Monday, April 5, 2010

INVERTEBRATES

BILATERAL INVERTEBRATES

FLATWORM
  • scientific literature as Platyhelminthes or Plathelminthes
  • name of the phylum comes from the Greek platy, meaning "flat," and helminth, meaning "worm," which is indicative of their ribbon-shaped, flattened appearance.
  • the first invertebrates to have a third germ layer, the mesoderm (Towle 1989)


Kingdom: Animalia

Subkingdom: Eumetazoa

Superphylum: Platyzoa

Phylum: Platyhelminthes

characteristics :

  • simple~ soft-bodied

  • bilaterially symmetrical

  • invertebrate animal

  • have no body cavity

  • have a beginnings of a head region

  • no specialized circulatory &respiratory organs which restricts them to flattened

  • shaped~ allow oxygen & nutrients pass their body through diffusion

  • acoelomates~ characterized by having 3 germs layer

structure of flatworm

habitat

  • marine, freshwater, damp terrestial environments

locomotion

  • undulating~ tiny bristles (cilia), help it move as 2 layers of muscles unnder its skin

reproduction

  • both male and female reproductive body parts.

  • able to produces sperm and eggs.

  • Hermaphrodites, able to fertilize themselves (asexual reproduction)

  • able to reproduce sexually with other worms, most common asexual

  • able to produce millions of eggs in a day.

    eggs are found in the rear section of the tape worm. When the eggs are ready to leave the body they break off and are excreted with digested food. The eggs will remain in the feces until another animal swallows it. The eggs cannot survive very long outside a host's body, so if they are not swallowed by another animal they will die.

Digestion

  • A flatworm has a combination digestive/excretory system. It takes food in and gets rid of wastes through the same opening



RINGED WORM

Kingdom: Animalia

Superphylum: Lophotrochozoa

Phylum: Annelida

The annelids ( also called Ringed Worm ), collectively called Annelida (from French annel├ęs "ringed ones", ultimately from Latin anellus "little ring"), are a large phylum of segmented worms, with over 17,000 modern species including ragworms, earthworms and leeches.

Characteristics

  • consists of multiple segments

  • each of which has the same sets of organs

  • Septa separate the segments of many species, but are poorly-defined or absent in some

  • annelids are soft-bodied

  • Their bodies are long,

  • segments that are divided externally by shallow ring-like constrictions called annuli and internally by septa ("partitions") at the same points, although in some species the septa are incomplete and in a few cases missing.

  • Annelids' cuticles are made of collagen fibers

  • Body bilaterally symmetrical, metameric, often with a distinct head

  • Triploblastic body

  • Asexual reproduction by fission and fragmentation capable of complete regeneration,asexual reproduction by budding in some.

  • Respiratory gas exchange through skin,gills or parapodia

Locomotion

  • Many annelids move by peristalsis (waves of contraction and expansion that sweep along the body), or flex the body while using parapodia to crawl or swim.

Respiration

  • In some annelids, including earthworms, all respiration is via the skin

  • many polychaetes and some clitellates (the group to which earthworms belong) have gills associated with most segments, as extensions of the parapodia in polychaetes.

  • gills of tube-dwellers and burrowers usually cluster around whichever end has the stronger water flow.

Reproduction and life cycle

  • Polychaetes can reproduce asexually

  • dividing into two or more pieces or by budding off a new individual while the parent remains a complete organism. Some oligochaetes, such as Aulophorus furcatus, seem to reproduce entirely asexually

  • others reproduce asexually in summer and sexually in autumn

  • asexual reproduction in oligochaetes is always by dividing into two or more pieces, rather than by budding

  • however, leeches have never been seen reproducing asexually

Sexual reproduction



SNAIL


Kingdom: Animalia

Phylum: Mollusca

Class: Gastropoda

The scientific name for the garden snail is Helix aspersa. It is a gastropod which in latin means, gastro for stomach and pod for foot or just "a belly footed animal".

