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

Invertebrates Lophotrochozoa Flashcards

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
What is Cysticercosis?
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
Phylum Rotifera
- 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
Rotifer anatomy
- 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
What do Pseudocoelom's function as?
- Hydrostatic skeleton - A simple circulatory system: body movement distributes nutrients and wastes dissolved in the coelomic fluid
29
What does the word rotifer refer to?
"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
Do rotifers usually exist as both males and females?
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
Parthenogenesis
Form of asexual reproduction in which an egg develops without being fertilized
32
What is the rotifer able to do?
the rotifer is able to repair damaged or mutated DNA using the other chromosomal copy as a template
33
Lophophorates
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
What are the two common phyla within Lophophorates?
Ectoprocts and Brachiopods
35
Phylum annelida
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
What are the three main classes of annelids?
- 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
Oligochaetes
- 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
Segmentation
- 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
What happens when worms mate?
- 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
Polychaetes
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
What is bioturbation of marine sediments?
- Displacement and mixing of sediment particles by benthic fauna - 'Ecosystem engineering' modifies geochemical gradients and redistributes food and microbes
42
Hirudinea
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
What are the medical uses for leeches?
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
Phylum Mollusca
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
Molluscan anatomy
- 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
What are the four major molluscan classes?
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
Polyplacophora
- 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
Gastropoda
- 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
Gastropod shells
- Shell typically conical - Species have lost shells & may rely on chemical defense
50
How do gastropods move & feed?
- 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
Terrestrial gastropods
- 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
Bivalvia
- Clams, oysters, mussels & scallops - Right & left valves (shells) - Valve hinge is at mid-dorsal line - Powerful adductor muscles close shell
53
Bivalve anatomy
- 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
What are most adult bivlaves?
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
How do scallops avoid predators?
Swimming in short bursts by flapping their shells and jetting water out of their mantle cavity
56
How do cephalopods move?
- 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
How do squids & octopuses feed?
They use beaklike jaws to bite their prey and inject poison to immobilize their victime
58
What is considered the ancestral cephalopod?
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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