Lecture 16 Protostome Animals Flashcards
What are protostomes?
- What are the major lineages of protostome?
- How many animal phyla are protostomes?
- What ecological role do protostomes fill?
- How many major subgroups are within protostomes?
- 5 major animal lineages including arthropods, mollusks, worms, etc
- 22/30 animal phyla are protostomes
- Ecological roles:Live in every aquatic and terrestrial habitat, can be detrivores, herbivores, or carnivores, extends to human health
- 2 major subgroups: lophotrochozans and ecdyosozoans
Animal diversity
Which protostome phyla have little diversity?
What are some diverse protostomes?
- The phylum, Priapula, contains only 16 named species
- Over 85,000 mollusks have been number, 1.2 million arthropod species (VERY DIVERSE)
- 3 traditional views of “protostomes vs deutorsomes”
- 3 newer views of “protostome vs deutorosome patterns”
Traditional:
1. Embryonic development of mouth before anus during gastrulation
2. Inability of isolated early embryonic cells to develop into complete embryo
3. Formation of coelom by splitting of blocks and mesodermal cells
Newer:
1. Anus developed before mouth in SOME protosomes
2. Some similar development characteristics evolved independently in different lineages (convergent evolution)
3. Synapomophies were lost in some groups
How do fossils indicate protostome lineages originated in the ocean
Which species /how did they survive on land?
- Protostomes made transition from aquatic to terrestrial environments multiple times as they diversified
- Snails (mollusks) and arthropoda survived on land and experienced adaptive radiation which is a period of rapid speciaiton
Why did protostomes/land plants transition from water to land?
Ecological oppurtunity
- Water to land transitions open up entirely new habitats and new resources to exploit
Protostomes: transition to land coincided with adaptive radiation of plants on land
Land plants: thrived in increased sunglight, CO2 compared to water
Why do we care about protostomes/ the importances of protostomes?
- Major direct source of food for humans (seafood)
- Ecosystem services like Pollination
- Some damage crops (pests)
- Silk and pearls
- Transmit human diseases and are parasites (mosquitos ie)
- Include two of the most important model organisms (Drosophila and Caenorhabditis elegans)
What are the key innovations of protostomes?
1. Roundworms and earthworms
2. Terrestrial arthropods and mollusks
- Roundworms and earthworms have high surface area to volume ratio and increases efficieny of gas exchange across their body surace in their moist environments
- Terrestrial arthropods and mollusks have gills or other respiratory structures located inside the body and minimizes water loss when moving onto land
What were some challenges to the transition to land for protostomes?
There had to be new adaptations that allowed protostomes to exchange gases, avoid drying out, hold up their bodies under their own weight
What were the key innovations of these protostomes?
1. Insects
2.Eggs
- Insects evolved a waxy layer to minimize water loss from body surface (stops respiration passages if environment dries)
- Desiccation-resistant eggs: Evolved repeatedly in polulations that made transition to life on land, eggs have thick membrane, snail and slug eggs have thick shells that retain water
Modular body plan allow for phenotypic innovation
What is the result of protostomes having compartementalized body plans?
What was the mechanism for dramatic diversification in new ecological contexts
- Body divided into different regions w/ different functions which was a key innovation for evolutionary flexibility
- Mechanism for dramatic diversification in new ecological contexts thru gene expression of regulatory genes which produced structural and functional innovation (hox gene ie)
What re lophotrochozoans
- Are they a monophyletic/paraphyletic group
- How many phyla/what do they include
- Monophyletic ggroup-all descendants of common ancestor
- 3 Phyla include rotifers, flatworms, annelids, and mollusks
What two morphological traits occur in some lophotrochozoans?
- Lophophore which is found in 3 phyla - for suspension feeding
- A type of larvae called trochophore which is common to many of the phyla- larvae can swim and feed
Lophophores and trochophore larvae
- Lophophore
- Trochophores
- Wheere did trochophore larvae occur in?
- Lophophore- specialized structure that rings mouth of these animals and functions in suspension feeding (helps them feed)
- Trochophores- type of larvae common to several phyla and have a ring of cilia around their middle that functions in sweeping and sometimes feeding
- Trochophore larvae- occurs in animals that undergo indirect development and live in different habitats and eat different foods (originated early)
What type of cleavage do lophotrochozoans possess?
Spiral pattern of cleavage is a synapomorphy
- Cells divide at oblique angles and has been highly conserved in some lophotrochoan phyla (but lost in others)
What are ecdysozoans?
- What is the purpose of the cuticle and exoskeleton?
- What happens during molting
- They protect ecdysozoans from predators and an effective structure for muscle attachments
- During molting animals soft body exposed and vulunerable and a hormone called ecdysone is important in regulation of molting cycle
