Lecture 9 Flashcards
four key features that led to the evolutionary success of arthropods
chitinous exoskeleton
metameric and tagmatic body plan
hemocoel
metamorphosis
describe the structure of the arthropod exoskeleton
support, protection, water conservation and muscle attachment points
chitin (secreted by hypodermis)
seta - epicuticle (lipo proteins) - procuticle; hardened pigmented procuticle - less hardened procuticle, - hypodermis - basement membrane
sclerotization: process, the hardening of the upper procuticle
vaginates for muscle attachment (exoskeleton plates come together and make a downwards fold)
where joints occur there is a thining of the exoskeleton which allows the joints to be flexible
Ecdysis:
hypodermis secrets enzymes that dissolve the lower levels of the exoskeleton (turns into molting gel)
hypodermis starts secreting cells to build a new exoskeleton
shedding of epicuticle and procuticle and new secretory pore canals form for new epicuticle
proteins cross link which helps with the hardening
embryonic development of hemocoel
internal cavity; part of open circulatory sysytem
derived from blastocoel
facilitates exchange of nutrients, waste, gases
coelom reduced
embryonic development of coelom
compare embryonic development of hemocoel vs. coelom
explain why metamorphosis was important to arthropod success
phylum anthropoda in general
ancient lineage (ediacaran); first land animals
cuticle consists of chitinous exoskeleton
ecdysis (molt) associated with growth
metameric and tagmatic body plan
paired jointed appendages
open circulatory system
hemocoel (main body cavity)
ventral nervous system
metamorphosis is common
tagmatization
evolutionary process in which a segmented organism’s body is reorganized into distinct functional units, known as tagmata (singular: tagma). Each tagma is a grouping of one or more segments that have become specialized for particular functions,
groups of segments fuse or specialize, forming tagmata that perform distinct roles. This reorganizational process is a major factor in the functional and morphological diversification of these animals.
holometabolous
profound/complete metamorphosis
4 stages: first larval molt, second larval molt, pupation and metamorphosis
larva and adults look like different species
larval stages rely on different resources (no comp = selective advantage)
e.g butterflies
ametabolous
larva look similar to adults
e.g silver fish
hemimetabolous
medium metamorphosis
larva slightly resembles adults
e.g dragonflies, mayflies and grasshoppers
