Unit 1 Vocab

Zoology

Acoelomate

Without a coelom, as in flat worms and proboscis worms

Adaptive radiation

Evolutionary diversification that produces numerous ecologically disparate lineages from a single ancestral one, especially when this diversification occurs within a short interval of geologic time

Acoelomate

Without a coelom, as in flat worms and proboscis worms

Adaptive radiation

Evolutionary diversification that produces numerous ecologically disparate lineages from a single ancestral one, especially when this diversification occurs within a short interval of geologic time

Allele

Alternative forms of genes coding for the same trait, and situated at the same locus in homologous chromosomes

Allelic frequency

An estimation of the proportion of gametes produced in a population (gene pool) that contains a particular allelic form of a particular gene

Blastocoel

The cavity within the hollow mass of embryological cells

Blastomere

An early cleavage cell

Blastopore

External opening of the archenteron in the gastrula.

Blastula

Early embryological state of many animals; consists of a hollow mass of cells

Carnivore

Any organism that eats animals

Carrying capacity

The maximum number of individuals of a particular species that can persist under specified environmental conditions

Cephalization

The evolutionary process by which specialization, particularly of the sensory organs and appendages, became localized in the head end of animals

Clade

A taxon or other group consisting of a particular ancestral lineage and all of its descendants, forming a distinct branch on the cladogram or phylogenetic tree

Cladistics

A system of arranging taxa by analysis of primitive and derived characteristics so that the arrangement reflects phylogenetic relationships

Cladogram

A branching diagram showing the pattern of sharing of evolutionarily derived characters among species

Coelom

The body cavity in triploblastic animals, lined with mesodermal peritoneum

Commensalism

A relationship in which one individual lives close to or on another and benefits, and the host is unaffected; often symbiotic

Common Descent

Darwin’s theory that all forms of life are derived from a shared ancestral population through a branching of evolutionary lineages

Competition

Some degree of overlap in ecological niches of two populations in the same community, such that both depend on the same food source, shelter, or other resources, and negatively affect each other’s survival

Competitive exclusion

An ecological principle stating that two species whose niches are very similar cannot coexist indefinitely in the same community; one species is driven to extinction by competition between them

Decomposer

A consumer that breaks organic matter into soluble components available to plants at the base of the food web; most are bacteria or fungi

Definitive host

The host in which sexual reproduction of a symbiont occurs; if no sexual reproduction, then the host in which the symbiont becomes mature and reproduces

Deme

A local population of closely related animals

Demography

The properties of the rate of growth and the age structure of populations

Density-dependent

Biotic environmental factors, such as predators and parasites, whose effects on a population vary according to the number of organisms in the population

Density-independent

Abiotic environmental factors, such as fires, floods, and temperature changes, whose effects on a population are unaffected by the number of organisms in the population

Derived character state

Condition of a taxonomic character inferred by cladistics analysis to have arisen within a taxon being examined cladistically rather than having been inherited from the most recent common ancestor of all members of the taxon

Deuterostomia

A group of higher phyla in which cleavage is indeterminate and ancestrally radial.  The endomesoderm is enterocoelous, and the mouth is derived away from the blastopore

Dioecious

Having male and female organs in separate individuals

Ectoderm

Outer layer of cells of an early embryo (gastrula stage); one of the germ layers, also sometimes used to include tissues derived from ectoderm

Ectoparasite

Parasite that resides on the outside surface of its host organism

Endoderm

Innermost germ layer of an embryo, forming the primitive gut

Endoparasite

Parasite that resides inside the body of its host organism

Evolution

All changes in the characteristics and diversity of life on earth throughout history

Evolutionary species concept

A single lineage of ancestral-descendant populations that maintains its identity from other such lineages and has its own evolutionary tendencies and historical fate

Evolutionary taxonomy

System of classification, formalized by George Gaylord Simpson, that groups species into Linnean higher taxa representing a hierarchy of distinct adaptive zones; such taxa may be monophyletic or paraphyletic but not polyphyletic

Frontal plane

Plane parallel to the main axis of the body and at right angles to the sagittal plane

Fundamental niche

A variety of roles potentially performed by an organism or population in an ecological community; limits on such roles are set by the intrinsic biological attributes of an organism or population

Gastrocoel

Embryonic cavity forming in gastrulation that becomes the adult gut; also called an archenteron

Gastrula

Embryonic stage, usually cap- or sac-shaped, with walls of two layers of cells surrounding a cavity with one opening (blastopore)

Gene pool

Collection of all the alleles of all the genes in a population

Gradualism

A component of Darwin’s evolutionary theory postulating that evolution occurs by the temporal accumulation of small, incremental changes by populations, usually across very long periods of geological time

Guild

Species of a local community that partition recourses through character displacement to avoid niche overlap and competition, such as Galapagos finch communities whose component species differ in beak size for specializing on different-sized seeds

Herbivore

Any organism subsisting on plants

Homeothermic

Having a nearly uniform body temperature, regulated independent of the environmental temperature

