Marine Bio Lecture 10-13 Quiz

Bilateral Symmetry

organisms that can be divided into two identical halves

Bilateral Symmetry

Drawing Reference: To visualize a bilaterally symmetrical animal, imagine a beetle or a flatworm:

Anterior

The front/head end.

Posterior

The rear/tail end.

Dorsal

The top or back surface.

Ventral

The bottom or belly surface.

Lateral

The sides (right and left).

Evolutionary Advancement of Bilateral Symmetry

It was a "game-changing" advancement that allowed for more complex movement and the development of specialized head regions.

Cephalization

The concentration of sense organs and a nervous system (forming a head and brain) at the anterior end of the body.

Are flatworms dorsoventrally or laterally compressed?

Flatworms are dorsoventrally compressed

Describe the basic nervous system of flatworms.

They have a Central Nervous System (CNS) consisting of a brain, eyes, sensory lobes, and ventrolateral nerve cords

List the 3 tissue layers of flatworms.

They possess three layers: epidermis, mesoderm, and muscles.

Do flatworms have a 1-way or 2-way gut? Where is/are the mouth/anus? 

They have a 2-way gut with a single opening (the mouth) for both food intake and waste

Do flatworms have a body cavity?

No

What is a pharynx? 

The pharynx is a muscular tube that projects from the mouth to swallow prey whole.

What other features do predatory flatworms have to help them feed?

Some predatory species also use a stylet located on the penis to aid in feeding

List 2 important ecological roles of flatworms

Meiofauna

Population Regulation: As parasites, they help regulate host populations.

Meiofauna

They funnel nutrients to larger organisms.

Population Regulation

As parasites, they help regulate host populations.

What marine environments do ribbon worms live in?

soft-sediment environments like mud and sand

Do ribbon worms have body segments?

They have an unsegmented body plan.

What is the structure and function of the proboscis in a ribbon worm?

This is a protrusible jaw used for feeding (predation and scavenging).

List 5 characteristics of the body that define Phylum Annelida (segmented worms).

Bilateral Symmetry, Segmented Body, Coelom, Complete Digestive Tract, Setae (Chaetae)

List distinct features of the body plan of members of Class Polychaeta.

They have a parapodia, setae/chaetae, a head with sensory organs, and protrusible proboscis.

Coelom

A fluid-filled body cavity that is completely lined with tissue derived from the mesoderm

Longitudinal Muscles

Muscles that run the length of the body; when they contract, they make the worm shorter and fatter.

Circular Muscles

Muscles that wrap around the body; when they contract, they make the worm longer and thinner

Parapodia

Paired, fleshy appendages found on the segments of polychaetes, typically used for locomotion

Setae (Chaetae)

Small bristles or hairs found on the body of annelids; they help anchor the worm or assist in movement.

Hydrostatic Skeleton

A system of support in which muscles contract against a fluid-filled body cavity (coelom) to provide rigidity and allow for movement.

Operculum

A hard "trapdoor" or lid used by some tube-dwelling polychaetes to seal their tube for protection.

What type of larvae do Polychaetes have? List 1 other phyla that has this type of larva.

Polychaetes have trochophore larvae. Phylum Mollusca

What does the similarity of trochophore larvae among these different Phyla say about their evolutionary relationship

he similarity of trochophore larvae among these different phyla indicates that they share a common evolutionary ancestor.

List 4 different lifestyles of polychaetes

burrowers, tube-dwellers, holoplankton and symbiotic

Burrowers

Species that live in sediment, either as deposit feeders (like lug worms) or predators (like sandworms).

Tube-dwellers

Species that build and live in protective tubes (e.g., Christmas tree worms) and typically filter-feed.

Holoplankton

Free-swimming species that spend their entire life cycle in the water column (e.g., Tomopteris).

Symbiotic

Species that live in a close association with another organism, often in a commensal relationship.

Where do soft sediment marine ecosystems occur?  

These ecosystems occur in areas where the environment is characterized by a mobile substrate and are impacted by waves and tides.

