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General Biology: OrganismL Biology and Evolution - Set 1 > Invertebrates Lophotrochozoa > Flashcards

Invertebrates Lophotrochozoa Flashcards

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1
Q

Lophotrochozoans

A

Clade identified by molecular data have the widest range of animal body forms
- Belong to clade Bilateria
- Bilateria consists of animals with bilateral symmetry and triploblastic development
- Most members possess structure called a lophophore or go through a trochophore larval stage

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2
Q

What are the 5 main body types in the Lophotrochozoans clade?

A

Platyhelminthes
- Dorsoventrally flattened, unsegmented
acoelomates; gastrovascular cavity or no
digestive tract
Rotifera
- Pseudocoelomates with alimentary canal
(digestive tube with mouth anus); jaws (trophi)
in pharynx; head with ciliated crown
Lophophorates
- Coelomates with lophophores (feeding
structures bearing ciliated tentacles)
Mollusca
- Coelomates with three main body parts
(muscular foot, visceral mass, mantle); coelom
reduced; most have hard shell made of calcium
carbonate
Annelida
- Coelomates with segmented body wall and
internal organs (except digestive tract, which is
unsegmented)

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3
Q

Phylum Platyhelminthes

A

~20,000 species of flatworms, living in marine, freshwater, and damp terrestrial habitats
- Many parasites species, such as flukes and
tapeworms
- May be flat, but they range in length from
microscopic to tapeworms over 20m long

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4
Q

What are the simplest bilaterians?

A

Though structurally more complex than cnidarians or ctenophores, flatworms are simpler than other bilaterians
- Flatworms are the simplest triploblastic
animals, with a middle embryonic tissue layer.
mesoderm
- Mesoderm gives rise to several internal organs
and to true muscle tissue
- Unlike other bilaterians, flatworms are
acoelomates

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5
Q

What are the four main classes of flatworms?

A

Turbellaria
- Most marine, some freshwater, a few terrestrial;
predators and scavengers; body surface ciliated
Monogenea
- Marine and freshwater parasites; most infect
external surfaces of fishes; life history simple;
ciliated larva starts infection on host
Trematoda
- Parasites, almost always of vertebrates; two
suckers attach to host; most life cycles include
intermediate hosts
Cestoda
- Parasites of vertebrates; scolex attaches to
host; proglottids produce eggs and break off
after fertilization; no head or digestive system;
life cycle with one or more intermediate hosts

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6
Q

Turbellaria

A

Nearly all free-living (nonparasitic) and mostly marine
- Freshwater. Genus Dugesia commonly known as planarians
- Polycladids (many reach 15 cm in length)

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7
Q

Planarian Anatomy

A

Planarians and other flatworms lack organs specialized for gas exchange and circulation
- Their flat shape places all cells close to the surrounding water, and fine branching of the digestive system distributes food throughout the animal
- Nitrogenous wastes are removed by diffusion and simple ciliated flame cells help maintain osmotic balance
- Like Radiata, most flatworms have a gastrovascular cavity with only one opening and waste is egested through mouth
- Planarians move using cilia on the ventral epidermis, gliding on a secreted mucus film
- Nervous system is more complex and centralized than the nerve net of cnidarians
- Planarians can learn to modify their responses
to stimuli

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8
Q

Cephalization

A

Paired eyespots detect light and lateral flaps provide chemical sensing

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9
Q

Planarian reproduction

A

Planarians can reproduce sexually
- These hermaphrodites can cross-fertilize one
another
- “Penis fencing” first to penetrate skin of other
with stylet takes on role of male

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10
Q

How do planarians regenerate?

A

The parent constricts in the middle, and each half regenerates the missing end. Effectively immortal

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11
Q

What organism is a major model for regeneration?

A

Freshwater turbellarians of genus Dugesia
- Can cut a flatworm into a maximum of 279 pieces and each one will grow into a new planarian

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12
Q

Blastema

A

The unpigmented area and is the area that is filled with stem cells (numbers refer to days after decapitation)

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13
Q

What happens to animals that are starved?

A

They will reduce their size, while maintaining their form and function. Feeding will reverse this condition and return the animals to their original size

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14
Q

What classes contain parasitic flatwoems?

