ERTH 2312 Final Exam

Paleoecology

the study of ancient organisms in the context of their environments that can be used to decipher the lifestyles of organisms and their relationships to each other

• “ancient ecology”

Ecology

study of adaptations of animals and plants to their environments (habitats), as well as interactions with organisms and flow of energy in communities

Differentiate between ecology and paleoecology

ecology studies interactions that are dynamic in space over short intervals of time whereas paleoecology studies data that is static in space and can be tracked over longer periods of geologic time

The principles of ecology can be applied to paleoecology

Actualism

ecology of modern organisms can inform our interpretation of the past. however, sometimes the past can be vastly different from the present with no modern analogues

What was unique about the Carboniferous Trophic Structures?

Unlike modern ecosystems, detritivores occupied the trophic level of primary consumers

Autoecology

ecology of the individual organism (ex. lifestyles, behaviour)

Synecology

the interactions between organisms and their environment (ex. ecosystem, community)

Paleoautoecology

study of traits of singular fossil organisms, which includes tooth wear, stable isotope analysis, trace fossils, paleopathology, and functional morphology, to understand behaviour and lifestyle

• tooth wear = diet preferences (ex. rough ate wood, soft ate fruits)

• stable isotopes = look at bone enrichment

• trace fossils = ex. coprolites

Paleosynecology

different levels above the individual, includes:

• population

• community

• habitat

• ecosystem

• macroecology (ex. climate)

Population

more than one individual of a species, living near one another, and potentially interacting

Community

groups of organisms that live together and interact with each other

(paleocommunities are usually named for one or more conspicuous species that live there)

Habitat

the environmental setting in which a community, or population, live (ex. forest, tundra, mud puddle, reef, etc.)

Ecosystem

the combination of habitats and organisms that exist together in a certain time and space

Ecotone

unique environments that are formed in the transitional areas between habitats

Ex. Intertidal ecotone presents a challenging environment for organisms found there. Characterized by tremendous fluctuations in a number of parameters including water cover, temperature, and salinity.

Describe the diversity and abundance in an ecotone

low diversity, but the few species that live there are often found in abundance (seen in trace fossil assemblages like Cruziana ichnofossils)

Ex. Foraminifera are highly zones in salt marsh ecotones and can be used to reconstruct paleo sea levels

Ecological niche

ecological space an organism occupies and the role it plays in its community and habitat

most habitats are occupied by several species in separate niches (fundamental — realized)

Ecological interactions

Thermodynamics (in the context of paleontology) states…

you need energy (enthalpy) to decrease chaos (entropy) and induce organized systems so life therefore consumes energy/enthalpy (photosynthesis/chemosynthesis) to decrease entropy on planetary scale

On a universal scale life is thermodynamically favored because it increases the rate energy is consumed and induces entropy long term

What is energy flow?

movement of energy throughout the food chain

• food chain: direct sequence from producers to consumers

• food web: combinations of many food chains

What are the different trophic levels?

• Producers: converts solar energy into food (autotrophs)

• Consumers: organisms that consumes other organisms to obtain energy (heterotrophs)

  • Primary

  • Secondary

  • Tertiary

• Decomposers: directly consumes dead organisms (occurs at all levels)

• Detritivores: consume detritus including waste (occurs at all levels)

  • Detritus is loose, dead particulate organic matter (decaying plant/animal material) or inorganic debris (rock fragments, rubble) produced by disintegration or wearing away

Biomass

amount of living matter in the ecosystem, or any part

Describe ecosystem dynamics in trophic pyramid

• energy is lost as it flows through the system

• biomass usually decreases at each trophic level (only about ~10% is transferred, ~90% is lost)

Why are aquatic trophic pyramids inverted?

primary producers, such as phytoplankton, have an extremely high turnover rate, reproducing and dying quickly while being rapidly consumed. Though their total mass at any given moment is low, their high production rate supports a larger biomass of zooplankton and fish

Why would we expect to find fewer Tyrannosaurus that Edmontosaurus specimens in a formation?

