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Both terms are relative: a derived trait for one clade may be an ancestral trait for a different clade. The term "derived trait" is often used interchangeably with the more technical term apomorphy. descendant developmental biology diploid. Denoted in shorthand with the somatic number 2n.
In the first stage of sexual reproduction, meiosis, the number of chromosomes is reduced from a diploid number (2n) to a haploid number (n). During fertilisation, haploid gametes come together to form a diploid zygote, and the original number of chromosomes is restored.
They tend to be unstable and to lose further chromosomes during subsequent mitotic divisions, until the 2n+1 and 2n-1 nuclei progressively revert to n. Consistent with this, in E. nidulans (where normally, n=8) nuclei have been found with 17 (2n+1), 16 (2n), 15 (2n–1), 12, 11, 10, and 9 chromosomes.
This glossary of biology terms is a list of definitions of fundamental terms and concepts used in biology, the study of life and of living organisms.It is intended as introductory material for novices; for more specific and technical definitions from sub-disciplines and related fields, see Glossary of cell biology, Glossary of genetics, Glossary of evolutionary biology, Glossary of ecology ...
An endosperm is formed after the two sperm nuclei inside a pollen grain reach the interior of a female gametophyte or megagametophyte, also called the embryonic sac.One sperm nucleus fertilizes the egg cell, forming a zygote, while the other sperm nucleus usually fuses with the binucleate central cell, forming a primary endosperm cell (its nucleus is often called the triple fusion nucleus).
"Binomial nomenclature" is the correct term for botany, [43] although it is also used by zoologists. [44] Since 1961, [45] "binominal nomenclature" is the technically correct term in zoology. [1] A binomial name is also called a binomen (plural binomina) or binominal name. [2]
Anatomical terms are not included here and appear in sub-categories of the main Anatomy category. Initially, some alignment between this category and the article Glossary of biology was considered, but the inclusion criteria for the Glossary is substantially broader and encompasses terminology, concepts, objects and processes.
The central binomial coefficients give the number of possible number of assignments of n-a-side sports teams from 2n players, taking into account the playing area side The central binomial coefficient ( 2 n n ) {\displaystyle {\binom {2n}{n}}} is the number of arrangements where there are an equal number of two types of objects.