Invertebrate taxonomy Flashcards
How many phyla are there today?
33
How many species in each Phylum?
Arthropoda
Mollusca
Nematoda
Porifera
Annelida
Cnidaria
Echinodermata
Arthropoda=1,000,000
Mollusca=110,000
Nematoda=80,000
Porifera=10,000
Annelida=9,000
Cnidaria=9,000
Echinodermata=6,000
What are the levels of organisation that we consider for our phyla.
Tissue formation
Symmetry
Embryonic development
Lophotrochozoa versus Ecdysozoa
What are Lophotrochozoa versus Ecdysozoa
Ecdysozoans have the ability to shed their exoskeleton several times throughout their life span they possess a special steroid hormone called ecdysteroids.
lophotrochozoan are the animals who possess a trochophore larvae and a feeding structure called lophophore.
Ecdysozoa include Arthropoda, Nematoda, and several smaller phyla.
Lophotrochozoa includes animals like annelids, molluscs, bryozoans, brachiopods, and platyhelminthes.
Phylum Porifera (Sponges)
Age and describe structure
Earliest fossils date from about 580 million years ago (mya) (Ediacaran). They are sessile aquatic animals, whose ‘body’ is riddled with pores.
The outer surface consists of flat cells; ‘collar cells’ with a flagellum and microvilli line the inner surface
The flagella draw water through the osculum into the sponge and the microvilli trap food particles.
Because they are aggregations of cells, you can push a sponge through a sieve and it will re-aggregate
Name some classes of sponges
Calcarea -Calcium sponges-Calcite
Common & made of calcite if present
Hexactinellida-Glass sponges-Silica-no exoskeleton
Demospongiae-Soft sponges-Silica
Present in some species (aragonite)
talk about bilaterians
Bilatarians have undergone ‘cephalisation’ where nerve and sensory cells are concentrated in the anterior (sometimes forming a brain). This allows rapid behavioural responses.
Phylum Cnidaria (jellyfish, anemones, corals)
Fossils date from about 580 mya (Ediacaran).
Diploblastic and mostly marine, they are distinguished by ‘cnidocytes’, specialized stinging cells which are present in the tentacles, have coiled nematocysts that spring out on contact to capture or sting prey
Medusa are bell-shaped, mobile organisms.
Polyps are tubular and fix to a surface Deep water corals are found to 2km deep and can grow over 30m in height and live for over 10,000 years
What are the four classes Cnidarians are divided into?
Hydrozoa -Siphonophores & hydra- Medusa phase
Present in some species, but shared with polyp-stage-Nematocysts are only present in siphonophores
Scyphozoa- jellyfish. Dominant medusa phase- Nematocysts Present
Cubozoa- Box jellies. Dominant medusa phase Nematocysts Present
Anthozoa- Corals & anemones. Never has a medusa phase and Nematocysts Present
What are the two phases jelly fish undergo throughout their life?
Jellyfish have a stalked (polyp) phase, when they are attached to coastal reefs.
Jellyfish (medusa) phase, when they float among the plankton.
The medusa is the reproductive stage; their eggs are fertilised internally and develop into free-swimming planula larvae.
What are protostomes and dueterostomes?
In Protostome= embryos, the first opening that appears is the mouth, the second becomes the anus. Typical of most phyla
In Dueterostomes the first opening in the embryo becomes the anus, the second becomes the mouth. Echinoderms and chordates
Phylum Echinodermata
Age
First ‘true’ echinoderm fossils date from Cambrian (500mya) Exclusively marine, & distinguished by interlocking spines and plates made of CaCO3
Larvae are bilateral, but adults are typified by 5-rayed symmetry
The water-vascular system is unique to echinoderms – it allows fluid to move to the ampulla that force fluid into the tube feet for movement
Echinoderms are divided into five main classes
Asteroidea- Starfish- Broad-based arms with skeletal support provided by calcareous plates
Ophiuroidea-Brittle Stars- Demarcated slender arms strengthened by paired fused ossicles forming jointed “vertebrae”.
Echinoidea-Urchins- Body is globoid and lacks arms
Holothuroidea-Sea cucumbers- Soft, cylindrical, tubular body
Crinoidea-Feather stars- Sessile & characterised by a mouth on the top surface surrounded by feeding arms.
Phylum Annelida
First fossils date from Cambrian (518mya). Terrestrial and marine; no single distinguishing feature
Long, segmented bodies divided externally by shallow ring-like constrictions (annuli) and internally by septa at the same points
Bodies covered by a collagen cuticle; except in the leeches, each segment bear setae (chiton-reinforced bristles)
Annelids are divided into two main classes
Polychaetes-Multiple setae per segment, ‘leg-like’ parapodia function as limbs. Mostly marine
Clitellates (Oligochaetes earthworms) or (Hirudinea leeches) Few or no setae, no parapodia. Possess unique reproductive organ (ring-shaped clitellum) which produces a cocoon to store and nourish fertilized eggs
earthworms=a sticky pad in the roof of the mouth
leeches= Possess two suckers, one at each end (feeding & locomotion)
Phylum Mollusca
First fossils date from Cambrian (540mya). Terrestrial and marine, distinguished by the mantle used by many species to secrete shells, and a muscular foot
The ‘skirt-like’ mantle encloses the mantle cavity - used for breathing and excretion
The tongue-like radula is hardened with chitin and used (except bivalves) for feeding
Ammonites, also molluscs, went extinct with the dinosaurs at the end of the Cretaceous; the largest was 2m across
Three main classes of molluscs
Gastropoda-slugs & snails
Terrestrial & aquatic. Well-defined head with 2/4 sensory tentacles with eyes; ventral foot; an anatomical process known as torsion rotates the visceral mass through 180° during development causing asymmetrical distribution of organs in adult
Cephlopoda-Squid, octopus, nautilus
Exclusively marine. Characterized by bilateral body symmetry, a prominent head, and a set of arms or tentacles modified from the primitive molluscan foot. Many apparently without shells, but cuttlefish, squid and octopuses possess an internal cuttlebone
Bivalva-clams
Benthic freshwater & marine. The shell consists of two bilaterally symmetrical valves
Phylum Nematoda
First fossils date from Devonian (400mya), but likely much older. Globally widespread in all habitats, distinguished by long, thin, unsegmented body – round in cross-section
Epidermis covered by a thick collagen cuticle. The head has only a few tiny sense organs and a mouth
Long muscles aligned longitudinally along the inside of the body, so body movement is only side to side.
Most nematodes (‘roundworms’) are microscopic, but parasitic species reach 13m long. Often exceed a million individuals m-2 and account for 80% of all individual animals on earth
Phylum Arthropoda
First fossils date from Cambrian (540mya). Distinguished by segmented bodies with jointed limbs.
Segments are arranged into three structural units (head, thorax, abdomen), but are often highly modified (e.g. wings, ovipositors, legs)
Sensory specialisations are common and include compound eyes and (paired) antenna
Many species undergo complex Metamorphosis as they pass through different life-history stages
Arthropods are divided into four extant sub-phyla
Chelicerates- Spiders, scorpions
Characterised by chelicerae, appendages near the mouth (sometimes used to inject venom)
Myriapods-Millipedes & centipedes
Multiple body segments, each bearing one or two pairs of legs
Crustaceans-Crabs, shrimp, barnacles
Biramous* appendages
Hexapods-Insects
Six thoracic legs
What is a biramous limb
A biramous limb, branches into two, and each branch consisting of a series of segments attached end-to-end.
