Mr. Bastin - Cnidarians

Taxonomy

Domain: Eukarya

Kingdom: Animalia

Phylum: Cnidaria (from Greek "nettle"

Cnidarian Basics (includes, live with anyone, feeding, where they live)

-most marine

-includes hydras, jellyfish, sea anemones, coral

-some colonial

-carnivorous w/ stinging tentacles

Structure

-simplest animals to have body symmetry + specialized tissues

-radial symmetry (can respond to stimuli from all directions

-central opening surrounded by tentacles (functions as bot mouth/anus)

Life cycle

sperm/egg

zygote

larva

polyp

budding polyp

young madusa

adult madusa

2 tissue layers (diploblastic)

-both the polyp and medusa have

-epiderm(is): outer layer of cells

-gastroderm(is): inner layer of cells lining gastrovascular cavity

-mesoglea: layer between

Feeding

Cnidocytes sting and capture prey + defend

nematocysts shoot poison barbs

-pulls paralyzed prey through mouth/anus into gastrovascular for digestion

-wastes expelled through mouth/anus

Response

-simple nerve net but lacks brain

-nerve net = loosely organized network of cells

-eyespots detect light

Movement

-microfilaments and gastrovascular cavity

>enables body to change shape

>allows medusa to move by jet propulsion

Reproduction

-both asexual and sexual

Asexual: polyps clone by budding

-swell to form new polyp

-seperate to form tiny medusas

-polyps also clone by splitting

Sexual:

-individuals usually male + female

-external fertilization in water (sperm and egg released by parents) (usually Medusa)

-zygote becomes free swimming larva

-larva attaches to hard surface to form polyps

-polyps form medusas

Class Hydrozoa

Hydra, Obelia

-solitary polyps

-lack medusa stage

Class Scyphozoa

-jellyfishes (cup animals)

-medusa most prominent stage

-sting for feeding + defense (painful to fatal)

Class Anthrozoa

-sea anemones and corals

-only occur as polyps (lack a medusa stage)

-solitary polyps

-capture prey with nematocysts

-fight for space with other anemones

Corals:

colonial polyps

larva settle onto hard surface

>produce colony by budding

]>cement to adjacent polyps

>over time, build up rocklike formations called coral reefs

Types of reefs

Fringing: near coastline and around islands/continents

Barrier: parallel to coastline but are separated by deeper, wider lagoons

Atolls: rings of coral that create protected lagoons

Corals rely on symbiotic zooxanthellae for?

-its a type of algae

-provides oxygen

-aids in CaCo3 (calcium carbonate) production

Threats to coral reefs

-Siltation

Ocean warming

results in coral bleaching (coral loses color without zooxanthellae)