Tyrannosaurus eats Edmontosaurus, so Edmontosaurus should be more abundant

How are terrestrial species distributed?

Horizontal distribution (changes of environment, climate, etc.)

How are marine communities distributed?

Horizontal distribution of marine species controlled by changes in sediment, salinity, turbulence, etc. (particularly in costal areas)

• continental shelf: submerged border of continent

• continental margin: edge of shelf which drops off down continental slope to abyssal plain @ 5000m

Vertical distribution important to understanding ecology of marine species (primary factor is light)

• Photic zone — Portion of water column penetrated by light where photosynthesis occurs

• Pelagic zone — Water column

• Benthic zone — Bottom dwellers

Who inhabits pelagic zone?

• Nektic (active swimmers)

• Planktic (transported by waves/currents)

  • Phytoplankton (microscopic floating “plants”)

  • Zooplankton (microscopic floating “animals”)

What are the different lifestyles for the benthic zone?

• Epifaunal — live on substrate

• Infaunal — live in substrate

• Vagile — capable of locomotion

• Sessile — immobile

Marine tiering became _____________ throughout the phanerozoic.

more complex

Note: Tiering can occur within communities due to competition for resources (vertical ecological structure)

Feeding groups of marine ecology

• Grazers: feed by selectively removing organics from the substratum

• Deposit feeders: animals which feed on the detritus deposited on the bottom (ex. sand dollar (echinozoa))

• Suspension feeders: animals that feed by selecting suspended microorganisms and detritus from the water column (ex. crinoids)

• Carnivores: animals that feed mainly on other animals (ex. shark)

Life Assemblage (Biocoenosis)

the organisms that truly lived together and interacted while alive

Death Assemblage (Thanatocoenosis)

the organisms found in together after death and decay

Fossil Assemblage (Taphocoenosis)

fossils preserved together in a single horizon/locality

Paleocommunity

assemblages, or associations, of organisms that are inferred to have interacted with one another

Why are fossil assemblages (taphocoenosis) not a perfect reflection of life assemblages (biocoenosis)?

Fossil material is altered, or lost, due to taphonomy. This includes processes like decay, disarticulation, transport, compaction, time averaging.

Time averaging

• Make things appear synchronous in the geologic record that were not in reality, which can artificially increase the diversity of the death assemblage (thanatocoenosis)

• Life Assemblage —> Death Assemblage —> Fossil Assemblage

• Fossil assemblages (taphocoenosis) from different depositional environments will have different temporal and spatial resolutions

How does time averaging differ from signor-lipps effect?

signor-lipps states that the last fossil of a species is rarely the last individual record of the species. time averaging instead looks at how fossil deposits may contain fossils from different life assemblages in the same sedimentary layer.

What is fidelity?

How well the death or fossil assemblage matches the living assemblage

• tracks changes between living assemblage and death assemblage in modern localities

• assessed experimentally, or using lagerstatten

We must always take these preservational biases into account and mitigate them while designing studies and interpreting paleoecological data

Why might the size distribution of a fossil assemblage differ from the life assemblage?

Preservation bias

• larger fossils likely have a higher survival

• the energy level of transport impacts size distribution

Macroecology

Evolution of new body plans and ecologies drove huge macroecological and macroevolutionary changes from the Ediacaran through the Devonian

1. Ediacaran fauna

2. Small shelly fauna

3. Cambrian explosion

4. Great Ordovician biodiversification

5. Nekton revolution

Ediacaran Biota

• oldest assemblage of large complex organisms

• soft body, high surface-volume ratios, radial or bilateral symmetry

• most species had worldwide distributions, and predators and scavengers had yet to evolve in great numbers

• no evidence the species were infaunal or pelagic —> life restricted to seabed

• few predators and scavengers —> short food chains dominated by suspension and deposit feeders

• tiering of benthos (evolution of stalks)

