Defining Life
* Biological Criteria: Growth, metabolism, movement, reproduction, reaction to stimuli.
* All life shares:
* Single origin of evolution.
* Common mechanisms for energy capture, protein synthesis, and genetic information transfer.
Evolutionary Principles
* Genetic changes drive new traits through natural selection.
* Key milestones:
* Darwin & Wallace (1858): Evolutionary theory.
* Mendel's genetics rediscovered (1910): Mutations & inheritance.
* Modern Synthesis (1930s-1953): Unified genetics and evolution.
* DNA structure discovered (1953).
Biomolecules
* Made of C, N, P, S, O, H.
* Functions: Energy storage, information encoding, structural support, catalysis, transport, defense, regulation, movement.
Organization of Life
* Cell Theory:
* Prokaryotes: No organelles, nucleoid DNA.
* Eukaryotes: Compartmentalized organelles, nucleus with DNA.
* Central Dogma of Molecular Biology: DNA -> RNA -> Protein.
DNA and RNA
* DNA: ATCG bases; stores genetic info; compacted in chromosomes.
* RNA: AUCG bases; translates DNA into proteins.
* Protein Encoding: Codons (3 nucleotides) map to 1 amino acid; redundancy enables error tolerance.
Metabolism
* Autotrophy: Photosynthesis, chemolithoautotrophy.
* Heterotrophy: Ingestion, parasitism, saprophytism.
* Energy Flow: Gross Primary Productivity (GPP) – Respiration = Net Primary Productivity (NPP).
Food Webs
* Classic: Phytoplankton -> Copepods -> Fish.
* Microbial Loop: Cycling of organic carbon via microorganisms intersects classic food web.
Biogeochemical Cycles
* Elements (C, N, P) cycle between living organisms and Earth systems.
* Marine Impact: Light, nutrients, and environmental changes (e.g., salinity, pH) affect marine life.
Mass Extinctions
* Notable events: End Permian (96% marine species lost), End Cretaceous (dinosaur extinction).
Key Takeaways
* Life evolved through genetic and environmental adaptation.
* Energy flow and element cycling are critical for ecosystems.
* Rapid environmental changes threaten biodiversity.
Classic Food Web vs. Microbial Loop
* Classic Food Web: Carbon flows from phytoplankton -> zooplankton -> fish.
* Microbial Loop: Recycles organic carbon via microorganisms, intersecting with the classic food web.
Primary Productivity
* Light/Nutrients Limitations:
* Key nutrients: Nitrate, phosphate, silicate, trace metals (Fe, Co, Ni, Zn).
* Photosynthesis occurs in the euphotic zone (up to 1% surface light).
* Phytoplankton Adaptations:
* Seasonal succession linked to temperature, mixing, and nutrient availability.
* Diverse pigments optimize light absorption.
Phytoplankton Diversity
* Cyanobacteria: Major photosynthesizers; some fix nitrogen.
* Diatoms: Silicon frustules; sink faster; diverse morphologies.
* Coccolithophores: Produce calcium carbonate plates; sensitive to pH changes.
* Dinoflagellates: Varied metabolism (photoautotrophy, mixotrophy, heterotrophy); can cause harmful algal blooms.
Carbon Pumps
* Biological Carbon Pump (BCP):
* Organic carbon (POC/DOC) sinks to deep ocean, stored for 100-1000 years.
* POC: Cells, remains, polysaccharides; sinks based on size/density.
* DOC: Dissolved organics; does not sink, cycles via diffusion.
* Microbial Carbon Pump (MCP):
* Microbes convert labile carbon into refractory DOC (RDOC) in deep ocean.
Marine Zooplankton
* Microzooplankton: Major grazers of phytoplankton.
* Mesozooplankton: Seasonal behaviors like diel vertical migration and diapause aid carbon export.
Marine Bacteria and Archaea
* Key Groups:
* SAR11: Most abundant bacteria; efficient genomes.
* Cyanobacteria: Photosynthetic (e.g., Prochlorococcus, Synechococcus).
* Archaea: Less abundant, thrive in nutrient-poor waters.
* Adapted lifestyles: Free-living vs. particle-associated.
Marine Viruses
* Biogeochemical Role:
* Viral shunt: Redirects organic carbon from living organisms to DOM pool.
* Lytic Cycle: Rapid infection and cell lysis.
