robert landsman - Academia.edu (original) (raw)
Papers by robert landsman
The Science Teacher 69(1), 56-60, 2002
Networking the Learner: Computers in Education, 2002
This study describes an instructional intervention in which high school biology students Jeamed t... more This study describes an instructional intervention in which high school biology students Jeamed to develop criteria for critically evaluating science Websites and scientific information contained in them. Results indicated that the process of leaming to critically evaluate Websites was what was most valuable to them. Students' Jists of criteria for critically evaluating Websites were more extensive after instruction. Furthermore, the majority of students reported leaming something new, indicated that they would spendmoretime evaluating scientific information on Websites, and reported increased confidence in their ability to evaluate scientific information on the Web.
Eubios Journal of Asian and International Bioethics, 2001
Making Connections-Electronic Media, 2000
Making Connections-Electronic Media, 2000
Making Connections-Electronic Media, 2000
Making Connections-Electronic Media, 2000
Koi USA 24(3), 1999, 1999
Nishikigoi International, (Spring), 68-69., 1997
Mid-Atlantic Koi, 10(8-9), 7-11. , 1997
Mid-Atlantic Koi 11(1), 5-13., 1997
Koi Health Quarterly, 1997
J. Comp. Physiol. A, 1993
Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology, 1993
1. Experiment 1 employed a repeated measures design to examine the effects of captivity on sex di... more 1. Experiment 1 employed a repeated measures design to examine the effects of captivity on sex differences in the electric organ discharge (EOD) of Gnathonemus petersii, newly imported from Africa, and maintained individually or in groups. 2. On the day of import, males exhibited longer durations of phases 2 and 3 of the EOD and lower peak power spectral frequencies (PPSFs) than females. 3. After 14 days in captivity in the laboratory, the sex differences were eliminated. After 37 days of captivity, all sex differences were still abolished, or even reversed depending on housing conditions. Males exhibited the most dramatic changes in EODs and females appeared to have higher testosterone (T) levels than males. 4. Experiment 2 was designed to investigate the effects of captivity on both behavior and endocrine status in 58 newly imported males. In this independent group design, EOD data and blood were collected from subjects over 15 days. 5. Decreases in phase 3 of the EOD and increases in PPSFs progressed over the 15 day experimental period, becoming statistically significant by days 10 and 15, respectively. Regardless of housing conditions, both T and 11-keto T dramatically decreased to near non-detectable levels by Day 5 in the laboratory. 6. Captivity causes rapid and profound changes in the endocrine system which result in dramatic changes in steroid-sensitive EODs. These findings directly link captivity, hormones, and behavior, and show why feral animals brought into captivity usually do not exhibit sexual behavior.
Reproductive Physiology of Fish, 1991
Hormones and behavior, 1990
The effects of androgens and estrogen on the external morphology and electric organ discharge (EO... more The effects of androgens and estrogen on the external morphology and electric organ discharge (EOD) waveform in Gnathonemus petersii, a weakly discharging electric fish, were investigated. Following preimplant data collection, juvenile and adult fish were gonadectomized and implanted with silastic capsules containing either high or low doses of testosterone (T), dihydrotestosterone (DHT), estradiol-17β (E2), or cholesterol. One group of fish was treated with high doses of DHT + E2. Radioimmunoassays revealed that low-dose implants resulted in plasma T levels comparable to and high-dose implants about sixfold greater than those found in adult males imported during breeding season. High-dose E2 implants resulted in higher plasma E2 levels in adults than those in juveniles. At either dose, both androgens induced male-like indentations in the dorsal margin of the anal fin of juveniles and adult females by 4 weeks postimplant. Both low and high doses of T decreased the peak power spectrum frequency (PPSF) of Fourier transformations of EODs and increased the durations of phases 2 and 3 of the EOD in juveniles and adults, but the high doses caused more rapid and profound effects. The two doses of T caused opposite effects on the durations of phases 1 and 4 in juveniles. The low dose of T decreased the durations of phases 1 and 4, while the high dose increased them. In adults, the high dose of T increased the duration of phase 1, but had inconsistent effects on the duration of phase 4. Total EOD durations were increased by both doses of T in juveniles, while adults showed inconsistent effects possibly due to individual variability in hormone sensitivity. Compared to T, DHT exerted similar, but less dramatic effects on all measures, but only at high doses. E2 significantly increased adult PPSFs, the first such finding in a mormyrid species. E2 had no effects on juvenile PPSFs, or on adult or juvenile EOD phase durations. The effects of DHT + E2 on PPSF and phases 2 and 3 were similar to those of DHT alone. These findings demonstrate quantifiable steroid-dependent plasticity in the durations of individual phases of EODs in an electric fish and are the first to show that the external morphology in Gnathonemus petersii is androgen-dependent. The result are discussed with regard to methodological considerations and hormone studies involving sex differences in EODs reported for this and other species.