Small Shelly Fauna

• first evidence of hard skeletonization

• some thought to be worms or worm-like organisms

• some show evidence of predation or scavenging

• likely mobile and sessile

Oceanic Shift:

• change to ocean between Late Proterozoic-Early Phanerozoic

• evolution of new trophic mode of planktonic suspension feeders changed ocean water quality

• new ecospaces

Cambrian explosion

• Rapid appearance of new body plans, diversification of Bilateria

• Cambrian substrate revolution indicates the evolution of a new feeding ecology, and increased tiering

• Increase predation, driven by sight

• Increased biomineralization, nutrient availability and defense

Great Ordovician Biodiversification

• No new phyla (except Bryozoa), but extensive radiation, many crown groups emerge

• Evolution of the plankton –diversification of acritarchs, development of feeding larvae

• Diversification of predators led to “evolutionary arms race” and increasingly complex food webs

Nekton Revolution

• Oversaturation of ecological space on the seabed drove evolution of nektonic forms

  • major Paleozoic ecological shift where actively swimming animals (nekton) rapidly colonized the marine water column, evolving from bottom-dwelling (benthic) ancestors

• Primarily cephalopods and fish

• Diversification continued well into the Devonian

Limiting Factors

variables in the environment that can restrict the growth, abundance, distribution of a population of organisms in an ecosystem

only one factor can be limiting at any one time

Examples:

• space

• environmental conditions (i.e. temperature, salinity, etc.)

• predation

• shelter

• resource availability (i.e. nutrients, water, etc.)

Liebig’s Law of the Minimum

the scarcest resource is the limiting factor

Law of limiting factors

Biological or ecological processes that depend on multiple factors are limited by the slowest factor (ex. photosynthesis)

Law of tolerance

An organism success or survival is dependent on a complex set of conditions with maximum, minimums and optimal ranges of environmental factors

What are the limiting factors in a marine environment?

• light

  • required for most ecosystems to operate, light intensity effects distribution of coral reefs, blue light penetrates deepest

• oxygen

  • low oxygen ~ low biodiversity, required for metabolism

• temperature

  • varies with latitude, geographic distributions, decreases with depth

• salinity

  • Freshwater, Brackish water (Lower diversity), Sea water, Hypersaline water (Very low diversity), Brine

  • Most organisms have a low range of tolerances for salinity, characteristic species, or assemblages, can give evidence for changes in salinity/sea-level (reconstruction)

• depth

  • related to other factors, including pressure

  • Carbonate Compensation Depth (CCD) limits distribution of organisms with carbonate skeletons

• substrate

  • grain size ~ energy level ~ community distribution, sessile epifaunal (deposit feeders, suspension feeders)

What is horizontal distribution in paleontology?

spatial distribution of a species in stratigraphic section determined by biotic factors (species ecology/life strategy) and abiotic factors (ex. climate, preservation bias, etc.)

Define Tissues and Organs

Tissue: groups of differentiated cells united for a common function

Organs: groups of tissues organized into structures for a common function

What are Germ Layers and the different types?

The three primary cell layers

1. Endoderm — digestive tract, liver, lungs, etc.

2. Mesoderm — kidney, muscle, bones, etc.

3. Ectoderm — skin, hair, nails, nervous system, etc.

Differentiate between a Protostome and Deuterostome?

Protostome:

• Eight-cell stage — spiral cleavage

• Gastrulation — blastophore becomes the mouth

• Examples — molluscs, arthropods, worms, lophophorates, etc.

Deuterostome:

• Eight-cell stage — radial cleavage

• Gastrulation — blastophore becomes the anus

• Examples — echinoderms, chordates, etc.

What makes the hypothesized origin of Porifera unique?

Porifera may be paraphyletic

What is a sponge? What are its groups?

