🐾General Biology II Unit 18 – Fungi and Animal Diversity

Key Concepts

• Fungi are eukaryotic organisms that form a separate kingdom from plants and animals
• Fungi play crucial roles in ecosystems as decomposers, symbionts, and pathogens
• Animals are multicellular, eukaryotic organisms that are heterotrophic and typically mobile
• Animal diversity is vast, with over 30 major phyla representing a wide range of body plans and adaptations
• Evolutionary relationships among animals can be inferred through comparative anatomy, embryology, and molecular data
• Understanding the ecological roles of fungi and animals is essential for maintaining healthy ecosystems and managing human impacts

Fungal Characteristics

• Fungi are heterotrophic organisms that obtain nutrients by absorbing organic compounds from their environment
• Most fungi are multicellular, with bodies composed of filamentous structures called hyphae
• Hyphae collectively form a network called a mycelium, which is the vegetative body of a fungus
• Fungal cell walls are composed primarily of chitin, a tough polysaccharide that provides structural support
• Fungi reproduce both asexually (through fragmentation, budding, or spore production) and sexually (through the fusion of compatible hyphae)
• Many fungi form symbiotic relationships with other organisms, such as lichens (with algae or cyanobacteria) and mycorrhizae (with plant roots)
• Some fungi are pathogenic, causing diseases in plants (rusts and mildews), animals (ringworm and athlete's foot), and humans (candidiasis and aspergillosis)

Fungal Diversity and Classification

• The fungal kingdom is divided into four major phyla: Chytridiomycota, Zygomycota, Ascomycota, and Basidiomycota
  • Chytridiomycota includes mostly aquatic fungi with flagellated spores (zoospores)
  • Zygomycota includes molds and some parasitic fungi that produce zygospores during sexual reproduction
  • Ascomycota, the largest fungal phylum, includes yeasts, molds, and many lichen-forming fungi that produce ascospores in sac-like structures called asci
  • Basidiomycota includes mushrooms, puffballs, and rust fungi that produce basidiospores on club-shaped structures called basidia
• Fungi exhibit a wide range of morphologies, from unicellular yeasts to complex multicellular structures like mushrooms and bracket fungi
• Many fungi have important economic and culinary uses, such as in the production of bread, beer, wine, cheese, and various fermented foods
• Some fungi, like the genus Penicillium, are used to produce antibiotics (penicillin) and other pharmaceuticals

Animal Diversity Overview

• Animals are a diverse group of organisms that have evolved a wide array of body plans, behaviors, and adaptations
• All animals are multicellular, eukaryotic, and heterotrophic, obtaining nutrients by ingesting other organisms or organic matter
• Animal cells lack cell walls, allowing for greater flexibility and mobility compared to plant and fungal cells
• Most animals develop from a blastula stage, which is a hollow ball of cells that undergoes gastrulation to form the three primary germ layers: ectoderm, mesoderm, and endoderm
• Animals exhibit various levels of tissue organization, from simple cellular layers (sponges) to complex organ systems (vertebrates)
• Symmetry is an important aspect of animal body plans, with most animals exhibiting either radial symmetry (cnidarians) or bilateral symmetry (most other phyla)
• Animal nervous systems range from simple nerve nets (cnidarians) to centralized brains and complex sensory organs (vertebrates)

Major Animal Phyla

• Porifera (sponges): simple, sessile animals with no true tissues or organs; possess a unique water canal system for filtering food particles
• Cnidaria (jellyfish, corals, and sea anemones): radially symmetrical animals with a sac-like body plan and specialized stinging cells called cnidocytes
• Platyhelminthes (flatworms): bilaterally symmetrical, soft-bodied worms with simple organ systems; includes free-living and parasitic forms (tapeworms and flukes)
• Nematoda (roundworms): unsegmented, cylindrical worms with a complete digestive system; includes free-living and parasitic species (hookworms and pinworms)
• Mollusca (snails, clams, and octopuses): soft-bodied animals with a muscular foot and often a protective shell; includes diverse forms adapted to various environments
• Annelida (segmented worms): cylindrical, segmented worms with well-developed organ systems; includes earthworms, leeches, and marine polychaetes
• Arthropoda (insects, crustaceans, and arachnids): segmented animals with a hard exoskeleton, jointed appendages, and a ventral nervous system; the most diverse animal phylum
• Echinodermata (sea stars, sea urchins, and sea cucumbers): spiny-skinned marine animals with a unique water vascular system and regenerative abilities
• Chordata (tunicates, lancelets, and vertebrates): animals with a notochord, dorsal hollow nerve cord, pharyngeal slits, and post-anal tail at some stage of development; includes all vertebrates (fish, amphibians, reptiles, birds, and mammals)

Evolutionary Relationships

• Evolutionary relationships among animal phyla are determined through various lines of evidence, including comparative anatomy, embryology, and molecular data
• The presence of shared derived characters (synapomorphies) suggests common ancestry among certain phyla
  • For example, the notochord and pharyngeal slits are synapomorphies that unite chordates as a monophyletic group
• Convergent evolution can result in similar structures or adaptations in distantly related groups, such as the wings of insects, birds, and bats
• Molecular data, particularly DNA sequence comparisons, have revolutionized our understanding of animal phylogeny and have helped resolve many long-standing evolutionary questions
• The current consensus on animal phylogeny recognizes four major clades: Porifera, Ctenophora (comb jellies), Cnidaria, and Bilateria (all other animal phyla)
  • Within Bilateria, there are three major groups: Deuterostomia (chordates, echinoderms, and hemichordates), Ecdysozoa (arthropods, nematodes, and other molting animals), and Lophotrochozoa (mollusks, annelids, and other spiral-cleaving animals)

Ecological Roles and Importance

• Fungi and animals play crucial roles in various ecosystems, contributing to nutrient cycling, energy flow, and the maintenance of biodiversity
• Fungi, as decomposers, break down dead organic matter and recycle nutrients back into the ecosystem, making them available for other organisms
• Mycorrhizal fungi form symbiotic relationships with plant roots, enhancing nutrient and water uptake for the plant in exchange for carbohydrates
• Animals occupy a wide range of trophic levels, from primary consumers (herbivores) to top predators (carnivores), and help regulate population dynamics and community structure
• Many animals, such as insects and vertebrates, serve as pollinators and seed dispersers, facilitating plant reproduction and ecosystem resilience
• Ecosystem engineers, like beavers and coral polyps, modify their physical environment, creating habitats for other species and influencing ecosystem processes
• Humans rely on many fungal and animal species for food, medicine, and other ecosystem services, highlighting the importance of conserving biodiversity and managing these resources sustainably

Lab Activities and Observations

• Examine the morphology and structure of various fungal specimens, such as mushrooms, molds, and lichens, using dissecting and compound microscopes
• Observe the growth and development of fungal cultures on different media, noting differences in colony morphology, color, and growth rates
• Perform staining techniques, such as lactophenol cotton blue, to visualize fungal hyphae and reproductive structures under the microscope
• Dissect representative animals from various phyla (e.g., earthworm, grasshopper, and frog) to compare and contrast their internal anatomy and organ systems
• Observe the behavior and adaptations of live animals in the lab or field, such as the feeding mechanisms of planaria or the locomotion of nematodes
• Use dichotomous keys and field guides to identify and classify fungal and animal specimens collected from local environments
• Analyze preserved specimens or models of animal embryos to identify key developmental stages and compare embryological features across different phyla
• Conduct experiments to investigate the ecological roles of fungi and animals, such as testing the decomposition rates of different substrates by fungal species or observing the effects of predator removal on prey populations in a microcosm