Exam 2 Flashcards

1
Q

Mollusc Features

A

Bilateral symmetra

Triploblastic

Eucoelomate

Unsegmented

Coelom reduced

Complete gut with specialization (often with ceca)
–Possess mouth and anus

Dorsal visceral mass

Secretory mantle produces shell (shell lost in many clades)

Mantle cavity

Muscular foot

Radula (NOT bivalves)

Open circulatory system with heart

Trocophore and veliger larvae

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2
Q

Phylum Mollusca: 2 Clades

A

Aculifera: Polyplacophora and 1 other class

Conchifera: Cephalopods, gastropods, bivalves, and 2 other classes

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3
Q

Class Bivalvia

A

2 lateral shells/valves

Radula LOST

Suspension/filter feeders
–Use gills + labial palps to filter feed

Sedentary (NOT larvae, they are mobile)

Little cephalization

Most are marine

Tiny to gigantic in size

DERIVED mollusc group

Little cephalization

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4
Q

Rotary crystalline style

A

Used to pull in string of food

Rotates to draw in food string

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5
Q

Most endangered North American group:

A

Bivalves

35 species extinct, 70 endangered/threatened, 180 critically imperiled

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6
Q

______________ makes bivalves especially susceptible to water pollution and changes in physical habitat

A

Filter-feeding

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7
Q

_____ are sensitive indicators of health of aquatic ecosystems

A

Bivalves

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8
Q

Phylum Mollusca: 4 Classes

A

Polyplacophora (chitons)

Cephalopoda (octopuses, squids, nautiluses)

Gastropoda (snails, slugs, nudibranchs)

Bivalvia (clams, mussels, scallops)

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9
Q

Useful taxonomic features used to distinguish MOLLUSCAN species:

A

Radula

Size and arrangement are species specific

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10
Q

Oldest part of bivalve shell

A

Umbo

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11
Q

Typhlosole

A

Fold in the intestine

Increase surface area for digestion, nutrient absorption

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12
Q

Class Gastropoda

A

Largest molluscan class

Diverse lifestyles (carnivores, herbivores, scavengers)

Diverse habitats

Univalve, coiled shells

Radula

Most closely related to bivalves

Trocophore and veliger larval stages

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13
Q

Typical freshwater mussel life cycle

A

Females lay eggs and brood them in specialized chambers in their gills

Males release sperm in water

Females draw in sperm

Larvae hatch and begin to develop inside female

Must infect host fish to finish development

Female attracts fish with a fleshy lure

Mussel releases the larvae (glochidia) into fish’s gills

Fish swims away to disperse young

Freshwater mussel’s most endangered animal in US

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14
Q

Glochidia

A

Mussel larvae

Parasitic (develop on fish host)

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15
Q

Bivalve Shell features

A

3 layers:

1) Nacreous layer: Innermost, “pearly,” closest to mantle
2) Prismatic Layer: Middle layer
3) Periostracum: Top/exterior layer

ALL made of calcium carbonate or calcium salts/proteins

Nacreous layer can produce pearls

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16
Q

Function of pearls

A

Defense mechanism

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17
Q

Gastropod Shell

A

Coiled

  • Small apex/tip: oldest part of shell
  • -Same idea as umbo in bivalves
  • Coils/whorls get larger as you get further down the structure
  • Body whorl:
  • -Largest whorl
  • -Contains most of animal
  • Inside columella:
  • -Supports entire length of shell
  • -Columellar muscle wraps around the columella
  • Shell aperture:
  • -External opening
  • -The “Achiles’ heel” of the animal
  • -Operculum:
  • –Thick plate seals up the shell aperture to prevent dessication
  • –Forms on posterior portion of the foot of the snail
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18
Q

Bivalves: Ctenidia/Gills

A

Used for respiration, filter feeding, and reproduction

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19
Q

Gastropod Foot

A

Most of the visceral mass is held within the main body whorl

Ctenidium = gill
-Sits in mantle cavity

Able to do twisting movements, flip self over, hunt and capture prey, all using ONE foot

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20
Q

Gastropod Larval stages

A

Trocophore

Veliger

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21
Q

Gastropod: Trocophore

A

Band of cilia around “equator”