• no true germ layers

• sessile, benthic, filter feeders with porous bodies

• some of the earliest, most basal, metazoans — can produce trace fossils

• global distribution (marine and freshwater, any depth, Antarctic waters)

Groups:

• Demospongea (common sponges) — silica (sometimes calcite) spines + larger

• Calcarea (calcareous sponges) — small, less complex, calcite spicules

• Hexactinellida (glass sponges) — silica spicules, looks like glass, small + complex

• Archaeocyathid (extinct)

• Stromatoporoid (extinct)

Describe the morphology of a sponge

• body of spongin

• skeletal structure made of spicules (calcite or silica) ← most likely to fossilize

• sack-shaped body with central opening (spongocel) and small pores (ostia)

• amoeboid sites eat trapped food, have cells for reproduction, have regenerating capacity

How do sponges feed?

By pumping water into their bodies using their ostia (pores). Water is moved by choanocytes (cells with flagella), and food is digested with amoeboid cells. Water is then expelled through the osculum (large opening at the top).

• can process ~1000 L per day

How do sponges reproduce?

Asexually — budding (new sponge grows as an outgrowth (bud) on the parent's body. The bud may fall off and grow elsewhere, or remain attached to form a colony)

Sexually — spawning (sponges release large amounts of sperm into the water column, which enters another sponge through its pores (ostia). Specialized cells called choanocytes (collar cells) trap the sperm and transfer it to an egg within the body)

Describe the evolution of sponges

• Earliest fossil thought to be from 890 mya

• First appeared in Cambrian (Cambrian Explosion)

  • Began thin-walled, evolved ridged bodies for reef building

Which group of sponges dominated the Ordovician?

Demosponges (thick walled)

What are Stromatoporoids?

• Mound/sheet shaped with calcareous skeletons

• Marine, shallow, carbonate rocks

• Grew together in bioherms, or biostromes and often “hosted” epibiont species

• Densely layered calcite skeletons, most with no spicules

• Different morphologies reflected the environment

• Small bumps called mamelons and cracks called astrorhizae that likely expelled water

• Horizontal laminae and vertical pillars

• Early Cambrian — Late Devonian

What are Archeocyathids?

• cup-shaped organisms

  • outer wall, inner wall, intervallum, septum, holdfast anchors

• shallow, marine water, tropical deposits

• first reefs

• evolved in Early Cambrian, reached global distribution, and went extinct before end of Cambrian (Biostratigraphy)

What groups are included under Cnidarians?

• Anthozoa (Rugosa, Tabulata, Scleractinia)

  • Corals, sea anemones, sea fans, sea pens

• Hydrozoa

  • Jellyfish, fire corals

• Scyphozoa

  • moon jellies, compass jellies

What are Cnidarians? What are their common traits?

• least complex of metazoans

• radially symmetrical with limited tissues and only two germ layers: Endoderm and Ectoderm

• global distribution - predominantly live in shallow, warm, marine waters

• Stinging Cells = Cnidoblasts

• Live as polyps (sessile/attached) or medusae (free-swimming) ← often exist as both during life cycle

Describe Cnidarian morphology?

• Hydra represents general body plan

• Enteron = open body cavity with a single opening for mouth, a n u s and reproduction

• Mouth surrounded by tentacles with stinging cells

  • Nematocysts = stingers found in entire cell called cnidoblasts

• Body made of two walls (endoderm and ectoderm) with gelatinous substance called mesoglea

Describe Coral reproduction

Asexual — budding polyps with colony, fragmentation where coral falls away and establishes a new colony

Sexual — gametes mix to form planulae which disperse via currents and establish new colonies

When were the earliest fossil Cnidarians?

Possibly in Ediacaran biota, appeared in Cambrian

Of the coral group Anthozoa, which groups are extant vs extinct?

