The series of mitotic cell divisions from blastomeres during which a single fertilised egg, the zygote, is transformed into a multicelluar body, the blastula. See Blastomere, Blastula, Gastrulation, Mitosis, Zygote
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Classical conditioning
A form of learning where an initially neutral stimulus is paired with a response-eliciting stimulus (see figure below). Classical conditioning: unconditioned stimulus (UCS) becomes associated with a conditioned stimulus (CS) over repeated trials so that CS comes to reproduce the unconditioned response (UCR) See Behaviorism, Delay(ed) conditioning, Discrimination, Eye-blink conditioning, Learning, Operant (or instrumental) conditioning
Cladistics
A method of biological classification using only genealogies in inferring phylogenetic relationships among organisms, which disregards their adaptations as they may not be due to homology. The outcome is a cladogram. See Adaptation, Clades, Cladogram, General theory of biological classification, Homology, Palaeontology, Phylogeny
Cladogram
In cladistics, a diagram of hypothesized relationships that assigns organisms to taxonomic groups called clades, but which is not the same as a phylogenetic tree as that adds non-phylogenetic information (e.g., times of transition). See Clades, Cladistics, Phylogenetic mapping, Phylogeny
Clades
In cladistics, they refer to taxonomic groups that consist of all species descended from a known or inferred ancestor as well as the ancestor itself. See Cladistics, Cladogram, Species
Cingulate gyrus
An important component of the limbic system, it is a gyrus in the medial part of the brain that partially wraps around corpus callosum, which is constrained from above by the cingulate sulcus, and located between this sulcus and that of the corpus callosum. It receives inputs from the anterior nucleus of the thalamus and …
Circular (or non-linear) causality
Broadly speaking, this form of causality is one in which the cause reproduces itself over time. It can be symbolised in the following way: A <–> B (i.e., A effects B, just as B effects A) in contrast to linear causality A –> B (i.e., A is the antecedent to or causes B). Also, it …
Chronological or postnatal age
The period of time since birth measured, for example, in terms of days, months or years. See Cohort effect, Corrected age, Gestational age, Period effect
Cilia
Smaller than flagella, they are microtubular, hairlike structures used by some single-celled organisms for locomotion through liquids. In addition, they cover the cells of certain tissues (e.g., the epithelium lining the lungs), and help these cells clear away fluids or particles. Structurally identical to flagella, the two terms are often used interchangeably. However, cilia are …
Chromosome
A threadlike, deeply stained, structure contained in the nucleus of a cell of eukaryotic organisms and composed mainly of DNA and protein in the form of chromatin. Each chromosome consists of two chromatids bound together at the centromere. According to classical genetics, it is the bearer of the genes in a linear order and thus …