Exam #3 - Zoology

Microevolution

Changes in allelic frequency in a population over time.

Macroevolution

Large scale evolutionary events such as speciation or extinction.

Gene pool

All the alleles present in a population.

Hardy-Weinberg equilibrium

Conditions under which allele frequencies remain constant across generations, requiring random mating, no mutations, no natural selection, a large population size, and no gene flow.

Cnidocytes

Unique cell type in cnidarians that contains cnidocysts, which expel a needle-like thread to puncture prey.

Choanoflagellates

Closest living single-celled relatives of all animals, known for their collar of microvilli used in filter feeding.

Bilateral symmetry

Body symmetry where the organism can be divided into mirror-image halves only in one orientation.

Free-living platyhelminths

Non-parasitic flatworms known as planarians that are predators and scavengers.

Ecdysozoans

A group of animals that have an external cuticle and undergo molting (ecdysis

Eukaryotic Groups

Excavata, SAR, Archaeplastida (red/green algae), Unikonta (fungi)

Eukaryote vs Prokaryote

Eukaryotes have a nucleus and membrane-bound organelles; prokaryotes do not.

Protists

Unicellular, simple eukaryotic organisms not classified as plants, animals, or fungi.

Malaria

A disease caused by a single-celled protist affecting red blood cells.

Dinoflagellates

Protists that release toxins harmful to fish and potentially humans.

Choanoflagellates

Closest living single-celled relatives to animals; use a collar of microvilli to filter feed.

Sponge Anatomy

Sponge lacks complex anatomy and filters food particles while creating currents.

Cnidarian Tissue Layers

Cnidarians have ectoderm and endoderm but lack mesoderm.

Nerve Net

A network of interconnected nerve cells found in cnidarians, providing basic sensory functions.

Tentacles in Cnidarians

Surround the mouth and anus, used to capture and handle prey.

Gastrovascular Cavity

A cavity in cnidarians where prey is forced for digestion.

Medusa

One cnidarian morph that is jellyfish-like and reproduces sexually.

Polyp

A cnidarian morph that reproduces asexually, often attached to a surface.

Paedomorphic Life Cycle

A life cycle that skips developmental stages, resembling an ancestral juvenile form.

Cnidocytes

Specialized cells in cnidarians that contain cnidocysts to capture prey.

Medusozoans

Cnidarians that alternate between medusa and polyp forms in their life cycle.

Anthozoans

Cnidarians, like sea anemones and corals, that are primarily colonial and lack a medusa stage

Major features of Bilaterians

3 germ layers, bilateral symmetry, and body cavity.

Major groups in the clade Lophotrochozoa

Platyhelminthes, rotifera, acanthocephala.

Free-living vs Parasitic Platyhelminthes

Free-living (planarians) are non-parasitic, predators that eat dead things; parasitic (tapeworms) have complex life cycles and no gut.

Rotifer

Multicellular organisms with specialized organs that reproduce sexually depending on environmental conditions, utilizing a virgin birth strategy.

Bivalvia

Organisms with two hinged shells, no radula, and a foot that helps with movement.

Cephalopoda

Mollusks with tentacles and a siphon, a centralized mass, and a radula present, with reduced shells.

Gastropoda

Mollusks with a ciliated foot for gliding, a spiral shell, and a radula that helps in feeding, exhibiting torsion.

Polyplacophora

Mollusks with a body under 8 dorsal plates, a flat foot, and a radula, characterized by a flattened mass.

Setae

Hair-like projections found in annelids that can serve various functions.

Closed vs. Open Circulatory System

Closed: Blood runs through vessels, segmentally arranged. Open: Complete digestive system, not segmentally arranged.

Leeches vs. Earthworms

Leeches: Blood-sucking ectoparasites; Earthworms: Feed on soil, hermaphrodites that don't fertilize.

Main Features of Ecdysozoans

Includes nematodes, arthropods, velvet worms, tardigrades, and horsehair worms; all have an external cuticle and undergo molting.

Nematodes

Parasitic roundworms with a complete digestive system and no circulatory system.

Tardigrada

Eight-legged organisms found in water, known for their resilience to extreme environments.