Bio 11 - Mollusca, Arthropoda, Echinoderm

HOW IS THIS WORSE THAN WORMS?????????

What are Mollusks (5)

• Soft-bodied animals w/ internal/external shell

• Specific developmental patterns

• Special kind of larvae (trochophores)

  • Swims in open water

  • Eats floating plants

• >100K species

• 3 main groups

  • Bivalves

  • Gastropods

  • Cephalopods

Examples of Mollusks (5) (4) (4)

BIVALVIA

• Abalone

• Clams

• Oysters

• Mussel

• Scallops

GASTROPODA

• Land slug

• Pond snail

• Nudibranch

• Sea butterfly

CEPHALOPODA

• Octopus

• Cuttlefish

• Nautilus

• Squid

Basic Mollusk Structures (4) (6)

FOUND IN ALL

• Foot

• Mantle

• Shell

• Visceral mass

FOUND IN MOST

• Radula

• Gills/modified mantle cavity

• Mouth

• Anus

• Nephridia

• Vessel/sinuses

Foot (M) (2)

• Soft muscular structure

• Usually has mouth + feeding structures

Mantle (M) (2)

• Thin delicate tissue layer

• Covers most of body like cloak

Shell (M) (2)

• Made by glands in mantle

• Secretes CaCO₃

Visceral Mass (M) (2)

• Under mantle

• Contains internal organs

Radula (M) (2)

• Flexible skin

• Has stiff cartilage rod

  • Covered in tiny teeth

Gills (M) (3)

• Aquatic animals

  • Ex. Octopi, snails, clams

• Inside mantle cavity

• Animals = smaller cavities

Modified Mantle Cavity (M) (5)

• Terrestrial animals

• Folded to fit larger surface in space

• Lined w/ blood vessels

• Requires moisture

  • O₂ → cells

• Lives in moist environments

  • Or is only active when moisture present

Mollusk Feeding (1) (2) (3) (2)

• Uses radula or gills

  • Pulls in + grinds food on cartilage w/ tip of radula

HERBIVORE

• Radula scrapes food off surfaces

• Eats buds, roots, flowers, algae

CARNIVORE

• Radula drills through shells

  • Extends mouth, rips apart + swallows

• Some = poisonous glands

• Octopi + slugs = jaws to help

FILTER FEEDERS

• Gills filter food from H₂O

• Phytoplankton sticks on mucus layer

  • Food → mouth via cilia on gills

Mollusk Respiration (3)

• Uses gills

• Aquatic = inside mantle cavity

• Terrestrial = modified mantle cavity

  • Moves when moisture in air

    • Ex. Night, rainstorms

Mollusk Internal Transport (3) (3)

CLOSED SYSTEM	OPEN SYSTEM
Blood circulates in network of vessels	Blood circulates in sinuses
Slow/sessile (Bivalves, Gastropods)	Fast/efficient (cephalopods)
Blood travels in closed loop	Blood flows in open spaces (blood transports to tissues easier)

Mollusk Excretion (3)

• One-way digestive tract

• Food = solid waste

  • Anus

• Cellular metabolism = poisonous NH₃

  • Nephridia

Mollusk Nervous System (1)

• Varies in complexity

  • Cephalopods > Gastropods > Bivalves

    • Cephalopods = more complex than some vertebrates

Bivalve Structures (2)

• Ganglia

  • Near mouth

• Nerve cords

• Ocelli

• Statocysts

• Chem. + touch receptors

Gastropod Structures (5)

• Ganglia

  • In head

• Nerve cords

• Simple eyes

  • Upper tentacles

• Statocysts

• Chem. + touch sensing

  • Lower tentacles

Cephalopod Structures (7)

• Brain

• Nerve cords

• Complex eyes

• Statocysts

• Tentacles w/ nerve rings

• Excellent memory

• Trainable behaviours

Mollusk Reproduction (5)

• Most = separate sexes

• Some hermaphrodites

  • Some can switch sexes

• Most = external fertilization

  • Broadcast spawning

• Tentacled = internal fertilization

  • Inside female

• Hermaphrodites fertilize each other

Types of Mollusks (2) (3) (2)

GASTROPODS

• One-piece shell

  • Protects body

• Defensive behaviour

  • Hiding/rapid movement

BIVALVES

• Hinged shells

• Free-swimming larvae

• Usually sessile adults

  • Once shell develops

CEPHALOPODS

• Small internal shells or none

• 8+ tentacles

  • Suckers to grab prey

What are Arthropods (4)

• Millions of species

• Wide diversity (habitat, size, shape)

  • From key adaptive radiation

• Some aquatic

• 4 subphyla

  • Trilobita

    • Oldest

  • Chelicerata

  • Crustacea

  • Uniramia

    • Most abundant

Trilobita (5) (1)

• Ancient marine animals

  • Extinct

• Oldest subphylum

• Thick coating

• Many segments

  • Pair of appendages on each one

    • Leg + gill

• 2 trends in descendants

  • Fewer segments

  • Appendages = specialized

    • Feeding, movement, etc

EXAMPLES:

