Metazoa

diplontic

what life cycle do metazoans have?

choanoflagellates

closest sister to metazoa

opisthokonts

clade

aquatic protists

what are choanoflagellates?

collar cell (ovoid shape) with a collar of microvilli surrounding single flagellum

body plan of choanoflagellates

1. similar cells in sponges and some other animals (choanocytes)
2. choanoflagellates have homologous metazoan cell signaling and adhesion genes (not found in other eukaryotes)
3. DNA sequence supports

evidence that choanoflagellates are sister to metazoa

cell specialization
communication via nutrient exchange
interdependency

describe multicellularity in metazoans

heterotrophs

ingestion then extracellular digestion in gut

what kind of feeders are metazoans as a whole

collagen and proteoglycans

collagen is a fibrous protein
proteoglycans are polysaccharide linked proteins

what do metazoans have in their cellular matrix?

multcellularity: yes, no
heterotrophy: no, no
extracellular digestion: probably not, yes
diplontic: yes, no
spermatozoa: yes, yes
blastula: yes, yes
septate junctions: yes, yes
collagen: yes, yes

Are the following a synapomorphy and is it unique to metazoans?

multicellularity
heterotrophy
extracellylar digestion in gut
diplontic life cycle
spermatozoa
blastula
septate junctions
collagen

spermatozoa, blastula, septate junctions, collagen

Unique SYNAPOMORPHIES of metazoa

porifera (sponges) and placozoans

which phyla do not have guts

symmetry around a central axis

what is radial symmetry

two-sided symmetry

What is bilateral symmetry?

distinct anterior and posterior ends
cephalization
segmentation

characteristics of bilateral animals

blastula --\> gastrula

only ecto and endoderm

diploblasty

3 layers: endo/ecto and mesoderm

triploblasty

hollow ball of cells

blastula

cells migrate from outside of cell to inside: internal cavity forms and the endo/ecto derm form

gastrula

the fluid-filled cavity of a blastula

blastocoel

middle germ layer; develops into muscles, and much of the circulatory, reproductive, and excretory systems

mesoderm; know the two forms

assymetric

symmetry of sponges

aquiferous system: branches water canals that bring water and food inside
then they filter feed on microscopic particles: captures on microvilli and digested intracellularly

how do sponges eat?

differentiated cell types but no tissues or organs
cells arranged in gelatinous matrix (mesosyl) with collagen and spicules

body of a sponge

skeletal elements of sponges

what are spicules

water flows into ostia (incurrent pores)
travels internal chambers
exits through oscula (excurrent pores)
propelled by movement of flagella of choanocytes
can vary in diff sponges

how does the aquiferous system of sponges work

choanocytes: internal with flagellum
pinacocytes: line hole of openings
amoebocytes: inside matrix, helps ingest food and produce gametes

different cells of a sponge

calcareous sponges: calcium carbonate spicules
siliceous spicules: demosponges, glass sponges

2 kinds of spicules

network of collagen
no spicules
harvested for bath sponges

what is spongin

reproduce through budding (asexual)
hermaphrodites that don't self fertilize (sexual)

sperm released into water and enter neighbor sponges through incurrent pores. microvilli take them in as "valuable cells" and introduce them to oocyte. egg fertilized to form zygote. cleavage happens to form blastula-like stage. embryo retained on parent sponge then released as swimming larvae that eventually settles and develops

how do sponge reproduce

true

this is because of their spicules and ability to produce biotoxins/antimicrobial agents to ward off competitors

true or false: sponges are often dominant organisms

cyanobacteria/algae live in mesosyl to perform nutrient exchange
other marine organisms inhabit sponges for shelter (ex: shrimp that enter sponge when young, eat food inside and then grow too large to leave)

symbiotic relationships with sponges

radial symmetry

symmetry of ctenophores

diploblastic

Are Ctenophora diploblastic or triploblastic?

complete gut

gut of ctenophores

nervous system
simple musculature

body of ctenophores

zooplankton, or other ctenophores

what do ctenophores eat

H1: porifera sister

2 hypotheses about early metazoan phylogeny

radial symmetry with oral and aboral ends

what symmetry do cnidaria have

incomplete gut
have a gastrovascular cavity

what gut do cnidaria have

diploblastic

Are cnidarians diploblastic or triploblastic?

polyp: sessile with oral end up
and medusa: bell shaped, oral faced down

2 body forms of cnidarians

cell with cnida (stinging sticky structures)
nematocysts

cnidocytes:

false: it is non centralized "a nerve net"

true or false: cnidarians have a complete nervous system that is centralized

they have eyes

what is so special about cube jellies

sexually variable

sperm and egg form a zygote
ciliated larvae (planula)
polyp
produce/release medusae asexually

How do cnidarians reproduce?

