Winter has begun and with less solar energy the northern hemisphere freezes, life is at its hardest; as the planet starts its incredible journey around the sun, Earth's northern pole tilts away from the warmth and light.

Spring is the season of opportunity; the great melt begins and new life erupts; life in the Southern Hemisphere gets rough with worsening conditions as animals prepare for shorter days.

Summer is the season of extremes; the top of the planet gets 24 hours of sunlight while the south is frozen in darkness.

Autumn is the season of change, offering new beginnings or a chance to take a new path; many species prepare for winter to secure their place for the next year's circle of life.

A newly-hatched penguin chick grows a fluffy coat and swims past killer whales to leave home; a panda cub's patience is tested by its mom's never-ending meal.

Scientists, community members and conservationists uncover new behavior, use pioneering and inventive techniques and put their lives on the line to protect the animals that roam the earth.