Animals II

Question 1

Characteristics of bilaterians

Answer 1

• Triploblastic
• All form true HOX genes –> highly conserved (in segmented animals, they control the type of appendages formed in each segment)

Question 2

Protostome groups

Answer 2

Lophotrochozoan = characterized by filter feeding structure- lophophore- and/or cilia-bearing larvae -trochophores (lophophorates not monophyletic)

Ecdysozoans = cuticle covers body and molts periodically for growth

Question 3

Lophotrochozoan gps

Answer 3

• flatworms
• rotifers
• annelids
• mollusks
• bryozoans
• brachiopods
• phoronids
• ribbon worm

Question 4

Arrow worms

• phylogeny
• coelom
• sex
• feeding

Answer 4

• used to be considered duterostomes (blastopore becomes anus and radial cleavage of zygote)
• develop coelom like protostomes
• basal protostome gp, prob sis to lophotrochozoans
• good model for ancestral bilaterian
• coelomate, but very simplee with nocirculatory or waste removal systems
• hermaphroditic
• marine: plankton predator

Question 5

Arrow worms

• phylogeny
• coelom
• sex
• feeding

Answer 5

• used to be considered deuterostomes bc blastopore becomes anus and radial cleavege of zygote
• develop coelom like protostomes
• now thought to be basal protostome and prob sis to lophotrochozoans
• coelomate, but very simple with no circulatory or waste removal systems
• hermaphroditic
• marine–> plankton predators

Question 6

Bryozoans

• def
• feed
• envirion
• first fossils

Answer 6

• along with entoprocts are colonial sessile animals made of many dif individuals (zooids), some of which secrete tubular housing of chitin, proteis, CaCO3
• coelomate
• filter feeders W/ lophophore
• 4000-4500 species
• dif from entoprocts in placement of anus –> theirs is outside ring or tentacles, but entoprocts are inside
• mostly tropical marine, some freshwater
• fossils f/ ordovician, but soft bodies ones prob b4

Question 7

Platyhelminthes

• coelom
• feeding
• environ
• anatomy

Answer 7

• 25,000 species
• structurally simple –> acoelomate
• marine, freshwater, terrestrial
• over 50% parasitic
• cephalization w/ anterior ganglion
• true gastrulation absent, but all 3 embryonic tissues present
• no complete gut –> intestine is a sac simlar to gastrovascular cavity of cnidaria

Question 8

Platyhelminth gps

Answer 8

turbellaria
monogenea
trematoda
cestoda

bottom 3 are only parasitic; each is monophyletic; prob their own monophyletic sis to nonparasitic ones

Question 9

Turbellaria

Answer 9

• “planaria”
• mostly free living predators and scavengers (16% of platyhelminth species)
• part of Acoela (gp that divered b4 bilaterians and are goo at regenerating)
• even small pieces can regenerate whole animal
• no senescence
• under control of specific master control gene regions
• came back from space two-headed

Question 10

Bipalium

Answer 10

• land planarians
• among biggest flatworms (up to 20”)
• hermaphroditic
• predators –> eat earthworms
• Native to Asia, but introduced elsewhere
• some are important invassive introduced species

Question 11

Monogenea

Answer 11

• ectoparasites of (mostly) fish (one known from mammal)
• hermmaphroditic
• simple life cycles
• well-developed attachment structures

Question 12

Trematoda

Answer 12

• flukes
• obligate parasites
• most (except schistosomes) are hermaphroditic
• attach to host with suckers
• often have separate intermediate and final hosts (gastropod then vertebrate)
• lots of human parasites

Question 13

Schistosoma

Answer 13

• trematoda
• causal agent of schistosomiasis
• affects 200 mil ppl worldwide –> worst parasitic disease besides malaria
• causes pain, anemia, dysentery

Question 14

Clonorchis

Answer 14

• liver fluke
• third most prevalent worm parasite of humans
• in japan, china, taiwan
• infect snails, then fish
• humans get it from raw fish
• live in lier for up to 30 yrs

Question 15

Cestoda

Answer 15

• tapeworms
• internal parasites
• vertebrate hosts (can be in ANY vertebrate)
• complex life cycle with many hosts and larva hosts
• host specificity variable, but highest in adults
• scolex with hooks or suckers
• no digestive system
• proglottids = reproductive sacs

Question 16

Diphyllobothrium

Answer 16

• fish tapeworm
• infects fish and mammals
• humans come in contact with it by eating raw fish
• usually symptomless or mild symptoms

Question 17

Cestoda proglottids

Answer 17

-fertilization results from outcrossing with other worms, although some proglottids can exchange gametes with each other

Question 18

Rotifers

Answer 18

• microscopic multicellular organisms with complete gut and relatively complex internal anatomy
• pseudocoelomate
• ciliated corona “wheel” captures food
• most are sexual, but bdelloid rotifers have been parthenogenetic for mills of years