Digestive tract:

  • Mouth
  • Anus

Looks like a diamond

Very short-lived

Plaktonic (free-swimming)

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22
Q

Veliger

A

Possess a SHELL

  • Even sea slugs, nudibranchs have shell in this larval stage
  • -They LOSE shell when they reach adulthood
  • -Why lose the shell?
  • –More mobile
  • –Produce toxins as chemical defense, no need for physical defense

Foot

Velum:

  • -Cilia on fringe edges
  • -Used for FEEDING and LOCOMOTION
  • –ONLY present in veliger stage

TORSION occurs in this larval stage

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23
Q

Torsion

A

Twisted development

Occurs only in veliger larval stage

ONLY occurs in gastropods

All INTERNAL organs (ctenidia, mantle cavity, gut) move 180degrees to shift shell above head
–Head, foot, mouth, and all external organs remain in the same place

Can occur QUICKLY (some >1hr)

Twisted/torted body position remains throughout life
–EXCEPTION: those who lose the shell lose this body plan

Purpose: UNCLEAR

  • Very small/microscopic stage = difficult to test
  • May provide more room for head retraction
  • -Better protects head
24
Q

Cephalopod adaptations

A

Squid:

  • Foot split into arms and tentacles
  • NO exterior shell
  • -Shell is INSIDE body
  • -Shell:
  • –Remnant of shell
  • –Blade-like
  • –Called GLADIUS/PEN
  • Mantle
  • -Surface tissue of cone-like portion
  • -Muscular layer now
  • Move via jet propulsion
  • -Use a jet of water
  • -Water enters mantle cavity (center of the “cone”-like body)
  • -Collar can clamp down to seal up the mantle cavity
  • -Mantle layer is highly muscularized (UNLIKE other molluscs) + special elastic fibers
  • -Muscles on the mantle push out water through the funnel
  • -Movement of animal opposite direction of water (jet)
  • -Possess hydrostatic skeleton; used differently from other animals with H.S.
  • –Water is taken in then shot out rather than moved around within the organism
25
Q

Class Cephalopoda: 3 groups

A

1) Ammonites
- EXTINC
- Abundant in Paleozoic oceans

2) Coleoids
- EXTANT
- Very general group; indluces:
- -Chambered nautilus
- -Octopods
- -Squid
- -Cuttlefish

3) Nautiloids
- EXTANT
- Contains those with shells

26
Q

Muscle surrounds cavity filled with water

A

Hydrostatic skeleton

27
Q

Cephalopods have a _________________ central nervous system

A

Very developed

28
Q

Due to much activity, cephalopods need ___________________

A

Closed circulatory system

  • -Need 3 hearts for faster nutrient transport in body
  • -Branchial hearts located right by gills
29
Q

Masters of camouflage

A

Used for defense to hide or for communication

Achieved via chromatophores

30
Q

Chromatorphore

A

Membranous bags with pigments in center

Can be bumpy or stretched out to show pigment
–This is how they change color

Generally 1 pigment per chromatophore

Timed to make it appear that squid and octopuses have multiple colors and intricate patterns

31
Q

Structures involved in jet propulsion

A

Mantle cavity

Mantle

Collar

Funnel

32
Q

Lophotrochozoans

A

Includes molluscs, flatworms, brachiopoda, and Phoroneieia

33
Q

Lophophore

A

Specialized FEEDING and RESPIRATORY structure

–Used for filter/suspension feeding

34
Q

Phylum Brachiopoda

A

AKA Lamp Shells

Bears striking resemblance to bivalves but they are in DIFFERENT groups
-Similar appearance INDEPENDENTLY evolved

Possess stalk (pedicle) used to attach to substrate

NOT very common

35
Q

Major difference between Brachiopods and Bivalves:

A

Orientation:
Brachiopods have a DORSAL and VENTRAL valve

Bivalves have a LEFT and RIGHT valve

36
Q

Phylum Brachiopoda Features

A

Coelomate

SUPERFICIALLY resemble bivalves

Marine
–Attach to HARD substrates: Found in area with LOW wav action

Shells range in size from 5-80mm for MODERN forms

Solitary

Benthic

Suspension/filter feeders

~400 extant species (contrast w/ ~8000 species marine bivalves)

12,000+ fossil species, mostly Paleozoic

Larger fossils are 30cm in length

37
Q

Permian Extinction: Brachiopods vs Bivalves

A

After extinction level event, brachiopods could NOT recover because they are too dependent on hard substrate and low wave action

Bivalves DID recover because they can survive in hard or soft substrate, high or low wave action, intertidal zones, etc.