* Lysogenic Cycle: Dormant phase, slower impact.
* Facilitate horizontal gene transfer and can carry auxiliary metabolic genes (AMGs).
Measurement and Impact
* Primary Productivity Measurement:
* Light/dark incubations (O₂ changes).
* Carbon isotopes (¹⁴C, ¹⁸O).
* Satellite data.
* Key Insights:
* Viruses and microbial processes drive nutrient cycling.
* Phytoplankton blooms regulate atmospheric CO₂ and cloud formation (e.g., DMS from coccolithophores).
Key Marine Animal Phyla
1. Porifera (Sponges)
* No true tissues, radial symmetry.
* Suspension feeders, made of spongin, glass, or calcium carbonate.
2. Cnidaria (Cnidarians)
* Stinging cells (cnidoblasts), radial symmetry.
* Classes:
* Anthozoa: Sea anemones, corals.
* Medusozoa: Jellies, hydroids (e.g., Portuguese Man of War).
* Diet: Zooplankton, small fish.
3. Mollusca (Mollusks)
* Features: Fleshy mantle, muscular foot, radula (beak-like structure).
* Classes:
* Bivalvia: Clams, scallops, oysters.
* Gastropoda: Snails, nudibranchs (sea slugs).
* Cephalopoda: Octopus, squid, cuttlefish, nautilus.
4. Annelida (Segmented Worms)
* Includes bristle worms (polychaetes) and earthworms.
5. Arthropoda (Arthropods)
* Segmented body, exoskeleton, jointed legs.
* Subphyla:
* Crustacea: Lobsters, crabs, shrimp, barnacles.
* Chelicerata: Spiders, horseshoe crabs.
* Hexapoda: Insects.
6. Echinodermata
* Radial symmetry, hydrostatic skeleton.
* Classes: Sea stars, brittle stars, sea cucumbers, sea urchins.
7. Chordata (Chordates)
* Features: Notochord, dorsal nerve cord, pharyngeal slits, post-anal tail.
* Subphyla:
* Tunicata: Sea squirts, salps.
* Cephalochordata: Lancelets.
* Vertebrata: Fish, mammals, birds, reptiles.
Important Features
* Sessile vs. Pelagic: Sessile organisms are immobile (e.g., barnacles), while pelagic species inhabit open water (e.g., jellies).
* Radial vs. Bilateral Symmetry: Radial symmetry (e.g., jellies), bilateral symmetry (e.g., humans, fish).
Additional Highlights
* Unique Behaviors: Diel vertical migration in zooplankton, bioluminescence in some cnidarians.
* Diverse Ecosystems: Spanning benthic (ocean floor) to pelagic environments.
* Species Diversity: Ranges from simple sponges to complex vertebrates like whales and sharks.
Marine Communities
* Definitions:
* Population: Individuals of the same species.
* Community: Populations of different species in a habitat.
* Ecosystem: Communities + abiotic factors (producers, consumers, decomposers).
* Niche: Organism's role in an ecosystem.
Abiotic and Biotic Factors in Coastal Ecosystems
* Abiotic: Wave action, tides, light, oxygen, nutrients, salinity.
* Biotic: Competition, predation, shading, toxins.
Key Coastal Ecosystems
1. Rocky Intertidal Zones:
* Zonation:
* Supra-littoral: Above tide; exposed.
* Littoral: Intertidal; between tides.
* Sublittoral: Always submerged.
* Seasonal sediment changes due to wave action.
* Shelled grazers, filter feeders, predators present.
2. Kelp Forests:
* Keystone species: Sea otters control urchins, protecting kelp.
* Giant kelp (Macrocystis) grows over 200 feet, provides habitat.
* Air bladders (pneumatocysts) ensure buoyancy.
3. Estuaries:
* Transition zones from freshwater to saltwater.
* Types: Salt wedge, partially mixed, well-mixed, fjord-type.
* Impacted by tides and anthropogenic activities like coastal development.
4. Mangroves:
* Roots provide habitat for marine life; limbs for terrestrial animals.
* Nursery grounds; nitrogen-fixing bacteria aid plant growth.
5. Seagrass Meadows:
* True plants with roots and flowers.
* Carbon sequestration hubs; symbiotic bacteria oxidize harmful sulfides.