List 2 major physical constraints of living in a soft sediment marine area

Two major constraints include a mobile substrate and extreme wave and tide impact

What kind of primary producers conduct the majority of photosynthesis in intertidal & shallow subtidal soft sediment ecosystems

benthic bacteria, benthic diatoms, and microscopic algae

Define epifauna. Provide soft sediment examples of each.

Organisms that live on the surface of the sediment (e.g., starfish, snails).

Define infauna. Provide soft sediment examples of each.

Organisms that live buried within the sediment (e.g., clams, polychaete worms).

Define bioturbation. 

The disturbance of sedimentary deposits by living organisms.

How can bioturbation help and how can it harm infauna?

While the slides identify it as an "organism impact," it generally helps by oxygenating deeper sediment layers but can harm some infauna by destabilizing their burrows or burying them

Provide examples of bioturbators in soft sediment ecosystems.

Examples include Grey Whales and various burrowing worms.

How does seagrass help to stabilize the sediments?

Seagrass helps to stabilize sediments with its root systems, preventing erosion and providing a more consistent habitat.

How does trawling impact soft sediment ecosystems?

It is a significant human impact that disrupts and damages soft-bottom ecosystems.

What is an estuary?

A partly enclosed coastal area where freshwater from rivers and seawater from the ocean mix.

What is ‘brackish’ water? 

This is water that is saltier than freshwater but less salty than seawater.

Why is estuarine water brackish?

It occurs in estuaries because of the constant mixing of these two sources driven by tides.

List 5 environmental features of an estuary.

Tidal fluctuation.

Extreme salinity variation.

High sediment load.

Anoxic mud layer.

High nutrient levels.

Briefly describe a salt wedge and state why they occur.

A layer of denser, saltier seawater that flows along the bottom of an estuary underneath the fresher river water. They occur because saltwater is denser than freshwater.

Why do estuaries have high loads of sediments?

estuaries have high loads because rivers carry silt and organic matter that settles as the water velocity slows upon meeting the sea.

What causes mud to become anoxic below the surface?

Mud becomes anoxic (lacking oxygen) below the surface because water cannot flow easily through small particle sizes (mud/silt/clay), causing oxygen to be used up faster than it can be replaced.

What causes the ‘rotten egg smell’ (sulfur) in mudflats?

This is caused by a toxic mud layer resulting from anaerobic bacteria producing hydrogen sulfide in the anoxic sediment.

Describe why estuaries are so biologically productive.

Estuaries are extremely productive due to high nutrient levels, shallow water for light penetration, and the constant export of detritus.

Why do estuaries have low species diversity compared to other ecosystems?

they have low diversity because the environment is very challenging with extreme physical fluctuations that only a few specialized species can tolerate

List 4 ways that estuaries are ecologically & economically important.

Highly productive areas.

Feeding and breeding grounds (nurseries) for many species.

Coastal protection from storms.

Support for commercial fisheries (70-90% of US East Coast catch is estuary-dependent).

Define diffusion

movement of particles from a higher concentration to an area of lower concentration

Define osmosis.

movement of particles across a semipermeable membrane from a lower salinity to a higher salinity

Define osmoconformer & provide a marine example.

internal salinity to match the outside environment. This is dangerous when salinity drops too low, as it can cause their cells to gain too much water and burst.

An example is certain Amphipods.

Define osmoregulation.

The ability of an organism to maintain a constant internal salinity regardless of external changes.

Describe examples of 2 different methods of osmoregulation found in estuarine organisms.  List an organism for each one.

Salt Extraction/Concentration: Marsh grasses like Cordgrass (Spartina) absorb salt or concentrate sugars to manage water balance

Full Osmoregulation: Fishes and some crabs actively pump salts in or out to maintain balance.

List 2 different ways that estuarine organisms can reduce their stress from the environment.

two ways include moving to areas with better conditions or burrowing into the sediment to find more stable salinity and moisture.

What proportion of US estuaries have been destroyed?

38% of all US estuaries have been destroyed; in California, that number is 91%.

List 5 threats to estuary ecosystems.

Dredging for harbors.

Filling in for development.

Dams.

Sea level rise.

Invasive species.

Which phylum contains the most number of species of all phyla on Earth (land & sea together)?

