Protists and Echinoderms

Question 1

Marine Algae

Answer 1

• Eukaryotes; have a nucleus, contain membrane-bound organelles
• Some multicellular, some unicellular
• First appeared 1.5 billion years ago

- Plant-like protists 
— perform photosynthesis like plants 
— contain chlorophyll like plants
- Not plant like because 
— lack an internal transport system
— lack roots 

• Endosymbiont Hypothesis
  — 2 prokaryotes living in a symbiotic relationship form a eukaryote; each prokaryote lost its independence; now they co-exist

Question 2

Phylum Pyrrophyta

Answer 2

• AKA Dinoflagellates
• 2 flagella for movement
• cell walls made of cellulose
• eyespot sensitive to light
• photosynthetic
• mostly live in salt water

1. bioluminescent
   - give off natural light when agitated
   - luciferan (protein) plus luciferase (enzyme) plus ATP produces light
   - Bioluminescent bay (Vieques)
2. red tide
   - waters turn reddish color due to sudden growth of particular species of dinoflagellates
   - due to influx of organic compounds and fertilizers
   - algal bloom causes oxygen levels to drop, killing more fish
   - make toxin (saxotoxin) which are eaten by shellfish, which are eaten by fish and birds killing them and possibly us

Question 3

Phylum Chrysophyta

Answer 3

• AKA diatoms
• Golden algae
• most common living thing in ocean
• single cell protists that float near surface; photosynthetic
• in group called plankton (drifters - no sure way to move)
• adaptations to increase photosynthesis:
  — contain chlorophyll in chloroplasts near cell wall
  — have cell walls made of silica/glass for light
• 25000 species
• when they die, their shells fall to ocean floor
  — makes diatomaceous earth; used in pool filters/aquariums
• algal bloom of diatoms = brown tide due to presence of Aureoumbra Lagunesis
• Located in Gult of Mexico
• Harmless to humans, may kill fish larvae

Question 4

Reproduction in Chlorophyta

Answer 4

• alternation of generation:
• switching back and forth from producing diploid (two sets of chromosomes - 2N - spore producing phase) to haploid (one set of chromosomes - N - gamete producing phase)
• sporophytes (2N) and gametophytes (N) look identical
• advantage of reproduction with or without other algae

Question 5

Phylum Phaeophyta

Answer 5

• Brown algae
• most of seaweeds in the ocean
• chlorophyll “a” (absorbs light from surface) and “c” (absorbs light from deeper)

accessory pigments:
- seawater absorbs red/violet light colors first, thus the blue appearance of the ocean at depths
- only blue can penetrate deep water
— there must be photosynthetic pigments designed to absorb light at greater depths
— fucoxanthin

• Rockweed
  — pneumatocyst; air pocket/air bladder to help keep algae up in water column
  — blade; leaf like structure containing chloroplasts
  — stipe; stem like structure
  — holdfast; root like structures
• Giant kelp
  – Macrocystis pyrifera
  – 30 meters (100 feet) long
  –Off Pacific coast of California
  – submarine forests providing food and habitat for a wide range of marine invertebrates and fishes
  grow at rates of 1-2 feet per day
  – Harvested in 1917-1918 for potash (chemical used in explosives and gunpowder)
  – Used as an anti-aging cream today
  – Sea otters wrap themselves to not float away while sleeping
  – Absorbs CO2 from the seawater, making it less acidic
  – modern primary source for algin

Question 6

Echinodermata

Answer 6

• e.g sea urchins, sea stars, sand dollars and sea cucumbers
• marine invertebrates with spiny skin
• 7,000 species
• radial symmetry (body parts radiate out from central point)
• endowment on made of ossicles (CaCO3 plates)
• motile (able to move under own control) but very slow moving

Question 7

Movement of echinodermata

Answer 7

water vascular system;

• system of water-filled tubes used in movement
• water enters through madreporitw, a sieve-like filtering opening on dorsal side of echinoderm
• water passes into ring canal then into radial canal of each arm
• water flows into ampulla, muscles contract, forcing water into tube feet causing it to extend out

Question 8

Class Asteroidea (Echinodermata)

Answer 8

• sea stars
• 1600 species
• usually 5 arms (up to 50)
• hunt clams, barnacles and coral reefs; peel open shells, insert stomach in between shells, digest within the shell and suck up the soup
• pedicellariae (small pincer-like structures on skin to get rid of debris and may help in feeding)

Question 9

Class Ophiuroidea (Echinodermata)

Answer 9

• brittle stars, basket stars,
• 2000 species
• long, highly branched arms
• no tube feet or ampullae
• fastest of all echinoderms

Question 10

Class Holothuroidea

Answer 10

• sea cucumbers
• no arms
• 5 rows of tube feet running down side of body
• modified tube feet around mouth
• protection:
  — sends out cuvierian tubes; long sticky toxic tubes from anus to entangle predator to allow time for escape
  — evisceration; expelling internal organs for the predictor to eat to distract them

Question 11

Class Echinoidea

Answer 11

• sea urchins and sand dollars
• bodies shaped like spheres/discs with no arms
• moveable spines
• tube feet among the spines
• pedicellariae (small pincer-like structures on skin to get rid of debris)
• Aristotle’s lantern; five piece mouth structure that scrapes algae off rocks (aids in producing sand this way)

Question 12

Class Crinoidea

Answer 12

• Have plant-like, stalk-like arms (5-200)
• mouth on dorsal side
• cirri are claw-like appendages used to grab a surface and hang on
• can swim by coordinated flapping of arms
• tube feet on arms capture plankton

Question 13

Phylum Rhodophyta

Answer 13

• Red algae
• chlorophyll “a” and “d”
• accesory pigment phycobilins – absorbs blue light; allow them to survive deep down (100 feet+)

uses by humans:

• carrageenan (chemical used in ice cream, toothpaste as thickener )
• agar (chemical used to grow bacteria in labs)
• Irish Moss, Nori (used in sushi wraps)