Marine Biology

What factors determine a Reynolds number, and what is the significance of high versus low Reynolds numbers in seawater?

• Determined by size, velocity, and fluid density, divided by dynamic viscosity.

• $Re > 1000$: Inertial forces predominate, allowing organisms to coast.

• $Re < 1$: Viscous forces predominate; movement stops instantly when propulsion ceases.

What characterizes laminar flow, turbulent flow, and a boundary layer?

• Laminar flow: Streamlines are parallel and regular, minimizing drag and energy use.

• Turbulent flow: Streamlines are irregular to chaotic, creating wakes and pressure drag.

• Boundary layer: A region near a surface where water velocity is less than 99% of the mainstream velocity due to the no-slip condition

How does pressure drag relate to swim speed and limit marine organisms?

• Pressure drag increases with the speed of swim

• This exponential rise in metabolic cost ultimately limits the maximum swimming speeds of marine organisms.

What is Bernoulli's principle, and how does it relate to hydrofoils and pressure drag?

• Pressure is inversely related to fluid velocity.

• Swimming animals use hydrofoil shapes where high-speed water over a curved surface generates reduced pressure (lift and thrust).

• Turbulent flow reduces water velocity behind an animal, creating a pressure differential that causes pressure drag.

What are the forms of asexual reproduction, and what is a module?

• Forms of asexual reproduction: Clonal growth via fission, budding, or parthenogenesis.

• Module: A structural unit in a colonial organism where individuals (zooids) are genetically identical clones derived from a single zygote

What is the difference between protandry and protogyny, and what conditions select for them?

• Protandry (male becomes female): Selected when small individuals do well as males, but large size yields significantly more offspring because eggs are energetically costly.

• Protogyny (female becomes male): Selected when older, larger males achieve higher mating success through aggression and territory/mate defense.

What are the costs and advantages of sexual reproduction?

• Costs: Females give up half their genes to progeny; requires time and energy to find mates and engage in male combat.

• Advantages: Generates genetic diversity via recombination and crossing over, conferring resistance to diseases/parasites and driving rapid evolution.

What problems are associated with free-spawning, and what solutions do animals use?

• Problems: Specificity, timing, and turbulence.

• Solutions: Species-specific binding proteins/receptors (e.g., bindin and lysin), egg-released sperm attractors, epidemic or mass spawning events, and spawning during slack water to minimize turbulence.

What is the difference between planktotrophic vs. lecithotrophic larvae, and anadromous vs. catadromous fish?

• Planktotrophic larvae: Many small eggs are produced (10^3–10^6), feed on plankton, and have long dispersal times.

• Lecithotrophic larvae: Fewer, larger eggs (10^2–10^3), live off yolk, and have short dispersal times.

• Anadromous fish: Adults live in salt water and spawn in fresh water (e.g., salmon).

• Catadromous fish: Adults live in fresh water and spawn in salt water (e.g., eels).

What are three potential advantages of planktotrophic larval dispersal?

• Escaping local extinction by exporting young to new areas.

• Bet-hedging by spreading offspring across multiple habitats.

• Broader geographic ranges and lower long-term extinction rates.

What strategies do estuarine larvae use to promote retention versus dispersal onto the shelf?

• Retention: Larvae rise into the water column on flooding tides and sink to the bottom during ebbing tides.

• Dispersal: Larvae are transported out to coastal waters during early stages and use behavioral cues to return to estuaries during later stages.

What are the basic characteristics of diatoms and dinoflagellates?

• Diatoms: Encased in a two-valved silica shell, radially symmetrical or chain-forming, and account for up to 50% of ocean primary productivity.

• Dinoflagellates: Covered in an organic theca with two flagella, nano- to microplankton sized, some heterotrophic, and responsible for red tides.

What are the features of calanoid copepods and their ecological importance?

• Features: Possess a long pair of antennae, swim using thoracic appendages, lack compound eyes (have a medial naupliar eye), and capture food using feeding currents and maxillipeds.

• Importance: They are the most abundant form of copepods and represent the dominant zooplankton group.

What are the basic details of zooplankton groups, emphasizing copepods and cnidarians?

• Copepods: Crustacean zooplankton that form the dominant zooplankton group and feed on phytoplankton/microzooplankton.

• Cnidarians: Gelatinous zooplankton (like scyphozoan and hydrozoan jellyfish) characterized by a muscular bell, a gastrovascular cavity, mesoglea for support, and stinging nematocysts

What are the names and basic features of the four classes of cephalopods?

• Squids: Triangular head, 8 arms, 2 tentacles, fins, and an internal pen; inhabit the open ocean.

• Octopuses: Round head, 8 arms, no tentacles or fins; inhabit benthic dens.

• Cuttlefish: Triangular head, 8 arms, 2 tentacles, and an internal cuttlebone; inhabit benthic dens.

• Nautiluses: External coiled gas-filled shell, up to 90 tentacles, and inhabit deep open water.

What is a photophore and how is it used?

• Structure: An organ containing a lens, reflector, and light-producing cells (sometimes housing bioluminescent bacteria).

• Functions: Camouflage via counterillumination (matching downwelling light intensity and wavelength) and signaling to conspecifics.

What are the two major fish groups?

• Chondrichthyes: Cartilaginous fishes (sharks, skates, rays) with a cartilaginous skeleton and replaceable rows of teeth.

• Osteichthyes: Bony fishes with a true bony skeleton and teeth fixed firmly in their jaws, representing the vast majority of fish diversity

How does body shape influence fish locomotion and the three swimming modes?

• Acceleration: Torpedo or teardrop-shaped bodies optimized for quick bursts.

• Cruising: Streamlined bodies with caudal-focused propulsion optimized for long-distance swimming.

• Maneuvering: Deep-bodied or flattened forms optimized for tight turns and complex environments.

What is the difference between anguilliform, carangiform, and thunniform swimming?

• Anguilliform: Undulations distributed evenly along the entire long, flexible body (e.g., eels).

• Carangiform: Undulations concentrated in the posterior half of the body.

• Thunniform: High-speed swimming where propulsion is strictly confined to the caudal region, stabilizing the head and minimizing pressure drag.

What is the structure and function of fish gills?

• Structure: Unidirectional water flow across gill arches, filaments, and secondary lamellae, with blood vessels moving in the opposite direction.

• Function: Operates via countercurrent gas exchange, maximizing oxygen uptake efficiency to support active fish in low-$O_2$ environments.

What is the structure and function of the fish swim bladder?

• Structure: Includes a gas gland, rete mirabile (parallel capillary countercurrent system), and pneumatic duct or oval release area.

• Function: Regulates buoyancy via gas secretion/absorption, utilizing the Root and Bohr effects to concentrate oxygen against gradients.

What is the structure and function of the fish lateral line system?

• Structure: A system of fluid-filled canals containing neuromast organs with cupulae and sensory hair cells connected to nerve fibers.

• Function: Detects water movement, pressure changes, and vibrations in the surrounding environment

What is the basic breeding behavior of most seabirds?

• Colonial breeding: Over 95% nest in dense colonies.

• Monogamy and displays: They are typically monogamous and rely on elaborate courtship displays.

• Protected nesting sites: They choose crowded, predator-free locations (like remote islands or cliffs) to raise their young.

What is the structure and function of salt glands in seabirds?

• Structure: Nasal salt glands containing secretory tubules, transport epithelia, and a countercurrent blood-flow arrangement.

• Function: Secretes excess concentrated salt ions from ingested seawater, allowing seabirds to survive without access to fresh water.