cnidarians

Question 1

what kind of symmetry

Answer 1

radially symmetrical

Question 2

what level organization do adults have

Answer 2

tissue level

Question 3

what are cnidocytes

Answer 3

specialized stinging cells

Question 4

what is the nematocyst capsule

Answer 4

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

Question 5

what is the polyp body type

Answer 5

mouth directed upward from substrate
- eg. sea anemone

Question 6

what is the medusa body type

Answer 6

mouth directed downward, tentacles are at the bottom
- contains more mesoglea
- eg. jellyfish

Question 7

when both forms are present what do they (re)produce

Answer 7

polyp: medusae
medusa: egg and sperm

zygote develops to a ciliated larva that can disperse

Question 8

can a stage be dominant/reduced and in some species, absent

Answer 8

yes

Question 9

what is a sac body plan

Answer 9

single opening as mouth and anus

Question 10

what is a hydra

Answer 10

freshwater cnidarian. small, tubular polyp

Question 11

what do hydra use for directional movement

Answer 11

circular and longitudinal muscle fibres
- body can contract or extend

Question 12

what can tentacles on hydra do

Answer 12

reach out and grasp prey

Question 13

how do hydra reproduce sexually

Answer 13

ovary or testis develops in body wall.

• eggs/sperm released into the water

Question 14

how do hydra reproduce asexually

Answer 14

budding

Question 15

explain hydra’s digestive system

Answer 15

• Endoderm secretes digestive juices (enzymes) into gastrovascular cavity
• Food is partially digested and completed in Food vacuoles by gastroderm cells

Question 16

what kind of digestion do hydra use

Answer 16

extracellular and intracellular

Question 17

what do hydra do for respiration since they have no respiratory system

Answer 17

diffusion

• oxygen diffuses from water into body cells. co2 diffuses out

Question 18

what do hydra do for circulation of nutrients

Answer 18

nutrients pass cell to cell by diffusion

Question 19

what do hydra do to excrete

Answer 19

wastes diffuse from cells to the environment

Question 20

what is the ectoderm

Answer 20

protective outer covering/tissue layer

Question 21

what is the endoderm / gastrodermis

Answer 21

inner covering that lines the gastrovascular cavity gut

Question 22

how is the nerve net formed and where

Answer 22

interconnected nerve cells that are below the epidermis (tissue from the ectoderm) and near the mesoglea

Question 23

what does the nerve net do

Answer 23

• communicates with cells throughout the body
• allows transmission of impulses at once
• connections between nerve cells and muscle fibres allow directional movement

Question 24

what is the mesoglea and what does it do

Answer 24

jellylike non cellular packing material
- separates tissues

Question 25

what does the gastrovascular cavity do

Answer 25

• carries on digestion
• acts as a circulatory system by distributing food and gases
• acts as a supportive hydrostatic skeleton