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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
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 ?