Lecture 2 Flashcards
Germ Layer/ Coelomic cavity
- Invertebrates are multicellular
- They are collections of cells, generally working together as a unit to perform the functions of life –> germ layer
- Two germ layers – Diploblasts
- ectoderm = outer layer
- endoderm = inner layer
- Three germ layers – Triploblasts
- ectoderm & endoderm
- mesoderm = middle layer, form muscles, circulatory system
- Body compartments
- gut (simple, or open)
- 2o Cavity (coelom, pseudocoelom)
- Symmetry
- radial / biradial
- bilateral
Bilaterians
- bilaterally symmetrical…
- Triploblasty
- eventual Cephalization
- eventual complete guts
Deuterosomes
- enterocoely
- anus from blastopore
- mouth 2nd
- radial cleavage
protosomes
- schizocoely
- mouth from blastopore
- mouth 1st
- spiral cleavage
- paired, ventral nerve cords
Schizocoely
- Split in the mesoderm that forms the coelom
Enterocoely
- evagination of archenteron into blastocoel, forming from a part of what will become the gut, this is why is is “entero”
radial cleavage
- Equal division
- generally equatorial
- Indeterminate cleavage – i.e. stem cells up to 4-cell embryo
-mitotic spindle aligns parallel or perpendicular to primary embryonic axis - blastocoel in the middle
- could be ancestral form of all bilterians
spiral cleavage
- first 2 divisions longitudinal – then 3rd division sets the mitotic spindle at an oblique angle
unequal sizes of new cells - Determinate cleavage – i.e. seperating one of the cell will not form a complete organism
aquatic vs. terrestrial life
- water is wet… this allows animals to transfer gases / wastes / nutrients across body wall –> many systems can be simplified
- terrestrial inverts live in danger of drying out –> requires sophisticated systems for osmoregulation, respiration
Humidity in water vs air
Water:
- High
- exposed respiratory surfaces
- external fertilization
- external development
- excretion of ammonia
Air:
-low
- internalized respiratory surfaces
- internal fertilization
- protected development
- excretion of urea and uric acid
Density in water vs air
water:
- high
- rigid skeletal supports unnecessary
- filter feeding lifestyle possible
- external fertilization
- dispersing developmental stages
Air:
- low
- rigid skeletal supports necessary
- must move to find food
- internal fertilization
- sedentary developmental stages
Specific heat in water vs air
water:
- high
- temperature stability
Air:
- low
- wide fluctuations in ambient temperature
Oxygen solubility in water vs air
water:
- low
- 5-6 mL O2/L of water
Air:
-high
- 210 mL O2/ L of air
rate of oxygen diffusion in water vs air
water:
-low
- animal must move (or must move water) for gas exchange
air:
- high
- about 10,000 times high than in water
Nutrient content in water vs air
water:
- high
- salts and nutrients available through absorption directly from water for all life stages
- adults may make minimal nutrient investment per egg
air:
- low
- no nutrients available via direct absorption from air
- adults supply eggs with all nutrients and salts needed for development
