Animal kingdom: Invertebrates and Porifera

• The animal kingdom is a diverse group of multicellular, eukaryotic organisms.
• Animals are heterotrophic, obtaining nutrients by ingestion.
• Animals are motile at some stage of their life cycle.
• Most animals reproduce sexually

Invertebrates

• Invertebrates are animals without a backbone or vertebral column.
• They represent over 95% of known animal species.
• Invertebrates occupy diverse habitats, including marine, freshwater, and terrestrial environments.
• Major invertebrate phyla include: Porifera (sponges), Cnidaria (jellyfish, corals), Platyhelminthes (flatworms), Nematoda (roundworms), Annelida (segmented worms), Mollusca (snails, clams, squid), Arthropoda (insects, spiders, crustaceans), and Echinodermata (starfish, sea urchins).

Porifera (Sponges)

• Sponges are simple, sessile animals.
• They lack true tissues and organs.
• They filter feed, drawing water through pores (ostia) and expelling it through an osculum.
• Their body is supported by a skeleton made of spicules or spongin fibers.

Cnidaria (Jellyfish, Corals, Anemones)

• Cnidarians have radial symmetry.
• They possess specialized stinging cells called cnidocytes.
• They can be solitary or colonial.
• They exhibit two basic body forms: polyp (sessile) and medusa (free-swimming).
• Examples include jellyfish, corals, sea anemones, and hydras.

Platyhelminthes (Flatworms)

• Flatworms have bilateral symmetry.
• They possess a flattened body shape.
• Many are parasitic, such as tapeworms and flukes.
• They lack a specialized respiratory and circulatory system.
• They have a simple nervous system with a cephalized brain.

Nematoda (Roundworms)

• Roundworms have a cylindrical, unsegmented body.
• Many are free-living in soil and aquatic habitats, while others are parasitic.
• They possess a complete digestive system with a mouth and anus.
• They have a pseudocoelom, a fluid-filled body cavity.
• Examples include hookworms, pinworms, and heartworms.

Annelida (Segmented Worms)

• Annelids have segmented bodies.
• They possess a coelom, a true body cavity.
• They have a closed circulatory system.
• They exhibit metameric segmentation, with repeating body units.
• Examples include earthworms, leeches, and polychaetes.

Mollusca (Snails, Clams, Squid)

• Mollusks are a diverse group with a soft body.
• Many possess a hard shell.
• They have a mantle, which secretes the shell.
• They have a muscular foot for locomotion.
• Major classes include: Gastropoda (snails), Bivalvia (clams, oysters), and Cephalopoda (squid, octopuses).

Arthropoda (Insects, Spiders, Crustaceans)

• Arthropods are the most diverse animal phylum.
• They have a segmented body.
• They possess a hard exoskeleton made of chitin.
• They have jointed appendages.
• Major classes include: Insecta (insects), Arachnida (spiders, scorpions), Crustacea (crabs, lobsters), and Myriapoda (millipedes, centipedes).

Echinodermata (Starfish, Sea Urchins)

• Echinoderms have radial symmetry (typically pentaradial).
• They possess a water vascular system for locomotion, feeding, and gas exchange.
• They have an internal skeleton made of ossicles.
• They are exclusively marine.
• Examples include starfish, sea urchins, sea cucumbers, and brittle stars.

Vertebrates

• Vertebrates are animals with a backbone or vertebral column.
• They belong to the phylum Chordata, subphylum Vertebrata.
• They have a well-developed brain and nervous system.
• They possess a closed circulatory system with a heart.
• Major vertebrate classes include: Agnatha (jawless fish), Chondrichthyes (cartilaginous fish), Osteichthyes (bony fish), Amphibia (amphibians), Reptilia (reptiles), Aves (birds), and Mammalia (mammals).

Agnatha (Jawless Fish)

• Jawless fish lack jaws and paired fins.
• They have a cartilaginous skeleton.
• Examples include lampreys and hagfish.

Chondrichthyes (Cartilaginous Fish)

• Cartilaginous fish have a skeleton made of cartilage.
• They possess jaws and paired fins.
• Examples include sharks, rays, and skates.

Osteichthyes (Bony Fish)

• Bony fish have a skeleton made of bone.
• They possess jaws and paired fins.
• They have a swim bladder for buoyancy.
• They are the most diverse group of fish.
• Examples include salmon, trout, and goldfish.

Amphibia (Amphibians)

• Amphibians are tetrapods that typically live both in water and on land.
• They have a moist skin.
• They undergo metamorphosis.
• Examples include frogs, toads, salamanders, and newts.

Reptilia (Reptiles)

• Reptiles are tetrapods with scales or scutes.
• They lay amniotic eggs.
• They are ectothermic (cold-blooded).
• Examples include lizards, snakes, turtles, and crocodiles.

Aves (Birds)

• Birds are tetrapods with feathers.
• They have wings and are adapted for flight.
• They lay amniotic eggs with hard shells.
• They are endothermic (warm-blooded).
• Examples include eagles, sparrows, and penguins.

Mammalia (Mammals)

• Mammals have hair or fur.
• They possess mammary glands that produce milk.
• They give birth to live young (except for monotremes).
• They are endothermic (warm-blooded).
• Examples include humans, lions, whales, and bats.

Habitats

• Animals occupy a wide range of habitats, including:
  • Marine (oceans, seas)
  • Freshwater (lakes, rivers, streams)
  • Terrestrial (land)
  • Aerial (air)
• Specific adaptations enable animals to thrive in their respective habitats.

Evolution

• The animal kingdom evolved from a common ancestor.
• Key evolutionary milestones include:
  • Development of multicellularity
  • Development of tissues and organs
  • Evolution of body symmetry (radial vs. bilateral)
  • Evolution of a coelom
  • Development of segmentation
  • Evolution of jaws
  • Evolution of limbs
  • Evolution of flight
  • Evolution of endothermy

Physiology

• Animal physiology encompasses the study of how animals function.
• Key physiological processes include:
  • Circulation: Transport of oxygen, nutrients, and waste products
  • Respiration: Gas exchange (oxygen uptake and carbon dioxide release)
  • Digestion: Breakdown of food for nutrient absorption
  • Excretion: Elimination of waste products
  • Nervous system: Coordination of body functions and responses
  • Endocrine system: Regulation of bodily functions through hormones
  • Reproduction: Production of offspring
  • Osmoregulation: Maintenance of water and salt balance
  • Thermoregulation: Maintenance of body temperature