invertebrates ii
TRANSCRIPT
Flatworms: Phylum Platyhelminthes
Bilateral symmetryThree germ layersOrgansAcoelomates Incomplete digestive system (one opening)Cephalization (concentration of sensory
organs and nerves in head)Some are hemaphrodites; Some are parasiticPlanaria: Organ systems ladder-like
Advantage?
Bilaterally symmetrical Three germ layers Cephalization Coelomate Mostly marine
◦ Some freshwater and terrestrial Visceral mass: includes internal organs Mantle: thin tissue
◦ Secretes shell in some molluscs Muscular foot for locomotion
Mollusca
Mollusk Diversity
Gastropods: snails, slugs, nudibranchs Chitons Cephalopods: octopuses, squid Bivalves: oysters, mussels Today:
◦ Dissect a clam◦ Dissect a squid◦ Compare
Segmented worms 3 germ layers Bilateral symmetry Coelomates Cephalization Include leeches, earthworms and
marine worms Have setae to assist in
movement (bristles) Earthworms have clitellum for
reproduction Today: view earthworm model
◦ No dissection
Annelida
Bean Beetles--Callosobruchus maculatus Phylum Arthropoda Herbivorous pests that live 1-2 weeks as
adults Lay single eggs that change into larvae
several days later Larvae burrow into bean and pupate Emerge 24-36 hours later
Experiment
Do female bean beetles discriminate between types of beans when choosing a place to lay eggs?◦ Design your own experiment◦ Collect results next week
We will use a Chi Square to analyze our data◦ Used to test an alternative hypothesis (Ha) vs. a
null hypothesis (Ho) Ha: There is a difference Ho: There is no difference
Chi2 Test Statistical test to test our hypothesis Test based on differences between the
observed results and the expected values (based on null hypothesis)
The formula for X2 is as follows:
◦ o is the observed frequency ◦ e is the frequency expected under the null
hypothesis of no difference between groups.
Example: Snail sediment type preference
20 snails 2 sediments: mud and sandNull hypothesis: There is no difference in
sediment preference for this species of snail. Expected results: 10 in mud, 10 in sand Actual results: 13 in mud, 7 in sand
Chi2 Test on snail results
Mud Sand
Observed 13 7
Expected 10 10
• Now you compare your experimental value (1.8) to a critical chi2 value.
Chi2 Test comparison
Degrees of Freedom: the number of independent cases◦ (number of rows-1)(number of columns-1)◦ (2-1)(2-1)=1 degree of freedom
p level: level at which the given statistic is on the border between rejecting or not the null hypothesis◦ Probability that values outside this set level are
due to chance sampling errors rather than real differences
Use p=0.05◦ At p=0.05 you are 95% sure your results are
real
Chi2 Table
If test>critical value @ p level, reject null hypothesis
If test<critical value @ alpha level, fail to reject null hypothesis
Bean Beetle Experiment Outline Week 1:
◦ Design your experiment Work first in your groups. Then we will come together as a class to
determine a final procedure
◦ Things to consider: How many beetles? How many different types of beans?
Beetles were raised on mung beans How many beans of each type? How many replicates?
Week 2◦ Record results◦ Compile class data◦ Statistical analyses using class data◦ Discuss lab report