Invertebrate taxonomy

Question 1

How many phyla are there today?

Answer 1

33

Question 2

How many species in each Phylum?
Arthropoda​
Mollusca​
Nematoda​
Porifera​
Annelida​
Cnidaria​
Echinodermata

Answer 2

Arthropoda​=1,000,000
Mollusca​=110,000​
Nematoda​=80,000
Porifera​=10,000
Annelida=9,000​
Cnidaria​=9,000
Echinodermata=6,000
​

Question 3

What are the levels of organisation that we consider for our phyla.

Answer 3

Tissue formation​
Symmetry​
Embryonic development​
Lophotrochozoa versus Ecdysozoa

Question 4

What are Lophotrochozoa versus Ecdysozoa

Answer 4

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.

Question 5

Phylum Porifera (Sponges)​
Age and describe structure

Answer 5

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​

Question 6

Name some classes of sponges

Answer 6

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)​

Question 7

talk about bilaterians

Answer 7

Bilatarians have undergone ‘cephalisation’ where nerve and sensory cells are concentrated in the anterior (sometimes forming a brain). This allows rapid behavioural responses.​

Question 8

Phylum Cnidaria (jellyfish, anemones, corals)​

Answer 8

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​

Question 9

What are the four classes Cnidarians are divided into?

Answer 9

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​

​

Question 10

What are the two phases jelly fish undergo throughout their life?

Answer 10

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.

Question 11

What are protostomes and dueterostomes?

Answer 11

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​

Question 12

Phylum Echinodermata​
Age

Answer 12

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 ​

Question 13

Echinoderms are divided into five main classes​

Answer 13

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. ​

Question 14

Phylum Annelida​

Answer 14

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)​

Question 15

Annelids are divided into two main classes​

Answer 15

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)

Question 16

Phylum Mollusca​

Answer 16

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​

Question 17

Three main classes of molluscs

Answer 17

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​

Question 18

Phylum Nematoda​

Answer 18

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 ​

Question 19

Phylum Arthropoda​

Answer 19

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​

Question 20

Arthropods are divided into four extant sub-phyla​

Answer 20

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​

Question 21

What is a biramous limb

Answer 21

A biramous limb, branches into two, and each branch consisting of a series of segments attached end-to-end.​