• Trilobite

Chelicerata (4) (2)

• Spiders + relatives

• 2 segments

  • Cephalothorax, abdomen

• 2 pairs of mouthparts

  • Special chelicerae

  • Longer pedipalps

• Forms societies

  • Each member = special role

    • Divides labour

EXAMPLES

• Red velvet mite

• Wolf spider

Crustacea (4) (2)

• Crustaceans

• 2 segments

  • Cephalothorax, abdomen

• 3 pairs of appendages (anterior)

  • Antennae

  • Mandibles

    • Short + heavy = grinds

    • Bristles = filters

• Exoskeleton = CaCO₃

EXAMPLES

• Barnacle

• Mantis shrimp

Uniramia (7) (2)

• Insects

• Makes up most of phylum

• 3 segments

  • Head, thorax, abdomen

  • Thorax = 3 pairs of legs, 2 pairs wings

• Pair of antennae

• Appendages don’t branch (not specialized)

• Varied feeding mandibles

• Social communication

  • Noise, pheromones, movement (waggle/round dance)

EXAMPLES

• Centipede

• Peacock butterfly

Arthropod Structures (3) (15)

KEY FEATURES

• Tough exoskeleton

• Jointed appendages

• Segmented body

OTHER STUFF

• Head

• Antennae

• Compound eyes

• Brain

• Thorax

• Digestive tract

• Nerve cord

• Walking legs

• Wings

• Abdomen

• Reproductive organs

• Tracheal tube

• Malpighian tubules

• Spiracle

• Heart

Exoskeleton (A) (4) (3)

• External supporting structure

  • Made of chitin

• Ranges from flexible → hard

  • Hard = protection

• Terrestrial = waterproof

  • Restricts water-loss

    • Lives in dry environments

• Doesn’t grow with animal

  • Needs to shed/molt

MOLTING

• Epidermis digests inner layer

  • Absorbs + recycles chitin

• Eats the molt

• New soft exoskeleton stretches + hardens over time

  • Soft = vulnerable

Jointed Appendages (A) (1)

• Allows movement + special functions

  • Ex. Antennae, claws, walking legs, wings, flippers

Segmented Bodies (A) (3)

• Sectioned body

  • Section = different structures

• Some = many visible segments

  • Centipedes + millipedes

• Some = fused segments

  • Makes larger body parts

Arthropod Feeding (1) (2) (2) (1) (2) (2)

• Wide diversity = different structures + diets

HERBIVORES

• Some = variety of plants

• Some = only one

CARNIVORES

• Some hunt other animals

• Some scavenge fresh corpses

EXTERNAL PARASITES

• Eats blood, body fluid, skin

INTERNAL PARASITES

• Passively absorbs nutrients

• Eats host internally

FILTER FEEDERS

• Marine animals

• Bristles on mouthparts

  • Filters tiny plants + animals

Arthopod Respiration (4)

• 3 types

  • Gills

  • Book gills/lungs

  • Tracheal tubes

• Most only have 1

• Some = book lungs + tracheal tubes

• Some have none

Gills (A) (4)

• Marine

  • Most of crustacea

• Feather-like rows under exoskeleton

• Same genetic code as mouthparts

• Mouth movement = constant water flow over gills

Book Gills/Lungs (A) (3)

• Book organs = tissue layered like book

  • More surface area = more efficient breathing

• Book gills = horseshoe crab

  • Under body

• Book lungs = ONLY chelicerata

  • In special sac

  • Connects to outside via spiracles

Tracheal Tubes (A) (5)

• Most terrestrial arthropods

  • Chelicerata + uniramia

• Spiracles = tracheal tubes (long + branches) → tissues

• Diffusion = O₂ → tissues

• Movement = tubes contract + relax

  • Pumps air through spiracles

• Only small animals

  • Not efficient for large animals

Arthropod Internal Transport (4)

• Open system

  • Heart pumps blood → arteries → small vessels

  • Blood → sinuses → tissues (direct access)

  • Sinuses → around heart → into heart via small openings

• Well-developed heart

• Spiders/insects = long + narrow heart

  • Stretches length of abdomen

• Lobsters/crayfish = smaller heart

  • Between thorax + abdomen

Arthropod Excretion (3)

• Undigested food → solid waste → anus

• Terrestrial = Concentrates + combines N₂ + solid waste

• Some aquatic = Green glands near antennae

  • Collects + empties via openings near head

Arthropod Brain (4)

• Most = well developed

• Brain = pair of ganglia

• Pair of nerves = down body → around esophagus

• Ganglia along nerve cords (one per segment)

  • Mini brains

  • Fused segments = multiple ganglia per segment

Arthropod Sense Organs (4) (theres a lot dont let it deceive you)

• Simple sense organ = Statocysts, chem receptors

• Complex sense organ = compound eyes (UV vision)

