Transcript Worms

Worms and Mollusks
Platyhelminthes: Flatworms
Nemotoda: Roundworms
Annelida: Annelids
Mollusca: Mollusks
Worm Body Structures
Phylum Platyhelminthes:
Flatworms
Phylum Platyhelminthes:
Flatworms
1. Unique
Characteristics
• Soft flattened worms
2. Body Symmetry
•
Bilateral symmetry
with head and tail
Flatworms (cont.)
3. Feeding
Behavior
• Most are free
living carnivores
or scavengers
• Some are
parasites – absorb
nutrients from
host
Flatworms (cont.)
4. Reproduction
• Sexual hermaphrodites
(have male and
female parts)
• Asexual - fission
(cut worm and each
piece grows)
Flatworms (cont.)
5. Specialization and Body Structure
• One opening – eat and excrete through it
• Simplest organisms to have 3 tissue
layers
• Acoelomates – no body cavity
Anatomy of a Flatworm
Eyespot
Ganglia
Head
Nerve
cords
Gastrovascular
cavity
Flatworms use a pharynx to suck
food into the gastrovascular
cavity. Digested food diffuses
from the cavity into other cells of
the body. Eyespots in some
species detect light.
Mouth
Excretory
system
Freshwater flatworms have
simple ganglia and nerve
cords that run the length of
the body. The excretory
system consists of a network
of tubules connected to flame
cells that remove excess
water and cell wastes.
Ovary
Testes
Pharynx
Most flatworms are
hermaphrodites, having male
reproductive organs (testes)
and female reproductive
organs (ovaries) in the same
organism.
Flame cell
Excretory
tubule
Groups of Flatworms
6. Examples
• Planarians
(Turbellaria)
–
•
Flukes (Trematoda)
–
•
Free living in water
Parasitic, infect
internal organs
Tapeworms
(Cestoda)
–
Long, flat, parasitic
Flatworms can cause illness…
Children with blood
flukes.
Tapeworms
Phylum Nematoda:
Roundworms
Phylum Nematoda:
Roundworms
1. Unique
Characteristics
• Slender worms
with tapering
ends, no
segments
2. Symmetry
• Bilateral
Roundworms (cont.)
3. Feeding
Behavior
• Carnivores,
parasites, or
detritivores
• Free-living or
parasitic
4. Reproduction
• Sexual - most
have separate
males and females
Roundworms (cont.)
5. Specialization and Body Structure
• Two openings – tube within tube
• Psuedocoelomates
– 3 tissue layers
and false body
cavity
Parasitic roundworms
6.
•
•
•
•
Examples
Trichnosis (meat)
Heartworm (dogs)
Ascaris - live in
host’s intestines;
causes severe
malnutrition
Hookworms - suck
host’s blood from
the intestines & the
lungs
Heartworm, a filarial worm
Dracunculus medinensis:
Guinea Worm
• Filarial nematode
• Ingest larvae, worm
grows and migrates to
skin
Wuchereria bancrofti
•
•Filarial
roundworm
•Causes
Elephantiasis
Human intestinal roundworm:
Ascaris lumbricoides
• A large and common
human parasite
• Up to 18 inches long
• 25 percent of world's
population infected
• Adult worms live in
small intestine & eggs
passed in feces
• Single female produces
up to 200,000 eggs daily
Hookworm
• 25% of people in the
world have this
• Eggs hatch & develop
in soil
• Enter unprotected
skin & travel to
intestines
Phylum Annelida: Annelids
“Little Ring”
Phylum Annelida: Annelids
1. Unique
Characteristics
• Segmented
bodies separated
by septa
• Help to aerate
soil
• Most advanced
worms
2. Symmetry
• Bilateral
Annelids (cont.)
3. Feeding Behavior
• Filter feeders to
external parasites
4. Reproduction
•
Sexual reproduction:
hermaphrodites that
do not self-fertilize
or separate sexes
Annelids (cont.)
