Bio 11 - Worms

I indeed do have a feeling that we may be cooked , one might even say cremated

What are Platyhelminthes (6)

• Simple animals

• Flatworms + unsegmented worms

• 2 types of living:

  • Free-living aquatic

    • Planarians

  • Parasite

    • Flukes

    • Tapeworms

• Bilateral symmetry

• Some cephalization

  • Has a head

• Specialized organs + tissues

  • More than sponges + cnidarians

Platyhelminthes Structure (11)

• Brain

• Eyespots/Ocelli

• Nerve cord

  • Free-living aquatic

• Mouth

  • Not in tapeworms

• Pharynx

• Gastrovascular cavity

• Ovary

• Oviducts

• Penis

• Testis

• Flame cells

  • Aquatic

Platyhelminthes Feeding/Digestive System (3) (3)

FREE-LIVING AQUATIC

• Carnivores/scavengers

• Nutrients move w/ diffusion

  • Intestine → body

• Waste leaves via mouth

PARASITES

• Hooks/suckers grab host (anterior end)

  • TAPEWORMS ≠ MOUTH

• Eats blood, tissue fluids, host body cells

  • Can also absorb food from host

• Dead-end intestinal sacs

  • TAPEWORM ≠ DIGESTIVE SYSTEM

Platyhelminthes Internal Transport (3)

• DOESN’T EXIST

• Diffuses through skin (cuz they’re so flat)

  • Transports O₂ + nutrients

  • Waste diffuses out too

• Flame cells: Specialized cells that removes extra H₂O

  • AQUATIC ONLY

Platyhelminthes Nervous System (7) (1)

FREE-LIVING:

• More complex

• Simple brain

• Nerve cords

  • From brain → end of body

  • Short cords go across

    • Connects long ones

• 1+ pair of ocelli

• Cells = sensitive to food chem.

• Cells = senses direction of water flow

  • HATES currents, LIKES still

    • Will swim away if current is too strong

• Gathers info on environment (response)

PARASITE:

• Don’t need

  • Some have none (tapeworms)

Platyhelminthes Movement (2)

• Cilia on epidermal cells

  • Swims in H₂O

  • Glides on surfaces

• Muscle cells = twisting + turning

Platyhelminthes Reproduction (2) (2) (1)

• Sexual/Asexual

  • Ace = aquatic only

• Most = hermaphrodites

AQUATIC

• Sexual = One lays eggs + other fertilizes

• Asexual = Fission/fragmentation (total regen)

PARASITES

• Sexual ONLY

  • Different in flukes + tapeworms

Platyhelminthes Reproduction - Flukes (1) (4)

FLUKES

• Involves snail + main host

  • Snail eaten by host or larvae leaves to infect

Blood Fluke:

• Larvae in snail

• Swimming larvae → main host

  • Lives in blood

• Lays eggs + bursts blood cells

• Eggs fertilized + releases larvae

  • Infects intermediate host (snail)

Platyhelminthes Reproduction - Tapeworms (5)

TAPEWORMS

• Involves mammal + intermediate host

• Sperm (testis) → Eggs (proglottids [same/diff worm])

  • Single proglottid = >100,000 eggs

• Proglottid burst/break = eggs released

  • Goes to intestine/host feces

• Food/H₂O w/ eggs = eaten by intermediate host

  • Hatches to larvae → cyst (dormant stage)

• Raw/undercooked meat w/ cysts = larvae active

  • Latches to intestine w/ suckers + hooks

What are Nematodes (7)

• Most abundant animal on earth

  • ~80% of all animals

    • 60 billion worms per person

• Unsegmented roundworms

• Bilateral symmetry

• Barely any cephalization

• Simplest animal w/ digestive system

  • 2 openings (mouth + anus)

• Mostly free-living

  • Can be parasitic too

• Found virtually everywhere

  • Ex. Soil, salt flats, polar regions

Nematoda Structures (6) (2)

• Mouth

• Ganglia

• Nerves

• Intestine

• Reproductive organs (male/female)

• Anus

• Female = big

  • Tail curves a bit ventrally

• Male = small

  • Tail curves a lot ventrally

Nematoda Feeding (4)

• Long tubular digestive tract

• Food → mouth → anus

• Free-living = carnivores but can eat other things

  • Algae

  • Fungi

  • Detritus

  • Protists

  • Bacteria

• Can be parasitic to plants + animals

  • Plant parasites like tomato plants

Nematoda Internal Transport + Excretion (2)

• No internal transport

  • Breathe + remove waste w/ diffusion

    • Betw. intestine + rest of worm

• Waste → anus

  • Excretory system

Nematoda Nervous System (4)