A

Trematoda with trematodes and Monogenea with monogeneans
- They live as parasites i nor on other animals
- Many have suckers for attachment to their host
- A tough covering protects the parasites
- Reproductive organs nearly fill the interior of these worms

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15
Q

Trematodes

A
  • Parasitize wide range of hosts
  • Most have complex life cycles with alternation of sexual and asexual stages
    • Many require an intermediate host in which the
      larvae develop before infecting the final hosts
      (usually a vertebrate), where the adult worm
      lives
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16
Q

Schistosomes

A
  • Eggs hatch in freshwater
  • Larvae swim to find a snail
  • Mature in snail and then are released and infectious to humans
  • Penetrate exposed skin
  • Mature and pairs mate in veins
  • Migrate to lumen of bladder or intestinal tract to lay
    eggs
  • Eggs excreted into urine or feces - continuing life
    cycle
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17
Q

Where are most eggs deposited and what do they cause?

A
  • Most eggs are excreted but some are retained and mature releasing antigens which cause a massive immune response, causing fevers
  • Developing eggs cause blockage of veins leading to high venous pressure and abdominal pain, anemia, and dysentery
  • Antischistosomal drug is Praziquantel
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18
Q

Molecular mimicry

A

Adults reside and release eggs in venous system for 40 years because aren’t killed by immune system
- Incorporate hoist antigens onto their surface to fool the immune system that the Schistosomes are not foreign
- Eggs and larvae don’t use molecular mimicry

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19
Q

Antigen

A

Molecules (often protein or polysaccharide) that prompt the generation of antibodies and causes an immune response

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20
Q

What are most monogeneans?

A

External parasites of fishes
- Simple life cycles, with ciliated, free-living larva that starts an infection on a host
- While traditionally aligned with trematodes, some structural and chemical evidence suggests that they may be more closely related to tapeworms

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21
Q

What anchors worms to digestive tracts?

A

Suckers and hooks on the head or scolex of a worm

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22
Q

What lies posterior to the scolex?

A

A long series of proglottids, sacs of sex organs

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23
Q

Life cycle of cestodes

A
  1. The larvae develop into mature adults within the
    human
  2. Proglottids loaded with of eggs are released from
    the posterior end of the tapeworm in feces
  3. Eggs in contaminated food or water are ingested
    by intermediary hosts, such as pigs or cattle
  4. Eggs develop into larvae that encyst in the
    muscles of their host
  5. Humans are infected by eating undercooked meat
    contaminated with cysts
  6. Repeat
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24
Q

Rudolph Leuckart

A

Proved that Taenia saginata occurs only in cattle and Taenia solium, only in pigs
- His studies led to the first meat inspection laws in Germany

25
Q

What is Cysticercosis?

A

An infection caused by ingestion of eggs of the pork tapeworm
- Eggs hatch, larvae migrate to muscle and brain,
and then encyst. Cysts get lodged in the brain
causes seizures: neurocysticercosis
- The most common cause of adult onset seizures
in some developing countries like Mexico

26
Q

Phylum Rotifera

A
  • Pseudocoelomates, with jaws, crowns of cilia
  • ~1,800 species, and live in freshwater, marine, on
    mosses or lichens or in damp soil
  • They are tiny (0.05 to 2 mm), smaller than many
    protists but are multicellular with specialized organs
27
Q

Rotifer anatomy

A
  • Have a complete digestive tract with separate mouth and anus
  • Internal organs lie in the pseudocoelom (body cavity that is not completely lined with mesoderm
28
Q

What do Pseudocoelom’s function as?

A
  • Hydrostatic skeleton
  • A simple circulatory system: body movement
    distributes nutrients and wastes dissolved in the
    coelomic fluid
29
Q

What does the word rotifer refer to?

A

“Wheel-bearer” - refers to the crown of cilia that draws a vortex of water into the mouth
- Food particles drawn in by the cilia are captured by
jaws in the pharynx and ground up

30
Q

Do rotifers usually exist as both males and females?

