Protostome
a multicellular organism whose mouth develops from a primary embryonic opening, such as an annelid, mollusk, or arthropod
Deuterostome
Any of a major group of animals defined by its embryonic development, in which the first opening in the embryo becomes the anus
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Protostome
a multicellular organism whose mouth develops from a primary embryonic opening, such as an annelid, mollusk, or arthropod
Deuterostome
Any of a major group of animals defined by its embryonic development, in which the first opening in the embryo becomes the anus
Cnidarians
hydras, jellyfish, sea anemones, corals
Ctenophores
comb jellies
Lophotrochozoa
crest or wheel animals = annelids (segmented worms) + mollusks + several smaller groups
Ecdysozoa
nematodes (roundworms) + arthropods (centipedes & millipedes, horseshoe crabs & spiders; crustaceans & insects
Phylum Porifera
Sponges
No tissues! Not diploblastic or triploblastic.
● May be asymmetrical
Sponges body plan
● Water is drawn in through pores into a central cavity called spongocoel
● Water exits through an opening called an osculum
● Flagellated collar cells (choanocytes) generate current
● Digestion cells (amoebocytes) are found in the mesophyll
Sponges reproduction
Reproduction is by fragmentation & sexual reproduction
○ Most sponges are hermaphrodites
Phylum Cnidaria
● 11,000+ species. Most are marine. Some are freshwater species
● Radially symmetrical
● Diplobastic
Phylum Cnidaria traits
cnidocytes
○ Specialized cells with stinging
organelles = nematocysts
Major Clades of Cnidarians
Hydrozoans, Scyphozoans, Anthozoans
Phylum Cnidaria: clade Anthozoans
Coral, Sea Anemones, Sea Fans
● Always polyps: single or colony
● Egg + sperm → → planula larva (with cilia) that may drift/swim to a new location before attaching.
Phylum Cnidaria: clades Scyphozoans
animal: Jellyfish, box jellyfish, “true Jellyfish”
Mostly marine, typically in coastal waters
● Free-swimming medusa is the dominant form
● Polyp stages are minimal
Cnidarians body plan
Two body types: Polyp & Medusa
The gastrovascular cavity has a single opening - that serves as both mouth & anus
● Mesoglea = thick, jelly-like substance that separates the only two tissue layers
● Nerve cells form nerve nets which connect sensory cells in the body wall to contractile cells & glands
Lophotrochozoa
One of two clades of protostomes
● Clade including flatworms, rotifers, nemerteans,
mollusks, & annelids
Lophotrochozoa traits
Lophophore = ciliated ring of tentacles surrounding the mouth in three small groups of animals
○ Trochophore Larvae = type of lara that characterized two major groups: mollusks & annelids
○ Bilateral symmetry (at least as larvae)
○ Triplobastic
Flatworms
Phylum Platyhelminthes & Clade Lophotrochozoa
● Free-living, marine, fresh-water & terrestrial environments
● Usually predatory on other invertebrates (not parasitic)
● Acoelomates with simple bilateral symmetry
Flatworm Characteristics
● Covered by ciliated epidermis
● Simple nervous system: two nerve masses
(ganglia) connected by two nerve cords
● Sense organs: simple eyespots +
statocysts (organs for balance)
● Gastrovascular cavity with one opening
(mouth)
● No organs for circulation or gas exchange
● Protonephridia = structures that function to
maintain osmoregulation, & metabolic
waste disposal
● Reproductive organs - hermaphroditic
Flukes (flatworm)
● Parasitic
● Complicated life cycles with alternation of sexual & asexual stages & intermediate hosts
Nemerteans (flatworms
● Includes ribbon worms
● About 1200 species
● Habitat: burrow into marine sediment, or (a few) inhabit deep see water, fresh
water or damp soil
Tapeworms (flatworms)
● Inhabit the intestinal tracts of every
kind of vertebrate
Lophotrochozoa - Phylum Mollusks: Four Major Classes
