Biology 102 Quiz 4

What is Mollusc closest related to?

Annelids

What are the 6 defining characteristics of Mollusc?

Shell, mantle, mantle cavity, ventral foot, dorsale visceral mass, radula

Shell

A protective outer layer made of calcium carbonate which sheds

Mantle

A thin layer in-between the visceral mass and the shell

Produces the shell

Chamber where water can be circulated across the gills

Mantle Cavity

In between the visceral mass and mantle

Gills are suspended here

Ventral Foot

Muscular; used for locomotion for generqal mollusc

Dorsal visceral mass

The location of digestive, excretory, and reproductive organs

Radula

Toothed tongue used for mechanical digestion

How many tissue layers do a mollusca have?

Triploblastic (3)

Are molluscs coelomates?

Yes, they have coeloms

Molluscs’ coelom

Cavity which only the heart is located

Hemocoel

Main cavity

Blood filled space surrounding tissues and organs

Related to open circulatory systems

Open circulatory system

Less efficient because of less pressure to pump blood throughout the body fast

Where the blood pours out of the vessels to the hemocoel

Gas exchange is between the blood in hemocoel and the cells

Closed circulatory system

More efficient due to the pressure of the blood

Blood remains in the vessels

Gas exchange is between the blood in the vessels and the cells

Adaptive radiation

rapid evolutionary diversification within one lineage, producing numerous descendants with a wide range of adaptive forms to fit a particular environmental niche

Characteristics for a good specialized gas exchange

• large surface area

• permeable to gases

• thin

• highly vascularized

• moist surface

Gas exchange process for Mollusc: Step 1

Gills

• In mantle cavity

• highly vascularized

• Gives oxygenated blood to the heart

  • in the coelom

Water gives gills O2

Gills give water CO2

Gas exchange process for Mollusc: Step 1

Muscular heart in the coelom

• Blood exits vessel

• Blood enters hemocoel

Blood gives cells O2

Cells give blood CO2

• Deoxygenated blood returns to the gills

Mollusc digestive tract details

Complete with regional specialization

• Radula - mechanical digestion

• Stomach and digestive gland - chemical digestion and absorption

• intestine - absorbs and caries indigestibles to anus

• food waste gets out of anus into the water of the mantle cavity and then surrounding environment

Steps of excretion

Step 1: Unselective Filtration

• Fluid enters kidney

Step 2: Selective Reabsorption

• The useful molecules are reabsorbed into the body

Step 3: Excretion

• Excreted into mantle cavity then surrounding environment

Nitrogenous waste in aquatic animals

Ammonia

Nitrogenous waste in terrestrial animals

Ammonia to urea to uric acid

Bivalvia

Clams, mussels, scallops, oysters

Polyplacaphora

Chitons

Gastropoda

Snails and slugs

Cephalopoda

Squids, octopus, cuttlefish, nautilus

Bivalvia modification: Shell

two pieces called valves

completely covers the animals for protection

Bivalvia cephalization

Lowest

Cephalization

amount of nerves in the head

Labial palps

Food from cilla on gills are sorted by size here

Incurrent siphon

Cilla on gills create current of water flowing in mantle cavity through here

Excurent siphon

Whatever that is not passed to mouth falls into the mantle cavity and is carried out with water leaving the mantle cavity through this

Bivalve feeding strategy

Active suspension feeding

Intestine

Passes indigestible to anus

Bivalve modification: foot

Wedge shaped

to burrow into sand

reduced length

hemocoel as hydroskeleton

• doesn’t move much

Function of gills in bivalves

traps food

has cilla to create water current

Bivalvia modification: head

Very low cephalization

No radula

Bivalvia modification: visceral mass

Compact within valve shells for protection

Bivalvia modification: Mantle

Blankets entire visceral mass

Bivalvia modification: mantle cavity

Large

Water circulated here for filter feeding

Bivalvia circulatory system

Open circulatory system

Circulatory system for Cephalopoda

Closed

• Veins from body carry deoxygenated blood to gill heart

• Gill hearts pump deoxygenated blood to gill

  • one base of each gill

• Gill obtain oxygenated blood

• Goes to systemic heart

• Arteries carry oxygenated blood to all cells

Veins

Carry deoxygenated blood 

• from body to gill hearts

Branchial/Gill hearts

recieve deoxygenated blood from veins and pump it to the gills

Gills

Gas exchange between blood and water in mantle cavity (O2 enters blood, CO2 enters water)

Systemic Heart

vessels carry oxygenated blood from gills to systemic heart which pumps it out to the body

Arteries

carries oxygenated blood from systemic heart to body where O2 moves from blood to cells and CO2 moves from cells to blood

Cephalopoda modification: mantle cavity

Water is taken into here by expansion of the mantle

• all organs in visceral mass is here

• Jet propulsion

• Water pressure build up here

  • Water releases out the funnel/siphon

Cephalopoda modification: mantle

forms outside of body because no shell

Cephalopoda modification: Reproductive System Females

ovary produces eggs

Accessory glands secrete a shell around the egg

gonad is at the top

oviduct opening is in the middle, opposing to anus on the right, shorter side

Attaches egg capsules on sea floor

Cephalopoda modification: Reproductive System Males

testis produces sperm

gonad is at the top

oviduct opening is in the middle, opposing to anus on the right, shorter side

Cephalopoda modification: Reproduction

Male squid deposit pack of sperm in female’s mantle cavity

Female releases eggs in packets and fertilize them with sperm

Eggs are attached to substrate where they develop and hatch

Chromatophore

Camouflage and communication

Pigment sac can be expanded or decreased in size by muscle contraction

Describe nervous system and sensory structures and how that relates to the level of cephalization

