L10 Biodiversity

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Kingdom Animalia

General Characteristics

The animal kingdom is the most complex group of organisms, characterized by several unique features that distinguish them from other life forms. Animals are essential for ecosystem health and human society.

Heterotrophic: Animals obtain nutrition by consuming other organisms and digesting food using enzymes.
Multicellular: Composed of multiple cells with specialized functions.
Eukaryotic: Cells contain a nucleus and membrane-bound organelles.
Motile: Most animals can move at some stage of their life cycle.
Sensory Ability: Animals possess specialized sensory organs to detect environmental changes.
No Cell Wall: Unlike plants and fungi, animal cells lack a rigid cell wall.

Close-up of an insect's face, showing sensory organs

Importance of Animals

Sources of food and products (meat, silk, pearls, etc.)
Maintain ecosystem health (pollinators, decomposers, etc.)
Companionship (pets)

Classification and Phylogeny

Major Divisions Among Animals

Animals are classified based on evolutionary relationships and developmental characteristics. The phylogenetic tree illustrates the major animal phyla and their evolutionary connections.

Development of Nerves: Specialized cells (neurons) coordinate movement and sensory functions.
Body Symmetry: Animals exhibit different types of symmetry, which is a key classification feature.

Phylogenetic tree of major animal phyla Neurons, specialized cells for coordination and sensing

Body Symmetry

Symmetry refers to the arrangement of body parts around a central axis or midline.

Radial Symmetry: Body parts arranged around a central axis (e.g., jellyfish).
Bilateral Symmetry: Body divided into left and right mirror-image halves, with dorsal (back) and ventral (belly) surfaces (e.g., humans).
No Symmetry: Some animals, like sponges, lack symmetry.

Diagram showing none, radial, and bilateral symmetry

Major Animal Phyla

Porifera: Sponges, lack true tissues and symmetry.
Cnidaria: Jellyfish, corals, sea anemones; exhibit radial symmetry and specialized stinging cells.
Platyhelminthes: Flatworms, simple bilateral symmetry.
Rotifera: Microscopic aquatic animals.
Mollusca: Snails, clams, octopuses; soft-bodied, often with a shell.
Annelida: Segmented worms like earthworms.
Arthropoda: Insects, spiders, crustaceans; jointed limbs and exoskeleton.
Echinodermata: Starfish, sea urchins; radial symmetry as adults.
Chordata: Vertebrates and some invertebrates; possess a notochord.

Diversity of cnidarians: jellyfish, corals, sea anemones Jellyfish, example of radial symmetry Flatworm, example of Platyhelminthes Snail, example of Mollusca Earthworm, example of Annelida Nematode, example of Rotifera or Nematoda Spider, example of Arthropoda Rotifer, example of Rotifera Butterfly, example of Arthropoda Octopus, example of Mollusca Starfish, example of Echinodermata Sea urchin, example of Echinodermata

Protostomes vs. Deuterostomes

Bilaterally symmetrical animals are divided into two major branches based on embryonic development:

Protostomes: Mouth forms before anus during development (e.g., arthropods, mollusks, annelids).
Deuterostomes: Anus forms before mouth (e.g., chordates, echinoderms).

Phylogenetic tree showing protostomes and deuterostomes

Chordates vs. Non-Chordates

Chordates are animals with a dorsal backbone or notochord, including vertebrates such as fish, amphibians, reptiles, birds, and mammals. All other animals are referred to as invertebrates.

Classification of animals: vertebrates and invertebrates

Cell Specialization and Germ Layers

Germ Layers in Embryonic Development

Most animals develop from embryos with three germ layers, which give rise to specialized tissues and organs.

Ectoderm: Forms the outer layer, including skin and nervous system.
Mesoderm: Forms the middle layer, including circulatory, reproductive, excretory, and muscular systems, as well as the coelom (body cavity).
Endoderm: Forms the inner layer, including the lining of the gut and some respiratory structures.

