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 ?