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Annelids. Phylum Annelida. Class Aelosomata. Class Polychaeta. Class Clitellata. Aelosomata. Marine worms. Subclass Errantia. Subclass Sedentaria. Subclass Oligochaeta. Subclass Hirudinae. earthworms. Leeches. Annelids. Class Polychaeta marine worms segmented

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Phylum annelida
Phylum Annelida

Class

Aelosomata

Class

Polychaeta

Class

Clitellata

Aelosomata

Marine worms

Subclass Errantia

Subclass Sedentaria

Subclass

Oligochaeta

Subclass

Hirudinae

earthworms

Leeches


Annelids

  • Class Polychaeta

    • marine worms

    • segmented

  • Class Clitellata

  • Subclass Oligochaeta

    • earthworms

    • segmented

  • Subclass Hirudinea

    • Leeches

    • segmented


Characteristics

  • Segmentation (metameric body plan)

  • Eucoelomate

  • 15,000 species

  • Closed circulatory system, but no heart

  • Hydrostatic skeleton

  • Excretion- protonephridia, metanephridia, diffusion or gills

  • Simple gut

  • Respiration- diffusion or gills

  • Central nervous system- brain and nerve cord

  • Reproduction- asexual or sexual (many gonochoric)

  • Sensory system of tactile organs, taste buds, statocysts,photoreceptor cells, and eyes with lenses.


Subclass Oligochaeta

  • Lack parapodia and have few setae

  • Lack the distinctive head region of polychaetes and have no eyes.

  • Scavengers that consume soil that contains organic matter

  • The ingested soil moves into a storage chamber called the crop, then to an area called the gizzard, where grinding action breaks down the soil particles. Undigested material passes out the anus in a form called castings, which are prized as soil fertilizer.


Metamerism (segmentation)

  • Each segment is also known as a metamere

  • Each metamere has a parapodia with numerous setae

parapod

chaetae


Body cavities

gut

Body Cavities

Mesoderm

coelom

Eucoelomate- body cavity completely lined with mesoderm

Ectoderm

Endoderm


Hydrostatic skeleton
Hydrostatic Skeleton

EarthwormPhylum Annelida




  • Nervous System and Behavior

  • A mass of ganglia (neural masses) forms an anterior brain that is usually dorsal to thepharynx.

  • They have either a pair of ventral nerve cords(primitive) or a single ventral nerve cord that runsthe length of the body.

  • Each segment has a swelling of the nerve cord called a segmental ganglion.

  • Sensory receptors include: chemoreceptors, touchreceptors, photoreceptors, statocysts and vibration receptors.

  • Behaviors vary depending on class/life style.



Digestive System

Esophagus

Gizzard

Pharynx

Crop

Buccal cavity

Intestine

Mouth


Reproductive System

Seminal

vesicle

Ovary

Testes

Egg funnel

and oviduct

Sperm duct

Seminal receptacle




Subclass Hirudinea

  • Leeches

  • Most live in fresh bodies of water, but some live among moist vegetation.

  • Suckers found on both ends

  • Unlike other annelids, its segments are not separated internally

  • Leeches lack both setae and parapodia

  • Most are predators or scavengers. Very few are parasites.

  • They secrete anticoagulants, hirudin, to keep blood from clotting and anesthetic that prevents the host from feeling their presence.




Class Polychaeta

  • Largest group of annelids

  • Primarily marine

  • Most segments include a pair of paddle–like parapodia

  • Well-developed head with eyes and other sensory structures


Class Polychaeta

Subclass Sedentaria

  • Fan worms,

  • Christmas-tree worms

  • Spaghetti worms

  • Chaetopterus

  • lugworms

  • Subclass Errantia

  • Sand worms,

  • Scale worms

  • Fire worms

  • palolo worms


Featherduster worms
featherduster worms

Subclass Sedentaria


Lugworm
Lugworm

Subclass Sedentaria


Chaeopteris
Chaeopteris

Subclass Sedentaria


Spaghetti worm
Spaghetti worm

Lanice conchilega

  • Hawaii has 11 species

  • 5 are endemic

Subclass Sedentaria


Christmas tree worms
Christmas tree worms

Spirobranchus giganteus

Subclass Sedentaria


Scale worm
Scale worm

Subclass Errantia


Fire worm
Fire worm

Eurythoe complanata

Subclass Errantia



Parapodia- movement and respiration