A

No, some rotifers exist only as females, producing more females from un-fertilize eggs
- Other species produce two types of eggs that
develop by parthenogenesis
- One type forms females and the other forms
degenerate males that survive just long enough to
fertilize eggs
- Egg forms a zygote, a resistant stage that can
withstand environmental extremes until conditions
improve
- The zygote then begins a new female generation
that reproduces by parthenogenesis until
conditions become unfavorable again

31
Q

Parthenogenesis

A

Form of asexual reproduction in which an egg develops without being fertilized

32
Q

What is the rotifer able to do?

A

the rotifer is able to repair damaged or mutated DNA using the other chromosomal copy as a template

33
Q

Lophophorates

A

Coelomates with ciliated tentacles around a lophophore - a horse-shoe-shaped or circular fold of body wall bearing ciliated tentacles surrounding the mouth
- Cilia draw water toward the mouth of these
suspension-feeders and tentacles trap food

34
Q

What are the two common phyla within Lophophorates?

A

Ectoprocts and Brachiopods

35
Q

Phylum annelida

A

Annelids (“little rings”) have segmented bodies
- ~15,000 species, ranging in length from <1 mm to
3 m for giant Australian earthworm
- Annelids live in the sea, most freshwater habitats,
and damp soil
- Most, including earthworms, burrow but some
aquatic species swim in pursuit of food

36
Q

What are the three main classes of annelids?

A
  • Oligochaeta
    • Reduced head; no parapodia, but chaetae
      present
  • Polychaeta
    • Well-developed head; each segment usually has
      parapodia with chaetae; tube-dwelling and free-
      living
  • Hirudinea
    • Body usually flattened, with reduced coelom and
      segmentation; chaetae absent; suckers at
      anterior and posterior ends; parasites, predators,
      and scavengers
37
Q

Oligochaetes

A
  • Includes earthworms (Lumbricus ssp.), vital
    components in the living biosystem that is soil
  • Eat their way through soil with undigested matter
    excreted as fecal castings
  • Activity critical for tilling and aeration of soil
  • Darwin estimated that 1 acre (432 m^2) of British
    farmland contains 50,000 earthworms producing 18
    tons of castings per year
    • Recent revisions suggest 0.25-1.75 million/acre
38
Q

Segmentation

A
  • Coelom of earthworm is partitioned by septa, but
    digestive tract, longitudinal blood vessels, and
    nerve cords penetrate septa and run animal’s
    length
  • Longitudinal and circular muscles contract against
    the coelomic fluid which acts as a hydrostatic
    skeleton
  • Skin is well vascularized and used for respiration
39
Q

What happens when worms mate?

A
  • They form slime tubes to help adhere to each other
    during copulation
  • The exchange of sperm may take as long as an
    hour
  • After mating worms separate and produce a
    cocoon about a quarter inch long
  • One or two worms will hatch from each cocoon
    after several weeks
40
Q

Polychaetes

A

Each segment has a pair of paddellike or ridgelike parapodia (“almost feet”)
- Each parapodium has several chitinous setae
- In many polychaetes, blood vessels in the
parapodia function as gills

41
Q

What is bioturbation of marine sediments?

A
  • Displacement and mixing of sediment particles by benthic fauna
  • ‘Ecosystem engineering’ modifies geochemical gradients and redistributes food and microbes
42
Q

Hirudinea

A

Majority of leeches inhabit fresh water, but land leeches move through moist vegetation
- Leeches range in size from ~1 to 30 cm
- Many feed on other invertebrates, but some blood-
sucking parasites feed by attaching temporarily to
animals, including humans
- Some parasitic species use bladelike jaws to slit
host’s skin, while others secrete enzymes that
digest hole through skin
- Leeches secrete hirudin, an anticoagulant, into
wound, allowing leech to snuck as much blood as
it can hold

43
Q

What are the medical uses for leeches?

