The Animal Kingdom (L12+7)

LECA → Amorphea → Obazoa →

Opisthokonta → Holozoa → Filozoa → Choanozoa → Metazoa

Amorphea

Obazoa and Amoebozoa

Opisthokonta

Holozoa and Holomycota (fungi)

Filozoa

Choanozoa and Filasterea

Opisthokonta means

rear-facing flagellum

Posterior flagellum

flagellum propels cell body away from the direction of the flagellum

Posterior flagellum examples

sperm cell, choanoflagellate, fungal zoopore

Anterior flagellum

flagellum propels the cell body forwards (euglena - unicellular flagellate)

Embryogenesis

process of going from a single cell to an adult

The origin of animals required the

evolution of unique and complex transcriptional regulatory mechanisms

Choanoflagellate that shares genes with Metazoa

Monosiga brevicollis

Monosiga brevicollis

shares Metazoan genes for integrins, cadherins and homeodomain

Closest Metazoan relative (Ichthyosporean)

Creolimax fragrantissima

Closest Metazoan relative (Filasterean amoeba)

Carpospore owczarzaki

Closest Metazoan relative (Choanoflagellate)

Salpingoeca rosetta

Creolimax fragrantissima

can make cysts and multicellular aggregations

Carpospore owczarzaki

has 3 life stages with 3 different cell types, part of Filasterea (Opisthokont, sister to Choanozoa)

Salpingoeca rosetta

can make rosette/chain colonies

Metazoa (groups)

Porifera, Placozoa, Cnidaria, Ctenophora, Ecdysozoa, Lophotrochozoa, Deuterostomia

Metazoa synapomorphies

multicellular, eukaryotic, heterotrophic, no cell wall

Porifera synapomorphies with Metazoa

collagen, multicellularity, septate junction, spermatozoa

Septate junctions

intercellular junctions in invertebrate epithelial cells, provide structural strength

Choanocytes

sponge collar cells, resemble unicellular choanoflagellates

Sponges filter

particles out of the water as a source of food

In porifera, flagellae

push water away creating a current so water is sucked into the ostia (small holes)

In porifera, flagellae are facing

the chamber and beating the water (up to 10x their body volume)

Placozoa

plate animal

Placozoa genus name

Trichoplax

Placozoa have

an upper and lower (facing substratum) side

Placozoa are

covered in cilia

Placozoa can reproduce

asexually but (genetic) evidence shows genes are mixed between generations

Placozoa evolved

from a more complex organism and became simpler

Placozoa shared genetic pathways with complex Metazoa:

Wnt signalling, TGF-B signalling, Neural processes, Cell adhesion

Gene expressed in pectoral fin (fish) and forelimb (tetrapods)

tbx5

Gene expressed in pelvic fin (fish) and hindlimb (tetrapods)

tbx4

Organisms differe because

development differs

zygote →

blastula → gastrula

Endoderm forms

gut

Ectoderm forms

skin and nerves

Archenteron

cavity formed in the gastrula from the widening of the blastopore

Blastula → Gastrula

invagination from blastopore forming archenteron lined by endoderm

Mesoderm forms

muscles, blood, bones, connective tissues

Cnidaria may have

their own form of mesoderm

Triploblasts (Bilateria) characters

bilateral symmetry, dorsal/ventral axis, through gut

Diploblast characters

radial symmetry, oral/aboral axis, blind gut

Oral/Aboral axis

axis relative to the position of the mouth

Types of triploblasts

acoelomate, pseudocoelomate, coelomate

Acoelomates

solid mesoderm; Platyhelminthes, Nemertea

Platyhelminthes

flat worms, tapeworms

Nemertea

ribbon worms

Pseudocoelomates

unstructured fluid-filled cavity; nematoda

Nematoda

roundworms

Coelomates

epithelium-lined fluid-filled cavity in the mesoderm; annelids, chordates, echinoderms, molluscs

Coelomates likely

evolved and were lost multiple times

Spiral cleavage

alternates between clockwise and anti-clockwise divisions

Radial cleavage

divides horizontally and vertically

Ecdysis

moulting of the cuticle

Ecdysozoa

Onychophora, Tardigrada, Arthropoda, Nematoda, Priapulida

Segmentation

repeated units of construction along the antero-posterior axis

Cnidaria exist in two forms

polyp and medusa

Polyp form

cylindrical shape, aboral end attached to substrate, mouth surrounded by tentacles

Medusa form

adult form, umbrella/bell shaped

Polyps can be

colonial or solitary

Cnidarian species

jellyfish, coral, sea anemones

Ctenophora

comb-jellies

Ctene (comb)

cone rows formed of compound cilia that coordinate beating to produce a current that propel the animal through the water

Compound cilia

several cilia that beat together

Ctenophores have

8 ctene rows

Most Ctenophora are

pelagic

Pelagic

move tentacles around to catch food (fish, other ctenophores)

Benthic

living on the sea bed

Ctenophore habitat

benthic, surface of ocean to deep sea