WEEK 3: CLASSIFICATION OF LIVING THINGS II

CLASSIFICATION OF ANIMALS

Kingdom Animalia

The kingdom Animalia is divided into vertebrates and invertebrates.

INVERTEBRATES

Invertebrates are animals without backbones. The main invertebrate phyla include:

1. Phylum Protozoa

Examples: Amoeba, Plasmodium, Trypanosoma

• Characteristics:
  1. Unicellular, acellular, or non-cellular.
  2. Mostly microscopic.
  3. Some are free-living in water, while others are parasitic in animals.

2. Phylum Porifera

Examples: Sponges

• Characteristics:
  1. Multicellular, sessile, and largely aquatic.
  2. Possess a single body cavity with several holes/pores.
  3. Body has two layers of cells.
  4. Skeleton is calcareous or siliceous.
  5. Absence of a nervous system.
  6. Reproduction is asexual by budding.

3. Phylum Coelenterata (Cnidaria)

Examples: Hydra, Sea anemone, Jellyfish

• Characteristics:
  1. Simple multicellular organisms.
  2. Aquatic habitat.
  3. Possess two body layers.
  4. True organs are absent.
  5. Possession of nematoblasts (stinging cells).
  6. Asexual reproduction is by budding; sexual reproduction is by fusion of gametes.

4. Phylum Platyhelminthes (Flatworms)

Examples: Liver fluke, Tapeworm, Planaria

• Characteristics:
  1. Flat and thin bodies.
  2. Bilaterally symmetrical.
  3. Possess three body layers (triploblastic).
  4. Nervous, excretory, and reproductive systems are present.
  5. Most members are hermaphrodites.
  6. Includes both free-living and parasitic species.
  7. The digestive body structure has a single opening (the mouth).

5. Phylum Nematoda (Roundworms)

Examples: Ascaris, Hookworm, Guinea worm, Filaria worm, Onchocerca

• Characteristics:
  1. Long, slender, and cylindrical bodies.
  2. Pointed ends.
  3. Three body layers.
  4. Both mouth and anus are present.
  5. Body covered with a cuticle.
  6. Bilaterally symmetrical.
  7. Sexes are separate.
  8. Members are free-living or parasitic.

6. Phylum Annelida (Segmented Worms)

Examples: Earthworms, Hirudo (Leech), Lumbricus

• Characteristics:
  1. Cylindrically elongated body.
  2. Three body layers.
  3. Body divided into smaller segments (metameric segmentation).
  4. Two openings in the alimentary canal (mouth and anus).
  5. Presence of nervous, excretory, reproductive, and circulatory systems.

7. Phylum Mollusca

Examples: Snails, Slugs

• Characteristics:
  1. Soft and unsegmented body.
  2. Three body layers.
  3. Body usually covered with a calcareous shell.
  4. Prominent head and foot.
  5. Eyes and tentacles present on the head.
  6. Body is short, composed of a head, a ventral muscular foot, and a visceral hump.

8. Phylum Arthropoda

Subdivided into five main classes: Insecta, Myriapoda, Arachnida, Crustacea, and Annelida (Note: Annelida is distinct, but often listed comparatively).

• Class Insecta:
  1. Pair of jointed antennae.
  2. Pair of compound eyes.
  3. Body divided into head, thorax, and abdomen.
  4. Thorax subdivided into prothorax, mesothorax, and metathorax.
  5. One pair of jointed legs per thoracic segment (3 pairs total).
  6. Respiration via tracheae.
  7. Wings may be present.
  8. Undergo metamorphosis. Examples: Cockroach, Housefly, Butterfly, Grasshopper
• Class Myriapoda:
  1. Body divided into two regions: Head and fused trunk/abdomen.
  2. Abdomen consists of many limb-bearing segments.
  3. Pair of simple eyes, jaws, and short antennae on the head.
  4. Breathing by means of tracheae.
  5. Subclasses:
     • Chilopoda (Centipedes): 1 pair of legs per segment; carnivorous.
     • Diplopoda (Millipedes): 2 pairs of legs per segment; herbivorous.
• Class Arachnida:
  1. Body divided into prosoma (cephalothorax) and opisthosoma (abdomen).
  2. Presence of chelicerae and pedipalps.
  3. Eight simple eyes.
  4. Eight walking legs (4 pairs).
  5. Respiration by book lungs. Examples: Spiders, Scorpions
• Class Crustacea:
  1. Body regions: Cephalothorax and abdomen.
  2. Pair of antennae for feeling and antennules for smelling.
  3. 5 pairs of walking legs (or more modified appendages).
  4. Pair of stalked compound eyes.
  5. Respiration by means of gills. Examples: Prawns, Shrimps, Crabs, Water fleas, Barnacles

9. Phylum Echinodermata

Examples: Starfish, Sea urchins

• Characteristics:
  1. Exclusively aquatic/marine.
  2. Radially symmetrical in adults.
  3. Triploblastic and coelomate.
  4. Calcareous exoskeleton.
  5. Tube feet with suckers for locomotion.
  6. Sexes are separate.

VERTEBRATES

Vertebrates are animals with backbones. They are divided into five classes:

1. Class Pisces (Fishes)

Examples: Tilapia, Dogfish

• Characteristics:
  1. Visceral/gill clefts persist for respiration in adults.
  2. Paired fins for locomotion (pectoral and pelvic fins).
  3. Well-developed lateral line system for sensitivity.
  4. Exoskeleton made of scales (e.g., cycloid, placoid).
  5. External fertilization in water.

2. Class Amphibia

Examples: Toads, Frogs, Salamanders

• Characteristics:
  1. Presence of pentadactyl limbs.
  2. Soft, moist skin without scales.
  3. Gills used for respiration at larval (tadpole) stage; lungs and skin used in adults.
  4. Middle ear present, but lacks external pinna.
  5. External fertilization.

3. Class Reptilia (Reptiles)

Examples: Lizards, Snakes, Crocodiles, Tortoises

• Characteristics:
  1. Pentadactyl limbs.
  2. Dry skin covered with horny scales.
  3. Lungs used as respiratory organs.
  4. Lay yolk-rich eggs with tough shells; no larval stage.
  5. Internal fertilization.

4. Class Aves (Birds)

Examples: Pigeons, Domestic fowls

• Characteristics:
  1. Forelimbs modified into wings for flight.
  2. Warm-blooded (homoiothermic) animals.
  3. Body covered with feathers.
  4. Presence of a horny beak; teeth are absent.
  5. Epidermal scales on legs and feet.
  6. Lungs used for respiration.
  7. Internal fertilization; lay hard-shelled eggs with abundant yolk.

5. Class Mammalia

Examples: Humans, Rats, Cats, Dogs

• Characteristics:
  1. Pentadactyl limbs.
  2. Warm-blooded (homoiothermic).
  3. Skin covered with hair/fur and contains sweat/sebaceous glands.
  4. Presence of mammary glands that produce milk for young ones.
  5. Four-chambered heart.
  6. Internal fertilization; mostly viviparous (give birth to live young).

EVALUATION

1. Describe Kingdom Animalia.
2. Explain the different phyla in Kingdom Animalia.
3. Describe the classes under Kingdom Animalia.

ASSIGNMENT

Draw and label the structure of a Tilapia fish, Lizard, Grasshopper, and Earthworm.