chapter 27
when did animals originate
more than 700 mya
what period did animals originate
ediacaran
what organism did animals originate from
choanoflagellates
animals are (how do they get energy)
heterotrophs who ingest their food
dickinsonia
Ediacaran fossil
kimberella
edicarian fossil
early diverging animal groups
sponges, cnidarians
sponges
the most primative animal
lack tissues and organs
suspension feeders
have choanocytes
choanocytes
flagellated collar cells that generate a water current through the sponge and ingest suspended food
in a sponge water id drawn though pores in the body into the ____ and out the ____
spongocoel (cavity) osculum (opening)
cnidarians
ancient clade of eumetazoans
eutometazoa
animals with true tissues (all except sponges and a couple other groups)
phylum cnidaria
one of the oldest groups in the cnidarians
jelly fishes corals and hydras
developed after the sponges before the ediacaran
exhibit radial symmetry and are diploblastic
body plan is a sac with digestive compartment have one hole
eumetzoa
animals with true tissues
jellyfish blooms are due to
overfishing the fish that eat jellyfish larvae
cambrian explosion
immense increase in animal diversity
about 10 million years long at the beginning of the Cambrian
earliest fossil appearance of many major groups of living animals
hypotheses regarding the cause of the cambrian explosion
new predator-prey relationships
a rise in atmospheric oxygen
evolution of the hox gene complex
bilaterians
animals with left and right sides
originated in the ediacaran right before the cambrian explosion
evolutionary life changed in the ediacaran because of
the rise of predators
body plan
set of morphological and developmental traits
symmetry
whether or not there is symmetry along an axis
radial or bilateral symmetry
bilateral symmetry
dorsal and ventral, right and left, and anterior and posterior ends
radial symmetry
symmetry is present along a radial plane
like a starfish
tissues
collection of specialized cells
germ layers
tissues that give rise to future muscle and organs
endoderm ectoderm and mesoderm
mesoderm
germ layer between the ecto and endoderm layers
endoderm
germ layer covering the embryos surface
ectoderm
innermost germ layer lines the digestive tube
archenteron
digestive tube
diploblastic
animals with two germ layers (endo and ectoderm)
triploblastic
animals that have three germ layers meso ecto and endoderm
coelom
a body cavity
cushions internal organs
cephalization
development of a head
points reflected from animal phylogeny
all animals share a common ancestor, sponges are basal animals, eumetazoa is a clade of animals with true tissues, most animal phyla are bilaterians, most animals are invertebrates
lophotrochozoa
a clade of bilaterians
includes mollusks and annelids
four main groups of mollusks
chitons gastropods bivalves and cephalopods
chitons
group of mollusk
oval shaped marine animals with eight dorsal plates
gastropods
snails, slugs
make up 3/4 of mollusks
have a single spiraled shell
bivalves
group of mollusks
clams oysters mussels and scallops
have a shell divided into halves
cephalopods
group of mollusks
squids and octopi
carnivores with beak-like jaws surrounded by tentacles of their modified foot
annelids
phylum of lophotrochozoa
bodies composed of fused rings
mollusks
phylum of lophotrochozoa
soft bodied protected by a shell
have a foot, visceral mass and a mantle
water filled mantle cavity and use a rasp like radula to feed
leeches
an annelid
many are parasites
secrete the chemical hirudin to prevent blood from coagulating
ecdysozoa
clade of bilateria
shed an exoskeleton through ecdysis
two largest phyla are nematodes and arthropods
nematoda
phylum of ecdysozoa
includes nematodes, guinea worm, and pinworms
arthropoda
phylum of ecdysozoa
2/3 of the known species, date back to the cambrian explosion
are found pretty much everywhere
body plan is segmented, hard exoskeleton and jointed appendages
4 main lineages of arthropopda
chelicerates
myriapods
insects
crustaceans
deuterostomia
phylum of ecdysozoa
includes echinoderms
vertebrates
animals with a backbone
originated 500 mya in the cambrian
first animals with mineralized mouthparts
cyclostomes
jawless vertebrates
2 groups myxini (hagfish) and petromyzontida (lamprays)
hagfish
myxini
30 species
cartilaginous skull and axial rod of cartilage derived from the notochord but lack jaw and vertebrae
petromyzontida
lamprays
38 species
oldest living lineage of vertebrates
cartilaginous segments surrounding the notochord and arches partly over the nerve cord
gnathostomes
jaw vertebrates
includes chondrichthyans and gnathostomes
chondrichthyans
sharks and rays
skeleton of mostly cartilage
most sharks are
streamlined and swift swimmers
carnivores
have a short digestive tract
have acute senses
the spiral valve
a ridge that increases the digestive surface area in sharks
ostichthyes
clade of gnathostomes
majority of vertebrates
includes bony fish and tetrapods
ray finned
a type osteichthyans
lobe fins
a lineage of osteichythyes
have muscular pelvic and pectoral fins
3 surviving lineages
lungfishes coelacanths and tetrapods