carniverous
capture pray with cnida-laden tentacles
extracurrical digestion in gastrovascular cavity
products taken into cells by phagocytosis and digested intracellularly

how do cnidarians feed

false

true or false: there are terrestrial cnidarians

anthazoa
hydrazoans
scyphozoa
carbozoa

4 major clades of cnidarians

first cnidarian clade
no medusa stage
solitary/colonial
CaCO3 secreted at base to form coral reef

anthazoa

hydra
no medusa shape
colonial hydroids (ex: portugal man of war)

hydrazoa

sea jellies
named for extensive mesoglea

scyphozoa

image forming eyes
very toxic stings
small groups

cubozoa

clownfish have protective coating that neutralizes the sting from anemone
clownfish gets protection and food leftovers
sea anemone gets defense and nutrients from clownfish excrement

talk about the clown fish and sea anemone symbiosis

1.5 mil species
triploblastic
bilateral anterior/posterior axis
cephalization

common features of bilateria

radial cleavage: cells divide parallel to axis and accumulate in even, symmetric layers

spiral: cells divide oblique angle to axis and new cells lie in furrows between existing ones

two kinds of cleavage and describe them

lophotorochozoans: annelids and molluscs

who has spiral cleavage

dueterostomes

who has radial cleavage

Triploblastic development

mouth first
blastophore becomes mouth
mesoderm forms near blastopore opening

protostomes

mouth second, blasto becomes anus
mesoderm develops elsewhere (not near blastophore)

deuterostomes

fluid filled body cavity surrounded by mesoderm
hydrostatic skeleton: gives body rigidity because of the essential incompressibility of liquids

what is coelom

Mesodermal cells completely fill the blastocoel
Gut is only body cavity

acoelomate plan

-Mesodermal cells line the outer edge of the blastocoel only partially lined with mesoderm
-Pseudocoelom is a false body cavity

pseudocoelomate plan

Band of mesoderm surrounds gut and then splits open

Schizocoelous Plan

Mesoderm forms by this, where cells from the central gut lining form pouches and expand into blastocoel

enterocoelous plan

becomes most organs and systems

what does the mesoderm develop

segmentation, increased sensory and locomotor ability

associations with bilateral symmetry

has band of cilia

trochophore larva

bilateral usually but some are secondarily asymmetrical (ex: snail)

mollusca symmetry

protostomes

are molluscs proto or dueterostomes

yes, coelom

true or false: molluscs have coelom (

complete

gut of molluscs

open- hemocoels
blood flows in cavities not vessels

circulatory system of molluscs

mantle, visceral mass, foot

body plan of mussels

rasping tongue like organ with teeth
molluscs have it

what is a radula and who has it

well developed

nervous system of molluscs

nephridia

excretory system of molluscs

locomotion
in bivalves: used for burying
in cephalopods: become arms/tentacles + siphon

foot of molluscs

dorsal body wall
fold of tissue that covers visceral mass and encloses mantle cavity
shells secreted by mantle

mantle of molluscs

all organs and stuff between foot and mantle

visceral mass of molluscs

-chitons: shell plates and repeated gills on underside
-gastropods: torsion
-bivalves: foot is burying structure
-cephalopods: foot is arms/tentacles with siphon for propulsion

modifications in the 4 clades of molluscs

a lot of species, most of them fossilized due to shells

diversity in molluscs

chitons, snails, slugs, nudibranchs, clams, mussels, squids, octopus, nautilus

name molluscs animals

mostly dioecious
fertilization is external in chitons and bivalves, internal in gastro/cephalopods
have trochophore larva
direct development

reproduction of molluscs

monoecious
exchange sperm and love darts

reproduction of snails

chitons
gastropods
bivalves
cephalopods

4 clades of molluscs

false: chitons have segmentation

true or false: molluscs do not have segmentation

classic: earliest members were segmented worms
new: segmented worms are sister to eveyrthing else

classic vs new view of mollusc phylogeny

dorsoventrally flattened
multiple shell plates and gills

describe chitons

shell divided into two halves (clams, oysters, mussles)
no cephalization
no radula
food/water brought in through ciphon instead

describe bivalves

univalve (coiled)
torsion
includes nudibranchs and solar powered sea slugs

describe gastropods

plummed sea slugs feed on sea anemones, can ingest cnidarians without getting stung, ingests nematocysts and transports them to tips of cerata (spikes on back of slug). can use the nematocysts for their own defense

cnidarians/sea slug story

feed on algae and absorb chloroplast into their own body
kleptoplasty: steal plastids to do photosynthesis

solar powered sea slugs

squids, octopuses

cephalopods

jet propulsion

locomotion in cephalopods

with shell

what does nautilus mean

can do observational learning and remember things

learning/memory in cephalopods

similar to vertebrate eye
single lens convergent evolution with that of vertebrates
common genes involves in eye development of 2 groups (rhodopsin and PAXG)

eyes in cephalopods

coelomate protostomes

are annelids proto or dueterostomes?