bio 205 chapters 1 + 2: introduction and environmental considerations, invertebrate classification and relationships

invertebrate

animals that lack a spine or vertebral column consisting of vertebrae

physical properties of water

high: humidity, density, specific heat, viscosity, light-extinction coefficient, nutrient content
low: compressibility, oxygen solubility, rate of oxygen diffusion

physical properties of air

high: compressibility, oxygen solubility, rate of oxygen diffusion
low: humidity, density, specific heat, viscosity, light-extinction coefficient, nutrient content

humidity is high

water
animals have exposed respiratory surfaces (gills), external fertilization and external development, and excrete ammonia

humidity is low

air
animals have internalized respiratory surfaces (lungs), internal fertilization and internal (protected) development, and excrete urea/uric acid

density is high

water
rigid skeletal supports unnecessary, filter-feeding lifestyles are possible, and external fertilization with dispersing developmental stages

density is low

air
rigid skeletal supports are necessary, must move to find food, and internal fertilization with sedentary developmental stages

compressibility is low

water
transmits pressure changes uniformly and effectively

compressibility is high

air
less effective at transmitting pressure changes

specific heat is high

water
has great temperature stability and no drastic temperature changes

specific heat is low

air
wide fluctuations in ambient temperature and drastic temperature changes are possible

oxygen solubility is low

water
5-6 mL of oxygen in 1 L of water

oxygen solubility is high

air
210 mL of oxygen in 1 L of air

viscosity is high

water
organisms sink slowly, and greater frictional resistance to movement

viscosity is low

air
faster rates of falling, and less frictional resistance to movement

rate of oxygen diffusion is low

water
animals must move or must move the water for gas exchange

rate of oxygen diffusion is high

air
about 10,000 times higher than in water

light-extinction coefficient is high

water
animals may be far removed from sites of surface water primary production

light-extinction coefficient is low

air
animals are never far from sites of primary production

nutrient content is high

water
salts and nutrients available through absorption directly from the water, and adults may make minimal nutrient investment per egg

nutrient content is low

air
no nutrients available via direct absorption from air, and eggs must be supplied with all nutrients and salts needed for development

radial symmetry

a body can be cut along multiple planes to yield 2 mirror images

bilateral symmetry

a body can only be cut along one single plane to yield 2 mirror images, exhibit cephalization

cephalization

the presence of an observable head

incomplete gut

early animals, a gut with one opening that serves as both the mouth and the anus

complete gut

later animals, a gut with two openings, one that serves as the mouth for ingestion and one that serves as the anus for excretion

zygote

a fertilized egg

embryonic development

zygote → 2 cells → 4 cells → 8 cells → morula → blastula

morula

solid ball of 16-64 cells

blastula

a hollow sphere of cells

blastocoel

cavity within the blastula

blastopore

opening of the blastula

gastrula stage

cells migrate in through the blastopore to form germ layers

diploblastic

animals that produce 2 embryonic germ layers, ectoderm and endoderm

triploblastic

animals that produce 3 embryonic germ layers, ectoderm, mesoderm, and endoderm

acoelomate

animals that lack a true body cavity, organs are embedded within tissues
phylum platyhelminthes

pseudocoelomate

animals that possess a fake or false body cavity in which organs sit that is incompletely lined by mesoderm
phylum nematoda

coelomate

animals that possess a true body cavity in which organs sit that is completely lined by mesoderm

protostomes

spiral and determinate cleavage, schizocoelous coelom formation, blastopore becomes the mouth

spiral and determinate cleavage

cells slightly rotate from the cells they split from, and they are predetermined to becoming a particular body component

schizocoelous coelom formation

mesoderm cells split to form the coelom

deuterostomes

radial and indeterminate cleavage, enterocoelous coelom formation, blastopore becomes the anus

radial and indeterminate cleavage

cells sit directly above the cells they split from, and they are not predetermined to becoming a particular body component

enterocoelous coelom formation

folds of mesoderm rise up from the archenteron and pinch closed to form the coelom

phylogeny

the evolutionary history of a species or group of species

phylogenetic trees

branching diagram depicting a hypothetical evolution of a group of species

monophyletic grouping

consists of a common ancestor and all of its descendants

polyphyletic grouping

consists of descendants with no direct common ancestor

paraphyletic grouping

consists of a common ancestor and only a portion of its descendants

autapomorphy

self-derived characteristic, seen in an individual for the first time

synapomorphy

shared characteristic derived from a common ancestor

symplesiomorphy

shared characteristic derived from a primitive ancestor, but not a direct common ancestor