Question 19

bdelloid rotifers

Answer 19

• survive stresses by entering dehydrated dormant state –> recover when wet
• can incorporate foreign DNA (even from food) during recovery
• suggests a novel form of genetic recombo that substitutes for sexual reproduction (tardigrades do something similar)

Question 20

Ribbon worms (nemertea)

Answer 20

• look like flatworms, but are coelomate with complete gut and closed circulatory system
• mostly marind; some freshwater and terrestrial
• predators with specialized probiscus in hollow rhynchocoel that can be extruded to kill or immobilize prey
• regenerative capacity

Question 21

Brachiopods

Answer 21

• 350 living species; 30,000 extinct
• extensive fossil record –> f/ cambrian
• useful in identifying geologic strata
• filter feeding species with prominent lophophore
• coelomate
• dorsal/ventral valves in contrast to R/L valves of mollusk bivalves

Question 22

Annelids

Answer 22

• 16,500 species
• Classes: Polychaeta (marine; many bristles), Oligochaeta (terrestrial; few bristles); Hirudinae (freshwater; no bristles)
• coelomate
• asexual reproduction thru fragmentation or regeneration
• hermaphroditic or dioecious
• centralized nervous system and complete digestive system

Question 23

Oligochaeta

Answer 23

few bristles
aquatic or terrestrial
earthworms
clitellum = permanent sexual organs

Question 24

polychaeta

Answer 24

mostly marine
free living
many bristles
no permanent sex organs

bristle worms, fan worms, bloodworms, beardworms that live at deep sea ocean vents

Question 25

Hirudinea

Answer 25

``` Mostly freshwater leeches -parasitic or predatory or scavengers -flat with reduced segmentation -often lack chaetae -prominent suckers -secrete anticoagulant- hirudin ```

Question 26

Other annelid gps

Answer 26

- echiura (spoon worms) - sipuncula (peanut worms) - both inglude unsegmented, marine detritivores - each was considered a separate phylum, but recently added to annelida

Question 27

annelid segmentatio

Answer 27

- specialized subunits = metameres - each portion or the coelom is partitioned--> repeat itself - greater precision of movement - simple mode of size increase - arisen several times independantly (in deuterostomes too)

Question 28

Mollusks

Answer 28

- 10,000 species - very diverse - coelomate - great range of aquatic habits; some terrestrial - all have foot, visceral mass, and mantle (but dif gps elaborate on these strutures) - have chitinous radula (may be reduced)

Question 29

mollusk classes

Answer 29

bivalvia gastropoda polyplacophora cephalopoda

Question 30

Bivalva

Answer 30

- 2 halves hinged at mid-dorsal line (R/L) - flat shell, reduced head, paired gills - most are suspension feeders - 9% are hermaphroditic - mantle forms siphons - marine and freshwater - clams oyesters, scallops, mussels

Question 31

Scallop eyes

Answer 31

- up to 200 in fleshy tissue under shell - not like camera lens type in cephalopod - each has 2 retinas and mirrors that focus image on 1 retina or other - mirrors are made of many layers of tiled guanin crystals stacked on each other - one retina is sensitice to dimmer light coming in at an angle, and the other captures movement in bright light

Question 32

Gastropoda

Answer 32

- most divers mollusk gp ~85,000 - TORSION = rotation of visceral mass - head with eye stalks - shell sometimes reduced or absent - foot for locomotion - hermaphroditic - marine, freshwater, and terrestrial - snails, slugs, limpets, nudibranchs - mantle is modified lung in terrestrial slugs/snails

Question 33

Gastropod torsion

Answer 33

180 degree twisting of visceral mass during embryonic dvlpmnt - head and foot stay in place - mantle cavity and anus moce to anterior - synapomorphy for gastropods - unclear if it's adaptive--> may have helped pull head into mantle cavity

Question 34

jorunna parva costasiella kuroshimae

Answer 34

-marine, shell-less gastropod leaf sheep ni=udibranch

Question 35

venomous cone snails

Answer 35

- over 50,000 neurotoxic peptides - fish-hunting snails -> dangerous to ppl - hypodermic-like radula tooth and venom gland - conotoxins are used to study ion channel func --> target specific receptors - source of novel therapeutic drugs for alzheimers, parkinsons, and epilepsy

Question 36

polyplacophora

Answer 36

- chitons - 8 plate hinged shell - foot for locomotion, but moves super slow - no head - radula scrapes algae from rocks - marine - mostly gonochoristic (seperate sexes)

Question 37

Cephalopoda

Answer 37

- reduced or internal shell - closed circulatory system - head (modified foot) with grasping tentacles - radula may be absent - siphon formed from foot allows locomotion thru jet propulsion - 800 spp --> all marine predators - no hermaphroditism or sex reversal - squids, octipi, cuttlefish, chambered nautiluses

Question 38

Cephalopod behavior

Answer 38

- active, intelligent with big brains and complex nervous system - well-developed sensory organs - vision similar to vertebrates --> camera lens eye - eyes a good example of convergent evolution - remarkable ability to change color, but most are color blind