Unit 3: Biodiversity - Animal and Fungal Diversity and Physiology

Comprehensive practice flashcards defining foundational vocabulary, evolutionary clades, anatomical features, and physiological mechanisms across all 13 lectures in Unit 3 (Biodiversity).

Endosymbiosis

An evolutionary process occurring approximately $2.5\text{ billion years ago}$ in which a large archaeal cell engulfed a smaller bacterial cell and the two began working together, leading to the evolution of eukaryotic cells.

Eukaryotic Supergroups

The taxonomic level between domain and kingdom created because protists do not form a single clade; includes Amoebozoa, Opisthokonta, Excavata, Archaeplastida, and SAR.

Opisthokonta

A eukaryotic supergroup comprising animals, fungi, and choanoflagellates, characterized ancestrally by cells with a posterior flagellum and the widespread use of chitin.

Protostomes

A major clade of bilateral animals whose mouth develops first from the embryonic blastopore during gastrulation.

Deuterostomes

A major clade of bilateral animals, including echinoderms and chordates, in which the anus develops first from the embryonic blastopore and the mouth forms second.

Gastrulation

The developmental stage wherein cells from the hollow blastula migrate inward to form an internal pocket (the archenteron or gut), establishing distinct germ layers.

Ectoderm

The outermost embryonic germ layer that develops into the epidermis (skin) and the nervous tissue.

Endoderm

The innermost embryonic germ layer that lines the embryonic pocket and develops into the digestive system and vertebrate respiratory tract.

Mesoderm

The middle embryonic germ layer situated between ectoderm and endoderm that develops into muscles, the circulatory system, vertebrate bone, and the reproductive system.

Cephalization

The evolutionary concentration of sensory organs and nervous tissues at the anterior end (head) of an animal, closely associated with directional movement and bilateral symmetry.

Hydroskeleton

A flexible, fluid-filled internal cavity found in soft-bodied animals used for support, movement, and often the circulation of nutrients and wastes.

Intracellular Digestion

A form of digestion where individual cells take food particles directly into themselves to break them down; Phylum Porifera (sponges) is the only animal phylum relying solely on this method.

Gastrovascular Cavity

A digestive pouch with only a single opening that serves as both mouth and anus, functioning in both digestion and nutrient distribution (found in cnidarians like Hydra and jellyfish).

Amylase

An enzyme secreted by the salivary glands in mammals that chemically digests starches (such as amylose) by cutting them into glucose molecules.

Epiglottis

A flap of tissue that covers the trachea during swallowing to prevent food and liquid from entering the lungs.

Peristalsis

Wave-like involuntary muscle contractions that push food along through the digestive tract.

Bile

A substance synthesized by the liver, stored in the gallbladder, and released into the small intestine that physically emulsifies large fat globs into tiny droplets for lipase to digest.

Villi

Microscopic, finger-like projections along the walls of the small intestine that vastly expand surface area to maximize the absorption of nutrients into capillaries.

Cecum

A pouch-like extension at the junction of the small and large intestines (known as the appendix in humans) that houses symbiotic microorganisms assisting in the digestion of cellulose.

Coprophagy

The behavior of re-ingesting feces practiced by rabbits and rodents so nutrients released by hindgut cecal symbionts can be absorbed by the small intestine on the second pass.

Malnutrition

A medical condition resulting from the absence or deficiency of one or more essential nutrients that the body cannot manufacture on its own.

Countercurrent Exchange

An efficient respiratory mechanism in fish gills where blood flows in the opposite direction to water passing over the gill lamellae, maintaining a positive oxygen concentration gradient along the entire pathway.

Spiracles

Openings located along the sides of an insect body through which air enters and exits branching internal tracheal tubes.

Alveoli

Microscopic balloon-like air sacs in mammalian lungs that provide a massive moist surface area for gas diffusion between inhaled air and surrounding blood capillaries.

Cross-Current Exchange

A highly efficient respiratory gas-exchange arrangement in avian lungs where capillary blood travels at a $90^∘$ angle across unidirectional air-conducting tubes.

Open Circulatory System

A transport system found in small animals like insects and daphnia in which hemolymph is pumped into a body cavity rather than through a continuous circuit of vessels, operating without blood pressure.

Closed Circulatory System

A circulatory system found in larger animals (such as annelids, cephalopods, and vertebrates) where blood remains enclosed inside continuous vessels, allowing for hydrostatic pressure to drive fluid over long distances.

Arteries

Vessels that carry blood away from the heart under high hydrostatic pressure, characterized by thick, muscular vessel walls.

Veins

Low-pressure vessels that carry blood toward the heart, equipped with internal flap-like valves to prevent backflow caused by gravity.