Rugosa = extinct

Tabulata = extinct

Scleractinia = extant

Anthozoa: Rugosa

• solitary or colonial

• calcite skeletons

• robust, horn-shaped

• prominent septa (6 primary, secondary arranged in 4 spaces

• Middle Ordovician to End Permian

Anthozoa: Tabulata

• colonial (many corallites living together)

• calcite skeletons

• reduced speta

• prominent tabulae

• Middle Ordovician to End Permian

Anthozoa: Scleractinia

• solitary or colonial

• aragonite skeletons

• prominent septa (divisible by 6

• absent tabulae

• Triassic — Recent (all modern corals)

Describe coral ecology

• corals are benthic

• reef building organisms that provide habitat/shelter

• some natural predators (boring animals, parrot fish)

• All modern corals form two groups:

  • Hermatypic — symbiotic algae called zooxanthellae (dinoflagellates)

  • Ahermatypic — no symbiotic algae and grow slow in cold deep water

What are the two most productive ecosystems?

Reefs and Rainforests

What are keep-up, catch-up, and give-up reefs?

What are the three major kinds of coral reefs?

• Fringing

• Barrier

• Atoll

Darwin’s Reef Formation VS Daly’s Reef Formation

Darwin and Daly's theories of reef formation differ primarily on the driving mechanism for the transition from fringing reefs to atolls: Darwin proposed a long-term subsidence (sinking) of volcanic islands, while Daly argued for changes in eustatic sea level (glacial control) over pre-existing platforms

Fringing → Barrier → Atoll

Both partially right

Describe Reef Anatomy

The 'Fore Reef Slope' (Zone 10), is the portion of the reef below storm wave base. Coral forms are often platy to catch sunlight

The 'Fore Reef Escarpment' (Zone 11) the most seaward part of the reef, consists primarily of storm derived coral rubble

The lowermost part of the 'Reef Crest' is known as the barren zone (Zone 6) and is almost exclusively comprised of Elkhorn coral groves in Caribbean reefs

The middle part of the 'Reef Crest' (Zone 5) is the highest part of the reef.

Large portions of the reef crest and flats (Zone 4) can be exposed during low tide.

The rear 'Back Reef' zone of the 'Reef Crest' (Zone 3) begins where the reef flats begin to slope downwards towards the lagoon and continues to the point where the reef flats

The 'Lagoon' (Zone 2) is usually floored by fine calcareous mud derived primarily breakdown of coralline algae and can also be covered by sea grass

Lophophores

complex tentacled feeding structures

Lophophorates

• organisms with lophophores

• similarities in structure of body cavities

• Brachiopods and Bryozoans

Bryozoan Morphology

• “moss animal” → colony of zooids

• each zooid encased in a protective covering

• skeleton mineralized with calcite → zooecia

• funiculus — tissue cords that connect zooids (to distribute nutrients)

• each zooid has a lophophore feeding structure (8-100 tentacles - circular or u-shaped)

  • lophophore tentacles gather and put food in mouth (center)

  • u-shaped guts (mouth is next to anus)

Bryozoan Reproduction

Asexual — budding of new zooids for colony expansion, broken pieces start new colony

Sexual — release sperm + eggs for external fertilization, captured with tentacles, brood chamber, produces free-living larvae that will settle

Bryozoan Ecology

• marine, sessile benthos

• sublittoral zone

• some deep water forms

• body plans linked to feeding strategy and environment

  • colony ~ environmental conditions

  • zooid size ~ water temperature (proxies)

• facies dependent

  • fan-like shape = low energy

  • coral-like shape = high energy

Bryozoan Evolution

• first appearance in lower Ordovician (possibly early Cambrian)

Brachiopods are split into two groups…

Inarticulate (no hinge) and Articulate (hinge)

Brachiopod Morphology

• Two valves — brachial (dorsal) valve and pedicle (ventral) valve → not identical, symmetric midline

  • pedicle valve usually larger

  • interlocking teeth and cardinal process (articulate species)

• Lophophore anchored to upper brachial valve

• Pedicle for anchoring to substrate

• Muscles for opening and closing (muscle scars on valves)

Brachiopod Feeding

• Lophophores capture food particles brought to mouth along brachial groove

• Draw water from sides and expel through front (produce little solid waste)

• Unlike Bryozoans, lophophore is not retractable and has supports (brachidium)

