cnidarians Flashcards
what kind of symmetry
radially symmetrical
what level organization do adults have
tissue level
what are cnidocytes
specialized stinging cells
what is the nematocyst capsule
specialized stinging structure
long, spiral, hollow thread that stings and some have spines that inject neurotoxins (paralyzing)
- some may be barbed
- some trap prey/predators
what is the polyp body type
mouth directed upward from substrate
- eg. sea anemone
what is the medusa body type
mouth directed downward, tentacles are at the bottom
- contains more mesoglea
- eg. jellyfish
when both forms are present what do they (re)produce
polyp: medusae
medusa: egg and sperm
zygote develops to a ciliated larva that can disperse
can a stage be dominant/reduced and in some species, absent
yes
what is a sac body plan
single opening as mouth and anus
what is a hydra
freshwater cnidarian. small, tubular polyp
what do hydra use for directional movement
circular and longitudinal muscle fibres
- body can contract or extend
what can tentacles on hydra do
reach out and grasp prey
how do hydra reproduce sexually
ovary or testis develops in body wall.
- eggs/sperm released into the water
how do hydra reproduce asexually
budding
explain hydra’s digestive system
- Endoderm secretes digestive juices (enzymes) into gastrovascular cavity
- Food is partially digested and completed in Food vacuoles by gastroderm cells
what kind of digestion do hydra use
extracellular and intracellular
what do hydra do for respiration since they have no respiratory system
diffusion
- oxygen diffuses from water into body cells. co2 diffuses out
what do hydra do for circulation of nutrients
nutrients pass cell to cell by diffusion
what do hydra do to excrete
wastes diffuse from cells to the environment
what is the ectoderm
protective outer covering/tissue layer
what is the endoderm / gastrodermis
inner covering that lines the gastrovascular cavity gut
how is the nerve net formed and where
interconnected nerve cells that are below the epidermis (tissue from the ectoderm) and near the mesoglea
what does the nerve net do
- communicates with cells throughout the body
- allows transmission of impulses at once
- connections between nerve cells and muscle fibres allow directional movement
what is the mesoglea and what does it do
jellylike non cellular packing material
- separates tissues
what does the gastrovascular cavity do
- carries on digestion
- acts as a circulatory system by distributing food and gases
- acts as a supportive hydrostatic skeleton