Homology

Similarity of parts or organs of different organisms caused by evolutionary derivation from a corresponding part or organ in a common ancestor, and usually having a similar embryonic origin

Hypothesis

A statement or proposition that can be tested by observation or experiment

Inheritance of acquired characteristics

The discredited Lamarckian notion that organisms, by striving to meet the demands of their environments, obtain new adaptions and pass them by heredity to their offspring

Intrinsic growth rate

Exponential growth rate of a population; the difference between the density-independent components of the birth and death rates of a natural population with stable age distribution

Limiting resource

A particular source of nutrition, energy, or living space whose scarcity is causally associated with a population having fewer individuals than otherwise expected in a particular environment

Macroevolution

Evolutionary change on a grand scale, encompassing the origin of novel designs, evolutionary trends, adaptive radiation, and mass extinction

Mesoderm

The third germ layer, formed in the gastrula between the ectoderm and endoderm; gives rise to connective tissues, muscle, urogenital and vascular systems, and the peritoneum

Metapopulation dynamics

The structure of a large population that comprises numerous semi-autonomous subpopulations, termed demes, with some limited movement of individuals among demes.  Demes are often geographically distinct

Microevolution

A change in the gene pool of a population across generations

Monoecious

Having both male and female gonads in the same organism, usually denoting that this is the typical condition of a species; hermaphroditic

Monophyly

Condition occurring when a taxon or other group of organisms contains the most recent common ancestor of the group and all of its descendants

Ontogeny

The course of development of an individual from egg to senescence

Paraphyly

The condition that a taxon or other group of organisms contains the most recent common ancestor of all members of the group but excludes some descendants of that ancestor

Parasitism

The condition of an organism living in or on another organism (host) at whose expense the organism is maintained

Parasitoid

Organism that kills the host during or at the completion of development

Parenchyma

In simpler animals, a spongy mass of vacuolated mesenchyme cells filling spaces between viscera, muscles, or epithelia

Phenotype

The visible or expressed characteristics of an organism: influenced by the genotype in interaction with environmental conditions

Phyletic gradualism

A model of evolution in which morphological evolutionary change is continuous and incremental and occurs mainly within unbranched species or lineages over long periods of geological time

Phylogenetic tree

A diagram whose branches represent evolutionary lineages; depicts the common descent of a species or higher taxa

Phylogeny

The origin and diversification of any taxon, or the evolutionary history of its origin and diversification, usually presented as a dendrogram

Polyphyletic

The condition that a taxon or other group of organisms is derived from more than one ancestral source

Pseudocoelom

Body cavity not lined with peritoneum and not a part of the blood or digestive systems; embryonically derived from the blastocoel

Punctuated equilibrium

Model of evolution in which morphological evolutionary change is discontinuous, being associated primarily with discrete, geologically instantaneous events of speciation that lead to phylogenetic branching; morphological evolutionary stasis characterizes species between episodes of speciation

Radial cleavage

Embryonic development in which early cleavage planes are symmetrical to the polar axis, each blastomere of one tier lying directly above the corresponding blastomere of the next layer

Realized niche

The role actually performed by an organism or population in its ecological community at a particular time and place as constrained by both its intrinsic biological attributes and its particular environmental conditions

Reproductive barrier

The factors that prevent a sexually propagating population from interbreeding and exchanging genes with another population

Resource

Available source of nutrition, energy, or space in which to live

Resource partitioning

To coexist in the same habitat, two or more species specialize on different portions of a shared resource

Sagittal plane

Pertaining to the median anteroposterior plane that divides a bilaterally symmetrical organism into right and left halves

Sink deme

A subpopulation whose members are drawn disproportionately from other subpopulations of the same species because of unstable environmental conditions resulting in the destruction of individuals in the subpopulation and then subpopulation is replenished by colonists from other subpopulations when favorable conditions are restored

Source deme

A stable subpopulation that serves differentially as a source of colonists for establishing, joining, or replacing other such subpopulations of the same species in nearby environmentally unstable areas

Species diversity

The number of different species that coexist at a given time and place to form an ecological community

Species richness

The number of different species that coexist at a given time and place to form an ecological community

Spiral cleavage

Type of early embryonic cleavage in which cleavage planes are diagonal to the polar axis, and unequal cells are produced by the alternate clockwise and counterclockwise cleavage around the axis of polarity

Survivorship

The proportion of individuals of a cohort or population that persist from one point in their life history, such as birth, to another one, such as reproductive maturity or a specified age

Systematics

Science of taxonomy and reconstruction of phylogeny

Systematization

Construction of a hierarchical taxonomy that conveys the structure of common evolutionary descent among species.  Each recognized taxon comprises an ancestral population lineage and all of its descendants

Transverse plane

A plane or section that lies or passes across a body or structure dividing it into cephalic and caudal pieces

Variation

Differences among individuals of a group or species that cannot be ascribed to age, sex, or position in the life cycle

Velarium

Shelf-like extension of the subumbrella edge in cubozoans

Velum

A membrane on the subumbrella surface of jellyfishes of class Hydrozoa