Transcript b. Cnidarians

Biology 11
Mrs. Trevelyan
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Cnidaria
1. PRESCRIBED LEARNING OUTCOMES
and VOCABULARY
2. VIDEOS:
-None 
3. TEXTBOOK PGS
Section 26.2 pgs 698-705
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Examples of Members:
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Overview…
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A Breakdown of Cnidarians…
 Includes jellyfish, sea anemones, coral, and hydra
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1. Unifying Characteristics
 Radial symmetry only
 Development of body layers (2 total! Outer and inner)
 Have a gastrovascular cavity with one opening
 Development of tissues (e.g. nerve, muscle and digestive
tissue)
 Mobility! Some (like jellylfish) can swim; others (like sea
anemones) are sessile.
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2. Structure
•Has 2 cell layers
with a jellylike
substance inbetween
1)epidermis outer layer
2) endodermis inner layer
•Has a mouth,
tentacles, and a
gastrovascular cavity
•Still no brain, heart
or blood
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2. Structure
•Exist in one of two forms:
a) cylinder-shaped polyp (sessile)
b) Umbrella-shaped medusa (mobile)
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3. Digestion
 Have a single opening (“mouth”) and a
digestive cavity (“stomach”)
 Use tentacles to catch and paralyze prey.
Tentacles have called NEMATOCYSTS that
use stingers to sting prey
 Tentacles move food to mouth where it
enters the gastrovascular cavity. Food is
then digested and absorbed into the
body
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4. Respiration/Excretion
RESPIRATION
 No respiratory glands/organs.
 Use diffusion at the cell level for gas exchange
EXCRETION
 No excretory glands or organs
 Solid wastes pass out through the “mouth”
 Gaseous wastes are eliminated by diffusion
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5. Nervous System
 Have a very simple web-like nervous system made up of a
nerve net (sensory neurons- touch and smell)
 Have groupings of nerves called ganglia
 No brain or central nervous system
 Can respond to stimuli
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6. Reproduction
Asexual Reproduction:
 Occurs at either the polyp or medusa stage using BUDDING
 Cnidarians that stay in the polyp stage (e.g. sea anenomes) also
reproduce sexually as polyps
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6. Reproduction
SEXUAL REPRODUCTION
• Usually occurs during the medusa stage
• Male and female medusa release eggs and sperm
• Fertilization occurs and a free- swimming larvae forms
• The larvae attaches to a rock and forms a polyp
• See figure 26.7 pg 700
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6. Reproduction
SEXUAL REPRODUCTION
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7. Additional Interesting Facts
 Many organisms feed on and live in coral and sea anenomes
(for protection)
 Important resources for people (fish and coral reefs)
 Protects coastal areas from damage (errosion)
Problem Today: Jellyfish Blooms (increase in pop’n)
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