BIOL 310 intro to phylogeny

4 main phyla

Arthropoda (crustaceans, spiders, scorpions, ticks, millipedes, centipedes, insects)

Annelida (Errantia + Sedentaria) 

Mollusca (Gastropoda, Bivalvia, cephalopoda)

Echinodermata 

Main features of Arthropoda

ecdysozoans (superphylum) animals with an exoskeleton that shed prior to growing within this is panarthropod which includes the phyla - Arthropoda, Tardigrada, and onychophora, lack cilia, embryos do not develop by spiral cleavage

these include animals that molt have segmented bodies paired appendages and a brain 

Arthropoda specific - have fully segmented bodies and limbs, regionally specialized section of the body (tagma, compound eyes and highly specialized appendages no cillia no nephridia

Arthropoda subphyla

crustacea, hexapoda, myriapoda, chelicerata (spiders horseshow crab), trilobita

Arthropoda subphylum Crustacea

2 pairs antennae

three tagmata (common in arthropods)

segments fused for common function thorax and head fused to form cephalothorax

biggest defining feature is nauplius larvae - one segment that grows into more and only has one eye

some may have a carapace which is a shell that covers head and thorax

have simple (light) and compound (images) eyes

form biramous appendage (branches to two parts) (very common in crustacea and not in others)

Arthropoda subphylum Hexapoda

6 legs all uniramous (no splitting) have 2 tagmata appendages dont attach to abdomen (attach to thorax) head has antenna 

main types hexapoda are insects and collembola (springtails) 

insects mouthparts sit on outside of head in collembola mouth parts are hidden in mouth capsule 

spiracles or gills attach to spiracles seen in insects 

in juveniles - appendages attach wherever no wings may have prolegs on abdomen complete metamorphoses results in fully mobile 

egg-nymph life cycle (incomplete) 

egg-larva- pupa-adult life cycle (complete) 5 

metamorphosis

exoskeleton is shed between stages because it limits body size the shedding is called a molt and each life stage between molts is called a instar

hemimetabolous metamorphosis

incomplete

gradual change young are nymphs and are wingless

bud-like growths (wing pads) in early instars show where wings will develop

stages are egg-nymph-adult

grasshoper dragonfly etc

holometabolous metamorphosis 

complete about 88% of insects do complete 

larvae and adults often live in completely different environments and have different morphology 

several larval instars then becomes pupa (inside cocoon or chrysalis) 

then emergages adult 

stages are egg-larva-pupa-adult 

Arthropoda subphylum Chelicerata

two parts in body the prosoma (7 segments) and the opisthosoma (up to 12 segments)

chelicerae are fangs in spiders little pinchy guys in others like ticks

have specialized appendages - chelicerae, pedipalps(non walking legs) and 4 walking legs (still 6 appendages)

no antennae no mandible most suck liquid from food and prey

chelicerata class merostomata

marine intertidal chelicerates horseshow crabs 

unsegmented carapace covers body in front of abdomen and telson (tail) 

gills on ventral abdomen 5 pairs of walking legs 

2 compound 2 simple eye 

used for vaccine research 

chelicereta class arachnida

scorpions ticks spiders mites 

great diversity 

two tagmata - cephalothorax and abdomen 

chelicerae and pedipalps 4 pairs walking legs 

ticks have a confusing life cycle with both 6 legged larvae- 8 legged nymph - adults 

Arthropoda subphylum Myriapoda

many legs  millipedes and centipedes many segments if each segment has two leg milli if one leg then cent

have a head with antennae mandibles and maxillae

Annelida (errantia and sedentaria) 

bilaterally symmetrical protostomes (mouth develops first)  found in marine freshwater and terrestrial 

complete digestive system and closed circulatory system 

complex nervous system and diverse reproductive strategies 

have outer covering that is cuticle they have an ectoderm and endoderm(gut)

they are eucoelomates  space found inside between mesodermal cell (between ecto and endo) is the coelom (which is completely lined) so two cavities the gut and the coelom 

metamerism is allowed grater complexity independent movement of each segment needs more complex nervous system if one segment is injured can still function

eucoelomate (segmented worms!)