Characteristics

  • most mollusks are marine

  • dorsal body wall forms pairs of folds called mantle whichencloses the mantle cavity, is modified into gills or lung, and secrete the shell (shell absent in some) ventral body wall specialized as a muscular foot variously modified but used chiefly for locomotion

  • body bilaterally symmetrical (bilateral asymmetry in some), unsegmented, often with definite head.

  • triploblastic body

  • Coelom limited mainly to area around heart and perhaps lumen around gonads part of kidney and occasionally part of the intestine

  • gas exchange by gills, lungs, mantle or body surface

  • their soft bodies are protected by a hard shell.

  • its body is long, moist and slimy.

  • when it is disturbed, it simply withdraws or pulls itself back into its shell.

  • retreats into its shell and seals the entrance in dry weather to protect its body from drying up.

Habitat

  • Snails can be found in a wide range of environments including ditches, deserts, and the abyssal depths of the sea.

Reproduction

  • All land snails are hermaphrodites (producing both spermatozoa and ova)
  • Some aquatic snails, such as Apple Snails, are either male or female
  • Prior to reproduction, most snails will perform a ritual courtship before mating. This may last anywhere between two and twelve hours
  • prolific breeders, snails inseminate each other in pairs to internally fertilize their ova. Each brood may consist of up to 100 eggs



ROUNDWORM




characteristics
  • unique sensory amphids & phasmids
  • marine, freshwater & terrestrial
  • free living & parasitic
  • body bilaterally symmetrical
  • triploblastic body
  • pseudocoelom functions as hydrostatic skeleton
  • non-living, flexible cuticle is molted
  • digestive system complete, muscular pharynx is triradiate in cross-section
  • body has longitudinal muscle only
  • no respiratory or circulatory system

habitat
  • successfully adapted to nearly every ecology niche from marine to fresh water, from polar regions to tropics, as well as from highest to the lowest elevations
reproduction
  • most nematode species are dioecious (seperate male & female individuals)
  • both sexes possess one or two tubular gonads
  • males
sperm produced at the end of gonad
migrate along its length as mature
testes each open into a relatively wide sperm duct and then into a glandular and muscular ejaculatory duct associated with the cloaca
  • females
ovaries each open into an oviduct followed by
a glandular uterus.
uteri both open into a common vagina (usually located in the middle of the ventral surface)
SIMPLE INVERTEBRATES

SPONGE


Domain: Eukaryota
Kingdom: Animalia
Phylum:
Porifera

arose roughly 500 millions ago & currently over 5000 different species

characteristics
  • multicellular body ( several type of cells differentiated for various function some of which organized into incipient tissues of a low level integration
  • body with pores (ostia), canals & chambers that form a unique system of water current on which sponges depend for food & oxygen
  • most marine, all aquatic
  • radial symmetry or none
  • Outer surface of flat pinacocytes, most interior surfaces lined with flagellated collar cells (choanocytes) that create water currents , a gelatinous protein matrix called mesohyl contains amebocytes of various type and skeletal elements

  • Skeletal structure of fibrillar collagen (protein) and calcareous or siliceous crystalline spicules, often combined with variously modified collagen(sponging)

  • No Organs or tissues, digestion intracellular, excretion and respiration by diffusion

  • Reaction to stimuli apparently local and independent in cellular sponges,but electrical signals occur in syncytial glass sponges,nervous system probably absent

  • Adult sponges are sessile, meaning that they are not able to move from place to place. This characteristic makes sponges seem superficially plant-like but sponges do not share other features of plants.

  • Sponges are not capable of photosynthesis.

  • Sponges are diploblasts meaning that they develop from two basic germ layers or cell layers: an ectoderm, or outer layer, and an endoderm, or inner layer

Movement

  • Although adult sponges are fundamentally sessile animals, some marine and freshwater species can move across the bottom at speeds of 1–4 millimetres (0.039–0.16 in) per day, as a result of amoeba-like movements of pinacocytes and other cells. A few species can contract their whole bodies, and many can close their oscula and ostia.