• Simple

• Several ganglia but no brain

• Several sense organs

  • Detects chem. from prey/hosts

• Nerves run down body

  • Controls movement

Nematoda Musculoskeletal (4)

• Muscles run in strips down body walls

• Aquatic: contracts like snakes (slithers)

• Soil-dwelling: thrashes to displace dirt

• Controlled by nerves

Nematoda Reproduction (4)

• Sexual ONLY

• Sex = separate

  • Some species = hermaphrodites

• Fertilization = inside females

• Parasitic = more complex cycles

  • Can go through 2-3 hosts before maturity

  • Sometimes uses different organs in same host

Examples of Nematoda (3) (4) (4)

Ascaris:

• Parasitic roundworms in humans

• Closely related species in other mammals

• Lives in intestines
  

Life cycle:

• Eggs leave via feces

• Intestines → Blood vessels → Lungs

• Breaks out of lungs

• Climbs throat + swallowed

C. Elegans:

• Free-living, transparent nematode

• Mostly hermaphrodites

• First to have entire genome sequenced

• Easy model due to simple nervous system + transparency

What are Annelids (4)

• Round + worm-like

  • Not all are worms

• Long segmented body

  • Separated by septa/septum

  • Most segments = identical

• Ranges from tiny aquatic worms → Giant earthworms

  • Up to 60cm long (earthworms)

• Few have special functions

  • Ex. Eyes, antennae, other sensory organs

Annelida Feeding (3) (2) (1)

PHARNYX (varies w/ species)

• Can extend through mouth

• Carnivore + herbivores = 2+ jaws

  • Attached to pharynx

  • Extends when hunting/eating

• Detritus feeder = sticky mucus sticks to food

  • Can also act as pump to suck soil + detritus
    
    

• Long tubular digestive tract/gut

  • Extends from mouth → anus

• Food enters mouth

  • My Parrot Eats Chilled Grapes Instead of Apples

    • Mouth → Pharynx → Esophagus → Crop → Gizzard → Intestine → Anus
      
      

• Can be filter feeders

  • Filters H₂O in tubular burrow

    • Catches food in mucus bag

  • Or first segment = featherlike structure

    • Filters food from H₂O

Annelida Structures (16)

• Mouth

• Pharynx

• Esophagus

• Crop

• Gizzard

• Intestine

• Anus

• Brain

• Ventral nerve cord

• Dorsal/Ventral blood vessel

• Hearts

• Longitudinal muscle

• Circular muscle

• Nephridia

• Septa

• Clitellum

Annelida Respiration (2)

• Aquatic = gills

• Terrestrial = breathe through skin (Absorb O₂ + expel CO₂)

  • Mucus layer to retain H₂O/moisture

    • Cuticle

Annelida Internal Transport (4)

• Closed circulatory system

• 2 main vessels

  • Dorsal = blood → Anterior

  • Ventral = blood → Posterior

• Ring vessels connect D + V vessel

  • In each septa

• Some anterior ring vessel = large w/ muscle tissue

  • Called hearts

    • Pumps blood w/ rhythmic contractions (similar to heartbeat)

Annelida Excretory System (2)

TYPES OF WASTE

• Solid (food)

  • Passes via anus

• Metabolic (cellular metabolism)

  • Passes via nephridia

    • NEPHRIDIA: Simple tubular organs paired in each segment

Annelida Nervous System (4) (3)

• Well developed

• Brain on top of gut

  • Also called cerebral ganglia (excluding earthworms)

• Large nerves wrap around gut

  • Connects brain to ganglia

• Nerves carry messages + help muscle movement

• Marine = best sensory organs

  • Ex. Sensory tentacles, statocysts, chem. receptors, 2+ pairs of eyes

    • Can detect light or barely see (pseudo eyes)

• Non-marine = simple sensory systems + cells

• Earthworms ≠ specialized organs

  • Only have simple sensing cells

Annelida Musculoskeletal System (3)

• 2 major groups

  • Longitudinal muscles (anterior→ posterior)

    • Contract = short + fat

  • Circular muscles (around body)

    • Contract = long + thin

• Aquatic swims w/ muscles

• Terrestrial burrows w/ muscles

Annelida Reproduction (2) (3)

ASEXUAL

• Sometimes used

• Budding

SEXUAL

• Mainly used

• External: Broadcast spawning (aquatic)

• Internal: Hermaphrodites exchange sperm (fertilize each other’s eggs)

  • Clitellum = mucus where gametes are released (during fertilization)

  • Ring falls off to protect eggs

Types of Annelids [basic info] (1)

• 3 types

  • Oligochaeta: earthworms + relatives

    • Few bristles underneath