A

Until this century, leeches frequently used by physicians for bloodletting
- Leeches still used for stimulating circulation for
blood to reattach fingers or toes
- Saliva consists of 30 different proteins that helps to
numb pain, reduce swelling and keep blood flowing

44
Q

Phylum Mollusca

A

Very successful phylum
- Includes snails & slugs, bivalves, and octopuses &
squids
- Most marine, though some inhabit fresh water, and
some snails & slugs are terrestrial
- Molluscs are soft-bodied animals but most have
hard, calcium carbonate shells
- Slugs, squids & octopuses have reduced or lost
shells completely
- Most molluscs have separate sexes, with gonads
located in the visceral mass
- Many marine molluscs have a ciliated trochophore
larvae

45
Q

Molluscan anatomy

A
  • Muscular foot
  • Visceral mass
  • Mantle
    • Mantle secretes the shell, drapes over the
      visceral mass, and creates water-filled chamber,
      the mantle cavity, with gills, anus, excretory pores
    • Many mollusks feed by using a straplike rasping
      organ, the radula, to scrape up food
46
Q

What are the four major molluscan classes?

A

Polyplacophora
- Marine; shell with eight plates; foot used for
locomotion; radula; no head
Gastropoda
- Marine, freshwater, or terrestrial; asymmetrical
body; usually with a coiled shell; shell reduced
or absent in some; foot for locomotion; radula
Bivalvia
- Marine and freshwater; flattened shell with two
valves; head reduced; paired gills; no radula;
most are suspension feeders; mantle forms
siphons
Cephalopoda
- Marine; head surrounded by grasping tentacles,
usually with suckers; shell external, internal, or
absent; mouth with or without radula; locomotion
by jet propulsion using siphon made from foot

47
Q

Polyplacophora

A
  • Chitons are marine animals with oval shapes and
    shells divided into eight dorsal plates
  • Use muscular foot to grip rocky substrate tightly
    and creep slowly over the rock surface
  • Shell of 8 plates
  • Grazers, use radulas to scrape and ingest algae
48
Q

Gastropoda

A
  • Most of >40,000 species are marine, but there are
    many freshwater species
  • Garden snails & slugs are terrestrial
  • During development, gastropods undergo torsion
  • Visceral mass is rotated up to 180 degrees such
    that anus and mantle cavity are above head in
    adults
49
Q

Gastropod shells

A
  • Shell typically conical
  • Species have lost shells & may rely on chemical
    defense
50
Q

How do gastropods move & feed?

A
  • Many gastropods have distinct heads with eyes at
    the tips of tentacles
  • They move by a rippling motion of foot or using cilia
  • Most use the radula to graze on algae or plant
    material
  • Cone shells use a modified radula for spearing
    prey
51
Q

Terrestrial gastropods

A
  • Gastropods are among the few invertebrate groups
    to have adapted successfully to life on land
  • In place of gills, lining of the mantle cavity functions
    as a lung
52
Q

Bivalvia

A
  • Clams, oysters, mussels & scallops
  • Right & left valves (shells)
  • Valve hinge is at mid-dorsal line
  • Powerful adductor muscles close shell
53
Q

Bivalve anatomy

A
  • The mantle cavity contains gills used for feeding &
    gas exchange
  • Most are suspension feeders, trapping fine
    particles in mucus that coats the gills
  • Culia convey the particles to mouth
  • Water flows into mantle cavity via incurrent siphon,
    passes over gills, and exits via excurrent siphon
54
Q

What are most adult bivlaves?

A

Sedentary
- Muscles secrete strong byssus threads that tether
them to solid substrates
- Clams can pull themselves into the sand or mud,
using the muscular foot as an anchor

55
Q

How do scallops avoid predators?

A

Swimming in short bursts by flapping their shells and jetting water out of their mantle cavity

56
Q

How do cephalopods move?

A
  • Use rapid movements to dart toward prey, which
    they capture with long tentacles
  • A mantle covers the visceral mass, but shell is
    reduced & internal in squids
  • Fast movements occur when mantle cavity
    contracts, firing water through excurrent siphon
    • By pointing the siphon in different directions, the
      squid can rapidly move in different directions
57
Q

How do squids & octopuses feed?

A

They use beaklike jaws to bite their prey and inject poison to immobilize their victime

58
Q

What is considered the ancestral cephalopod?

A

Ammonites
- Ancestral cephalopods were probably shelled
mollusks that became active predators
- Shelled cephalopods, ammonites, were dominant
invertebrate predators for 100’s of millions of years,
perishing in cretaceous mass extinction
- Some were as large as truck tires
- Loss of the shell occurred later

General Biology: OrganismL Biology and Evolution - Set 1 (23 decks)

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