Transcript Document
Do Now In the early 1990’s Students and Scientists in Minnesota and elsewhere had found malformed frogs. Then the issue hit the national media in 1995. Why would this be important to humans ? Malformed Frogs & Toads Frogs and Toads 14 species in MN 92 species in USA 3,300 species in the world Vs. Frogs have: smooth or slimy skin strong, long legs and webbed hind feet two bulging eyes lay eggs in clusters Toads have: warty and dry skin stubby bodies with short hind legs parotid glands behind eyes lay eggs in long chains Both are Cold blooded - their body temperature adjusts with the outside environment. glass Frog Red-eyed Treefrog poison dart frog White’s Treefrog Horned Toad Fire-bellied Toad Ornate Horned Frog Strawberry Poison Dart Frog poison dart frog African Dwarf Frog MN Frogs and Toads Habitats for frogs and toads forests grasslands lakes, ponds, marshes rivers and streams Why We Care 1. Frogs and toads are a part of the planet’s bio-diversity. 2. Frogs and toads interact in interesting ways with each other and the environment, i.e. both prey and predators 3. Frogs As Bio-indicators 1) Double life—amphibious What does this mean ? 2) Permeable skin 3) Absorb and concentrate toxins-biomagnification Biomagnification • Biological magnification is when certain substances such as pesticides or heavy metals like mercury move up the food chain, work their way into rivers or lakes, and are eaten by aquatic organisms such as fish, which are then eaten by large birds, animals or humans. External Malformations • • • • • extra or missing limbs branching limbs spikes or protuberances missing eyes abnormal webbing Internal Malformations • reproductive • digestive • urinary Malformed Frog Pictures Causes of Malformations • • • • • • genetic origins parasite disruption of limb formation chemical contamination viruses ultraviolet radiation physical trauma (predation, people) Possible Chemical Contaminants • • • • Agrochemicals (pesticides) Heavy metals Acid Rain (sulphur dioxide reacting with rain) Chlorofluorocarbons (CFCs) Types of Agrochemicals • herbicides Maneb-fungicide • pesticides propylthiourea • fertilizers Correlations to Human Health Concerns • high nitrate levels (from fertilizers) in human drinking water and frog breeding ponds are hazardous • human birth defects result from pesticide application • UV radiation results in blindness and skin cancer in humans and other animals; DNA damage in developing frog eggs Where have all the frogs gone? Global Population Decline • • • a concern during the past decade frog declines widespread and welldocumented possible causes include habitat destruction, increased UV radiation, and chemical contamination Global Population Declines • Loss of habitat from filling in wetlands to create more farmland for crops, and to build more houses and roads Global Population Declines • • • • • • Increasing ultraviolet radiation Pollution by chemicals Acid rain Pathogens Parasites Introduction of non-native species Global Population Declines Monteverde, Costa Rica: Golden Toad last seen 1988 Global Population Declines Other places experiencing declines include: Puerto Rico Ecuador Venezuela Brazil U.S. Rocky Mountains Cascade Mountain Range in Washington, Oregon, and California Exit Card • In order to leave class you must hand in a sheet of paper with the following questions answered…. 1. Why do we care if there are frogs living with malformations ? 2. How can this information help humans ?