Ground-elder was likely introduced into the UK by the Romans and has since become naturalised. A medium-sized umbellifer, it is an invasive weed of shady places, gardens and roadsides.

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.…

Cotoneaster was introduced to the UK in 1879 from Eastern Asia as an ornamental plant. It is now an invasive non-native species which is taking over valuable habitats including limestone…

A breeding bird of fast-flowing, upland rivers, the grey wagtail can also be seen in lowland areas, farmyards and even towns in winter.

The common octopus is a highly intelligent, active predator. It even has a secret weapon - special glands produce a venom that it uses to incapacitate its prey!

This striking black-and-white moth flies during the day in open woodlands, moorlands, and bogs. It's most common on Scottish moors.

Sea-buckthorn is a spiny, thicket-forming shrub of sand dunes. It's native to the east coast of England but considered an invasive species elsewhere. It is most obvious in autumn when it is…

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.

An attractive, olive-green bird, the greenfinch regularly visits birdtables and feeders in gardens. Look for a bright flash of yellow on its wings as it flies.