Image forming eyes

Large brain

complex nervous system

For active predatory sensing to catch prey

Cephalopoda modification: head

Radula and beak (inside buccal bulb)

• powerful jaws

• grabs and tears pray at large pieces

• Radula grinds smaller pieces

Cephalopoda modification: Esophagus

From the buccal bulb to the stomach

• carries the shredded food to stomach

Cephalopoda modification: Stomach

Stomach secretes digestive enzymes

Cephalopoda modification: Cecum and intestine

Thin walled sac that lies on top of gonads

• digestion and absorption occur here

Food carries onto intestine

• Absorbs and brings food waste to anus

Cephalopoda modification: Ink Sac

Used to escape

Cephalopoda modification: Shell

Called pen

• provides support, stability, and leverage for muscles of mantle

• light so that squids can swim away fast

Cephalopoda modification: Cartilaginous Cranium

Brain is encased here

• for protection

Cephalopoda modification: Stellate Gangila

Control synchronous contraction of muscles of the mantle

Cephalopoda modification: foot

Modified into arms and tentacles to catch prey

Cephalopoda modification: visceral mass

elongated in ventral and dorsal axis

Gastropoda modification: shell

coiled, elongated and raised off of the foot

one piece

can retract into shell for protection

Gastropoda modification: torsion

During development:

rotation of visceral mass and mantle on the foot

• mantle cavity (including anus) moves to the anterior body

  • above the mouth and head

• gut and nervous system are twisted

Gastropoda modification: cephalizatoin

second highest

Gastropoda modification: terrestrial slug gas exchange

No shell

• air enters through pneumostome into lung

  • Lung=vascularized mantle cavity

Gastropoda modification: sensory structures on head

two retractable tentacles on the head

• upper pair have light sensitive eye spots on the ends

• lower pair have receptors for chemical touch

Gastropoda modification: head

Radula

tentacles for senses

• light and chemical sensing

• eyes

Gastropoda modification: foot

large, flat

• used for locomotion

• wave motion

• uses hemocoel as hydroskeleton

Gastropoda modification: Mantle/Mantle Cavity

Either posterior or anterior space where gills or lungs are located (depending on the development)

Polyplacophora environment

Intertidal zone

• low tide

  • exposed to air

• high tide

  • exposed to powerful surf and are underwater

  • sticks to uneven rocky surfaces

Snails vs Slugs

Slugs have no shell, get energy from sunlight

Snails have shell

Polyplacophora modification: foot

Broad, flat, length of animal

adaptive for clinging to rocks

Polyplacophora modification: shell

8 plates, joint to conform to shape of rocks

• helps hold to rocks

Polyplacophora modification: feeding strategy

grazing feeding strategy

Gastropod feeding strategy

Diverse

• herbivore

• carnivory

• deposit feeding

• etc

Polyplacophora modification: cephalization

low level (3rd)

Polyplacophora modification: mantle cavity

Space between outside wall of visceral mass and mantle

• open to environment and contains gills

• gills are located inside two mantle cavities

Polyplacophora modification: mantle

extends past shell

• seals off mantle cavity and visceral mass from environment

• brought down to rocks and foot is raised slightly to make a suction cup when crashing waves

Polyplacophora modification: head

low cephalization

has radula (grazes on algae)

prevents desiccation

Anthropoda clades

ecdysozoa

Mollusca clades

spiralia

Defined success of anthropods

Diversity - millions of identified and many yet to be recognized

Abundance - 90% of all known animal species

Distribution - live in every type of environment

Reasons for anthropod success

• segmentation+tagmatization

• small size

• waxy cuticle layer

• versatile exoskeleton

• excretion of uric acid

• flight

• internal fertilization

tagmatization and diversity

Fusion: segments fuse to form functional groups

Specialization: specialization of appendages associated with different tagmata

• allowed for modifications to suit diverse environments

  • like walking legs, antennae, mouth parts, wings, etc

Anthropod cuticle (location, living, significance)

Waxy outer layer

Non living - chitin

barrier that prevent desiccation - more well developed in terrestrial anthropods

Forms exoskeleton

Anthropod cuticle/exoskeleton functions

shape and support

attachment for muscles for locomotion

protection

prevents water loss

integral part of sensory receptors

Cuticle and contraints on size

1) Molting: squishy stage until exoskeleton hardens

2) exoskeleton weight and strength: the exoskeleton thickness in relation to its body is much heavier

Movement 3 key points

Paired Joint appendages
Anatomoical diversity

used for locomotion

• grasping, defense, mating, etc

Muscles attached to exoskeleton for movement

• arranged in localized bands of muscle

  • antagonist at joints

• inside skeleton

Brain, nerve cord, with segmental ganglia

• concentration of neurons

• ganglion in each segment composed of nerves connected to muscles of appendages and sensory structures in that segment — precise movement

Sensilla

senses things outside of cuticle

Gills (Anthropods - definition and subphylum)

occur between water and blood in the gills ti cells

Happens in crustaceans

Book Gills (Anthropods - description and subphylum)

Layers of gills on ventral side, between water and blood to cells

Happens in chelicerate (horseshoe crab)

Book lungs (anthropods - description and subphylum)

Internal chamber(keeps from drying out) - small opening for air

layers of blood filled parts, between air and blood to cells

Happens in chelicerate (spiders)

Tracheal system (anthropods - description and subphylum)

internal holes called spiracles that leads air to the rest of the body through trachae

between air and cells

Happens in Hexapoda and Myriapoda

Spiracles

small openings in the body to allow air to enter in tracheal system

Tracheae

Series of branching tubes involved with the tracheal system

Are anthropods coelomates

Yes, but coelom is reduced

Main body cavity, circulatory system, digestive system for anthropods

Hemocoel

open circulatory system

complete digestive tract with regional specialization