  • Up to 2000 lenses

  • SIMPLE: shapes + motion

  • COMPLEX: colour + motion

• Crustaceans + insects = sense of taste

  • Can have preferences

  • Taste + smell receptors on mouth/ antennae + legs

  • Sensory hairs detects movement in air/water

• Well developed ears

  • Hears above human range

  • Ear drums = weird places

    • Grasshopper = behind legs

Arthropod Defenses (5)

• Sense organs = detect + evade predators

• Venomous stings/bites, powerful claws, other chem. defense

• Crabs drop limbs to distract

  • Regens after

• Visual trickery = camouflage

• Mimicry = copies colours of venomous/poisonous species

Arthropod Musculoskeletal System (4)

• Well developed muscles

  • Coordinated by nervous system

• Muscles = flex + extend

• Contraction = force made → exoskeleton

• Has joints

Arthropod Reproduction (3) (3) (2)

• Sexual

• Male + female ONLY

• Internal fertilization

SPIDERS + SOME CRUSTACEANS

• Male deposits sperm package

• Female picks it up

• Self fertilization

MOST INSECTS + CRUSTACEANS

• Special reproductive organ

• Deposits sperm into female

Arthropod Development (3) (3) (3)

• Mainly metamorphosis

• Low juvenile hormone = molting slows

  • Larvae → pupa

• Plant defense = chemicals that slows growth + dev.

  • Stops molting

DIRECT DEVELOPMENT

• INCOMPLETE metamorphosis

  • Doesn’t need to develop as much

• Eggs → young animal

• Young = no functional sex organs

INDIRECT DEVELOPMENT

• COMPLETE metamorphosis

  • 4 stages

• Eggs → larvae

• Molts multiple times → pupa

  • Rearranges body → adult structure

    • Ex. cocoon → butterfly

What are Echinoderms (6)

• Spiny-skinned animals

• 5-part radial symmetry

• Variety of species

  • Starfish, sand dollars, sea urchins, sea cucumbers

• Endoskeleton = plates of CaCO₃

• Water vascular system pumps H₂O in + out of tube feet

  • H₂O enter = foot expands

  • H₂O exit = foot contracts

    • Makes suction

• Tube feet (like suction-cups)

  • External structures for various functions

Echinoderm Body Plan (4)

• 5-part radial symmetry

• Oral (mouth) + aboral (no mouth) instead of anterior + posterior

• Water vascular system exposed via madreporite

  • Starfish: madreporite connects to ring canal around digestive system

• Radial canals connect ring canal → body segments + tube feet

Echinoderm Structures

• Endoskeleton

• Water vascular system

• Tube feet

• Radial canal

• Body cavity

• Madreporite

• Ring canal

• Upper + Lower stomach

• Digestive gland

• Anus

Echinoderm Feeding (4) (2) (2) (2)

CARNIVORES

• Tube feet pry open shells of prey (mollusks)

• Stomach exits mouth

• Digests prey in shell + returns

• Ex. Starfish

HERBIVORES

• Scrapes algae from rock w/ 5-part jaw

• Ex. Sea urchin
  

FILTER FEEDERS

• Waves tube feet around

  • Catches floating plankton

• Ex. Brittle stars + sea lilies
  

DETRITUS FEEDERS

• Sea roomba on ocean floor

  • Takes in sand + detritus

  • Sand → feces

• Ex. Sea cucumber

Echinoderm Respiration (3)

• Trades CO₂ for O₂

• Tube feet = main resp. organ

  • Thin-walled tissue

  • Gasses diffuse here

• Some = skin glands

Echinoderm Internal Transport (4)

• NONE

• Shared betw. other systems

• Digestive glands + body cavity fluid = nutrient circulation

• Water vascular system = circulates H₂O, gasses, + minerals

  • Carries metabolic waste → tube feet

    • Diffuses out via gills/tube feet

Echinoderm Excretion (2)

• Solid waste (feces) → anus (aboral)

  • Brittle stars = no anus → uses mouth

• Metabolic waste diffuses out gills/feet w/ gas trade

Echinoderm Nervous System (5)

• NOT well-developed

  • Small ganglia

  • Radial nerves + nerve rings around mouth

• Sensory cells react to food chem.

  • Scattered everywhere

• Starfish = eyespots on arm ends

  • Light-sensing + made of 200+ cells

    • Light + dark only

• Sometimes = statocysts

• Hides from predators in crevasses

  • Helpless if flipped (tube feet up)

Echinoderm Musculoskeletal (2) (2) (2) (2)

• Thin muscles on endoskeleton helps movement

• Moves w/ tube feet (suctions)

SAND DOLLARS + URCHINS

• Rigid box of fused plates

• Creeps + burrows

STARFISH + RELATIVES

• Plates around flexible joints

• Crawls

  • Some can swim periodically

SEA CUCUMBERS

• Vestigial plates = free movement

• Crawls like big worm

Echinoderm Reproduction (2) (2) (2)

• Sexual + asexual

• Mostly male-female

  • Some hermaphrodites

SEXUAL

• Broadcast spawning

• Larvae = free-living before metamorphosis

  • Develops externally

ASEXUAL

• Regenerates

  • Regrow limbs or regrow body

• Ex. Starfish