Embryonic development stages: zygote, cleavage, blastula, gastrula Diagram of coelom and internal organs

Human-Animal Interactions: Protostomes

Negative Interactions

Protostome animals can negatively impact humans as competitors, pathogens, and vectors.

Competitors: Insects and slugs compete with humans for food crops, causing food loss and increased costs.
Pathogens and Vectors: Parasitic diseases caused by nematodes, tapeworms, and flukes affect human tissues. Vectors like mosquitoes and ticks spread diseases such as malaria and Lyme disease.

Diversity of protostome animals Tomato hornworm, competitor for food crops Tapeworm, example of parasitic pathogen Nematodes, example of parasitic worms Tick, vector for disease

Positive Interactions

Protostome animals provide food and economic benefits to humans.

Clams, scallops, shrimp, lobster: important seafood sources.
Oysters: source of pearls.
Caterpillars: produce silk.
Insects: pollinate food crops.

Silkworm caterpillar producing silk

Vertebrate Diversity and the Web of Life

Diversity of Vertebrates

Vertebrates are extraordinarily diverse in size, sensory abilities, behavior, and life cycles.

Size: Range from the blue whale (150,000 kg) to the bee hummingbird (1.8 g).
Sensory Ability: Includes echolocation (bats) and infrared detection (viper snakes).
Behavior: Migration and hibernation are examples of complex behaviors.
Life Cycles: Vary widely among vertebrate species.

Diversity of vertebrate and invertebrate size Hibernating mammal, example of vertebrate behavior Tiny frog, example of vertebrate size diversity Tiny lizard, example of vertebrate size diversity

Sensory Ability Diversity

Echolocation: Used by bats to navigate and hunt.
Infrared Radiation Detection: Used by viper snakes to detect prey.

Dust mite, example of invertebrate size diversity

Defence Mechanisms in the Animal Kingdom

Variety of Defence Mechanisms

Animals have evolved a wide range of defense mechanisms to protect themselves from predators and environmental threats.

Sea cucumber: expels intestines as a defense.
Texas horned lizard: shoots blood from its eyes.
Hairy frog: breaks finger bones to use as claws.
Bombardier beetle: sprays hot poison.
Flying fish: escape predators by gliding above water.

Additional info: These mechanisms illustrate the diversity and adaptability of animal survival strategies.

Summary Table: Animal Classification

The following table summarizes the classification of major animal groups based on the presence or absence of a backbone and their physiological characteristics.

Group	Examples	Backbone	Cold/Warm-blooded
Arthropoda	Insects, Crustaceans, Arachnids, Diplopoda	No	Cold-blooded
Mollusca	Snails, Octopus	No	Cold-blooded
Fish	Salmon, Guppy	Yes	Cold-blooded
Amphibia	Frog, Toad	Yes	Cold-blooded
Reptiles	Snake, Turtle	Yes	Cold-blooded
Birds	Penguin, Sparrow	Yes	Warm-blooded
Mammals	Elephant, Human	Yes	Warm-blooded

Classification table of animals with and without backbone

Summary Table: Chordate Phylogeny

This table outlines the evolutionary relationships among chordates and their distinguishing features.

Group	Key Features
Agnatha	Jawless fish, notochord, segmented body, gill slits
Chondrichthyes	Cartilaginous fish, true vertebrae, jaws, paired appendages
Actinopterygii	Ray-finned fish, bony skeleton
Amphibia	Two pairs of limbs
Reptilia	Amniotic egg, waterproof skin
Aves	Feathers
Mammalia	Milk, hair

Phylogenetic tree of chordates

Key Terms and Definitions

Coelom: The body cavity in animals that contains internal organs.
Notochord: A flexible rod-like structure found in chordates.
Blastula: Early stage of embryonic development.
Gastrula: Stage where germ layers form.
Symmetry: Arrangement of body parts around an axis or midline.

Relevant Equations and Diagrams

While animal classification does not rely on mathematical equations, diagrams such as phylogenetic trees and embryonic development stages are essential for understanding relationships and processes.

Additional info: For further study, refer to recommended videos and textbook pages for detailed explanations of animal diversity and classification.