Instructions
Read each section carefully and answer the questions to the best of your ability. This worksheet explores the fascinating world of herpetology, focusing on the life cycle, biology, and conservation of frogs.
Part 1: The Frog Life Cycle and Metamorphosis
Fill in the blanks with the most appropriate terms from the list below. Some terms may not be used.
Word Bank: metamorphosis, froglet, gills, lungs, amplexus, tadpole, thyroxine, cutaneous, frogspawn, pulmonary
- The life cycle begins with eggs, often laid in a gelatinous mass called ______________________.
- During mating, the male frog grasps the female in a process called ______________________, during which he externally fertilizes the eggs as she lays them.
- Once hatched, the fully aquatic larva, known as a ______________________, swims using its tail and breathes through ______________________.
- The dramatic transformation from the larval stage to the adult form is called ______________________.
- This complex biological process is primarily controlled by the hormone ______________________, produced by the thyroid gland.
- During this transformation, the tadpole develops legs, its tail is absorbed, and its respiratory system switches from gills to ______________________ for breathing air.
- The intermediate stage, which has legs but still possesses a tail, is often referred to as a ______________________.
Short Answer Question:
- Explain why the biphasic (two-stage) life cycle of a frog makes it particularly vulnerable to environmental disturbances.
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Part 2: Frog Biology and Anatomy
Match the anatomical structure in Column A with its primary function in Column B.
| Column A: Structure | Column B: Function |
|---|---|
| 9. Tympanic Membrane _____ | A. A common chamber that receives material from the digestive, urinary, and reproductive systems. |
| 10. Cloaca _____ | B. A fused bone at the posterior end of the spine that provides stability for jumping. |
| 11. Nictitating Membrane _____ | C. The external eardrum, used for transmitting sound waves. |
| 12. Urostyle _____ | D. The ability to absorb oxygen through thin, moist skin. |
| 13. Cutaneous Respiration _____ | E. A transparent third eyelid that protects the eye underwater while maintaining vision. |
Multiple Choice Questions:
- An adult frog has a three-chambered heart consisting of:
- a) One atrium and two ventricles
- b) Two atria and one ventricle
- c) One atrium and one ventricle
- d) Two atria and two ventricles
- What is the primary function of a frog's vomerine teeth, located on the roof of its mouth?
- a) To chew food before swallowing
- b) To inject venom into prey
- c) To filter water for plankton
- d) To grip and hold prey in place
Part 3: Frog Conservation
Answer the following questions in complete sentences.
- Frogs are often called "indicator species" or "bioindicators." What does this term mean, and what two characteristics of frogs make them so effective in this role?
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- List and briefly describe three major anthropogenic (human-caused) threats to frog populations globally, excluding the spread of disease.
Threat 1: ___________________________________________________________________
Threat 2: ___________________________________________________________________
Threat 3: ___________________________________________________________________
- The fungal disease chytridiomycosis has devastated amphibian populations worldwide. The fungus attacks and degrades keratin, a protein found in the skin. Based on your knowledge of frog biology from Part 2, explain why a disease that damages the skin is so lethal to a frog.
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Answer Key
Part 1: The Frog Life Cycle and Metamorphosis
- frogspawn
- amplexus
- tadpole, gills
- metamorphosis
- thyroxine
- lungs
- froglet
- A frog's biphasic life cycle makes it vulnerable because it depends on both healthy aquatic and terrestrial ecosystems. Pollutants or habitat destruction in the water can kill eggs and tadpoles, while similar disturbances on land can harm adult frogs. They are exposed to threats in two different environments during their lives.
Part 2: Frog Biology and Anatomy
- C - The external eardrum, used for transmitting sound waves.
- A - A common chamber that receives material from the digestive, urinary, and reproductive systems.
- E - A transparent third eyelid that protects the eye underwater while maintaining vision.
- B - A fused bone at the posterior end of the spine that provides stability for jumping.
- D - The ability to absorb oxygen through thin, moist skin.
- b) Two atria and one ventricle
- d) To grip and hold prey in place
Part 3: Frog Conservation
- An "indicator species" is an organism whose presence, absence, or abundance reflects a specific environmental condition. Frogs are effective bioindicators because of their 1) permeable skin, which readily absorbs chemicals from the environment, and their 2) biphasic life cycle, which exposes them to pollutants in both water and on land.
- (Answers may vary but should include three of the following or similar points.)
Threat 1: Habitat Loss/Fragmentation: The destruction of forests, wetlands, and ponds for agriculture or urban development removes the places where frogs live, breed, and find food.
Threat 2: Pollution: Chemical pollutants like pesticides, fertilizers, and industrial waste can run off into water bodies, causing developmental deformities, suppressing immune systems, and killing frogs directly.
Threat 3: Climate Change: Changes in temperature and rainfall patterns can dry up breeding ponds, alter hibernation cycles, and shift habitats, making it difficult for frog populations to adapt.
Threat 4: Introduced/Invasive Species: Non-native predators (like certain fish or bullfrogs) can prey on local frogs, while other invasive species can outcompete them for resources. - A disease that damages a frog's skin is lethal primarily because frogs rely on cutaneous respiration (breathing through their skin) for a significant portion of their oxygen intake. Damaged skin disrupts this process. Additionally, the skin is crucial for osmoregulation (maintaining water and electrolyte balance). A compromised skin barrier can lead to dehydration and fatal electrolyte imbalances.