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pregnancy

(Encyclopedia)pregnancy, period of time between fertilization of the ovum (conception) and birth, during which mammals carry their developing young in the uterus (see embryo). The average duration of pregnancy in h...

Hertwig, Oscar

(Encyclopedia)Hertwig, Oscar ôsˈkär hĕrtˈvĭkh [key], 1849–1922, German embryologist. He studied medicine with Haeckel and Gegenbaur. In 1875 he established the fact that fertilization consists of the union ...

Kölreuter, Joseph Gottlieb

(Encyclopedia)Kölreuter or Koelreuter, Joseph Gottlieb both: yōˈzĕf gôtˈlēp kölˈroiˌtər [key], 1733–1806, German botanist. In 1764 he became professor of natural history and director of the botanical g...

progesterone

(Encyclopedia)progesterone prōjĕsˈtərōnˌ [key], female sex hormone that induces secretory changes in the lining of the uterus essential for successful implantation of a fertilized egg. A steroid, progesterone...

stem cells

(Encyclopedia)stem cells, unspecialized human or animal cells that can produce mature specialized body cells and at the same time replicate themselves. Embryonic stem cells are derived from a blastocyst (the blastu...

Spallanzani, Lazzaro

(Encyclopedia)Spallanzani, Lazzaro lädˈdzärō späl-läntsäˈnē [key], 1729–99, Italian naturalist. He was professor at the universities of Modena (1763–69) and Pavia (from 1769). Spallanzani studied regen...

seed

(Encyclopedia)seed, fertilized and ripened ovule, consisting of the plant embryo, varying amounts of stored food material, and a protective outer seed coat. Seeds are frequently confused with the fruit enclosing th...

pollen

(Encyclopedia)pollen, minute grains, usually yellow in color but occasionally white, brown, red, or purple, borne in the anther sac at the tip of the slender filament of the stamen of a flowering plant or in the ma...

reproduction

(Encyclopedia)CE5 Examples of asexual reproduction reproduction, capacity of all living systems to give rise to new systems similar to themselves. The term reproduction may refer to this power of self-duplicati...

Good Agricultural Practices

(Encyclopedia)Good Agricultural Practices (GAP), economically, socially, and environmentally responsible methods and technologies for the raising and marketing of agricultural and horticultural products. Good agric...