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Paul Kammerer's Experiments on Sea-squirts in the Early Twentieth Century
In the early twentieth century, Paul Kammerer, a zoologist working at the Vivarium in Vienna, Austria, experimented on sea-squirts (Ciona intestinalis). Kammerer claimed that results from his experiments demonstrated that organisms could transmit characteristics that they had acquired in their lifetimes to their offspring. Kammerer conducted breeding experiments on sea-squirts and other organisms at a time when Charles Darwin's 1859 theory of evolution lacked evidence to explain how offspring inherited traits from their parents.
Subject: Experiments, Organisms
Bacteria of the genus Wolbachia are
bacteria that live within the cells of their hosts. They infect a
wide range of arthropods (insects, arachnids, and crustaceans) and
some nematodes (parasitic roundworms). Scientists estimate that
Wolbachia exist in between seventeen percent and seventy-six percent of
arthropods and nematodes. The frequency of the bacteria makes them
one of the most widespread parasites. In general, they are divided
into five groups, from A to E, depending of the species of their
The Southern Gastric-Brooding Frog
The Southern Gastric-Brooding Frog (Rheobatrachus silus) was an aquatic frog that lived in south-east Australia. In 2002, the International Union for Conservation of Nature Red List declared the frog extinct, although no wild specimens had been reported since 1981. As the common name alludes to, the R.
Intraspecies Chimeras Produced in Laboratory Settings (1960-1975)
When cells-but not DNA-from two or more genetically distinct individuals combine to form a new individual, the result is called a chimera. Though chimeras occasionally occur in nature, scientists have produced chimeras in a laboratory setting since the 1960s. During the creation of a chimera, the DNA molecules do not exchange genetic material (recombine), unlike in sexual reproduction or in hybrid organisms, which result from genetic material exchanged between two different species. A chimera instead contains discrete cell populations with two unique sets of parental genes.