○ Polyplacophora (Chitons)
○ Gastropoda (snails & slugs)
○ Bivalvia (clams, oysters, etc)
○ Cephalopoda (squids,
octopuses, cuttlefish, & chambered nautiluses)
Mollusk Characteristics
● Soft body - covered by a calcium carbonate shell
● Broad, flat, muscular foot
● Body organs concentrated as a visceral mass
Mollusk Circulatory Systems
Closed circulatory system
-Cephalopoda
Open circulatory system
-Polyplacophora
-Gastropoda
-Bivalvia
Mollusks - Polyplacophorans (Chiton)
Marine animals with flattened bodies
● Shell composed of eight separate, overlapping dorsal plates
Mollusks - Gastropods
Largest & most diverse mollusk group
● May have spirally coiled, flattened, or absent shell
● Twisting of the visceral mass
(torsion) is a unique feature of
gastropods
Mollusks - Bivalves
● Soft body which is laterally compressed & enclosed by a two-part shell
● Shell hinges dorsally & opens
ventrally
● Clams & oysters = filter feeders
Mollusks - Cephalopods
● Octopods, Squids, Cuttlefish, Nautilus
● Fast-swimming predators with mouths surrounded by tentacles
Lophotrochozoa - Phylum Annelids
Includes Polychaetes, Earthworms, Leeches
● Segmented worms with bilateral symmetry
● Nervous system consists of a ventral nerve + one pair of ganglia (simple brain)
● Coelomates
Annelids - Polychaetes
● Marine worms
● Free-swimming, burrow in mud, or
live in secreted tubes
● Parapodia on each segment function in locomotion & gas
exchange
Annelids - Oligochaetes
Most live in freshwater or moist terrestrial habitats
● Hermaphroditic,
common earthworm
Annelids - Hirudinida
● Leeches
● Most are blood-sucking
parasites
● Most live in freshwater habitats
Lophophorates Three Groups
Brachiopoda
● Phoronida
● Bryozoa
Lophophorates
● Marine animals
● Live on ocean floor
● Captures suspended particles
● Coelomate
Rotifers
● “Wheeled Animals”
● Multicellular
● Aquatic
● Microscopic
● “Cell Constant
Ecdysozoa
● Nematodes & Arthropods
● Ecdysis = molting
Ecdysozoa - Nematodes
Includes decomposers, predators of smaller organisms, parasites
Roundworms
● Bilateral symmetry
● Complete digestive tract
Parasitic Nematodes
Hookworms
Heartworms
Pinworm
Ecdysozoa - Arthropods
● Most biologically successful group of animals
● Includes 80% of all known animals
● Open circulatory system
● Digestive system
● Reproductive organs contained in small coelom
Arthropod Adaptations
● Segmentation
● Hard exoskeleton
● Paired, jointed appendages
● Variety of effective sense organs, including antennae & compound eyes
Arthropod Exoskeleton
Exoskeleton makes specialized
respiratory systems for gas
exchange necessary
Five (Main) Arthropod Groups
● Trilobites (extinct)
● Myriapoda
● Chelicerata
● Crustacea
● Hexapoda
Arthropod -Trilobites
● Inhabited shallow Paleozoic seas more than 500 mya
● Extinct for ~ 250 my
● Lived on sea bottom; filtered mud for food
Arthropod- Arachnids
Spiders, Mites, Ticks, Scorpions
● Six pairs of jointed appendages
● Gas exchange by tracheal tubes, book lungs, or both
Arthropod - Crustaceans
● Includes: lobsters, crabs, shrimp, barnacles
● Mandibles
● Biramous appendages
● Two pairs of antennae
Crustaceans - Decapods
● Decapods are the largest & most familiar order of crustaceans
● Lobsters, crayfish, crabs, & shrimp
Hexapods
● Uniramous appendages
● One pair of antennae
● Simple & compound eyes
● Complex mouthparts adapted for piercing, chewing, sucking, or lapping
Hexapods - Insects
Most successful group of animals on the planet in terms of the number of individuals, number of species, diversity, & geographic distribution
●articulated, tracheal hexapods
● Life stages: egg → larva → pupa
→ adult
● ants, bees, termites
Adaptations for Insect Success
Ability to fly
● Reproductive capacity
● Metamorphosis
● Bites & stings
● Tough exoskeleton
● Segmentation