Ny State Living Environment Unit 4: Reproduction

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Asexually reproducing

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Producing offspring without the production of gametes (sex cells). Includes binary fission, vegetative propagation, mitosis, etc. Offspring are genetically identical to parents and each other.

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Birth

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The event in which a more or less fully developed offspring is delivered or expelled from the body of a parent (almost always the female parent).

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Chromosomes

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A single molecule of DNA and (usually) proteins. They are the units of DNA that are passed on to offspring. In sexually reproducing organisms, they come in pairs. Prokaryotes (bacteria) generally have a single, circular one without proteins.

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Cloning

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In animals, a form of asexual reproduction in which the nucleus of a body cell of an adult individual is inserted into the egg of a female, which then develops into an offspring that is identical, genetically, to the adult donor of the nucleus.

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Development

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The process by which the features of an organism - tissues, organs, organ systems, mature into fully functional systems (from zygote to adulthood) and then begin to decay (adulthood to death).

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Differentiation

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The process by which identical cells (in the early embryo) specialize to take on different shapes and functions in a developing organism - for example nerve cells, muscle cells, skin cells, etc.

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Egg

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A female sex cell or gamete. Produced in ovaries. Always larger than the male sex cell.

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Embryo

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The early stages in the development of offspring in sexually reproducing organisms.

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Embryonic development

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The changes that occur in offspring after the formation of a zygote and before birth or hatching.

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Estrogen

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A hormone that is primarily responsible for female sexual development, regulating the menstrual cycle, and maintaining pregnancy (it also plays a role in males).

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Fertilization

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The union of the male and female sex cells, which creates a zygote with the full number of chromosomes needed for the offspring to develop.

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Fetus

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A stage of development after the embryo has all of its organs and systems in place. In humans that happens at around 8 weeks.

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Gamete

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A sex cell. In males, the sperm. In females, the egg.

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Genetic material

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DNA or (in some viruses) RNA. The molecules in an organism that determine an individual's heritable traits. Sometimes also used to describe chromosomes, which contain the DNA.

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Genetically identical

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Two or more individuals who have the exact same set of chromosomes, DNA, or other genetic material.

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Internal development

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The growth and development of offspring INSIDE the parent's body. Almost always occurs inside the female's body. Most common in mammals, but also occurring in some species from other classes (reptiles, fish, amphibians, insects, etc.).

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Internal fertilization

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The union of sperm and egg INSIDE the female's body.

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Mate

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In terms of reproduction, the opposite-sex partner of an individual.

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Meiosis

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A process by which sex cells (gametes) are produced. Reduces the chromosome number by half, which is then restored (the full chromosome number) during fertilization.

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Milk

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A liquid mixture of carbohydrates, proteins, and fats, and water produced by female mammals as a food source for their young offspring.

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Mitosis

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A form of asexual reproduction in which the DNA/chromosomes in the nucleus are replicated and then distributed to two daughter cells, which are then genetically identical to each other and to the parent cell.

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Offspring

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The products of reproduction, the new organisms created by reproduction to keep a population alive as individuals within the population die.

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Ovary

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The primary female sex organ where eggs are produced and matured.

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Parent

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The producer of one or more offspring. In asexual reproduction, only one parent is required. In sexual reproduction, generally 2 parents are required.

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Placenta

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A temporary organ that develops during (mainly) mammalian pregnancy that is part mother and part embryo tissue. The site of materials exchange between mother and embryo/fetus, it connects the umbilical cord in the embryo with the uterus of the mother.

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Pregnancy

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Usually applied to a condition of female mammals, covering the period of time between fertilization and birth of offspring. Some put the beginning at the moment of implantation in the uterus rather than the moment of fertilization.

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Progesterone

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A hormone released by the ovaries that is mainly responsible for regulating the menstrual cycle and pregnancy.

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Reproduction

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The process by which a parent or parents produce offspring. Parent can mean a single cell or an individual multicellular organism.

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Reproductive cell

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Mainly refers to sperm and egg cells, or gametes. Also spores produced by some green plants, fungi, and some protists.

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Reproductive cycle

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The sometimes complex series developmental stages that lead to the continuous generation of offspring that mature to adults who then produce new offspring and so on. Similar to "life cycle."

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Reproductive technology

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Recent developments that enhance or facilitate attempts to produce offspring or enhance the chances of producing healthy offspring. Particularly important for individuals who are having difficulty having children or who are at risk of having children with certain hereditary diseases.

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Sex cells

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Gametes. In males, sperm. In females, eggs.

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Sexually reproducing

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Specifically used for organisms that produce gametes. Since a gamete has half the necessary genetic information, it generally needs a "partner." In other words, two parents are required for sexual reproduction, and the offspring are similar to but not identical to their parents. Except in rare cases of identical twins, the offspring are also genetically different from each other.

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Sperm

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The male sex cell or gamete. Typically smaller than the female sex cell, capable of movement, and produced in much larger quantities.

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Testes

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The primary male sex cell, where sperm are produced. Also produces primary male sex hormone, testosterone.

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Testosterone

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Primary male sex hormone, responsible for male sexual development among other functions.

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Uterus

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The organ in the female reproductive system where the embryo is implanted, nourished, and where it develops until birth. The placenta forms here.

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Zygote

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The fertilized egg. The egg united with the sperm. Ideally contains the full number of chromosomes necessary for normal development.