developmental biology & circulatory systems Flashcards
(40 cards)
what are tissues and who possesses them
ensembles of similar cells that together carry out a specific function
- All animals except sponges
what formation was a milestone in the evolution of animals
epethelia - allows compartmentation and therefore specialised systems
how are germ layers created
during gastrulation
how many germ layers can animals have
DIPLOBLASTIC: 2 germ layers
or
TRIPLOBLASTIC: 3 germ layers
what are the 3 germ layers
- 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
how many germ layers do cnidarians have and what are they
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)
in what animals did Extracellular digestion first appear
radial animals
what is the cavity called in cnidarians
coelenteron
name the 2 types of canals cnidarians have and what they do
- 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
the circulatory system is a transport of…
Dissolved gases
Nutrients
Waste products
Hormones
advantages of Aquatic respiration
- 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)
disadvantages of Aquatic respiration
- 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
what happens to [O2] when temp or salinity increases
decreases
explain gills as a respiratory surface
- Thin-walled extensions of the body
- Can be external or internal
- May be specialised (e.g. crustaceans, bivalves) or multipurpose (polychaete parapodia, echinoderm tubefeet)
what do Small animals rely on for efficient diffusion rates
every cell being close to the ambient medium - diffusion rate of O2 suggests they can be no more than 0.5 mm thick
what kind of animals use their whole body surface for respiration
Poriferans, cnidarians, acoelomate worms, small crustaceans
what kind of animals have no transport system / circulatory system
Porifera
Cnidaria, cnetophora
Platyhelminthes
Rotifera
Lophophores
Nematodes
*larger metazoans require transport systems
how many orders of magnitude are there
15
what is the smallest polychaete and crustacean
Dinophilus gyrociliatus
Stygotantulus stocki
what is the cavity (coelenteron) in diploblastic animals also used for
internal transport (circulation), hydrostatic support, excretion, reproduction
where does the body cavity form
within the mesoderm
what is the body cavity called if it is lined with mesoderm-derived epithelium
coelom
what is the body cavity called If it is not lined with an epithelium
pseudocoelom
Advantages of coeloms
- 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
