Desert plant associations

Announcements *we will leave in 1h from the start of the lab (22) and in 15 minutes (24) *the assignment for this lab is a report -same format (I expect to see typed tables, graphs,..) -points distribution in the last slide -no revision * Matthew Lopez will present next lab. period. *there is a handout of the final project example titles. -prospectus of the final project is due next week(5 points) -simple out line of an experiment -number of samples -names of the group members -analysis proposed to test the hypothesis

Desert plants *dry environment *evolved adaptation -nurse plants (cactus) -evade drought -fleshy water storing leaves -leaves only when water is abundant -small size leaves -cacti have spines rather than typical leaves -root system adaptation -fewer stomata and less evaporation

Association between plants * Nursing plant hypothesis(H A ) seedling cacti survive only in the shade of trees and shrubs. *predator hypothesis(H A ) *mutualism hypothesis(H A ) *random distribution (null hypothesis or H 0 )

Target plants 1- Carnegiea gigantea Saguaro cactus Straight spines

Target plants 2- Ferocactus wislizenii Barrel cactus Hook end spines (curved)

Target plants 3- Ambrosia deltoidea Triangle Leaf Bursage, (Rabbit Bush)

Criteria for association 1-height of the target plant 28cm (height of data sheet) i.e. juvenile plant 2-base of the target plant lie below the branches of tree or shrub. each group of 3 must count 15 individuals for each target and determine whether associated or not

Test your hypothesis * Chi square X 2 X 2 =  (O-E) 2 E *45% represent nonrandom distribution *degree or freedom 1 *Compare your results with table 1 appendix C *is it significant or not *due accept or reject the null hypothesis

Test your hypothesis Example: Saguaro cactus associated non associated total observed Expected 45*95 = 43 55*95 = X 2 =…..

Important -watch out for rattlesnakes -don’t put your hands under rocks -look carefully under plants

Lab. Reports point distribution  Title: 1 point  Abstract: 4 points  Introduction: 3 points  Materials and methods: 1point  Results: 3 points  Discussion: 3 points