do now - in the early 1990’s students and scientists in minnesota and elsewhere had found...
TRANSCRIPT
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
14 species in MN
Frogs and Toads
92 species in USA
3,300 species in the world
smooth or slimy skin warty and dry skin strong, long legs and stubby bodies with short
webbed hind feet hind legs two bulging eyes parotid glands behind
eyes
lay eggs in clusters lay eggs in long chains
Both are Cold blooded - their body temperature adjusts with the outside environment.
Vs.
Frogs have: Toads have:
Red-eyed Treefrog
glass Frog
poison dart frog
White’s Treefrog
Horned ToadFire-bellied Toad
Ornate Horned Frog poison dart frog
Strawberry Poison Dart FrogAfrican Dwarf Frog
MN Frogs and Toads
Habitats for frogs and toads
rivers and streams
lakes, ponds, marshes
grasslands
forests
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
• herbicidesManeb-
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 well-
documented• 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 ?