Key traits of animals
all multicellular. lack cell walls but have extracellular matrix
Extracellular matrix (ECM)
structural support. composition depends on tissue type. fibrous component contains collagen
All animals are
heterotrophic and motile at some life stage
Most animals feed by
ingestion
all but sponges have
nerve cells and muscles
Most animals are
diploid and form gametes via meiosis
Metazoans
all animals
Eumetazoans
animals with tissues
When did animals originate?
700 mya. chemical evidence of steriods by sponges same as today around 710 mya
First animal fossils
about 560 mya. soft-bodied, resembled sponges, cnidarians and mollusks
Ediacaran biota
first animal fossils named after time period they date to
What was the protistan ancestor of animals?
Choanoflagellates. DNA evidence shows sister taxa
Choanocytes
collar cells of sponges, resemble choanoflagellate cells
Animals are what kind of phylogenetic group?
monophyletic
Basal phylum
diverged early from root of the tree. in animals this is Porifera
Most animals are in the groups
Bilateral, and most are invertebrates.
Radial symmetry
multiple planes of symmetry (i.e. jellyfish) can sense environment from all sides because uniform distribution of nerve/sensory cells
Bilateral symmetry
single plane of symmetry. Central NS and Cephalization
Central NS and Cephalization
concentration of nerves/senses at anterior (head). can coordinate complex movements & sense environment when entered
Tissue
group of cells organized into structural and functional units.
Tissues form as
germ layers (embryonic tissue layers)
ectoderm
gives rise to skin and nervous system
endoderm
gives rise to lining of digestive system
Diploblasts
animals with two germ layers (i.e. jellyfish)
Triploblasts
animals with three germ layers
Endoderm in triploblasts
leads to lining of digestive, respiratory, reproductive systems
Mesoderm
gives rise to muscles, bones and most organs. allows for development of complex muscles for movement
Coelom
Fluid filled body cavity between inner and outer tubes. Chamber acts as hydrostatic skeleton
Hydrostatic
Involves fluid filled cavity
Hydrostatic skeleton
muscles work against fluid filled cavity
Body cavity allows
space for organ development, support and movement of larger bodies that lack limbs, and circulation of nutrients, gases and wastes.
Acoelomates
No body cavity
Psuedocoelomates
Body cavity partially lined with mesoderm
Coelomates
body cavity completely lines with mesoderm
Cambrian explosion
appearance of ancestors of several modern day phyla
Diversification of animals in Cambrian
time period in which animals could have larger bodies thanks to more O2, and could make more ATP in aerobic metabolism
evolution of predation
Non-bilaterian phyla
Porifera and Cnidaria
Sponges
benthic: freshwater and marine species. sessile. filter feeders. covered with pores for water intake
Choanocytes in sponges
drive water flow and engulf food. amoebocytes also engulf food
Spicules
provide support to sponge. made of CaCO3, SiO2, or spongin
Cnidaria
radially symmetrical diploblasts. mesoglea (inner gelatinous layer). jellies, sea anemones, corals and hydrozoans. polyp and medusa stages of life.
Synapomorphy of cnidarians
cnidocytes. specialized in capturing prey. possess gastrovascular cavity
Nematocyst
coiled structure, discharges when disturbed. grabs prey. part of cnidocyte.