Saguaro National Park is well-known for its namesake cacti, but what else can you find in the park when it comes to living things? An answer to that question is coming in late October, when the park is the focus of a two-day "bio-blitz."

The affair is being sponsored by the National Park Service and the National Geographic Society along with the Friends of Saguaro National Park and the Arizona-Sonora Desert Museum. The goal? To discover, document and celebrate all that lives in the 91,445-acre park.

Part scientific endeavor, part festival and part outdoor classroom, the BioBlitz will bring together more than 150 leading scientists and naturalists from around the country, thousands of local citizens of all ages, more than 2,000 students from the greater Tucson area and more than 100,000 schoolchildren who will join via the Internet on a National Park Foundation Electronic Field Trip.

Together they will comb the park, observing and recording as many plant and animal species as possible in 24 hours. Inventory activities include counting cacti, catching insects by day and night, spotting birds, exploring washes, examining aquatic organisms, and observing and using technology to better understand the diverse ecosystems of the national park.

Participants are invited to work with experts to count, map, and learn about the park’s diverse organisms, ranging from microscopic bacteria to towering saguaro cacti. This free event is open to “explorers” of all ages. While children ages 8 and older may participate in inventory teams with their parents, there also will be age-appropriate activities for younger kids at the BioBlitz’s “base camp” at the Tucson Mountain District’s Red Hills Visitor Center at 2700 N. Kinney Road, Tucson. Off-site parking and shuttle service is mandatory and will be provided from the nearby Old Tucson Studios.

“This will be a great family event, and we invite everyone who knows Saguaro, or wants to know the park better, to come out and experience the fun of discovery in the outdoors," said Saguaro Superintendent Darla Sidles. "We want to make people aware of the amazing biodiversity that exists within the park and in their own backyards. Having that increased awareness will encourage us all to appreciate and protect these amazing resources that make our Tucson home so special.”

Festivities will begin on Friday, Oct. 21, at 9 a.m. with the opening of the Biodiversity Festival, followed by the kickoff ceremony at 11:30 a.m. The 24-hour race to document the biodiversity of Saguaro National Park will begin promptly at noon, when teams go near and far throughout both districts of the park to begin the species inventory.

Due to limited space on inventory teams, advance registration is required to ensure a spot on a team. To register, go to www.nationalgeographic.com/bioblitz. “Base camp” will be a center of activity, but teams will be located in both east and west districts of the park, and check-in may take place in field stations where appropriate. This information will be available on the registration site.

Ongoing entertainment and educational opportunities will take place at “base camp” and the Biodiversity Festival. People can watch scientists doing round-the-clock research to identify and document species collected in the field.

The festival, which runs 9 a.m.-4 p.m. on Friday, Oct. 21, and 9 a.m.-4 p.m. on Saturday, Oct. 22, will feature live music, animal demonstrations, science experiments, talks by leading scientists, educational activities provided by prominent science and environmental organizations, food and art. Members of the public can even “graduate” from the Biodiversity University by participating in select activities at base camp. No registration is required for the festival. For a schedule of events, go to www.nationalgeographic.com/bioblitz.

In the week leading up to BioBlitz, renowned naturalist J. Michael Fay, a National Geographic Explorer-in-Residence and Wildlife Conservation Society scientist, will bring to Tucson the experience of his 2,000-mile walk across the wilds of Africa and his more recent Redwood Transect. Beginning in the Rincon Mountains on the east side of the park, crossing the city and the Tucson Mountains, and arriving at “base camp” Friday for BioBlitz opening ceremonies, Mr. Fay will traverse the park and document every living thing he sees. While he has not been in Tucson for nearly three decades, he began his early research in the area, receiving his B.S. from the University of Arizona. He will share his observations during his Tucson transect in a presentation Saturday at the Biodiversity Festival.

"Saguaro National Park has amazing biodiversity, with each district featuring unique ecosystems,” said John Francis, National Geographic’s vice president of research, conservation and exploration. “As a father of two and a global citizen, I am concerned about how people safeguard nature on our planet, not just in the parks where it is protected and studied, but in their backyards and cityscapes that can be enriched and restored with care. I hope schoolkids and adults will be inspired by Mike Fay and others who can show the importance and joy of protecting Saguaro National Park and surrounding treasures.”

Those who cannot attend the BioBlitz in person can take a virtual adventure at www.nationalgeographic.com/bioblitz.

Throughout the event, the site will feature a streaming Twitter feed, blogs, video clips of scientists and regularly updated photo galleries that capture the finds and experiences of participants. Additionally, teachers, students and families across the country are encouraged to participate in the BioBlitz experience remotely via the National Park Foundation Electronic Field Trip (EFT). Live EFT broadcasts will be held on Friday, Oct. 21, at 1 p.m. and 4 p.m. (ET) and will feature engaging lessons about biodiversity and how these important activities can be done in everyone’s backyard. The Saguaro EFT, made possible through support from the Lowe’s Charitable and Educational Foundation, will also be available for post-event viewing. For more information and to register for the EFT, go to www.electronicfieldtrip.org/saguaro.