Lecture 19: Animals Pt. 2 Flashcards
what did the common ancestor to mollusks look like?
-an unsegmented, marine worm
visceral mass on a mollusk
-it holds the organs, what you can eat
foot on a mollusk
- muscular, for locomotion or anchoring
- can be used for food capture and can also excrete mucus
- in cephalopods, its been divided into tentacles
mantle on a mollusk
- thickened sheet of skin that covers respiratory organs and creates shell
- mollusks have them even if they don’t have a shell
cephalization in the mollusks
-some have very pronounced heads, some have no heads at all (so varying levels of cephalization)
radula
- specialized mouthparts, scrape stuff off of rocks to eat
- some have been modified into drills to bore through others shells
mollusk reproduction
- many are hermaphroditic, and some have different sexes but can change sex
- land ones often use external fertilization
- marine ones often use external fertilization
polyplacophora
- aka chitons
- -herbivorous
- typically live in shallow waters (inter-tidal zones)
- most use external fertilization, some use internal and some even develop their embryos internally
gastropods
types: snails, nudibranchs, and slugs
- some creep along and others free swim
- tentacles are common (used for eyes and chemo-/mechano- sensing).
- most are marine
bivalves
- marine and freshwater
- ligament holds shell closed and most filter feed
- have in-current (brings stuff in) and ex-current (water and gametes out) syphons
- free swimming larvae, external fertilization
- types: mussels, oysters, scallops, clams
cephalopods
- exclusively marine
- active predators
- they have arms and tentacles
- are coloring changing and use jet propulsion
- are highly intelligent and have a highly developed nervous system/eyes
- types: octopus, squid, nautilus
what makes an ecdysozoan?
- they grow by molting
- monophyletic
molting
-have a hard outer covering (aka exoskeleton)
nematodes
- aka roundworms
- species rich, pseudocoelomates
- typically parasitic and have separate sexes
- hydrostatic skeleton and can also be active predators -have complete guts and are covered by a protective cuticle (which they shed 4 times)
- have lateral muscles and are eutley
- types: hookworms, pinworms
eutley
-adult has a fixed number of cells, makes it nice for us to study them and then compare it to other organisms
model organisms
-define the way we study a certain topic or field
horsehair worms
- ecdysozoan
- larvae and adults are very different and they range widely in length
- almost all are freshwater and the adults have no mouth and a non-functioning gut
- we think they may only feed as larvae.
water bears
- extremely small and live on sand/water film on plants
- can remain dormant for a very long time and ecdysozoan
onychophorans
- aka velvet worms
- completely terrestrial (only one)
- closely related to arthropods
- have segments and are unjointed
- external cuticle contains chitin
- have internal fertilization and egg development
- ancestor to arthropods probably looked like it
species richness in arthropods
-2/3rds of all species on Earth are arthropods (and most of those are insects)
trilobites
- had jointed appendages and heavy exoskeletons
- they were fossilized which lets us see this (also had heads)
jointed appendages and body segments in arthropods
body segmented into head, thorax, abdomen
-body plans are dominated by jointed appendages which is good bc they can extend and retract
exoskeleton in arthropods
- have them, made from excreted chitin and protein (it’s what the muscles are attached to)
- they then grow a new skeleton under the old one. -the Exoskeleton has to get thicker as the muscles get bigger, that’s why they stay relatively small
molting in the arthropods
-old skeleton pops open, arthropod puffs itself up to make the new exoskeleton harder, but he’s very vulnerable at this point so he goes into hiding
4 groups of arthropods
- arachnids
- myriapods
- crustaceans
- insect
arachnids
- have chelicerae as mouth parts, four pairs of legs
- types: ticks, spiders, scorpians
myriapods
- mouth parts are mandibles
- bodies consist of head and one pair of antennae and repeated segments
- types: centipedes (one pair of legs on each segment), millipedes (some segments have 2 pairs of legs)
Crustacean
- mouth parts are mandibles
- 2 pairs of antennae
- fertilized eggs stay attached to female body
- three part bodies
- types: Shrimp, lobster, crab
insects
- mouth parts are mandibles
- bodies have three regions (1 pair of antennae, 3 pairs of legs, very successful!) -types: grasshopper, pill bug, fly, dragonfly
