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BIO237 - marine invertebrates > developmental biology & circulatory systems > Flashcards

developmental biology & circulatory systems Flashcards

1
Q

what are tissues and who possesses them

A

ensembles of similar cells that together carry out a specific function
- All animals except sponges

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1
Q

what formation was a milestone in the evolution of animals

A

epethelia - allows compartmentation and therefore specialised systems

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2
Q

how are germ layers created

A

during gastrulation

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3
Q

how many germ layers can animals have

A

DIPLOBLASTIC: 2 germ layers
or
TRIPLOBLASTIC: 3 germ layers

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4
Q

what are the 3 germ layers

A
  • Ectoderm (outer layer): epidermis, nervous system
  • Mesoderm: muscle, bones, blood vessels, blood cells and coelomocytes. Lining of coelom. Gonads
  • Endoderm (inner layer): epithelial lining of multiple systems, especially the gastrointestinal and respiratory tracts
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5
Q

how many germ layers do cnidarians have and what are they

A

2 - diploblastic (no mesoderm)
- Ectoderm = epidermis (No brain or central nervous system) - can be separated from the gastric pouches
- Endoderm = gastrodermis (No separate muscles; musculo-epithelial cells)

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6
Q

in what animals did Extracellular digestion first appear

A

radial animals

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7
Q

what is the cavity called in cnidarians

A

coelenteron

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8
Q

name the 2 types of canals cnidarians have and what they do

A
  • Interradial canals: take the food from the mouth to the margin
  • Perradial canals: carry seawater inwards
    *Nutrients from food circulates in seawater canals in the mesoglea
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9
Q

the circulatory system is a transport of…

A

Dissolved gases
Nutrients
Waste products
Hormones

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10
Q

advantages of Aquatic respiration

A
  • Respiratory surface supported by water
  • Respiratory surface will not dry out
  • CO2 removal is easier
  • Current atmospheric [CO2] is 400 ppm
  • Seawater can hold much more CO2 (carbonate-buffering system)
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11
Q

disadvantages of Aquatic respiration

A
  • Seawater contains ca. 35x less O2 than air [O2] ↓ as temp or salinity ↑
  • Oxygen diffuses 10 000x slower in water than air
  • Water is denser and more viscous - moves more slowly over the respiratory surface
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12
Q

what happens to [O2] when temp or salinity increases

A

decreases

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13
Q

explain gills as a respiratory surface

A
  • Thin-walled extensions of the body
  • Can be external or internal
  • May be specialised (e.g. crustaceans, bivalves) or multipurpose (polychaete parapodia, echinoderm tubefeet)
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14
Q

what do Small animals rely on for efficient diffusion rates

A

every cell being close to the ambient medium - diffusion rate of O2 suggests they can be no more than 0.5 mm thick

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15
Q

what kind of animals use their whole body surface for respiration

A

Poriferans, cnidarians, acoelomate worms, small crustaceans

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16
Q

what kind of animals have no transport system / circulatory system

A

Porifera
Cnidaria, cnetophora
Platyhelminthes
Rotifera
Lophophores
Nematodes
*larger metazoans require transport systems

17
Q

how many orders of magnitude are there

A

15

18
Q

what is the smallest polychaete and crustacean

A

Dinophilus gyrociliatus
Stygotantulus stocki

19
Q

what is the cavity (coelenteron) in diploblastic animals also used for

A

internal transport (circulation), hydrostatic support, excretion, reproduction

20
Q

where does the body cavity form

A

within the mesoderm

21
Q

what is the body cavity called if it is lined with mesoderm-derived epithelium

A

coelom

22
Q

what is the body cavity called If it is not lined with an epithelium

A

pseudocoelom

23
Q

Advantages of coeloms

A
  • coelenteron can now become a specialised, unidirectional digestive tract
  • Coelom and its lining mesothelium for hydrostatic support, circulation, reproduction and excretion
  • Coeloms (together with blood-vascular systems) can act as transport systems for mass flow of internal fluids (allow animals to increase in size)
  • Acoelomate organisms e.g. platyhelminths, must rely on diffusion - distance between any individual cell and the environment is physiologically limited
24
Q

explain the coelom in echinoderms

A

large and complicated - Important for circulation and respiration
- Coelomic fluid is essentially seawater - but contains populations of cells (coelomocytes)
- Water vascular system is part of the coelomic system; seawater is drawn in through the madreporite, circulated and let out

