Protostomes Flashcards
What are the 2 sub-clades of Bilateria?
- Protostomes (first mouth)
- Deuterostomes (second mouth)
What is the blastopore?
The blastopore is a pore/hole produced when cells fold inward and form the
archenteron during gastrulation
A second pore is formed as the
archenteron travels inward and upward and reaches the end
In protostomes, the blastopore becomes
the mouth and the second pore becomes the anus
In deuterostomes, the blastopore becomes
the anus and the second pore becomes the mouth
When did present day protostome and deuterostome phyla arise?
During the Cambrian Explosion
The 2 subclades of the Clade Protostomia:
Lophotrochozoa and Ecdysozoa
All Protostomes form 2 sister clades found from
molecular phylogenetics using the SSU rRNA gene
Which clade contains a diverse group of animals, some of which have lophophores or trochophore?
Lophotrochozoa
Lopophores
tentacle mouths
Trochophore larvae
A distinct larval stage with band of cilia
Lophotrochozoa contain:
- lophophores (tentacle mouths)
- trochophore larvae (a distinct larval stage with band of cilia)
Which sister clade contains animals that undergo ecdysis/molting?
Ecdysozoa
Ecdysozoa
Animals that undergo ecdysis/molting
*All lophotrochozoans share a MRCA but their
evolutionary relationships
remain unclear (which
is why all of the phyla branch out together)
Lophotrochozoa are named after:
A. Lophophores
(bryozoans and brachiopods)
B. Trochophore larvae: (mollusks and annelids)
Flatworms and rotifers have neither
What are platyhelminthes?
Flatworms
Platyhelminthes are soft bodied animals with:
few organs and incomplete digestive tract
Incomplete digestive tract is
an evolutionary reversal
2 sub clades of platyhelminthes
- free-living predators
- mostly parasites
Planarian is a _____ and reproduces by ______ and is used to study _______
1) free-living predator
2) asexual fragmentation
3) regeneration
Notable parasites of platyhelminthes are:
Blood flukes: causes schistosomiasis which kills 200,000/year
Tapeworms: reside in the large intestine but larvae can infect the brain and cause neurocysticercosis.
Rotifer literally means “wheel bearer” – refers to
their ciliated mouths that look like rotating wheels
Rotifers are very complex microscopic organisms with: (4)
- eyespots
- a brain
- protonephridia (kidneys-like organs)
- complete digestive tract with mouth & anus
Some rotifers exist in populations that are almost entirely female and
can reproduce
through parthenogenesis (virgin birth)
What is parthenogenesis (virgin birth)?
a form of asexual reproduction in which females lay fertile eggs that become embryos without the
need for male sperm
(Lophophore phyla) Bryozoans =
moss animals
(Lophophore phyla) Brachiopods =
arm-foot
Byrozoans and Brachiopods are phyla of sessile organisms that use _______ to ______ bacteria and protists
lophophores to capture bacteria and planktonic protists
Bryozoans form large colonies that look like coral but are not cnidarians!
Brachiopods look like clams but are not even mollusks!
This is an example of:
convergent evolution
Trochophore phyla: What are the most complex lophotrochozoans?
Annelids and mollusks
The larval stage of annelids and mollusks is characterized by
trochophore larvae
Annelids
(“little rings”) are segmented worms
*Annelids have: (5)
- circulatory system
- kidney like organs
- cluster of nerve cells
- ventral nerve chord
- complete digestive system with mouth & anus
Annelids can be ____, _____, or _______
sedentary (earthworms and leeches), sessile, warning predators
Mollusks are a diverse phylum with
3 sub-clades
What are the 3 sub-clades of mollusks?
- Bivalves (2 valves): clams
- Gastropods (stomach foot): snails, slugs
- Cephalopods (head foot): octopi, squid
What is the synapomorphy of mollusks?
an organ called a mantle
What does a mantle produce?
produces a calcium carbonate shell in most mollusks
All extant cephalopods lack:
This is an example of
a shell
evolutionary reversal
What is the synapormphy of clade ecdysozoa?
molting of cuticle
The MRCA of ecdysozoans evolved
cuticle
What is the cuticle of ecdysozoans?
A tough outer layer that protects them from dehydration on land - critical to colonization of land
What are the first animals to colonize land?
Ecdysozoan
What must ecdysozoans do to grow?
Ecdysis: must shed their old, inflexible cuticle (ecdysis) to
expose the new, soft cuticle underneath which expands and then hardens
2 clades of ecdysozoans
nematodes and arthropods
C. elegans is an important model for ______ because
developmental bio; every cell
division during development can be tracked
What are nematodes?
Nematodes are tiny, ubiquitous, unsegmented worms with a cuticle made of collagen.
Are nematodes free-living or parasitic?
Most are free-living predators but many are parasitic
How can parasitic nematodes affect humans?
Some parasitic roundworms block lymphatic ducts and cause elephantiasis
(Affects ~120 million per year in tropical countries)
What make up most of animal diversity?
Arthropods
Arthopod Synapomorphies
- segmentation
- jointed appendages
- exoskeleton
- tracheal system
Segmentation
allows for complex body patterns
Jointed appendages
Jointed appendages that allow for improved movement on land
* “Arthropod” means “jointed foot”
* Critical for colonization of land!
Exoskeleton
extra tough cuticle
made of chitin + proteins
* Prevents dehydration and provides
protection
* Chitin in arthropods and fungi is a
product of convergent evolution!
Tracheal system
Tracheal system allows arthropods to breathe through their exoskeleton (via
spiracles) and deliver oxygen to cells
Segmentation is a product of
convergent evolution
