Chapter 2- Classification and Relationships Flashcards
Terms and Definitions
The arrangement of organisms into groups based on shared characteristics, often to understand evolutionary relationships.
Classification
Organisms that consist of more than one cell, often organized into tissues and organs.
Multicellular
Multicellular animals that develop from a blastula, typically differentiated into various cell types.
Metazoans
The term used to describe a group of ancient, multicellular organisms that lived during the Ediacaran period, before the Cambrian explosion.
Ediacaran fauna
The rapid diversification of life that occurred during the Cambrian period, approximately 541 million years ago, resulting in the emergence of many modern animal phyla.
Cambrian explosion
Relating to the form or structure of organisms.
Morphological
Pertaining to the evolutionary history and relationships among or within groups of organisms.
Phylogenetic
Related to the structure of organisms, particularly regarding the organization of their physical parts.
Anatomical
Observable characteristics related to the form and structure of organisms.
Morphological traits
Shared, derived characteristics that can be used to infer evolutionary relationships among taxa.
Synapomorphies
Referring to a group of organisms that includes an ancestor but not all of its descendants.
Paraphyletic
Describing a group of organisms that includes a single ancestor and all of its descendants.
Monophyletic
A diagram that illustrates the arrangement of the different taxonomic groups based on their evolutionary relationships.
Dendrogram
A classification approach that considers both the evolutionary history and the degree of similarity among different organisms.
Evolutionary systematics
A method of classification based on the common ancestry and shared characteristics of species, using synapomorphies to define groups.
Cladistics
Features that originate from a common ancestor and can be used to determine evolutionary relationships.
Homologous characters
Traits that have similar functions but do not arise from a common evolutionary origin.
Analogous characteristics
The direction of change in evolutionary traits, distinguishing between ancestral and derived states.
Polarity
A statistical technique used to assess the reliability of a phylogenetic tree by resampling the data.
Bootstrapping
Diagrams that represent the evolutionary relationships among various biological species based on similarities and differences in their physical or genetic characteristics.
Phylogenic trees
A branching point on a phylogenetic tree where a common ancestor is represented.
Node
Two lineages that share an immediate common ancestor.
Sister groups
A species or group that is used to root a phylogenetic tree, helping to infer the direction of evolution.
Outgroup
Multicellular animals that develop from a blastula, typically differentiated into various cell types.
Metazoans
Organisms that consist of a single cell.
Unicellular
Referring to organisms that do not have a cellular structure.
Acellular
Organisms that can be divided into two mirror-image halves along a single plane.
Bilaterally symmetrical
The concentration of sensory and nervous tissues at one end of an organism, leading to the formation of a head.
Cephalization
Organisms that can be divided into similar halves by multiple planes passing through the central axis.
Radially symmetrical
Layers of cells that develop during embryonic development and give rise to different tissue types in the organism.
Germ layers
Organisms that have two germ layers: ectoderm and endoderm.
Diploblastic
The outermost germ layer that develops into the outer covering of the body and the nervous system.
Ectoderm
The innermost germ layer that develops into the innermost lining of the digestive tract and associated organs.
Endoderm
Organisms that have three germ layers: ectoderm, endoderm, and mesoderm.
Triploblastic
The middle germ layer that develops into muscles, the circulatory system, and other internal structures.
Mesoderm
Organisms that possess a coelom, a fluid-filled body cavity lined with mesoderm.
Coelomates
Animals with a true coelom fully lined with mesodermal cells.
Eucoelomates
A group of coelomate animals in which the mouth develops from the blastopore during early embryonic development.
Protostomes
The process of coelom formation in protostomes, whereby the coelom forms through a split in the mesoderm.
Schizocoely
A group of coelomates in which the anus develops from the blastopore, with the mouth forming later.
Deuterostomes
The process of coelom formation in deuterostomes, in which the coelom arises from pouches of the archenteron.
Enterocoely
The region of an egg where the embryo develops and is typically associated with the formation of future embryonic tissues.
Animal pole
The region of the egg opposite the animal pole, associated with the formation of the yolk and supportive tissues.
Vegetal pole
A type of cleavage in embryonic development where the cells divide symmetrically and align vertically.
Radial pattern
A type of embryonic development where cells divide at an oblique angle, creating a spiral arrangement.
Spiral cleavage
The smaller cells resulting from cleavage during early development.
Micromeres
The larger cells resulting from cleavage during early development.
Macromeres
A type of development in deuterostomes where the potential of embryonic cells remains flexible, allowing them to develop into complete organisms if separated.
Indeterminate or regulative
A type of development in protostomes where the fate of embryonic cells is fixed very early in development.
Determinate or mosaic
A small bulge that forms at one end of certain embryos, playing a role in determining cell fate.
Polar lobe
The fluid-filled cavity that forms within the blastula, playing a role in embryo development.
Blastocoel
A body cavity that is not lined with mesoderm-derived tissue.
Pseudocoel
An organism possessing a pseudocoel, which provides a fluid-filled body cavity.
Pseudocoelomate
Animals that lack a body cavity between the digestive tract and the outer body wall.
Acoelomate
Any named group of organisms, such as a species or group of species.
Taxon
A group of organisms that includes an ancestor and all its descendants.
Monophyletic
A group that includes an ancestor but not all of its descendants.
Paraphyletic
A group of organisms that can interbreed and produce fertile offspring.
Species
The first part of a species’ scientific name, indicating the genus to which the species belongs.
Generic name
The second part of a species’ scientific name, identifying the particular species within the genus.
Specific name
The combination of the genus and specific name, used to identify a species uniquely.
Species name
A proposed system of nomenclature for classifying organisms based on phylogenetic relationships rather than traditional taxonomic ranks.
The PhyloCode
The process where unrelated or distantly related organisms evolve similar traits due to similar environmental pressures.
Convergence
The existence of shared ancestry between a pair of structures, or genes, in different taxa.
Homology
Referring to structures derived from a common ancestor.
Homologous
The direction of evolutionary change in traits or characteristics.
Polarity
Relating to land; organisms that live on land.
Terrestrial
Relating to the ocean; organisms that live in saltwater environments.
Marine
The area between the high tide and low tide marks, where organisms are exposed to air at low tide and submerged at high tide.
Intertidal
The region of the ocean just below the intertidal zone, usually permanently underwater.
Subtidal
The vast area of the sea that is not near the coast; also known as pelagic zones.
Open ocean
Organisms that can move freely and actively.
Mobile
Organisms that are inactive or fixed in one place and do not move around (e.g., attached to surfaces).
Sedentary
Referring to organisms that drift or float in water, unable to swim against currents.
Planktonic
Animals that primarily eat plants.
Herbivores
Animals that primarily eat other animals
Carnivores
Organisms that filter small particles from the water as it flows past them.
Suspension feeders
Organisms that ingest sediment and extract organic matter as it moves through their digestive systems.
Deposit feeders
Interactions between two different organisms living in close physical proximity, often with benefits to one or both.
Symbiotic associations
The various types of interactions in a symbiotic relationship, which can include mutualism, commensalism, and parasitism.
Symbioses
Organisms that live on the surface of another organism, often benefiting from the relationship.
Ectosymbionts
Organisms that live within the body or cells of another organism, often having a mutualistic relationship.
Endosymbionts
A symbiotic relationship in which both partners benefit.
Mutualism
A symbiotic relationship in which one organism benefits while the other is neither helped nor harmed.
Commensalism
Organisms that live on or in a host and benefit at the host’s expense, often causing harm.
Parasites
The organism that provides a living environment and resources to a parasite or symbiont.
Host