Phylum Arthropoda contains the most number of species of all phyla on Earth (accounting for 75% of all animals).

List the 5 key body plan characteristics that all arthropods share.

• Segmented, flexible body (Head, Thorax, Abdomen).

• Jointed appendages moved by muscles.

• Exoskeleton made of chitin.

• Bilateral Symmetry.

• Ventral nerve cord and Dorsal circulatory system.

How do arthropods grow?

Arthropods grow by molting (shedding their old exoskeleton and growing a new, larger one).

Define autotomy

The voluntary "self-amputation" or dropping of an appendage (legs or claws) to escape a predator.

When can arthropods regenerate lost appendages?

Arthropods can regenerate lost appendages during the molting process.

Crustaceans are specialized for life in __________ and therefore all breathe using _______.

water, gills

How does the exoskeleton of many crustaceans differ from other Arthropods?

Their exoskeleton is often calcified (hardened with calcium carbonate).

Define carapace.

A large, shield-like plate of the exoskeleton that covers the head and thorax.

Which organisms have carapace

crabs, lobsters and shrimp

Do crustaceans broadcast or internally fertilize eggs?

They typically use internal fertilization.

What does the female crustacean do with her eggs?

The female usually carries the eggs (often under her abdomen or "apron") until they hatch.

What 2 features enhance crustacean eyesight?

Eyesight is enhanced by compound eyes and by being placed on movable stalks.

Crustaceans have complex behaviors.  List one way in which they can communicate with each other or other species.

They can communicate through visual displays (e.g., waving claws) or chemical signals (pheromones).

What is a statocyst?  List the function & briefly describe it.

A sensory organ used for balance. It is a fluid-filled chamber containing a "heavy" granule (statolith) that tells the animal which way is up.

Define maxillipeds

Specialized appendages (usually 3 pairs) used for sorting and handling food near the mouth.

Which Crustaceans feed as scavengers?

crabs, lobsters

Which Crustaceans feed as predators?

mantis shrimp and decapods

Which Crustaceans feed as filter feeders?

barnacles, copepods, krill

Which Crustaceans feed as parasites?

certain isopods (fish lice)

Which feeding mode is most common among Crustaceans?

filter feeding

Class Cirripedia (barnacles) are unique crustaceans in that their body has an additional protective covering that consists of _________________________.

heavy calcareous (calcium carbonate) plates

Explain how barnacles feed.

They are filter feeders that use their feathery legs (cirri) to sweep the water for food.

Barnacles are cemented to the substrate, which creates a challenge for reproduction.  What are the 2 ways in which they overcome this challenge?

Being hermaphroditic (having both male and female organs).

Having the largest penis to body size ratio in the animal kingdom to reach neighbors.

Why are humans interested in Class Merostomata (horseshoe crabs)?

because their blue blood (which contains LAL) is used to test medical equipment and vaccines for bacterial contamination.

Which phylum do sea spiders (Class Pycnogonida) feed on?

feed on Cnidarians (like sea anemones and hydrozoans).

List two examples of insects in/on/near marine environments and state where they can be found.

Water Striders (Halobates): Found on the ocean surface (pleuston).

Seaweed Flies: Found in the intertidal zone on decaying seaweed

Describe 5 distinct characteristics of the body plan of echinoderms.

spiny skin, pentamerous radial symmetry, endoskeleton, water vascular system, tube feet

Define endoskeleton.

An internal support structure

Describe the skeleton of echinoderms.

In echinoderms, it consists of calcareous plates (ossicles) that may be fused or embedded in the skin, often supporting protruding spines.

What type of nervous system do echinoderms have?

They have a nerve ring (centralized) with radial nerves extending down each arm/section. They lack a brain.

What are 3 functions of the water vascular system?

locomotion, feeding, gas exchange

Describe how tube feet work. 

They function via a hydrostatic pressure system. Water enters through the madreporite, travels through the canals to the ampulla (a bulb-like sac), which squeezes water into the tube foot to extend it.

Which classes have suckers on their tube feet?

Class Asteroidea (sea stars) and Class Echinoidea (sea urchins/sand dollars).