Chapter 8—Stuff to know
description
Transcript of Chapter 8—Stuff to know
Fossils & Evolution—Chapter 8 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 4Devonian(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
15°C
Modern symbiont-bearing corals and foraminifers occur mainly in water that is warmer than 15°C (winter sea surface temperature)
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
Limiting factors:Oxygen
soft-bodied
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 algaeuse red light
red algaeuse 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 fluctuationsTerm salinity (‰)Freshwater 0–0.5Brackish 0.5–30Seawater 30–40Hypersaline 40–80Brine > 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 sessilefilter-feeders
modern fauna dominated by taxawith 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