coelom is important because each has a completely independent liquid cavity separated by septa so is can be manipulated independently resulting in high level of movement

liquid in space results in hydrostatic skeleton 

longitudinal and circular muscles surrounding body

Annelides Sub class errantia

mostly free moving traditionally called polychaetes - having many satae

most are marine some freshwater

important food source for other animals

metameric

repeating segments of the same thing

polychaetas group in annelids

parapodia - paired appendages inly found in polychaetes no other annelids

have respiratory capillaries and may have gills too paddle like shape and strong musculature

sensory cirri

annelids sedentaria

tube dwelling worms

includes some polychaetes and the clade clitellates (earthworms and leeches)

similar to errantia but

head may have long tentacles for food capture and parapodia are reduced in size specialized as an anchor

Mollusca 

bilaterally symmetrical unsegmented and coelomate protostomes

open circulatory system with hemocoel and reduced coelom (limited to small chamber around heart)

mantle covers the body and secretes shells or sclerites forming a mantle cavity that houses key organs (houses gills lungs and surface acts in gas exchange)

well developed head (mostly)

radula (rough ribbon like organ)

foot used for movement (adhesion, extend burrow, fin like for swim)

includes cephalopods, bivalves, and gastropods 

bivalves (mollusca)

most are marine also freshwater most are sedentary filter feeders create currents with cilia on their gills

no head no radula

very little cephalization

bivalve shell

2 valves held together by hinge ligament drawn together by adductor muscles

umbo is the oldest part growth occurs in rings

pearls produced when an irritant is lodged between shell and mantle layers of nacre secreted around irritant

gastropods (mollusca) 

univalve one piece shell may be coiled or uncoiled 

they have unique juvenile development torsion is rearranging of body during development of the adult 

they can help by preventing overgrowth and shells may be right handed (dextral) or left-handed (sinistral)

have a tough operculum that covers opening to protect the snails head 

cephalopods (molluscs)

none are freshwater

they have a uniquely modified it is mostly in the head with the anterior end extending as a ring of arms, foot with mantle is a funnel shape called a siphon

they forcefully expel water through the siphon which can point forward or backward and force can be controlled

have a streamlined body

lateral fins (squids and cuttlefishes) are stabilizers and flutter to allow swimming motion

Echinodermata (phylum)

sea stars sea urchins sea cucumbers 

radial symmetry (adaptation to living on ocean floor) penta radial 

very bad at osmoregulation only found in marine env 

calcereous endoskeleton with ossicles (plates)

coelomic water vascular system extending as podia (tube-feet)

echinodermata class Asteroidea

sea star

central disc with arms radiating outwards usually 5

the underside is the oral surface with mouth ambulacral area runs from mouth to tip of each arm

the ambulacral groove is bordered by rows of podia and used for shuffling movement and movable spines surround and protect the podia which cover much of animal surface

their endoskeleton is made up of calcerous plates (ossicles) bound together with special connective tissue (called catch collagen) which can be controlled by the nervous system to change from liquid to solid

on this have spines and pedicellarie (pincer like jaws controlled by muscles keep body surface free of debris)

have ampulla that are muscular sacks that jold fluid above podia and contraction forces fluid into the podia to stiffen them for walking contractions of muscles at the base of podium creates a suction cup

bilaterians 

bilateral symmetry 

most in two large groups the deuterostomes and protostomes

deuterostomes

radial cleavage, enterocoely, anus from blastopore (anus first then mouth), so mouth second

protostomes

spiral cleavage, mouth from blastopore so mouth first, paired ventral nerve cords, schizocoely 

schizocoley 

mesoderm begins forming then a schizom occurs in the mesoderm creating coelom (protostomes)

enterocoely

mesoderm forms with cavity already present to form coelom (deuterostormes)

diploblasts

two germ layers

ectoderm (outer) and endoderm (inner)

Triploblast 

gectoderm and endoderm and mesoderm 

protostomes include what

Ecdysozoa (which inludes many inverts, artho etc) and Spiralia/lophotrochozoa

spiralia/lophotrochozoa

these are protostomes and the animals develop by spiral cleavage mostly made up of trochozoa and lophophorata