Chapter 2 Flashcards
**evolutionary theory
The set of testable hypotheses that assert that living organisms can change over time and give rise to new kinds of organisms, with the result that all organisms ultimately share a common ancestry.
**evolution
The process of change over time.
**essentialism
The belief, derived from Plato, in fixed ideas, or forms, that exist perfect and unchanging in eternity. Actual objects in the temporal world, such as cows or horses, are seen as imperfect material realizations of the ideal form that defines their kind.
**Great Chain of Being
A comprehensive framework for interpreting the world, based on Aristotelian principles and elaborated during the Middle Ages, in which every kind of living organism was linked to every other kind in an enormous, divinely created chain. An organism differed from the kinds immediately above it and below it on the chain by the least possible degree.
taxonomy
A classification; in biology, the classification of various kinds of organisms.
genus
The level of the Linnaean taxonomy in which different species are grouped together on the basis of their similarities to one another.
species
(1) For Linnaeus, a Platonic natural kind defined in terms of its essence. (2) For modern biologists, a reproductive community of populations (reproductively isolated from others) that occupies a specific niche in nature.
**catastrophism
The notion that natural disasters, such as floods, are responsible for the extinction of species, which are then replaced by new species.
**uniformitarianism
The notion that an understanding of current processes can be used to reconstruct the past history of the earth, based on the assumption that the same gradual processes of erosion and uplift that change the earth’s surface today had also been at work in the past.
**transformational evolution
Also called Lamarckian evolution, it assumes essentialist species and a uniform environment. Each individual member of a species transforms itself to meet the challenges of a changed environment through the laws of use and disuse and the inheritance of acquired characters.
common origin
Darwin’s claim that similar living species must all have had a common ancestor.
**natural selection
A two-step, mechanistic explanation of how descent with modification takes place: (1) every generation, variant individuals are generated within a species due to genetic mutation and (2) those variant individuals best suited to the current environment survive and produce more offspring than other variants.
**variational evolution
The Darwinian theory of evolution, which assumes that variant members of a species respond differently to environmental challenges. Those variants that are more successful (“fitter”) survive and reproduce more offspring, who inherit the traits that made their parents fit.
fitness
A measure of an organism’s ability to compete in the struggle for existence. Those individuals whose variant traits better equip them to compete with other members of their species for limited resources are more likely to survive and reproduce than individuals who lack such traits
aptation
Any useful feature an organism has
adaptation
The shaping of any useful feature of an organism, regardless of its origin.
exaptation
The shaping of a useful feature of an organism by natural selection to perform one function and the later reshaping of it by different selection pressures to perform a new function.
pangenesis
A theory of heredity suggesting that an organism”s physical traits are passed on from one generation to the next in the form of multiple distinct particles given off by all parts of the organism, different proportions of which get passed on to offspring via sperm or egg.
**Mendelian inheritance
The view that heredity is based on nonblending, single-particle genetic inheritance.
principle of segregation
A principle of Mendelian inheritance in which an individual gets one particle (gene) for each trait (i.e., one-half of the required pair) from each parent.
principle of independent assortment
A principle of Mendelian inheritance in which each pair of particles (genes) separates independently of every other pair when germ cells (egg and sperm) are formed.
genetics
The scientific study of biological heredity.
homozygous
Describes a fertilized egg that receives the same particle (or allele) from each parent for a particular trait.
heterozygous
Describes a fertilized egg that receives a different particle (or allele) from each parent for the same trait.
gene
Portion or portions of the DNA molecule that code for proteins that shape phenotypic traits.
alleles
All the different forms that a particular gene might take.
chromosomes
Sets of paired bodies in the nucleus of cells that are made of DNA and contain the hereditary genetic information that organisms pass on to their offspring.
mitosis
The way body cells make copies of themselves. The pairs of chromosomes in the nucleus of the cell duplicate and line up along the center of the cell. The cell then divides, each daughter cell taking one full set of paired chromosomes.
meiosis
The way sex cells make copies of themselves, which begins like mitosis, with chromosome duplication and the formation of two daughter cells. However, each daughter cell then divides again without chromosome duplication and, as a result, contains only a single set of chromosomes rather than the paired set typical of body cells.
locus
A portion of the DNA strand responsible for encoding specific parts of an organism’s biological makeup.
linkage
An inheritance pattern in which unrelated phenotypic traits regularly occur together because the genes responsible for those co-occurring traits are passed on together on the same chromosome.
crossing over
The phenomenon that occurs when part of one chromosome breaks off and reattaches itself to a different chromosome during meiosis; also called incomplete linkage.
discontinuous variation
A pattern of phenotypic variation in which the phenotype (e.g., flower color) exhibits sharp breaks from one member of the population to the next.
polygeny
The phenomenon whereby many genes are responsible for producing a phenotypic trait, such as skin color.
continuous variation
A pattern of variation involving polygeny in which phenotypic traits grade imperceptibly from one member of the population to another without sharp breaks.
pleiotropy
The phenomenon whereby a single gene may affect more than one phenotypic trait.
**mutation
The creation of a new allele for a gene when the portion of the DNA molecule to which it corresponds is suddenly altered.
DNA (deoxyribonucleic acid)
The structure that carries the genetic heritage of an organism as a kind of blueprint for the organism’s construction and development.
genome
The sum total of all the genetic information about an organism, carried on the chromosomes in the cell nucleus.
**genotype
The genetic information about particular biological traits encoded in an organism’s DNA.
**phenotype
The observable, measurable overt characteristics of an organism.
**norm of reaction
A table or graph that displays the possible range of phenotypic outcomes for a given genotype in different environments.
**niche construction
When an organism actively perturbs the environment or when it actively moves into a different environment.
