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.

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…

One of the most eye-catching sights on the rocky shore, this mind-boggling species resembling a collection of beautiful pressed flowers is actually a colony of individual animals!

The turtle dove is the UK's fastest declining bird species and is on the brink of extinction. A small and pretty pigeon, it breeds in lowland England and winters in Sub-Saharan Africa.

One of the most colourful fish in UK seas, the cuckoo wrasse looks like it belongs in the tropics. Don't be fooled though, it's very much a native species.

The White-clawed crayfish is a freshwater, bronze-coloured crustacean with pale undersides to its claws - hence the name. It is under threat from an invasive and introduced species of crayfish.…

Buddleia is a familiar shrub, well-known for its attractiveness to butterflies. It is actually an introduced species, however, that has become naturalised on waste ground, railway cuttings and in…