Experientia, 1988
Effects of silastic and pellet methyltestosterone implants on the waveform of the electric organ ... more Effects of silastic and pellet methyltestosterone implants on the waveform of the electric organ discharge of the weakly electric African mormyrid, Gnathonemus petersii, were investigated. Within seven days of implantation, the duration of the discharge increased dramatically while the associated peak power frequency of the Fourier spectrum decreased in all treated fish. By day 35, hormone-treated fish exhibited up to five-fold increases in EOD duration, as well as multiple discharges and variations in the shape of the positive phase of the discharge. Testosterone treatment also changed body morphology, making immature and adult female fish resemble adult males.
Reproductive Physiology of Fish, 1987
The Science Teacher 69(1), 56-60, 2002
Networking the Learner: Computers in Education, 2002
This study describes an instructional intervention in which high school biology students Jeamed t... more This study describes an instructional intervention in which high school biology students Jeamed to develop criteria for critically evaluating science Websites and scientific information contained in them. Results indicated that the process of leaming to critically evaluate Websites was what was most valuable to them. Students' Jists of criteria for critically evaluating Websites were more extensive after instruction. Furthermore, the majority of students reported leaming something new, indicated that they would spendmoretime evaluating scientific information on Websites, and reported increased confidence in their ability to evaluate scientific information on the Web.
Eubios Journal of Asian and International Bioethics, 2001
Making Connections-Electronic Media, 2000
Making Connections-Electronic Media, 2000
Making Connections-Electronic Media, 2000
Making Connections-Electronic Media, 2000
Koi USA 24(3), 1999, 1999
Nishikigoi International, (Spring), 68-69., 1997
Mid-Atlantic Koi, 10(8-9), 7-11. , 1997
Mid-Atlantic Koi 11(1), 5-13., 1997
Koi Health Quarterly, 1997
J. Comp. Physiol. A, 1993
Journal of Comparative Physiology A-neuroethology Sensory Neural and Behavioral Physiology, 1993
1. Experiment 1 employed a repeated measures design to examine the effects of captivity on sex di... more 1. Experiment 1 employed a repeated measures design to examine the effects of captivity on sex differences in the electric organ discharge (EOD) of Gnathonemus petersii, newly imported from Africa, and maintained individually or in groups. 2. On the day of import, males exhibited longer durations of phases 2 and 3 of the EOD and lower peak power spectral frequencies (PPSFs) than females. 3. After 14 days in captivity in the laboratory, the sex differences were eliminated. After 37 days of captivity, all sex differences were still abolished, or even reversed depending on housing conditions. Males exhibited the most dramatic changes in EODs and females appeared to have higher testosterone (T) levels than males. 4. Experiment 2 was designed to investigate the effects of captivity on both behavior and endocrine status in 58 newly imported males. In this independent group design, EOD data and blood were collected from subjects over 15 days. 5. Decreases in phase 3 of the EOD and increases in PPSFs progressed over the 15 day experimental period, becoming statistically significant by days 10 and 15, respectively. Regardless of housing conditions, both T and 11-keto T dramatically decreased to near non-detectable levels by Day 5 in the laboratory. 6. Captivity causes rapid and profound changes in the endocrine system which result in dramatic changes in steroid-sensitive EODs. These findings directly link captivity, hormones, and behavior, and show why feral animals brought into captivity usually do not exhibit sexual behavior.
Reproductive Physiology of Fish, 1991
Hormones and behavior, 1990
The effects of androgens and estrogen on the external morphology and electric organ discharge (EO... more The effects of androgens and estrogen on the external morphology and electric organ discharge (EOD) waveform in Gnathonemus petersii, a weakly discharging electric fish, were investigated. Following preimplant data collection, juvenile and adult fish were gonadectomized and implanted with silastic capsules containing either high or low doses of testosterone (T), dihydrotestosterone (DHT), estradiol-17β (E2), or cholesterol. One group of fish was treated with high doses of DHT + E2. Radioimmunoassays revealed that low-dose implants resulted in plasma T levels comparable to and high-dose implants about sixfold greater than those found in adult males imported during breeding season. High-dose E2 implants resulted in higher plasma E2 levels in adults than those in juveniles. At either dose, both androgens induced male-like indentations in the dorsal margin of the anal fin of juveniles and adult females by 4 weeks postimplant. Both low and high doses of T decreased the peak power spectrum frequency (PPSF) of Fourier transformations of EODs and increased the durations of phases 2 and 3 of the EOD in juveniles and adults, but the high doses caused more rapid and profound effects. The two doses of T caused opposite effects on the durations of phases 1 and 4 in juveniles. The low dose of T decreased the durations of phases 1 and 4, while the high dose increased them. In adults, the high dose of T increased the duration of phase 1, but had inconsistent effects on the duration of phase 4. Total EOD durations were increased by both doses of T in juveniles, while adults showed inconsistent effects possibly due to individual variability in hormone sensitivity. Compared to T, DHT exerted similar, but less dramatic effects on all measures, but only at high doses. E2 significantly increased adult PPSFs, the first such finding in a mormyrid species. E2 had no effects on juvenile PPSFs, or on adult or juvenile EOD phase durations. The effects of DHT + E2 on PPSF and phases 2 and 3 were similar to those of DHT alone. These findings demonstrate quantifiable steroid-dependent plasticity in the durations of individual phases of EODs in an electric fish and are the first to show that the external morphology in Gnathonemus petersii is androgen-dependent. The result are discussed with regard to methodological considerations and hormone studies involving sex differences in EODs reported for this and other species.