6. Coral Reefs:
* <1% of ocean floor but highest biodiversity.
* Symbiotic zooxanthellae provide nutrients to corals via photosynthesis.
* Threats: Pollution, overfishing, climate change.
7. Oyster Reefs:
* Provide storm buffering and algae control.
* Artificial substrates used for restoration (reef balls, shell bags).
Ecological Processes
* Population Dynamics:
* Carrying Capacity: Maximum sustainable population.
* Growth types: Exponential (J-shaped) vs. logistic (S-shaped).
* Larval Ecology:
* Planktotrophic: Many small eggs; larvae depend on plankton for food.
* Lecithotrophic: Fewer energy-rich eggs; larvae develop quickly.
* Holoplankton vs. meroplankton (entire vs. partial planktonic lifecycle).
Human and Ecosystem Connectivity
* Coastal ecosystems (mangroves, seagrasses, coral reefs) are interconnected.
* Provide ecosystem services: nutrient cycling, storm buffering, habitat for fish.
Key Features of Polar Regions
* Arctic vs. Antarctic:
* Arctic: Shallow, largely landlocked ocean surrounded by continents.
* Antarctic: Landmass with deep continental shelf, surrounded by dynamic ocean currents.
Arctic Ecosystem
* Sea Ice:
* Reduced by ~50% since the late 20th century.
* Contains brine channels inhabited by biota like pennate diatoms.
* Annual recolonization due to its ephemeral nature.
* Food Web:
* Primary producers: Sea ice algae, phytoplankton.
* Consumers: Benthic invertebrates, marine mammals, and seabirds.
* Seasonal Biogeochemistry:
* Winter: Net heterotrophic.
* Spring/Summer: Net phototrophic with blooms of algae and pelagic organisms.
* Climate Change Impacts:
* Rising temperatures, melting permafrost, and concentrated pollutants.
Antarctic Ecosystem
* Sea Ice vs. Ice Sheet:
* Sea ice is more variable; ice sheet mass steadily declining.
* Record low sea ice extent in 2022 and 2023.
* Unique Physical Oceanography:
* Upwelling supports higher productivity and deep photic zones.
* Formation of Antarctic Bottom Water (downwelling).
* Food Web:
* Sea ice algae are crucial primary producers.
* Krill (Euphausia superba): Keystone species; consumed by most predators and aids carbon sequestration.
* Benthic invertebrates play a smaller role due to deeper waters.
* Polar Fish Adaptations:
* Icefish lack hemoglobin; antifreeze proteins prevent freezing.
Marine Protected Areas (MPAs)
* Purpose: Conservation and sustainable use; some restrict fishing.
* Ross Sea MPA:
* Established in 2016 under CCAMLR, covers 1.55 million km².
Physical Characteristics of the Deep Sea
* Low temperature, high pressure, low light, high salinity, and low energy input.
* Extreme environments: Abyssal plains, hydrothermal vents, brine pools, cold seeps.
Adaptations to Deep Sea Life
* Biochemical: Pressure-resistant enzymes, osmolytes, fluid cell membranes.
* Morphological:
* Large eyes for low light.
* Bioluminescence for prey attraction, species recognition, or defense.
* Specialized mouths and appendages for resource scarcity.
* Gigantism due to reduced predation and cold temperatures.
* Marine Mammals: Collapsible lungs and bradycardia to handle pressure and conserve oxygen.
Deep Sea Ecosystems
1. Abyssal Plains:
* Stable, low-energy environments supported by organic material from surface waters.
* Key features: Whale falls provide temporary energy bursts and connect ecosystems.
2. Hydrothermal Vents:
* Energy from chemosynthesis (hydrogen sulfide -> carbohydrates and sulfur).
* Mutualism: Tube worms and chemosynthetic bacteria.
3. Cold Seeps and Brine Pools:
* Methane or brine expelled from seafloor creates unique ecosystems.
* Specialized bacteria process methane and other compounds.
4. Seamounts:
* Promote localized upwelling, providing nutrients for filter feeders.
* Support larval dispersion and zooplankton retention.
Bioluminescence
* Roles: Predation, communication, reproduction, and defense.
* Chemical basis: Diverse luciferases and photoproteins.
Ecological Connectivity
* Whale falls, cold seeps, and hydrothermal vents serve as “way-stations,” linking dispersed habitats.