Lecture 2 (4/8) Flashcards
Diploblasts
- Germ layers
- Examples
- Body cavity
- Organ development
- Nervous system
- Symmetry
- Mesodermal features
- Ectoderm and endoderm
- Jellyfish, corals
- Lack true body cavity (acoelomate)
- Limited organ development
- Typically simple nerve net
- Mostly radial symmetry
- No mesoderm
Triploblasts
- Germ layers
- Examples
- Body cavity
- Organ development
- Nervous system
- Symmetry
- Mesodermal features
- Ectoderm, mesoderm, endoderm
- Mammals, birds, fish, insects, etc.
- May have true coelom, pseudocoelom, or acoelomate (no body cavity)
- Well-developed organs
- More complex nervous system
- Mostly bilateral symmetry
- Includes muscles, circulatory systems, etc.
Nematode symmetry
Bilaterally symmetrical
Pseudocoelom
Fluid-filled body cavity that acts as a hydrostatic skeleton to facilitate movement
Are nematodes pseudocoelomates?
Yes
What is the outermost layer of nematodes called and what is it primarily composed of?
The cuticle, which is mostly made of collagen
What is the cuticle’s role?
It is a tough, non-cellular outer layer that plays a crucial role in maintaining the shape of the nematode, facilitating movement, and regulating gas exchange
What happens to the cuticle during molting?
The old cuticle is shed and a larger new one is formed
What are the three types of behaviors nematodes exhibit?
Locomotion
Physiological events
Integrated movements
Cuticular sense organs
What do they do and what are the two sense organs?
Sense a wide range of stimuli
Amphids and phasmids
Amphids
What are they?
How many and where are they located?
What are they connected to?
Primary chemosensory organ in nematodes
Paired structures located in head region
Connected to the nerve ring
Phasmids
What are they and where are they located?
Chemosensory organ in posterior region
What two phyla contain significant helminths?
Platyhelminthes and Nematoda
Soil transmitted helminths
Ascaris, hookworms, and whipworms
Vector transmitted worms
Filarial worms
Vectored by arthropods
