L9: Phylum Arthropoda Flashcards
Outline four key features that led to the evolutionary success of arthropods Describe the structure of the arthropod exoskeleton Compare embryonic development of hemocoel vs coelom Explain why metamorphosis was important to arthropod success
T/F: Metameric and tagmatic body plan
True
What kind of circulatory system is present?
Open
Anatomically where is the nervous system located?
Ventrally
What is metamorphosis
Immature form looks much different and functions differently than adult form
What is a hemocoel and its function?
Internal cavity, filled with blood as part of the open circulatory system
Derived from blastocoel
Allows exchange of nutrients, wastes, and gases throughout body
What is the function of the exoskeleton?
Support, protection, water conservation, muscle attachment points
What is the exoskeleton made of?
Chitin and other proteins
What part of the animal secretes materials for the exoskeleton?
The hypodermis (epidermis)
What is ecdysis?
The shedding of the exoskeleton to accomodate changes in body size/morphology. Occurs during molting
Describe the process of ecdysis during molting
Hypodermis secretes enzymes (molting gel) that causes the lower layer of the exoskeleton to dissolve. The hypodermis then secretes new material for the new exoskeleton, the molting gel rises to upper layers.
The old exoskeleton begins to split and fall off
The new material left will eventually harden
Describe the difference in tagmatization between ancestral and modern arthropods
Ancestral forms had no tagmatization except at front of animal where sensory structures were
Modern animals have clearly defined tagmatization throughout body with paired appendages
What is the difference between a coelom and hemocoel?
Coelom is a fluid filled cavity surrounded by mesoderm, while a hemocoel is a blood-filled cavity that is from a persistant blastocoel
T/F: Metamorphosis is always a profound change in body shape and function
False: some things undergo a big change, while others have limited changes
What are the three different variations of metamorphosis?
- Ametabolous
- Hemimetabolous
- Holometabolous
Describe ametabolous metamorphosis
Limited metamorphosis
Young and adult look similar
Describe hemimetabolous metamorphosis
Mildly similar young form to adult form
Describe holometabolous metamorphosis
Complete metamorphosis
Have four stages of development
Why is metamorphosis advantagous?
Larval stages rely on different resourses than adults, reduces competition between them
