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Transcript of Metazoa (animals)
Eukaryotes, heterotrophs, pluricellular.
Survivors from 100 phyla (Cambrian explosion).
1.Acoelomate (without body cavity)
2.Pseudocoelomate (body cavity without a mesoderm lining)
3.Eucoelomate (true body cavity)
BILATERIAN BODY CAVITIES
Only between Bilaterians
Protostomes: ("first mouth") in which the oral end of the animal develops from the first developmental opening, the blastopore.
Deuterostomes: ("second mouth"), including Echinodermata and the ancestors of the Chordata, the oral end of the animal develops from a second opening on the dorsal surface of the animal; the blastopore becomes the anus.
Protostomes & Deuterostomes
Radial (Cnidaria & Ctenophora); similar halves by more than two planes.
(all of the other phyla); two mirrored halves. Better fitted for directional movement and cephalization.
Serial repetition of similar body segments, called "metameres".
Found in Annelida, Chordata and Arthropoda.
Presence of a head
Only in bilaterally symmetrical animals
-Missing link between Protozoa and Metazoa.
-Parasites of other animals (0.5 to 1mm; 20 to 30 cells).
-Trichoplax adhaerens: marine,
platelike animal, only 2 to 3mm
-Discovered by Franz Eilhard Schulze
-Feed by absorbing food particles.
-Generally reproduce asexually, by dividing or budding, but can also reproduce sexually.
- 87% of its protein-coding genes
similar to known genes in other animals.
Depend on water currents
Irregular and Radial symmetry
5000 marine species
150 fresh water species
Pinacocytes, Choanocytes, Amoebocytes
Collagen, silicon, calcium
Sexual and asexual (external and internal buds) reproduction
-Cnidocytes, which contain the stinging organeles (nematocysts)
-Asexual and sexual
-Sessile and slow moving or
-Anemones, Jellyfishes, Hydroids,
-Dimorphism (polyp and
-Marine forms, specially in warm waters.
-8 rows of comblike plates for locomotion.
-No nematocysts, but in one species.
-Organ system level of organization.
-Nearly all marine
-About 650 species
-Less than 20 cm long, but a few can reach
-Complete digestive system
-No respiratory system
-Separate sexes and asexual reproduction by fragmentation; few hermaphrodites
-Sensory ciliated pits or head stilts
-First observed in 1928 in the Baltic
-Over 80 species
-0.5 to 1mm
-In interstitial spaces of sandy sediments
-Endure low oxygen conditions
-Ofter occur in large numbers
-No circulatory system, no anus
-Males, females and hermaphrodites (internal fertilization)
-Glide, swim in loops and spirals and bend the head from side to side
-Body cavity is a Pseudocoel
-Some are microscopic and a few are a meter or more in length
-No definite muscular arrangement
-No circulatory and respiratory organs
-Excretory, digestive and reproductive organs present
-Separate sexes; males smaller than females
Phylum Nematoda: Roundworms
Respiratory organs (gills/lungs)
Open circulatory system, with a heart
Mantle that sometimes secretes a shell
Unique features: radula and muscular foot
Highly developed eye (photosensitive cells in retina face light source)
One of the largest phyla (50,000 sp + 35,000 fossil sp)
Chitons, tooth shells, snails, slugs, nudibranchs, sea butterflies, clams, mussels, oysters, squids, octopuses, nautilus
Present metamerism (body divided in segments)
Segmented worms (annelus=ring)
Common sp: earthworms, freshwater worms, leeches, marine worms.
Posses setae (chitinous hairs or bristles) which help for locomotion
Cerebral ganglia (brain)
Closed circulatory system with "hearts"
Sexual and asexual reproduction
Free moving, but radial
Marine forms, including sea stars, sea urchins, sea cucumbers and sea lilies
Name from external spines or protuberances (dermal ossicles and jawlike pincers)
Most common animals in deep ocean
In all oceans of the world and at all depths
No head or brain
Unique water-vascular system: hydraulic power to operate tiny feet (food gathering and locomotion)
Sexual and asexual repr.
Regeneration of lost parts*
Evolution of a hard exoskeleton
Loss of intersegmental septa.
Development of hemocoel (reduccion of coelom).
Loss of closed circulatory system.
Metamerism, but segments more specialized than in annelids.
Complete digestive system.
Respiration by gills, body surface, tracheae or lungs.
Paired excretory glands.
Nervous system of annelids (dorsal brain); well developed sensory organs.
Sexes usually separate.
: a skeletal rod present at some sage in the life cycle.
Single, dorsal, tubular nerve cord
(end of cord usually enlarged from brain).
in floor of pharynx and thyroid gland derived from endostyle.
(usually projecting beyond the anus at some stage, but may or may not persist).
Complete digestive system.
, if present, restricted to outer body wall, head and tail.
Subphylum Urochordata (Tunicata)
Urochordates or "tail chordates" include about 2000 sp.
Found in all seas, from shoreline to great depths.
Most are sessile as adults, but some are free living.
In most species, only the larval form resembles the chordates.
During adult metamorphosis, notochord and tail disappear; dorsal nerve reduces to a single ganglion.
Lancelets: slender, laterally compressed, translucent animals
About 5 to 7 cm in length.
Inhabit the sandy bottoms of coastal waters around the world.
Generic name "Amphioxus"
Brain and spinal cord
Specialized sense organs
Jaws with teeth
Paired pectoral and pelvic fins
Swim bladder and lung
All have a cranium, whereas some jawless fishes lack vertebrae.
Such as all chordates: notochord, dorsal tubular nerve cord, pharyngeal pouches, thyroid gland, postanal tail.
Integument of two divisions (inner and outer dermis); various skin modofications.
Cartilage or bone endoskeleton.
Muscularized digestive tract.
Closed circulatory system with a ventral heart, arteries, veins and capillaries; blood and hemoglobin.
Highly differentiated brain.
Excretory and endocrine systems.
Nearly always separate sexes with gonads.
Mostly bony skeleton; varying numbers of verebrae; ribs can be present, fused or absent; notochord does not persist.
Body forms can or cannot have a neck.
Usually four limbs.
Forelimbs usually with four digits.
Smooth and moist skin with many glands.
Large mouth with small teeth.
Respiration by ungs (absent in some salamanders), skin and gills.
Three chambered heart.
Internal fertilization in salamanders and caecilians, but external in frogs and toads.
Metamorphosis usually present.
Body covered with hair
Sweat, scent, sebaceous and mammary glands
Middle ear with 3 ossicles, 7 cervical vertebrae, pelvic bones fused.
Diphyodont teeth; single jaw bone.
Movable eyelids, fleshy external ears
4 chambered heart, persistent left aorta
Lungs with alveoli, larynx, muscular diaphragm
Excretory system of kidneys and bladder
Highly developed brain, cerebral cortex and 12 parts of cranial nerves.
Cloaca in monotremes
Separate sexes; penis, testes, ovaries, oviducts and uterus; Sex determination by males.
Internal fertilization (embryos develop in unterus, placental attachment), fetal membranes
Young nourished by milk from mammary glands