Lab 7 - Phylum Echinodermata & Chordata

differentiation

how cells become different from each other

morphogenesis

movement of cells to different positions, leads to formation of shape of tissues, organs and the organism

unfertilized egg

large, contain nutrients and organelles needed in early embryo, has visible nucleus

fertilization

fusion of sperm and egg

fertilization envelope

blocks more sperm from entering egg

cleavage

series of cell divisions where egg’s cytoplasm is divided into smaller cells, embryo goes through cell division without growth

blastomeres

cells during cleavage stage

morula

solid ball of 8 or more cells

blastula

hollow ball of cells, forms as cells reorganized into a single layer

blastocoel

fluid-filled interior space

gastrulation

formation of the gastrula from the blastula, gastrula contains three germ layers due to differentiation and migration of cells

gastrula

archenteron and blastopore forms

archenteron

hollow tube that becomes digestive tract

blastopore

opening of archenteron, becomes anus

bipinnaria

sea star larva

phylum echinodermata

marine, unique traits evolved to live on bottom of ocean, deuterostome development, triploblastic, coelomate, complete digestive system

phylum echinodermata body plan

larvae have bilateral symmetry, adults have pentaradial symmetry, embryos have segmentation/metamerism

pentaradial symmetry

arranged in 5 parts around a central axis

phylum echinodermata nervous system

nerve ring, lack cephalization and a CNS, senses concentrated at ends of arms

unique echinoderm characteristics

water vascular system, dermal skeleton

water vascular system

network of water vessels connected to appendages called tube feet, derived from the coelom, used for locomotion, circulation, gas exchange, excretion, and sensing, movement coordinated by nervous system

dermal skeleton

internal skeleton made of ossicles, embedded within the skin, made of calcium carbonate

ossicles

bony elements in the dermal skeleton

class crinoidea

feather stars, flowerlike with many thin, branched arms, filter feeders, often attached to substrate, delicate

class ophiuroidea

brittle stars, body made of central disc and 5 thin arms, arms allow them to move rapidly and swim, most are scavengers on small particles, arms break easily

class echinoidea

sea urchins, have a rigid skeleton of interlocking plates - spines stick out of skeleton, spines move around, mostly grazers that eat algae

class holothuroidea

sea cucumbers, soft-bodied, reduced skeleton, mouth with feeding tentacles, most are scavengers, expel intestines as anti-predator defense

class asteroidea

starfish, body made of central disc usually with 5 arms, in shallow water, most are predators of invertebrates

starfish anatomy

aboral and oral surfaces

aboral surface

anus, central disc, madreporite, eye (sense organ), dorsal side

oral surface

mouth, spines, tube feet, ventral side

madreporite

a sieve-like plate, lets water in and out

water vascular system components

internal canals, tube feet, ampullae, madreporite

ampullae

bulbs on top of tube feet

water vascular system movement

ampulla contracts → fluid forced into tube foot → foot lengthens and sucker adheres, sucker releases and tube foot contracts → fluid forced into ampulla → foot shortens

phylum chordata characteristics

all chordates share 4 characteristics at some point in their development

phylum chordata 4 key characteristics

notochord, dorsal hollow nerve chord, pharyngeal gill slits, post anal tail

notochord

dorsal rod that is rigid but flexible

notochord functions

support, site of muscle attachment, signals surrounding tissues during development, develops into parts of the backbone

dorsal hollow nerve cord

fluid-filled tube of nerves, develops into brain and spinal cord

pharyngeal gill slits/clefts

slits are multiple openings in pharynx supported by bars/arches, used for filter feeding in non-vertebrates, develop into support for gills, jaws or inner ears in vertebrates

post anal tail

elongation of the body that extends beyond anus, used for locomotion, balance, and communication

subphylum cephalochordata

lancelets, filter feeders on sandy ocean bottom, adult has all 4 chordate characteristics

myomeres

repeated sections of muscle, V-shaped

lancelet flow of water

mouth/buccal cavity → gill slits → atriopore (opening)

lancelet movement of food

mouth → pharynx → intestine (liver secretes digestive enzymes) → anus

subphylum urochordata

tunicates/sea squirts, sedentary filter feeders, covered by protective covering made of cellulose and proteins

subphylum urochordata larval stage

free-swimming, has all 4 characteristics, backwards metamorphosis

subphylum urochordata adult stage

sedentary, filter feeds through pharyngeal slits with siphons, lacks notochord, nerve cord, tail

subphylum vertebrata

have endoskeleton, made of vertebrae bone, the vertebrae and cartilage between vertebrae develop from notochord

endoskeleton

includes the backbone (aka vertebral column, spinal column, spine)

characteristics in most vertebrates

anterior skull enclosing large brain, well-developed circulatory system, rigid internal skeleton, extensive muscular system