planeria and flatworm Flashcards
Platyhelminthes Characteristics
- Bilateral Symmetry: head and tail region
- move with a sense of direction
- primitive hunters
Platyhelminthes are
- triploblastic: ectoderm, endoderm, and mesoderm which builds the muscular, excretory, and reproductive systems.
- acoelomates: no body cavity. body filled systems with cells.
Platyhelminthes: true organs
- rudimentary digestion and excretory system
- flattened dorsal-ventrally
- cephalization (concentration of sensory structures and nerves at the anterior end)
look at diagram of planarian
- eyespots
- pharynx
- ventral surface
- dorsal surface
Flatworm Circulatory/Respiratory system
- no true circulatory or respiratory system
- respire by diffusion (shape maximizes surface area)
- gasses diffuse directly across moist outer surface
Digestive System of Flatworm:
- free living Platyhelminthes
- Blind digestive tract: only one opening (no anus)
- Parasitic Platyhelminthes
- Feed on tissues and fluids form host
- Have suckers or hooks to attach to host
Flatworm Excretory System
- Removes metabolic wastes
- movement of ciliated cells (flame cells) draws cellular waste away from body cells into tubes leading to external pores
Flatworm Nervous System
- centralized nervous systems: brain+nerve cords
- two cord like nerves that run along the ventral side of the body
- can detect differences in light
- some have light sensitive organs called ocelli
- detects chemicals gradients (auricles) (chemoreception)
- enables them to move towards food
Flatworm reproduction system
- Hermaphroditic: contains both male and female reproductive organs
- Sperm are shed into environment
- Sperm are taken in through a genital pore where ova are fertilized
there are 3 classes of Platyhelminthes
- class Turbellaria (planaria)
- free living
- marine and freshwater
- nervous system - Class Trematoda (parasitic flukes)
- Obligate parasites
- life cycle requires 1-3 hosts
- host usually starts as mollusk then then vertebrate - Class parasite: Endoparasitic (tapeworms)
Tapeworms
- anterior end is a scolex (head)
- lack a brain
- body segments called proglottids (detach from worms carrying fertilized eggs)
- Hermaphroditic: cross fertilize between worms or self fertilize
- no digestive system
- absorbs nutrients through skin
- release waste into surrounding
- requires 1-3 hosts
- reach up to 10-20m
Look at tapeworm diagram life cycle
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The Coelomate
- Coelom: muscle lined body cavity
- chamber for heart and blood vessels complex digestive systems, excretory organs, and organs for gas exchange
Phylum Annelida has how many species
15, 000
Annelids have
- segmented bodies allow for potential specialization.
- Sections containing one or more of a series of repeating anatomical features
3 classes of Phylum ANNELIDA Segmented Worms
- Class Oligochaeta (earth worms)
- Class Polychaeta (tubeworms)
- Class Hirudinea (leeches)
look at earthworms diagram cycle
look
Class Oligochaeta Movement
- Longitudinal and circular muscles line digestive tube and inside of cuticle (coelom) allowing for:
- Movement without affecting digestion
- Ability to move food along digestive tract while stationary
Digestive system of earthworms
-The earthworm eats soil which contains dead plant matter
-Pharynx: muscular enlargement contributing to swallowing of detritus
-Esophagus: peristalsis moves material to crop
-Crop: storage area for material until gizzard has room
-Gizzard: muscular walls and coarse textured interior
• specialized grinding organ
-Intestine: digestive glands secrete enzymes
• Nutrients absorbed along its length
Earthworms Circulatory System
- Closed system: heart and blood vessels
- two major blood vessels (ventral, dorsal)
- Branch into tissues of digestive tract and cuticle
- Runs anteriorly in dorsal/posteriorly in ventral
- Thickened muscular blood vessels act as a heart
- Contract to maintain blood flow
Earthworms Respiration System
- Has no respiratory organ.
- It takes in oxygen directly through its skin and gives off carbon dioxide.
- Its skin secretes mucus to prevent dehydration and suffocation
Earthworm excretory system
- Nephridia: open-ended tubules collect liquid wastes materials
- Excreted through pores in cuticle
- A pair of nephridia are found in each segment of the worm
Earthworm nervous system
Paired ventral nerve cord runs length of worm
- Branches run into tissues of each segment
- Small, bi-lobed brain found on anterior side of pharynx
Reproduction Earthworm System
-Hermaphroditic with testes and ovaries as well as sperm
receptacles and yolk sacs
-During mating, worms line up with ventral sides together
-Clitellum secretes slime to aid sperm transfer
• Sperm receptacles: store sperm
-Ova is released encased in yolk from yolk sac and sperm retained
in receptacles
-Fertilization occurs outside worm in another slime cocoon secreted by clitellum
-Trocophore: Larva develops from zygote, and grows into worms
-Larva resembles larva of mollusks, suggesting evolutionary link
