Wize High School Grade 11 Biology Textbook > Invertebrates: Part 2 - Molting [Under construction]
Deuterostoma (Sea Stars, Urchins and Sea Squirts)
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Deuterostoma
Very iconic species that are often seen near shore. When sea urchins are not kept in check by natural predators they can devastate kelp forest ecosystems. Wasting disease is also a major threat to sea stars in the wild.
- 2 phyla: Echinodermata and Chordata
- Mostly based on DNA
- Shared developmental characters
- Triploblastic
- Radial, indeterminate cleavage
Phylum: Echinodermata
- Sea stars, urchins, sea cucumbers
- Calcareous endoskeleton: skeleton made of calcium carbonate
- Good for creating fossils
- Movement
- Slow
- Sessile
- Marine
- Body
- Diffuse nervous system: lack brain
- Mouth is at the center of arms
Characteristics
- Adults: Penta-radial symmetry (five sides)
- Larvae: Bilateral symmetry (2 sides)
- Separate sexes
- Broadcast spawning: fertilization in open water, planktonic larvae
- Water Vascular System
- Network of hydraulic canals branching into tube feet
- Madreporite = "Mother pore" allows water to flow in and out of system
- Water pressure and adhesion operates tube feet
- Tube feet: made up of ampulla and podium
- Used for locomotion, feeding, gas exchange
Classes of Echinodermata
Class Asteroidea
- Sea stars
- 5+ arms
- Active predators
Class Echinoidea
- Sea Urchins and Sand dollars
- No arms
- Spines: used for locomotion and protection
- Eat seaweed
Class Holothuroidea
- Sea cucumbers
- Elongate
- Deposit or suspension feeders
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Intro to Chordates
Fascinating, simple creatures that represent the very start of vertebrate evolution. This lineage is the link that relate humans to invertebrates.
Four Synapomorphies
- Notochord
- Elastic rod (like the spinal chord in Verts)
- Dorsal, hollow nerve cord
- Pharyngeal clefts
- Beginning of ear canal and Jaws
- Muscular post-anal tail
Subphylum Cephalochordata
- Lancelets
- Marine
- Adult has chordate features
- Segmentation
- Serial arrangement of muscles
- Little cephalization
- Sedentary suspension feeders
- Hox genes and brain development
- Not in sponges
- Conserved DNA sequence (important)
- Number of replications can be repeated
- Regulatory genes that produce proteins
- Controls anterior and posterior development in embryo
Subphylum Urochordata
- Sea Squirts
- Larval stage contains all 4 synapomorphies
- Adults do not look chordate
- Undergo metamorphosis
- Sessile
- Filter / suspension feeders
- Pharyngeal basket: evolved from precursor to gills, uses to catch food
Practice: Echinodermata
Which of the following features are present in Echinodermata? (select all that apply)
Practice: Echinodermata
What structure do Echinoderms use for locomotion?
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