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