-
Cnidaria
- metazoan: have true tissue but lack organs
- radial symmetry
- 2 germ layers (endoderm and ectoderm)
- acoelomate: lack body cavity
-
Cnidocytes
contain nemtocysts - stinging organelles
-
Nematocysts
- stinging organelles in Cnidarians
- when stimulated, ejact small harpoon-like projection w/ toxins
- involved in anchoring, feeding, or defense
-
Anthozoa
coral and sea anemones
-
Hydrozoa
hydras and some corals
-
Cubozoa
box jellyfish and sea wasp
-
Scyphozoa
jellyfish and sea nettles
-
Cnidarian Body Plan (2)
- sessile polyp: attached to surface
- medusa: free-swimming
- in both forms, ring of tentacles surrounds mouth to capture food/protect organism
-
GVC
- Gastrovascular Cavity
- allows for ingestion of "food" much larger than individual cells
- helps distribute food in preliminary phases of digestion
- lined with gastrodermis
-
Gastrodermis
- has gland cells that secrete digestive enzymes => proteasesaids in digestion
-
Proteases
- secreted by glands in gastrodermis
- hydrolyzes peptide bonds
-
Pseudopods
- engulf partially digested material
- stores food in food vacuoles where final digestion occurs
- formed from nutritive-muscular cells
-
Nutritive-Muscular cells
- contain flagella that beat and move fluid within gastrovascular cavity
- form pseudopods
-
Cnidarian Body Wall
- two cellular layers:
- outer epidermis: dervied from ectoderm
- inner gastrodermis: derived from endoderm
- mesoglea: space inbetween these layers
-
Mesoglea
- spaced between outer epidermis and inner gastrodermis
- filled with extracellular matrix
- thick and "jelly-like"
- fuctions like endoskeleton -> provides support and attachment point for muscle cells
-
Cnidarian Nervous system
- primative/ in form of an irregular net that allows animal to respond to stimuli in a coordinated fashion
- limited sensory capabilities
- no sign of cephalization = central nervous system
-
Hydra
- freshwater
- lacks medusa stage
-
-
Hydra Basal Disk
where it attaches to surface
-
Hydra Reproduction
- both asexual and sexual (with gametes
- produce young asexually by mitotic cell division
- some dioecious: male and female repro organs
-
Cnidarian: Symmetry
radial with oral and aboral surface
-
Cnidarian: other body plans
medusa and polyp
-
Cnidarian: # Germ layers
- 2 (development of tissues, no organs)
- ectoderm -> epidermis
- endoderm -> gastrodermis
-
Cnidarian: Metamerism
segmentation: none
-
-
Cnidaria: Skeletal System
- none in hydrazoa
- CaCO3 in coral (anthrozoa)
- mesoglea: space btwn epidermis and gastrodermia that functions like endoskeleton but is NOT a true cellular layer
-
Cnidaria: Cephalization
central nervous system: none
-
Cnidaria: Nervous System
- primative
- irregular net
- respond to stimuli in coordinated fashion (i.e. outer tentacles engulf while inner contracts)
- limited sensory capabilities
-
Cnidaria: Digestive System
- Gastrovascular cavity
- tentacles used to gather food
- gastrodermis lines cavity -> glands that secrete protease
- nutritive muscular cells form pseudopods -> engulf partially digested food and transport them to final digestion site
-
Cnidaria: Circulatory System
- none (Diffusion)
- cilia surrounding cavity moves fluid and food
-
Cnidaria: Respiratory System
none (Diffusion)
-
Cnidaria: Excretory System
none (Diffusion)
-
Cnidaria: Sexual Cycle
- monoecious or dioecious
- hydras can be either dioecious or hermaphroditic
-
Cnidaria: Locomotion
- Tumbling, swimming, floating, gliding
- tentacles and body contract and release for swimming in medusa stage
- in polyp stage, nematocysts help attach it to surface
-
Cnidaria: Notes
- cnidocytes with nematocysts
- 10,000 species, mostly marine
- hydras are freshwater and have no medusa stage
- evolved 580 mya
-
Cnidaria: Classes
- anthrozoa: coral and amemone
- hydrozoa: hydras, obella/obelia
- cubozoa: box jellyfish, sea wasps
- scyphozoa: jellyfish, sea nettles
|
|