolution—Chapter 8

24. Predation scars on gastropod shell Fossils & Evolution—Chapter 8

25. Escalation: increase in “crushers” through time Fossils & Evolution—Chapter 8

26. Escalation: decrease in umbilicate and/or thin-shelled snails through time Fossils & Evolution—Chapter 8

27. Escalation: increase in heavily fortified snails through time Fossils & Evolution—Chapter 8