38
Q

About _________- of marine life perished in Permian extinction

A

90%

39
Q

Phylum Cycliophora

A

NOT to be confused with Ciliophora

First described in 1995 on lobster “lips” (mouthparts); brand new animal phylum discovered!

Attached to setae on mouthparts

Acoelomate filter feeders

Obligate commensals of lobsters

At least 3 species described

Complex life cycle with multiple asexual and sexual forms

40
Q

Phylum Annelida Features

A

Triploblastic

Coelomate

Segmented body (segmented worms)

Head differentiated into two parts: prostomium and peristomium

Bristles or setae present

Majority marine polychaete worms

Many are burrowers or live in tubes, some are active predators

In marine (some extreme), freshwater, and terrestrial environments

Evolutionary relationships and taxonomy subject to change!!

41
Q

Class Polychaeta

A

Diversity of marine worms

Able to survive in strange places

  • Hydrothermal vents
  • Whale fall

Distinguished by PARAPODIA
–Have many setae, but all annelids have setae

42
Q

Class Oligochaeta

A

Now included in Class Sedentaria

Includes earthworms

43
Q

Class Hirudinea

A

Now Class Sedentaria

Leeches

44
Q

Earthworms take on “dirty jobs”

A

Till/mix soil

Recent study found that some earthworms species helped waste water in septic system filter fields spread more evenly through the soil

Only species that burrow near the surface aid in distributing wastewater

45
Q

Annelid Notable Feature:

A

Setae/Chaetae

Used to provide traction

Retractable

Variable forms

46
Q

Segmented/Metameric structures

A

Nephridium

Ganglia

Septa

Lateral vessels/circulatory system structures

47
Q

NONmetameric structures

A

Digestive tract
–Including gut

Crop

Gizzard

Reproductive organs

48
Q

Hydrostatic skeleton of earthworms

A

One SEGMENT acts as hydrostatic skeleton

Filled with coelomic fluid

49
Q

Earthworm Feeding/Digestion

A

Mouth to esophagus to crop to gizzard to intestines to anus

50
Q

Crop

A

Stores food

Does NOT digest food

51
Q

Gizzard

A

Mechanical digestion

Grinds food down into tiny bits

52
Q

Intestine

A

Digestion and nutrient absorpotion occur here; TYPHLOSOLE increases surface area for absorption

53
Q

Peristaltic Movements

A

Muscular wave moves down body in anterior to posterior direction

Waves of contraction:

  • When LONGITUDINAL muscles contract, those segments become wide and short, as fluid is pushed outward; setae out for traction
  • When CIRCULAR muscles contract, those segments become thin and long, as fluid is pushed toward ends of body; these are the muscles contracted first when burrowing; when these are contracted, setae are retracted

Alternating waves of longitudinal and circular muscle contraction through the body

Regions of the worm go through circular contraction at discrete times
-NOT all of the segments go through at the same time

54
Q

Burrowing or Bioturbation of Soils

A

Earthworm castings: Essentially earthworm “poop”; very good nutrition for plants/fertilizer

When the earthworm stretches out to move forward, the setae retract, setae act as cleats when short/wide and protrude from the body

55
Q

____________ polychaetes also use peristaltic waves

A

Sedentary

56
Q

Internal support for a range of active, precise movements

A

Efficient transport: Closed circulatory system

Nephridia well developed

Parapodia in polychaetes

Ventral nerve cord with giant fibers

Coelomic fluid acts as a hydrostatic skeleton

57
Q

Function of peristaltic movement in polychaetes

A

RESPIRATION

Moves the water and brings it into its “tube” to aerate the worm