• In some inarticulate forms there is a u-shaped gut with a separate anus, other species have a curved gut that just ends

• Most forms reverse the movement of the lophophore cilia or “sneeze” to expel blockages or any solid waste

Brachiopod Reproduction

• Sexual Reproduction

  • external fertilization (release sperm + eggs in water)

  • some have brood chamber

  • distinct male/female

• Lingulid larvae swim and filter feed as plankton

  • swim and feed with lophophore

  • increase size, sink to bottom and become sessile

  • Articulate brachiopods only exist as plankton for a few days

Brachiopod Ecology

• suspension feeding benthos

• anchor to substrate using pedicle and filter feed with lophophores

• some infaunal and unattached forms

• coral-like forms

• valve morphology ~ environmental conditions + energy levels

• some with clasping spines to connect with substrate

• stable isotopes in shells reflect environmental conditions

Brachiopod Evolution

• Early Cambrian — Recent

• Survived 5 mass extinctions

  • Late Ordovician extinction reduced 80%

  • Permo-Triassic extinction reduced 90%

What are the origins of Brachiopods?

Outdated — Brachiopod Hypothesis

• evolved from Halkieria-like ancestor

• two protective shells on either size of body that folded in on itself

Current, Accepted Hypothesis

• related to tommotiids (extinct Cambrian invertebrates)

• two valves

• evolved as a result of retaining the bivalved larval characteristics of some tommotiid taxa

Mollusca Groups include…

General Mollusca Morphology

• unsegmented, soft body

• bilateral symmetry (distinct head and tail)

• feeding structure = radula (except for bivalves)

• muscular foot for movement (burrowing, swimming) — can be highly modified

• calcareous shell for protection

• head - contains sensory organs and radula (made of chitin)

• visceral mass - digestive, excretory, reproductive, circulatory systems in celomic cavity

• mantle - sheet of tissue, dorsal to visceral mass, secretes the shell

What are Monoplacophorans?

• single-shelled mollusc that inhabit deep water (once thought to be extinct)

• soft-parts are segmented; shell is limpet-like in shape

What are Bivalvia?

• clams, oysters, etc.

• 2 valves

• intertidal to marine and freshwater

• variety of ecological strategies (attached, free swimming, burrowing, etc.)

• good facies fossil

Bivalve Morphology

• two valves, secreted by mantle

• plane of symmetry parallel to commissure

• no head - anterior determined by position of the mouth

• interlocking teeth and sockets called dentition

• ligament along hinge line pops shell open

• adductor muscles keep shell closed

• pallial line is scar where mantle attaches

• beak/umbo — earliest part of shell to form, where growth lines extend from

Bivalve Reproduction

• male or female, some hermaphroditic

• marine bivalves release sperm/eggs in water

• larvae mature in plankton (some feeding, some exist on yolk sac)

Bivalve Feeding

• mostly detritivores

• some scrape detritus off sea floor

• gills (ctenidia) modified into filter-feeding apparatus

• water pulled into shell from posterior (sometimes uses siphons), passes over gills and then is expelled

• food particles moved by cilia through mucus on gills to mouth

• exceptions

  • some “suck” prey into mouths

  • giant clams + symbiotic algae

  • ship worms + bore into wood

  • endosymbiotic form in sea cucumber esophagus

Bivalve Evolution

• earliest forms have 2 valves with a working hinge and ligament

• may have evolved from Rostroconcha (no functional hinge)

• Early Cambrian — Present

  • appeared in Early Cambrian

  • evolved rapidly in Ordovician

  • stable low diversity in Paleozoic

  • radiated in the Mesozoic

• Long siphons (burrowing) and muscular foot (mobility) may have been advantageous over brachiopods

• General increase in size over history

Bivalves VS Brachiopods

Brachiopods

• 2 valves

• feed with lophophore

• middle of valve symmetry (intravalve)

• attach via pedicle

Bivalves

• 2 valves

• filter feed with gills

• symmetry between valves (intervalve)

• muscular foot