Introduction to Protozoa and Protists

Protozoa

• Flagellates: Move using flagella (whip-like organelles). Unicellular.
• Ciliates: Move using cilia (tiny hair-like organelles). Alveolates. Similar structure to eukaryotic cilia.
• Amoebas: Move using pseudopods (temporary extensions). Unicellular, adaptable shape. Found in various water bodies; can cause illness.
• Forams: Marine protozoa. Secretes shell. Extends pseudopodia (extensions) through pores.
• Choanoflagellates: Closest living relatives to animals. Unicellular predators. Use flagella surrounded by a collar for movement and hunting.

Fungus-like Protists

• Slime Molds: Fungus-like protists. Key decomposers/recyclers. Found on decaying matter. Diet consists of bacteria.
• Cellular Slime Molds: Protists with unicellular amoeboid cells. Form multicellular structures (slug-like) during food shortages. Develop fruiting bodies for spore dispersal.

Algae

• Dinoflagellates: Protists forming "blooms." May be toxic. Can be bioluminescent. Two flagella; half heterotrophic, half photosynthetic. Mostly marine plankton.
• Diatoms: Unicellular photosynthetic algae. Glassy silica cell walls. Thousands of types; two main shapes: pennate (cigar/pen-shaped) and centric (disk/drum-shaped).
• Green Algae: Photosynthetic protists. Unicellular, colonial, or multicellular. Chlorophyll a & b (green colour). Store carbohydrates as starch. Cell walls are cellulose. Closest algal relatives to plants.

Animal-like Protists (Porifera)

• Sponges (Porifera): Sessile, suspension feeders. No body symmetry. Flagellated collar cells (choanocytes).

Animal Phyla

Cnidaria

• Cnidarians: Radial symmetry. Sessile or motile (jellyfish, anemones, corals). Cnidocytes (stinging cells). Medusa (free-swimming) and polyp (sessile) forms.

Platyhelminthes

• Flatworms: Bilateral symmetry. Acoelomates (no body cavity). Incomplete digestive system (one opening). Parasitic flatworms (tapeworms) have a scolex (hooks and suckers).

Annelida

• Segmented Worms: Segmented bodies. True coelom. Bilateral symmetry. (leeches).

Nematoda

• Roundworms: Pseudocoelomates (body cavity partially lined with mesoderm). Complete digestive tract (two openings).

Mollusca

• Mollusks: Bilateral symmetry. Gastropods (snails), bivalves (clams), cephalopods (octopuses).

Arthropoda

• Arthropods: Segmented bodies. Jointed appendages. Exoskeleton made of chitin. Compound eyes (mosaic vision). Molting. Arachnids (spiders), crustaceans (crabs), insects.

Echinodermata

• Echinoderms: Larvae have bilateral symmetry; adults have radial symmetry. Water vascular system. Capable of regeneration. Sea stars, sea urchins, sea cucumbers, and sand dollars.

Chordata

• Chordates: Notochord, dorsal hollow nerve cord, pharyngeal slits, post-anal tail.
• Urochordates: Tunicates.
• Cephalochordates: Lancelets.
• Vertebrates: Complex internal skeleton.

Agnatha (Jawless Vertebrates)

• Jawless Fish: Hagfish and lampreys. Cartilage skeleton. Cylindrical body. No fins.
• Hagfish: Primitive. Scavengers. Slimy.
• Lampreys: Vertebrates without hinged jaws. Adults are often parasitic.

Chondrichthyes (Cartilaginous Fish)

• Cartilaginous Fish: Flexible skeletons. Predators. Powerful jaws.

Osteichthyes (Bony Fish)

• Bony Fish: Swim bladder for buoyancy control. Bone skeleton. Protected by an operculum.

Amphibia

• Amphibians: First tetrapods (four limbs). Limbs support weight on land. Carnivorous. Primarily water-dwelling or damp habitats. Salamanders, frogs.

Reptilia

• Reptiles: Lizards, snakes, crocodiles, turtles. Ectothermic (cold-blooded). Scales present

Reptilia/Aves (Birds)

• Birds: Endothermic (warm-blooded). Feathers. Good vision. Courtship displays. Hard-shelled eggs.

Mammalia

• Mammals: Mammary glands. Hair/fur. High metabolic rate. Long parental care. Usually give birth to live young. Endothermic. Teeth vary in shape.

Hominins

• Hominins: Bipedal. Homo
  • Homo habilis: "handy man," first tool use.
• Homo erectus: Upright posture. Larger brain, face. Speech possible.