Module 01: Intro to Insects and Their Terrestrial Relatives Flashcards
What are the characteristics of vertebrates?
internal endoskeletons
spinal column made of vertebrae which provides support and allows them to be big
what are the characteristics of intertebrates?
supported by structures outside their bodies
some have hard outer exoskeletons
What are arthropods?
organisms with jointed feet or appendages (like antennae, mouth parts, reproductive organs)
(arthron- means joint, -podos means foot)
includes crabs, spiders, scorpions, insects, etc.
How many known species of arthropods are there? What percentage of names species are they?
1.2 million known species
60% of all named organisms
What five characteristics make up the common body plan of arthropods?
bilateral symmetry
segmented body
ventral nerve cord
dorsal blood vessel
exoskeleton
What is bilateral symmetry? How does it compare to radial symmetry?
characteristic of arthropods
symmetry only along the anterior posterior axis
organisms with radial symmetry can be divided into 2 similar halves by any plane passing through their center
What are the three axis that are important to know when studying the morphology of organisms with bilateral symmetry?
anterior posterior axis - front to back
dorsal ventral axis - top to bottom
lateral axis - side to side
How does the ventral nerve cord of arthropods differ from those of vertebrates?
vertebrates have dorsal nerve cords
arthropods’ nerve cords are not protected by a spinal column
How does the open circulatory system of arthropods differ from those of vertebrates?
arthropods do not have a network of blood vessels, just a large dorsal blood vessel with openings on either end
What are the two main parts of the exoskeleton?
cuticle and epidermis
What are the parts of the cuticle?
waxy epicuticle
exocuticle
endocuticle
How is the exoskeleton both hard and flexible to allow movement?
exocuticle is hardened
endocuticle is unhardened, pliable, and stretchy
cuticle is selectively hardened
What is the purpose of the waxy epicuticle?
prevents water loss + acts as barrier against disease causing pathogens
What is the process by which the exocuticle is hardened?
tanning
process by which proteins are crosslinked in sclerotization
can also be caused by mineralization + calcification
What are tagmata?
fused regions of an arthropod’s segmented body which have specific functions
What differentiates the cuticle and epidermis?
cuticle is external nonliving structure
epidermis is a living cellular layer that secretes the cuticle
What is the cuticle made of?
chitin + protein
What is the basement membrane?
thin tissue separating epidermis from body cavity
What are three purposes of the exoskeleton in general?
protection
support for internal organs
internal ridges provide spots for muscle attachment
What is the major disadvantage of exoskeletons? What process does this disadvantage require to take place?
limits growth
means that arthropods need to molt (shed old exoskeleton and replace it with a new one)
What is step 1 of the molting process?
apolysis
old cuticle separates from epidermis
ecdysteroid molting hormones from prothoracic glands cause epidermal cells to replicate
What is apolysis?
process by which old cuticle separates from epidermis in molting
ecdysteroid molting hormones from prothoracic glands cause epidermal cells to replicate
What is the purpose of ecdysteroid molting hormones? Where do they come from?
cause apolysis
come from prothoracic glands
What is step 2 of the molting process?
digestive fluids flow between cuticle and epidermis and break down endocuticle into metabolites which are absorbed by epidermis
What is step 3 of the molting process?
epidermal cells secrete new cuticle
What is step 4 of the molting process?
ecdysis - old cuticle is cast off
What is ecdysis?
process in molting by which old cuticle is cast off
What does the arthropod do while its cuticle is soft after molting?
contracts muscles + swallows air or water to increase internal fluid pressure and body volume -> stretch the cuticle to allow for growth
when did the first arthropods appear in the fossil record?
cambrian period
520+ million years ago
What are trilobites?
dominant arthropod group in camprian through permian periods
spine exoskeletons for defense
lived in marine environments
When did the earliest terrestrial fossils appear in the fossil record? what is notable about them?
silurian period (440-420 million years ago)
they were arthropods!
Why were arthropods well suited to be the first species to become terrestrial?
stiff exoskeletons and jointed appendages provide support against gravity, protection from drying out, and a good means of movement
how old is the oldest insect fossil?
400 million years
in what two forms are insect fossils found?
imprints in rock
encased in amber
what is phylogeny?
evolutionary history of related organisms
what is taxonomy?
classification system used to define, name, and group organisms
rank the taxonomic categories in order of increasing specificity
domain
kingdom
phylum
class
order
family
genus
species
What are four subphylums of the phylum arthropoda?
Chelicerata
Myriapoda
crustacea
hexapoda
what is the kingdom, phylum, and subphylum of insects?
kingdom = animalia
phylum = arthropoda
subplylum = hexapoda
What are some examples of species belonging to the subphylum cheicerata?
horseshoe crabs
scorpions
spiders
ticks
mites
(very diverse ecological roles!)
What are some examples of species belonging to the subphylum myriapoda?
millipedes
centipedes
What are some examples of species belonging to the subphylum crustacea?
crabs, lobsters, some isopods