These Arab recruits line up in a barracks square in the British Mandate of Palestine, on December 28, 1940, for their first drill under a British solider. Some 6,000 Palestinian Arabs signed up with the British Army during the course of World War II. (AP Photo)

A small section of the expanding remains of the Veil Nebula, a massive star that exploded about 8,000 years ago. The entire nebula is 110 light-years across, covering six full moons on the sky as seen from Earth, and resides about 2,100 light-years away in the constellation Cygnus, the Swan. (Photo by Reuters/NASA/ESA/Hubble)

A traffic police officer directs vehicles at a street junction during sunset in Pyongyang, North Korea, Thursday, August 25, 2016. (Photo by Dita Alangkara/AP Photo)

A butterfly flies into the jaws of a crocodile inhabiting the Tarcoles River, the most polluted basin in Central America and one of the most polluted in Latin America, in the place of Tarcoles, province of Puntarenas, Costa Rica, 05 June 2018. Costa Rica, a country recognized worldwide for its environmental policies, seeks to be a leader in the replacement of single-use plastic with renewable and compostable alternatives, despite its lag in terms of recycling and integrated waste management. (Photo by Jeffrey Arguedas/EPA/EFE)

Elvis Presley impersonator Sean Wright poses next to the Elvis Express train at Sydney's Central station before it departs for the 26th annual Elvis Festival being held in the New South Wales town of Parkes in Australia, January 11, 2018. (Photo by Daniel Munoz/Reuters)

Youtubers wearing masks of pigs film a video at a shopping district which has fewer people than usually amid the coronavirus disease (COVID-19) outbreak in Tokyo, Japan, May 19, 2020. (Photo by Kim Kyung-Hoon/Reuters)

Parade goers draped in American flags walk down the street before a Fourth of July parade begins Saturday, July 4, 2020, in Bristol, R.I. The town, which lays claim to the nation's oldest Independence Day celebration in the country, held a vehicle-only scaled down version of its annual parade Saturday due to the coronavirus pandemic. (Photo by David Goldman/AP Photo)

The National Geographic Photo Ark is a travelling exhibition of photographer Joel Sartore’s quest to create a photo archive of biodiversity around the world. So far, Sartore has captured studio portraits of more than 6,000 species – a number that he hopes to double. On 1 July, the ark will open at Melbourne zoo – the first time it has been exhibited in the southern hemisphere. More than 50 portraits will be on display, including many of Australian endangered animals being protected by programs at the zoo itself. These captions have been edited from text supplied by Melbourne zoo. Here: Barking owl. (Photo by Joel Sartore/National Geographic Photo Ark/The Guardian)