Animal Biology and Diversity Practice Flashcards

Comprehensive flashcards covering key concepts from Animal Introduction, Sponges, Cnidarians, Lophotrochozoans, Ecdysozoans, and Deuterostomes.

What are five defining characteristics shared by members of Kingdom Animalia?

Animals are multicellular eukaryotes that lack cell walls (utilizing an extracellular matrix), are heterotrophic through ingestion, and with the exception of sponges, possess specialized tissues.

Which protist lineage shares the most recent common ancestor with Kingdom Animalia?

Choanoflagellates.

According to global biomass estimates, which invertebrate group accounts for the largest proportion of total animal biomass?

Arthropods, which make up approximately $42\%$ of all animal biomass.

What is the key developmental difference between diploblastic and triploblastic animals?

Diploblastic organisms develop two embryonic germ layers (ectoderm and endoderm), whereas triploblastic organisms develop three germ layers (ectoderm, mesoderm, and endoderm).

How do protostomes and deuterostomes differ in blastopore fate and cleavage pattern?

In protostomes, the blastopore becomes the mouth, and cleavage is spiral and determinate. In deuterostomes, the blastopore becomes the anus, and cleavage is radial and indeterminate.

What distinguishes a true coelomate from an acoelomate and a pseudocoelomate?

A true coelomate has a body cavity completely lined with mesoderm; an acoelomate lacks a body cavity entirely; and a pseudocoelomate has a body cavity only partially lined with mesoderm.

Why are sponges (Phylum Porifera) categorized as Parazoa rather than Eumetazoa?

Sponges lack true tissues, have no body symmetry, and do not form a gastrula stage during embryonic development.

What is the structural function of choanocytes in Phylum Porifera?

Choanocytes are flagellated collar cells lining the inner spongocoel that beat their flagella to generate a water current and capture food particles for intracellular digestion.

What two primary body forms are found within Phylum Cnidaria?

The sessile polyp form and the free-swimming medusa form.

What is the distinction between a cnidocyte and a nematocyst?

A cnidocyte is the specialized cell found in cnidarians, whereas the nematocyst is the stinging organelle inside the cell containing a coiled thread and barbs used to inject venom into prey.

At what heat stress threshold is coral mortality likely to occur during a bleaching event?

Coral death becomes likely when heat stress reaches or exceeds $8\text{ Degree Heating Weeks}$ ($8\text{ DHW}$) within a $12\text{-week}$ window.

What body cavity and digestive traits are characteristic of flatworms (Phylum Platyhelminthes)?

Flatworms are acoelomate triploblasts that possess an incomplete digestive system (gastrovascular cavity with a single opening via a protractible pharynx) or no digestive tract in parasitic forms.

What anatomical structures do adult tapeworms (Class Cestoda) use for host attachment and reproduction?

Tapeworms use a scolex (equipped with hooks and suckers) for attachment to the host intestine and produce repeating segments called proglottids containing reproductive organs.

What role does the clitellum play in earthworm (subclass Oligochaeta) reproduction?

The clitellum secretes a mucus cocoon into which eggs and sperm are released, serving as the site for external fertilization and embryonic development.

How do invasive European nightcrawlers (Lumbricus terrestris) affect boreal forest soils?

They rapidly consume and decompose the organic leaf litter layer ($\text{O horizon}$), accelerating greenhouse gas emissions ($\text{CO}_2$), leaching nutrients, and reducing forest plant diversity.

What six characteristic parts make up the basic generalized mollusk body plan?

The muscular foot, mantle, shell, visceral mass, gill, and radula.

Which major class of Phylum Mollusca lacks a radula and feeds by filter-feeding?

Class Bivalvia (clams, mussels, scallops).

What specialized larval stage occurs in the life cycle of many freshwater bivalves to parasitize fish?

The glochidium larva.

What main physical features characterize nematodes (Phylum Nematoda)?

Nematodes possess a pseudocoelom, a complete digestive system, move via thrashing, and are enclosed by a collagen cuticle (exoskeleton) that is molted during growth.

Which parasitic nematode causes Lymphatic Filariasis (Elephantiasis) in humans?

Filarial worms transmitted by mosquitoes that inhabit and block the host's lymphatic system.

What four subphyla make up Phylum Arthropoda?

Subphylum Chelicerata, Subphylum Myriapoda, Subphylum Crustacea, and Subphylum Hexapoda.

How do Class Diplopoda (millipedes) and Class Chilopoda (centipedes) differ in segment anatomy and diet?

Millipedes have $2$ pairs of legs per segment and are herbivorous or detritivorous, whereas centipedes have $1$ pair of legs per segment and are venomous carnivores.

What is the key physiological difference between complete and incomplete metamorphosis in insects?

Complete metamorphosis (holometabolous) includes a distinct larval stage, a pupal stage, and an adult stage that differs in morphology and diet. Incomplete metamorphosis (hemimetabolous) involves gradual nymphal instars that resemble the adult without a pupal stage.

What contrast exists between larval and adult body symmetry in echinoderms?

Echinoderms are bilaterally symmetrical as larvae but develop pentaradial symmetry as adults.

How does the water vascular system function in echinoderms?

It uses a network of hydraulic canals connected to ampullae and tube feet (podia) to drive locomotion, feeding, gas exchange, and excretion.

Why is the Ochre Sea Star (Pisaster ochraceus) considered a keystone species in intertidal communities?

By preying on dominant mussels, Pisaster ochraceus prevents mussels from monopolizing space, thereby maintaining intertidal community diversity of algae, barnacles, and limpets.

What four morphological features define Phylum Chordata?

Pharyngeal gill slits or pouches, a dorsal hollow nerve cord, a notochord, and a muscular post-anal tail.

Which chordate subphylum retains all four primary chordate hallmarks into adulthood?

Subphylum Cephalochordata (lancelets).

Why are tunicates (Subphylum Urochordata) classified as chordates despite adults lacking a notochord, post-anal tail, and dorsal nerve cord?

All four chordate hallmarks are fully present in their free-swimming larval stage before undergoing metamorphosis into sessile adult tunicates.

What traits define Subphylum Vertebrata compared to non-vertebrate chordates?

Vertebrates possess a cranium (skull), a vertebral column enclosing the nerve cord, a three-part brain, paired sense organs (eyes), gills, an endoskeleton that grows with the animal, and a closed circulatory system.

According to fossil evidence, how did jaws and lungs originate in early gnathostomes?

Jaws derived from bony skeletal supports/gill arches in placoderm skulls, while lungs originally arose as outpocketings of the esophagus in ancient fish swallowing air at the water surface.

What are the four extra-embryonic membranes of the amniotic egg and their functions?

The amnion protects the embryo in fluid; the allantois stores metabolic wastes; the yolk sac contains nutrients; and the chorion allows for gas exchange.

What are the three main mammalian lineages based on embryonic development?

Monotremes (egg-laying mammals), Marsupials (pouched mammals with brief internal development), and Eutherians (placental mammals with full embryonic development in the uterus).

What molecular development contributed to increased neuron production in Homo sapiens compared to Neanderthals?

A single amino acid substitution led to increased neuron production during brain development in Homo sapiens.