Malacologist

A scientist who specializes in the study of mollusks.

Mantle

A specialized layer of dorsal epidermal tissue in mollusks that secretes the shell and covers the visceral mass.

Radula

A flexible, tongue-like organ lined with microscopic chitinous teeth used by many mollusks to scrape or rasp food into small particles.

Parapodia

Paired, lateral, paddle-like appendage structures on each body segment of annelids used for locomotion and increased respiratory surface area.

Setae

Stiff, bristle-like structures embedded within annelid parapodia that provide mechanical traction, structural support, and aid in burrowing.

Phylum Nematoda

A vast phylum of unsegmented roundworms characterized by a high-pressure hydroskeleton, a tough exterior cuticle, longitudinal contraction muscles only, and absence of a circulatory system.

Caenorhabditis elegans

A microscopic nematode species used as a model organism in science, whose complete developmental cell lineage, genome, and connectome (every neuron and synapse) have been fully mapped.

Elytra

The hardened, protective front pair of wings in beetles (order Coleoptera) that cover and protect the delicate membranous flight wings beneath.

Halteres

Small, knobbed, club-like balancing organs in true flies (order Diptera) that represent an evolutionary modification of the second pair of wings.

Water Vascular System

A unique hydraulic network of seawater-filled canals found exclusively in echinoderms, functioning in gas exchange, nutrient circulation, and locomotion via tube feet.

Tube Feet

Small, flexible projections extending from grooves on the underside of echinoderms that extend and contract via fluid pressure from the water vascular system.

Notochord

A flexible, dorsal cartilaginous rod derived from mesoderm that serves as an anchor for muscle attachment in all chordate embryos and gives rise to parts of the spine in vertebrates.

Tiktaalik

A fossil lobe-finned fish lineage from about $375\text{ million years ago}$ that represents the transitional phase when vertebrate ancestors first moved onto land.

Amniotic Egg

A shelled egg containing an internal fluid-filled environment (amniotic fluid) and specialized extraembryonic membranes that enabled reptiles, birds, and mammals to reproduce independently of bodies of water.

Monotremes

An order of mammals native to Australia (including the platypus and echidna) that retain the ancestral reptilian reproductive trait of laying eggs.

Marsupials

A group of mammals characterized by a very brief internal embryonic gestation, after which the underdeveloped young migrates to a maternal pouch to nurse and complete development.

Hyphae

Microscopic, thread-like filaments composed of rows of fungal cells encased in chitinous walls that constitute the actual vegetative body of a fungus.

Mycelium

A dense, visible mass or network of intertwined fungal hyphae growing through a food substrate.

Septum (Fungal)

Cross-walls that partially divide adjacent fungal cells within a hypha, containing large pores that permit the exchange of cytoplasm, organelles, and nuclei.

Extracellular Digestion

A nutritional strategy in which an organism secretes digestive enzymes into its surrounding food substrate to break down complex organic polymers externally before absorbing the resulting nutrients.

Lignin

A tough structural compound supporting plant cell walls in woody tissue that can be easily decomposed only by specialized fungal digestive enzymes.

Chytridiomycota

The most ancestral fungal phylum, consisting of aquatic fungi with flagellated swimming spores, currently causing global amphibian die-offs by infecting and thickening their skin.

Mycorrhizae

Mutualistic associations formed between fungi (primarily Glomeromycota) and plant roots, exchanging soil water and minerals for photosynthetic sugars.

Basidiomycota

A fungal phylum known as club fungi that produces club-shaped microscopic spore-bearing structures; includes most typical mushrooms and agricultural pathogens like corn smut.

Ascomycota

The largest fungal phylum (encompassing $75\%$ of described fungi) that includes morels, yeasts, penicillium, ringworm, athlete's foot, ergot, and the fungal partners of most lichens.

Lichen

A pioneer symbiotic partnership between a fungus (usually an ascomycete) and a photosynthetic partner (algae or cyanobacteria), where the photosymbiont provides fixed carbon and the fungus provides physical protection and water retention.

Pseudopods

Temporary cytoplasm-filled projections of an amoebozoan cell membrane utilized for motility and capturing food items through phagocytosis.

Physarum polycephalum

A plasmodial slime mold that exists as a single giant coenocytic cell holding millions of nuclei, capable of finding optimal paths through mazes and laying down chemical repellent trails to record visited locations.

Dictyostelium

A cellular slime mold that spends its life as independent solitary amoeboid cells but aggregates via chemical signaling under starvation to form a migrating multi-cellular slug and fruiting body.

Chemotaxis

The directional movement of cells or organisms toward or away from a chemical stimulus, demonstrated when individual Dictyostelium amoebae aggregate in response to emitted chemical pulses.