Experientia, 1988
Effects of silastic and pellet methyltestosterone implants on the waveform of the electric organ ... more Effects of silastic and pellet methyltestosterone implants on the waveform of the electric organ discharge of the weakly electric African mormyrid, Gnathonemus petersii, were investigated. Within seven days of implantation, the duration of the discharge increased dramatically while the associated peak power frequency of the Fourier spectrum decreased in all treated fish. By day 35, hormone-treated fish exhibited up to five-fold increases in EOD duration, as well as multiple discharges and variations in the shape of the positive phase of the discharge. Testosterone treatment also changed body morphology, making immature and adult female fish resemble adult males.
Reproductive Physiology of Fish, 1987
Electric Fishes: History and Behavior, 1995
Behavioral plasticity (or variability) is the rule, not the exception, and in many instances, env... more Behavioral plasticity (or variability) is the rule, not the exception, and in many instances, environmental perturbations are a major cause of variability observed in behavior. To the extent that changes or differences in environmental conditions persist, differences in response between and/or within members of a single species will persist in both field and laboratory. Consequently, the scientist who employs behavior as an end point in his/ her research must carefully assess alternative hypotheses to explain variability in results, and sometimes the elimination of outliers may be the elimination of the most valuable findings. Serendipity does not just occur, it is ferreted out by the reflective investigator.
Exemplary science in grades 9-12: Standards-based success stories, 2005
Society for Neuroscience Abstracts 16, Part 2, 1312. , 1990
Society for Neuroscience Abstracts 17, Part 2, 1201., 1991
Society for Neuroscience Abstracts 20, Part 1, 372., 1994
Society for Neuroscience Abstracts 22, Part 2, 1337., 1996
Society for Neuroscience Abstracts 22, Part 1, 252. , 1996
Society for Neuroscience Abstracts 23, Part 1, 249. , 1997
Society for Neuroscience Abstracts 23, Part 2, 2388., 1997
Society for Neuroscience Abstracts 23, Part 2, 1323., 1997
Society for Neuroscience Abstracts 23, Part 1, 279, 1997
Should teachers be called neuroeducators? It is known that the structure and function of our brai... more Should teachers be called neuroeducators? It is known that the structure and function of our brains define much about how we learn and think. Yet, science is showing that the reverse effect also holds true—an environment that encourages learning and thinking can alter the connectivity of neurons and functioning of the brain. This impact will prepare our nation's youth to compete and succeed in the connectivity-driven 21st Century and may even lead to a healthier brain through old age. Some of the most recent compelling neuroscience findings on how thinking and learning are influenced by and influence the brain to promote the teacher to the role of neuroeducator will be presented.
Participants will experience a guided investigation using the Research Investigation Process mode... more Participants will experience a guided investigation using the Research Investigation Process model of scientific inquiry and view how to incorporate STEM directly into the classroom.
Under guidance of their teachers and a visiting scientist, students in Shiprock, NM and Honolulu,... more Under guidance of their teachers and a visiting scientist, students in Shiprock, NM and Honolulu, HI collaborate as student scientist volcanologists and earth scientists. They share scientific ideas and learning across thousands of miles as they propose, design and conduct comparative studies involving the environment and earth science together in their virtual laboratory.
A scientist joins a community of teacher-learners to experience successful implementation of auth... more A scientist joins a community of teacher-learners to experience successful implementation of authentic scientific inquiry in content areas extending beyond science, resulting in K–12 student achievement of standards.
Participants (students) and scientist (teacher) will co-lead a scientific research investigation,... more Participants (students) and scientist (teacher) will co-lead a scientific research investigation, using the RIP, that addresses standards and can be taken directly into the classroom.