5. Specialization
and Body
Structure
•
•
Complex organ
systems
Coelomates with
2 openings
(simplest animals
with true coelom)
Groups of Annelids
6. Examples
•
Earthworms - live in soil,
fresh water
•
Leeches - suck blood and
body fluids
•
Polychaetes - marine
Oligochaetes: Earthworms
• Burrow, aerate, and
mix soil
• Food source
• Feces = fertilizer
Earthworm Anatomy
Anus
Setae
Body segments
Gizzard Crop
Dorsal
blood vessel
Clitellum
Mouth
Brain
Ganglion
Circular muscle
Longitudinal
muscle
Nephridia
Ganglia
Ring
vessels
Reproductive
organs
Ventral
blood vessel
Leeches
• Can suck up to five
times their own
weight in blood
• Used medicinally
• Secrete a fluid to
prevent blood from
clotting
Polychaetes
Comparing Flatworms, Roundworms,
and Annelids
CHARACTERISTIC
FLATWORMS
ROUNDWORMS
ANNELIDS
Shape
Flattened
Cylindrical with tapering
ends
Cylindrical with tapering
ends
Segmentation
No
No
Yes
Body cavity
Acoelomate
Pseudocoelomate
Coelomate
Digestion and
excretion
Gastrovascular cavity with
one opening only; flame
cells remove metabolic
wastes
Tube-within-a-tube
digestive tract; opening at
each end; metabolic
wastes excreted through
body wall
Tube-within-a-tube
digestive tract; opening at
each end; nephridia
remove metabolic wastes
Respiration
Through skin; no
respiratory organs
Through skin; no
respiratory organs
Through skin; aquatic
annelids breathe through
gills
Comparing Flatworms, Roundworms,
and Annelids
Comparing Flatworms, Roundworms, and Annelids
CHARACTERISTIC
FLATWORMS
ROUNDWORMS
ANNELIDS
Circulation
No heart, blood vessels,
or blood
No heart, blood vessels,
or blood
Blood circulated through
blood vessels in closed
circulatory system
Response
Simple brain; nerve cords
run length of body;
eyespot and other
specialized cells that
detect stimuli
Several ganglia in head
region; nerve cords run
length of body; several
types of sense organs
Well-developed nervous
system with brain and
several nerve cords; many
sense organs
Movement
Gliding, twisting,
and turning
Thrashing
Forward peristaltic
movement
Reproduction
Sexual (hermaphrodites);
asexual (fission)
Sexual (primary males and
females)
Sexual (some are
hermaphrodites; some
have separate sexes)
Phylum Mollusca: Molluscs
Molluscus = ‘soft’
Q:Why are clams,
squids, snails, slugs,
and octopi in the same
family??
A:They share similar
developmental
stages!!
Phylum Mollusca: Molluscs
1. Unique
Characteristics
• Soft-bodied
animals with
internal or external
shell secreted by a
mantle
• Live in aquatic
environments
Molluscs (cont.)
• Body plan
– Muscular foot (to
move)
– Shell (not present in
some)
– Radula (in snails and
slugs) to eat
Mollusk Body Plan
Squid
Snail
Shell
Mantle cavity
Foot
Clam
Early
mollusk
Gills
Digestive tract
Shell Formation
Molluscs (cont.)
Symmetry – Bilateral
Feeding Behavior
Some filter feed (clams, oysters, mussels)
Some feed using a radula, a rough edged
tongue used to scrape up food (snails, slugs)
4. Reproduction
• Sexual - external fertilization
5. Specialization and Body Structure
• Coelomate
2.
3.
•
•
Groups of Molluscs
6. Examples
• Gastropods (snails, slugs)
– Use foot to move; 1 shell or
no shell
•
Bivalves (clams, oysters)
– Two shells held together by
muscles
•
Cephalopods (octopi,
squid)
– Soft-bodies with head
attached to one foot
– Foot divided into tentacles
or arms