Endangered Species in the Sonoran Desert

Big Ideas:
Endangered Species
Interdependence of Organisms

Objective:
Students will be able to identify and explain some causes of endangerment and extinction for species as well as explain the effects of extinction on an ecosystem. 

Background:
Endangered species are those that are at risk of going extinct.  Extinctions and endangered species are being focused on in conservation biology because of the high rates of extinction that are occurring, due to human effects on the environment. Extinction is not a new problem though.  Species are constantly going extinct, and scientists believe that about 99% of all species that have ever lived have gone extinct (Rosenzweig 1995).  Extinctions can be caused by either natural disasters and other chance accidents, or species interactions.  (Rosenzweig 1995). Natural occurrences such as ice ages, volcanoes, rising sea levels or other such events most likely account for a large number of extinctions, but species interactions can also account for many. 
Predation by species can be responsible for extinctions.  Often, when a new predator is introduced into an environment, it can over hunt its prey, causing it to go extinct.  Competition can also lead to one species going extinct, when it is unable to find enough food, resources or space. Introduced and invasive species can be responsible for many extinctions by out competing other species or over harvesting their prey.  Humans are often guilty of these actions; hunting species to extinction, or destroying habitats where they live. 
Scientists are concerned with extinctions because of the harm that can be caused to the environment when key species are removed. Life in ecosystems are extremely interconnected and certain species fill different niches. Species fill specific positions in an ecosystem, and other species may be unable to survive as well without them.  Humans also rely on many different species for resources, medicines, and environmental health.  

Activities:
Species Interactions Activity
Threatened and Endangered Species at Arizona Sonora Desert Museum
Endangered Species Docent Outreach from Tohono Chul Park

Further information:
US Fish and Wildlife Service:  http://endangered.fws.gov

Endangered Species of Arizona 
(list taken from:
Official World Wildlife Fund Guide to Endangered Species of North America. Ed. John R. Matthews. Washington D.C.: Beacham Publishing Inc., 1990.)

Plants

Arizona agave  (Agave arizonica)
Kearney's blue star (Amsonia kearneyana)
No common name (Carex specuicola)
Cochise pincushion cactus (Coryphantha robbinsorum)
Arizona cliffrose (Cowania subintegra)
Nichol's Turk's head cactus (Echinocactus horizonthalonius var.  nicholii)
Arizona hedgehog cactus (Echinocereus trigolchidiatus var. arizonicus)
Brady pincushion cactus (Pediocactus bradyi)
Peebles Navajo cactus (Pediocactus peeblesianus peebles)
Siler pincushion cactus (Pedicactus sileri)
San Francisco Peaks groundsel (Senecio franciscanus)
Tumamoc globeberry (Tumamcoa macdougalii)

Mammals

Sonoran pronghorn  (Antilocapra americana sonoriensis)
Ocelot (Felis pardalis)
Jaguarundi (Felis yagouraroundi tolteca)
Sanborn's long-nosed bat (Leptonycteris sanborni (=yerbabuenae))
Hualapai vole (Microtus mexicanus haulpaiensis)
Mt. Graham red squirrel (Tamiasciurus hudsonicus grahamensis)

Birds 

Masked bobwhite (Colinus virginianus ridgwayi)
Northern aplomado falcon (Falco femoralis septentrionalis)
Yuma clapper rail (Rallus longirostris yumanensis)
Thick-billed parrot (Rhynchopsitta pachryrhyncha)

Reptiles

Desert tortoise (Gopherus (=Xerobates) agassizii)

Fish

Desert pupfish (Cyprinodon macularius)
Humpback chub (Gila cypha)
Sonora chub (Gila ditaenia)
Bonytail chub (Gila elegans)
Yaqui chub (Gila purpurea)
Virgin River chub (Gila robusta seminuda)
Yaqui catfish (Ictalurus pricei)
Little Colorado spinedace (Lepidomeda vittata)
Spikedace (Meda fulgida)
Beautiful shiner (Notropis formosus)
Woundfin (Plagopterus argentissimus)
Gila topminnow (Poeciliopsis occidentalis)
Yaqui topminnow (Poeciliopsis occidentalis sonoriensis)
Colorado squawfish (Ptychocheilus lucius)
Apache trout (Salmo apache)
Gila trout (Salmo gilae)
Loach minnow (Tiaroga cobitis)

National Science Education Standards met by this lesson:
National Science Education Standards online: http://books.nap.edu/html/nses/html/index.html

Life Science (Content Standard C) grades 5-8
      Diversity and Adaptations of Organisms:
*Extinction of a species occurs when the environment changes and the adaptive characteristics of a species are insufficient to allow its survival.  Fossils indicate that many organisms that lived long ago are extinct.  Extinction of species is common; most of the species that have lived on the earth no longer exist.

Source:
National Resource Council. (1996). National Science Education Standards. Washinton DC: National Academy Press.

Official World Wildlife Fund Guide to Endangered Species of North America. Ed. John R. Matthews. Washington D.C.: Beacham Publishing Inc., 1990.

Rosenzweig, Michael. Species Diversity in Space and Time. Cambridge, UK: Cambridge University Press, 1995.