Protostomes

Protosomes

large group of bilaterally symmetrical animals

Protosome

initial invagination (blastopore) becomes mouth in formation of gut

Bilateria

bilaterally symmetrical triploblasts. Many appear in Cambrian explosion

Invertebrate bilaterates

95% of animal species

Ecdysozoans

synapomorphy: extracellular protective exoskeleton (hard) or cuticle (soft). Must molt for growth (Ecdysis)

Roundworms (Phylum Nematoda)

unsegmented. psuedocoelomates. complete digestive tract. hydrostatic skeleton. longitudinal muscles only. cuticle with collagen. gas exchange through body wall

Nematoda

mostly free living, some parasitic in humans (Ascaris).

Arthropoda

Features:

segmented bodies organized in regions called tagmata.

exoskeleton made of chitin. allows for muscle attachment.

Exoskeleton allows for

muscle attachment. protect from predation and desiccation. in crustaceans strengthened by CaCo3

Paired, jointed appendages

enable movement of rigid body (“jointed foot”)

Physiology of Arthropoda

coelomates

open circulatory system

complete digestive tract

complex mouthparts for food

Land adaptations of protostomes

Live in moist soils/habitats. Gills/lungs inside body. waxy layer on body surface (cuticle), (insects).

without skeleton limited in size

Challenges of living on land

Desiccation of body

Respiratory gas membranes must be moist

Supporting the body without water.

Modular body plans

small set of elements used to create a body. can be rearranged in different ways to create a body. by changing expression of existing genes

Genetic toolkit

share common toolkit of genes, especially genes responsible for development. differential gene expression

Lophophore

ciliated feeding structure. ex. barnacle foot

Trochophore

ciliated larval stage

Lophotrochozoa

includes phylums Mollusca, Platyhelminthes, and Annelida. no molting and grow incrementally.

Phylum Platyhelminthes

flatworms (flukes, turbellarians, tapeworms)

flattened body plan to allow gas exchange

gastrovascular cavity

acoelomates (no body cavity)

Which phylum contains acoelomates?

Platyhelminthes

Which phylums have incomplete digestive tracts?

Platyhelminthes and Cnidarians

Phylum Annelida (Lophotrochozoa)

earthworms + relatives, marine annelids (free-living), and leeches (ectoparasites)

Phylum Mollusca (Lophotrochozoa)

coelomates (greatly reduced coelom)

Foot, visceral mass and mantle specialized modular body plan

Foot

large muscle at base of clam

Visceral mass

houses internal organs, digestive, reproductive and excretory organs in mollusks

Mantle

secrete shell.

Radula

rasp-like tongue

Mollusks have

open circulatory system and a complete digestive tract

Class Bivalvia

clams, mussels, scallops and oysters. 2 hinged valves form shell. foot is digging organ. and they are filter feeders

Class Gastropoda

snails slugs and relatives. most have one part shells or none

Class Cephalopoda

squids, octopuses, chambered nautilus, and cuttlefish

foot = tentacles

no or reduced shell

closed circulatory system

complex camera eyes.

Tardigrada

tardigrades. segmented bodies and limbs. can withstand hot and cold, extreme pressure and low O2

Onychophorans

velvet worms sister taxa to arthropods.

Class Chilopoda (Arthropoda>Myriapoda)

carnivorous. one pair of legs per segment (two legs in a segment). has venomous claws/fangs

Class Diplopoda ( Arthropoda>Myriapoda)

detritivores. two pairs of legs per segment (four legs in a segment)

Subphylum Chelicerata

chelicerae (appendages) can be used in feeding, defense, sensory reception etc. four pairs walking legs, and one pair of pedipalps

Class Arachnida (Arthropoda>Chelicerata)

spiders, ticks, mites and scorpions. two major tagmata, Cephalothorax and abdomen. fang tipped chelicerae, some are predators and some ectoparasites

Which arthropod classes have a cephalothorax and abdomen?

Arachnida and Crustaceans

Subphylum Pancrustacea

insects + crustaceans

Crustaceans (Arthropoda>Pancrustacea)

mostly aquatic, land example pillbug. major component of zooplankton (ex. copepods and naupilus larva)

Crustacean body

2 pairs of antennae. biramous (branched) appendages, two tagmata: cephalothorax and abdomen. reinforced exoskeleton of CaCO3, like with barnacles

Insecta (Arthropoda>Pancrustacea)

most can fly. head, thorax and abdomen. 1 pair of antennae (head)

1 pair of mandibles (head)

3 pairs of walking legs (thorax)

1-2 pairs of wings. (thorax)

What class has a head, thorax and abdomen as its tagmata?

Insecta.

Metamorphosis

morphological transformation from larva to adult

Hemimetabolous insects

incomplete metamorphosis. egg>nymph>adult

Holometabolus insects

complete metamorphosis. egg>larva>pupa>adult

Lepidopterans

complete metamorphosis. moths and butterflies. larva resemble bird droppings

Hymenopterans

ants, bees and wasps. highly social insects. undergo complete metamorphosis