Overview
This lecture covers the diversity, structure, and classification of the animal kingdom, focusing on key invertebrate and vertebrate groups, their biology, and evolutionary adaptations.
Diversity of the Animal Kingdom
- Animals are multicellular, heterotrophic organisms that lack cell walls and are mostly capable of movement.
- The animal kingdom is divided into invertebrates (no backbone) and vertebrates (with backbone).
- Major invertebrate phyla include Porifera (sponges), Cnidaria (jellyfish, corals), Platyhelminthes (flatworms), Nematoda (roundworms), Annelida (segmented worms), Mollusca (snails, octopuses), Arthropoda (insects, spiders, crustaceans), and Echinodermata (starfish).
- Vertebrates are represented by classes such as fish, amphibians, reptiles, birds, and mammals.
Structural and Functional Characteristics
- Invertebrates show a range of body symmetries: asymmetrical (sponges), radial (cnidarians, echinoderms), and bilateral (most others).
- Key body systems in animals include digestive, circulatory, nervous, respiratory, and reproductive systems.
- Arthropods have exoskeletons, segmented bodies, and jointed limbs.
- Mollusks possess soft bodies, often protected by a calcareous shell.
- Echinoderms have a unique water vascular system for movement and feeding.
Classification of Vertebrates
- Fish are aquatic vertebrates with gills, fins, and often scales; can be cartilaginous (sharks) or bony.
- Amphibians live in water and on land and typically undergo metamorphosis (tadpole to adult frog).
- Reptiles have dry, scaly skin and lay shelled eggs on land.
- Birds are warm-blooded, have feathers, and lay hard-shelled eggs.
- Mammals are warm-blooded, have fur or hair, and females produce milk for young.
Evolutionary Adaptations
- Evolution in animals is marked by increasing body complexity and specialization of organs.
- Adaptations to different environments include development of gills, lungs, limbs, wings, and insulation (fur, feathers).
Key Terms & Definitions
- Invertebrate — animal without a backbone.
- Vertebrate — animal with a backbone.
- Symmetry — arrangement of body parts relative to a central line or point.
- Exoskeleton — external skeleton that supports and protects an animal’s body.
- Metamorphosis — developmental transformation from larva to adult.
Action Items / Next Steps
- Review textbook pages on animal classification and structure.
- Prepare a table comparing main invertebrate phyla characteristics.
- Complete assigned reading on vertebrate evolution.