25
Q

how does the coelom relate to respiration in echinoderms

A

Small, fingerlike extensions of the coelom (papulae) protrude through the body wall and are responsible for respiration and waste removal

26
Q

explain the coelom in animals with open blood systems e.g molluscs, brachiopods, arthropods

A

Coelom = greatly reduced - main body cavity = haemocoel, divided into blood-filled spaces that bathe all the tissues

27
Q

explain circulation in molluscs

A
  • slow
  • Oxygenated (arterial) blood -> heart -> discharged through ventricle into haemocoel
  • Venous (deoxygenated) blood enters the base of the gill, is oxygenated as it passes through the lamellae and then continues into ventricle
28
Q

explain mollusc gills

A
  • Pair of cnetidia (gills, sing. cnetidium) inside mantle cavity
  • Each cnetidium = central axis + 2 lamellae
  • Blood inside the gills flows in the opposite direction to the water flow
  • Water current driven by cilia lining mantle cavity and on cnetidia
29
Q

explain Cnetidia in bivalves

A
  • highly specialised as feeding organs in lamellibranchs
  • Greatly enlarged for filter feeding
30
Q

what is Segmentation (metamerism)

A
  • Bilateral pairs of fluid-filled coelomic cavities
  • Compartments separated by mesenteries (longitudinal) and septa (transverse)
  • Allows specialised functions (e.g. gonads, nephridial systems)
31
Q

explain crustacean circulatory system

A
  • variable
  • Smaller crustaceans - poorly developed circulatory systems, often without any heart
  • Large crustaceans can - well-developed circulatory systems and have modified thoracic or abdominal appendages into gills
32
Q

explain decapod circulatory system

A
  • no true veins, only arteries
  • Oxygenated haemolymph (blood) flows from gills into the pericardial sinus
  • It then flows into heart openings (ostia) during diastole
  • The haemolymph is pumped out through the arteries during systole
  • Haemolymph leaves the arteries and flows between the tissues (the haemocoel) to a series of ventral sinuses and then to the gills
  • Crustacean heart is therefore bathed in oxygenated blood
33
Q

what kind of animals have Closed circulatory systems

A

Annelids, phoronids, chordates, cephalopods

34
Q

explain circulatory systems in annelids

A
  • No true heart – contractions of dorsal longitudinal blood vessel drive blood forward
  • Blood flows posteriorly through ventral blood vessel
35
Q

explain Polychaete respiration

A
  • Generally, body surface = insufficient for gaseous exchange
  • Parapodial lobes as respiratory surfaces or specialised protusions
36
Q

what are Respiratory pigments

A

Proteins that combine reversibly with oxygen and therefore increase the carrying capacity of the blood (most common = haemoglobin (Hb)
*O2 + CO2 can be transported in solution - but most animals use respiratory pigments (all end in “in”)

37
Q

haemoglobin (Hb) characteristics

A
  • Metalloprotein containing iron and haem groups
  • Can be contained within corpuscles or in solution
  • If contained within corpuscles, the concentration can be much higher without affecting the partial pressure in the blood
  • Primarily for oxygen transport - but can also be used as an oxygen store or in a simpler form (myoglobin) - facilitates O2 diffusion
38
Q

Haemocyanin (Hc) characteristics

A
  • Copper-based metalloprotein distributed within the haemolymph of arthropods, molluscs and larval stages of certain insects
  • Mollusc and arthropod haemocyanins are considered to have evolved from a common primordial protein
  • Lower oxygen-carrying capacity than haemoglobin + cannot be contained within corpuscles
  • Multiple functionalities (not just oxygen transport/storage) including immunity
39
Q

how can CO2 be transported

A
  • Reversibly bound to Hb
  • As bicarbonate (HCO3)-
  • In solution

BIO237 - marine invertebrates (15 decks)

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