Feeding and excretion

  • filter food particles out of the water flowing through them

  • Particles larger than 50 micrometers cannot enter the ostia

  • pinacocytes consume them by phagocytosis (engulfing and internal digestion)

  • Particles from 0.5 to 50 micrometres (2.0×10−5 to 0.00197 in) are trapped in the ostia, which taper from the outer to inner ends

  • Collar bodies digest food and distribute it wrapped in vesicles that are transported by dynein "motor" molecules along bundles of microtubules that run throughout the syncytium.

Respiration

  • Sponges' cells absorb oxygen by diffusion from the water flow system, into which carbon dioxide and other soluble waste products such as ammonia also diffuse

  • Archeocytes remove mineral particles that threaten to block the ostia, transport them through the mesohyl and generally dump them into the outgoing water current, although some species incorporate them into their skeletons.

Habitats

  • worldwide - from the polar regions to the tropics

  • Most live in quiet, clear waters, (sediment stirred up by waves or currents would block their pores, making it difficult for them to feed and breathe)

  • greatest numbers of sponges are usually found on firm surfaces such as rocks, but some sponges can attach themselves to soft sediment by means of a root-like base.

Reproduction

  • Asexual

Sponges have three asexual methods of reproduction:

  1. after fragmentation

  2. by producing gemmules.

  • Sexual

Most sponges are hermaphrodites (function as both sexes simultaneously)

although don't have gonads (reproductive organs) but sperm are produced by choanocytes or entire choanocyte chambers that sink into the mesohyl and form spermatic cysts while eggs are formed by transformation of archeocytes, or of choanocytes in some species.


JELLY FISH


Kingdom: Animalia

Phylum: Cnidaria

Class: Scyphozoa



Characteristics of phylum cnidaria

  • Cnidocytes present, typically housing stinging organelles called nematocyst

  • Entirely aquatic, some in fresh water, but most marine

  • Radial symmetry or biradial symmetry around a longitudinal axis with oral and aboral ends no definite head

  • Two type of individuals, polyps and medusa

  • Adult body two layered (diploblastic) with epidermis and gastrodermis derived from embryonic ectoderm and endoderm respectively.

  • Mesoglea. An extracellular matrix (jelly) lies between body layers, amount of mesoglea varies,some have mesoglea with cells and connective tissue from ectoderm

  • Incomplete gut called gastrovascular cavity often branched or divide with septa



Life cycle

  • Most jellyfish undergo two distinct life history stages (body forms) during their life cycle

  • the polypoid stage, when the animal takes the form of a small stalk with feeding tentacles

  • polyp may be sessile, living on the bottom or on similar substrata such as floats or boat-bottoms, or it may be free-floating or attached to tiny bits of free-living plankton or rarely, fish or other invertebrates

  • polyps generally have a mouth surrounded by upward-facing tentacles like miniatures of the closely-related anthozoan polyps (sea anemones and corals), also of the phylum Cnidaria.

  • polyps may be solitary or colonial, and some bud asexually by various means, making more polyps.

Locomotion

  • Medusae swim by a form of jet propulsion: muscles, especially inside the rim of the bell, squeeze water out of the cavity inside the bell, and the springiness of the mesoglea powers the recovery stroke

  • tissue layers are very thin, they provide too little power to swim against currents and just enough to control movement within currents.

Feeding and excretion

Respiration

  • no respiratory organs

  • both cell layers absorb oxygen from and expel carbon dioxide into the surrounding water

  • when the water in the digestive cavity becomes stale it must be replaced, and nutrients that have not been absorbed will be expelled with it

  • some Anthozoa have ciliated grooves on their tentacles, allowing them to pump water out of and into the digestive cavity without opening the mouth.

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