offspring

Sperm

...needed to create life. Generally, the sex of the offspring is determined by the sperm, through the chromosomal pair "XX" (for a female ) or "XY" (for a male ). Sperm cells were first observed by Antoni van Leeuwenhoek in 1679 . Contents showTocToggle("show","hide") 1 Sperm structure and si...

Species

.... If these variable traits are heritable, then the offspring of the survivors will also possess them. Thus, ove...here members of one population can produce fertile offspring with a second population, and members of the second population can produce fertile offspring with me...

Sociobiology

... females with more bearing opportunities may value offspring less. Also, females may arrange bearing opportunities to maximize the food and protection from mates. Criminality is actively under study, but extremely controversial. There are persuasive arguments that in some uncivilized environments crimin...

Reproduction

...t unless raised in an artificial environment, most offspring do not survive to adults . A rabbit (mature after 8 months) produces 10 - 30 offspring per year, a Nile Crocodile (15 years) produces 50, and a fruit fly (10-14 days) produces up to 9...

Red Queen

...ales make up half the population, yet they bear no offspring directly and generally contribute little to the survival of offspring. In addition, males and females must find each other to mate, and sexual selection often favors traits that reduce the survival of organisms. Thus, sex is highly inefficient. ...

Parthenogenesis

...n, which may have both benefits and costs, is that offspring are typically genetically identical or nearly iden...o parthenogensis is gynogenesis . In gynogenesis, offspring are produced by the same mechanism as in parthenogenesis, but with the requirement that the egg be s...

Neutral theory of molecular evolution

...ell participates in the genesis of an embryo and offspring does the mutation contribute a new allele to the population. Neutral substitutions create new neutral alleles. Through drift, these new alleles may become more common within the population. They may subsequently decline and disappear, or in rare cas...

Natural selection

...multaneously. If a particular variation makes the offspring which manifest it better suited to survival or to successful reproduction, that offspring and its descendants will be more likely to survive than those offspring without the variation. The ...

Muller's ratchet

...osymbiont of insects, which is only transmitted to offspring from the mother. Another example is mitochondria...roduction allows most plants and animals to create offspring with good copies of two genes via crossover. That is, if one animal has the deleterious mutation in...

Molecular evolution

...ating populations, which simply cannot have enough offspring to maintain the same gene distribution as the parental generation. Gene flow : or gene admixture is the only one of the agents that makes populations closer genetically while building larger gene pools. Selection , in particular natural sel...

Mendelian inheritance

...offspring. This theory accounted for the fact that offspring tended to resemble their parents without all members of a population eventually averaging themselves out. Mendel proposed instead a theory of particulate inheritance, in which characteristics were determined by discrete units of inheritance that wer...

Life

...odification: the ability of a life form to produce offspring that are like its parent or parents, but with the ...w evolution , assuming that the variations in the offspring allow for differential survival. The study of this form of heritability is called genetics . In all...

Jean-Baptiste Lamarck

...be passed on. Nowadays, the idea of passing on to offspring characteristics that were acquired during an organism's lifetime is called Lamarckian . This view was, until very recently, thought to be completely inconsistent with modern genetics, but recent discoveries, as discussed in the article on epigenet...

Hepatitis B

...confers a 20% risk of passing the infection to her offspring at the time of birth. This risk is as high as 90% if the mother is also positive for the Hepatitis B e antigen. Roughly 16-40% of unimmunized sexual partners of individuals with hepatitis B will be infected through sexual contact. The virus that...

Gregor Mendel

...upon plants." He found that the plants' respective offspring retained the essential traits of the parents, and therefore were not influenced by the environment. This simple test gave birth to the idea of heredity. Mendel read his paper, Experiments on Plant Hybridization , at two meetings of the Natural Hist...

Genetic recombination

... which the combination of genes in an organism's offspring becomes different from the combination of genes in... alleles are different. This process explains why offspring from the same parents can look so different. In this way, it is theoretically possible to have any c...

Genetic drift

... the role of random sampling in the production of offspring . Like selection, it acts on populations , alteri...ce. Therefore the frequency of an allele among the offspring often differs from its frequency in the parent generation. In the offspring generation, the allele m...

Gene

Genes are entities that parents pass to offspring during reproduction . These entities encode ...g organisms carry their genes and transmit them to offspring as DNA, but some viruses carry only RNA. Because they use RNA, their cellular hosts may synthesize...

Gamete

...e set from the egg—that is, the cells of the offspring will have genes expressing characteristics of both the "father" and the "mother". A gamete's chromosomes are not exact duplicates of either of the sets of chromosomes carried in the somatic cells of the individual that produced the gametes. They can ...

Eugenics

...ncurable disease which would be passed on to their offspring . . ." [1] Sweden forcibly sterilized 62,000 "unfits" as part of a eugenics program over a forty year period. Similar incidents occurred in Canada , Australia , Norway , Finland , Estonia , Switzerland and Iceland for people the governme...

Epigenetics

...t in changes in the way genes are expressed in the offspring (see Waterland citation). In both cases, the object of study includes how gene regulatory information that is not expressed in DNA sequences is transmitted from one generation (of cells or organisms) to the next - that is (harking back to the Greek...

Reproduction

...t unless raised in an artificial environment, most offspring do not survive to adults . A rabbit (mature after 8 months) produces 10 - 30 offspring per year, a Nile Crocodile (15 years) produces 50, and a fruit fly (10-14 days) produces up to 9...

Allele

...nd "purple" alleles for petal color, the resulting offspring would have violet petals. Another exception is co-dominance , where both alleles are active and both traits are expressed at the same time; for example, both red and white petals in the same bloom or red and white flowers on the same plant. Codomin...