Animal Diversity, Development, and Major Animal Phyla: Study Guide - Exam 3

Fungi: Ecological Importance and Symbiosis

Ecological Roles of Fungi

Fungi are essential decomposers in ecosystems, breaking down dead plants and animals and recycling nutrients. They also form mutualistic relationships with plants, aiding in nutrient absorption and disease resistance.

• Decomposition: Fungi decompose organic matter, returning nutrients to the soil.

• Symbiosis: Mycorrhizal fungi form partnerships with plant roots, enhancing water and nutrient uptake.

• Pathogens: Some fungi cause diseases in plants and animals.

Example: Mycorrhizal fungi help crops grow better by increasing nutrient absorption.

Fungal Classification

• Glomeromycetes: Form arbuscular mycorrhizae with plant roots.

• Ascomycetes: Sac fungi, produce spores in asci (e.g., yeasts, morels).

• Basidiomycetes: Club fungi, produce spores on basidia (e.g., mushrooms).

Major Animal Phyla and Their Characteristics

Distinguishing the Five Major Phyla

Phylum	Key Features
Porifera	Sessile, no true tissues, asymmetrical, filter feeders (sponges)
Cnidaria	Jellyfish, corals; stinging cells (cnidocytes), radial symmetry, diploblastic
Platyhelminthes	Flatworms; bilateral symmetry, acoelomate, simple organs
Rotifera	Microscopic, wheel-like ciliated corona, pseudocoelomate
Other	Additional info: Mollusca, Annelida, Arthropoda, Echinodermata, Chordata are also major phyla but not listed here.

Cnidarian Classes: Hydrozoa, Scyphozoa, Anthozoa

• Hydrozoa: Both polyp and medusa stages (e.g., Hydra, Obelia).

• Scyphozoa: True jellyfish; dominant medusa stage.

• Anthozoa: Only polyp stage; corals and sea anemones.

Animal Body Plans and Symmetry

Tube-Within-a-Tube Body Plan

A tube-within-a-tube body plan allows for a complete digestive tract, with separate mouth and anus, enabling continuous feeding and specialization of digestive regions.

• Advantage: More efficient digestion and absorption.

• Example: Earthworms, humans.

Radial vs. Bilateral Symmetry

• Radial Symmetry: Body parts arranged around a central axis (e.g., jellyfish).

• Bilateral Symmetry: Single plane divides body into mirror images (e.g., humans, insects).

Significance: Bilateral symmetry is associated with cephalization (development of a head region) and more complex movement.

Animal Development: Early Stages

Key Stages

• Fertilization: Sperm and egg fuse to form a zygote.

• Cleavage: Rapid cell divisions without growth.

• Blastula: Hollow ball of cells.

• Gastrulation: Formation of germ layers (ectoderm, mesoderm, endoderm).

Germ Layers

• Ectoderm: Outer layer; forms skin, nervous system.

• Endoderm: Inner layer; forms digestive tract lining, lungs, liver.

• Mesoderm: Middle layer; forms muscles, bones, heart, kidneys.

Coelom and Body Cavities

Types of Body Cavities

• Acoelomate: No body cavity (e.g., flatworms).

• Pseudocoelomate: Body cavity not fully lined with mesoderm (e.g., roundworms).

• Coelomate: True body cavity fully lined with mesoderm (e.g., earthworms, humans).

Protostomes vs. Deuterostomes

• Protostomes: Mouth develops from the blastopore first (e.g., mollusks, annelids, arthropods).

• Deuterostomes: Anus develops from the blastopore first (e.g., echinoderms, chordates).

Animal Diversity: Trends and Adaptations

Triploblastic Animals

Animals with three germ layers (ectoderm, mesoderm, endoderm). Includes most animal phyla except sponges and cnidarians.

Water Vascular System

Found in echinoderms (e.g., sea stars), this system of fluid-filled canals aids in movement, feeding, and gas exchange.

• Function: Movement via tube feet, capturing food, respiration.

Chordates and Vertebrates

Key Chordate Features

• Notochord

• Dorsal hollow nerve cord

• Pharyngeal slits

• Post-anal tail

Vertebrate Circulatory Systems

Group	Heart Chambers
Fish	2 (1 atrium, 1 ventricle)
Amphibians/Reptiles	3 (2 atria, 1 ventricle)
Birds/Mammals	4 (2 atria, 2 ventricles)

Significance: More chambers allow for more efficient separation of oxygenated and deoxygenated blood.

Reproductive Strategies

• Oviparous: Eggs develop outside the mother's body.

• Viviparous: Young develop inside the mother, nourished directly (e.g., mammals).

• Ovoviviparous: Eggs develop inside the mother, but young are not directly nourished by her (e.g., some sharks).

Birds and Reptiles: Evolutionary Relationships

Birds are more closely related to reptiles (specifically, crocodilians) than to mammals. Both belong to the group Archosauria.

Summary Table: Animal Phyla and Key Features

Phylum	Symmetry	Body Cavity	Development
Porifera	Asymmetrical	None	None
Cnidaria	Radial	None	Diploblastic
Platyhelminthes	Bilateral	Acoelomate	Triploblastic
Rotifera	Bilateral	Pseudocoelomate	Triploblastic
Annelida	Bilateral	Coelomate	Triploblastic

Additional info: This study guide covers topics from animal diversity, development, and major animal phyla, corresponding to chapters on Animal Diversity, Protostomes, Deuterostomes, Animal Development, and related systems in a General Biology course.