Mae'r siarc main yma’n cael ei enw o'r pigau o flaen ei asgell ddorsal. Gall ddefnyddio'r pigau yma i amddiffyn ei hun drwy gyrlio mewn bwa a tharo ysglyfaethwr.

Our only venomous snake, the shy adder can be spotted basking in the sunshine in woodland glades and on heathlands.

A scarce but distinctive brown seaweed with curved, funnel-shaped fronds. It is a warmer water species at the northern edge of its range on the south coast of England.

Selfheal is a low-growing, creeping plant that likes the short turf of grasslands, roadside verges or even lawns. Its clusters of violet flowers appear in summer.

The Common walnut tree produces a large, brown nut that is familiar to so many of us. It is an introduced species in the UK, and can be seen in towns, gardens and parks.

Fat hen is a persistent 'weed' of fields and gardens, verges and hedgerows. But, like many of our weed species, it is a good food source for birds and insects.

Freshwater pearl mussels spend their adult lives anchored to the river bed, filtering water through their gills and improving the quality of the water for other species.

The Migrant hawker is not a particularly aggressive species, and may be seen feeding in large groups. It flies late into autumn and can be seen in gardens, grasslands and woodlands.

Pineappleweed is an introduced species that has become a widespread 'weed' of disturbed ground, such as pavements and roadsides and gardens. It has feathery leaves and yellow flower…