Images Dated 9th February 2004

Mendels peas

Mendel's peas. Historical artwork of the peas (Pisum sp.) used by Gregor Mendel (1822-1884) in his experiments into heredity. He cross-bred peas that produced yellow (A) and green (B) peas. This produces a generation in which the peas are yellow (C). This is because the colour of the peas is controlled by an allele in which yellow colour is dominant. An allele is a pair of genes that have different effects on the same characteristic, for instance controlling pea colour. By breeding the C generation peas together, Mendel found that the next generation had a mixture of pea colours (D). The ratio of yellow to green peas was 3:1. His work formed the basis of genetic theory

© SHEILA TERRY/SCIENCE PHOTO LIBRARY

Venuss girdle, a type of comb jellyfish

Venus's Girdle. Macrophotograph of a coiled, ribbon-like Venus's Girdle or Sea Sword, Cestus veneris, appearing glassy-blue. C. veneris is a comb jellyfish which feeds on plankton. It has rows of tiny, cilia-like tentacles along the length of its body. These capture plankton and direct it to the creature's mouth. C. veneris can grow up to 8cm wide and 150 cm long. Whilst feeding, C. veneris normally hangs straight in the water and is almost transparent but for a greenish-gold glimmer from the tentacles. When disturbed it swims with snake-like movements and appears blue. Venus's Girdle also has the ability to phosphoresce at night

© SINCLAIR STAMMERS/SCIENCE PHOTO LIBRARY