Lecture 16: Protostomes 1

Question 1

How many animal phyla are protostomes out of 30?

Answer 1

22/30 are protostomes

Question 2

What 3 important ecological roles do protostomes fill?

Answer 2

1. Live in virtually every aquatic and terrestrial havbitat
2. Can be detritivores, herbivores, or carnivores
3. Importance extends to human health

Question 3

What are the 2 major subgroups of protostomes?

Answer 3

1. Lophotrochozoa
2. Ecdysozoa

Question 4

What 3 things are unique to protostomes compared to deuterostomes?

Answer 4

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 of mesodermal cells

Question 5

Where do fossils indicate protostome lineages originated?

Answer 5

The ocean.
Protostomes made the transition from water to land multiple times

Question 6

What is adaptive radiation?

Answer 6

A period of rapid speciation.

Question 7

What is the benefit of the land transition?

For protostomes/land plants?

Answer 7

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 due to more sunlight and CO2

Question 8

What 3 adaptations must protostomes have to make the land transition?

Answer 8

1. Exchange gases with air
2. Avoid drying out
3. Hold up their bodies under their own weight

Question 9

What is the importance of protostomes?

Answer 9

1. Major direct source of food (seafood)
2. Provide ecosystem services (pollination)
3. Some damage crops (pests)
4. Some produce materials (silks/pearls)
5. Cause/transmit human diseases
6. Include drosophila and roundworm

Question 10

What are the key innovations of roundworms and earthworms?

Answer 10

• High surface-area-to-volume ratio
• Increases efficiency o f gas exchange across their body surface in moist environments

Question 11

What are the key innovations of arthropods and mollusks?

Answer 11

• Have gills or other respiratory structures inside body
• Minimizes water loss when moving onto land

Question 12

What are the key innovations of insects?

Answer 12

Insects evolved a waxy layer to minimize water loss from body surface.
- If environment dries, openings to respiratory passages can be closed

Question 13

What are the key innovations of dessication-resistant eggs?

Answer 13

• Evolved repeatedly in populations that made transition to life on land
• Insect eggs have thick membrane that keeps in moisture
• Snail and slug eggs have thick shell that retains water

Question 14

What are compartmentalized body plans and who has them?

Answer 14

Protostomes have compartmentalized body plans in which:
- bodies are divided into different regions with different functions

Question 15

What are lophotrochozoans?

Answer 15

Lophotrochozoans are one of the major subgroups of protostomes. They are a monophyletic group with 13 phyla that includes rotifers, flatworms, annelids, and mollusks.
- could have a lochophore
- could have a trochophore
- grow continuously/incrementally
- spiral cleavage

Question 16

What is a lophophore and a trochophore?

Answer 16

A lophophore is a feeding structure found in 3 phyla and a trochophore is a type of larva found in many of the phyla.

The lophophore is a specialized structure that rings mouth of these animals and functions in suspension feeding.

The trochophore larvae has a ring of cilia that functions in sweeping and sometimes feeding.

Trochophore larvae occurs in animals that undergo indirect development:
- live in different habitats and eat different foods
- originated early evolution of lophotrochozoans

Question 17

What is spiral cleavage?

Answer 17

Lophotrochozoans undergo spiral cleavage, which is when cells divide at oblique angles and spiraling patterns of cells in blastula results

Question 18

What two traits are unique to ecdysozoans?

Answer 18

1. Cuticle and exoskeleton
   - protect animals from predators
   - provide structure for muscle attachment

Question 19

What is molting?

Answer 19

Ecdysozoans grow intermittently by molting: shedding of the soft cuticle or exoskeleton.

Once animal molts: fluid expands body and larger exoskeleton forms.

Sometimes morphological transformations occur during these molts