People's Education Edition Biology for Grade 8, Volume 2

Description

"Reproduction and Development of Amphibians" Reproduction and Development of Biological Organisms PPT Courseware

Review the past and learn the new

1. What is abnormal development?

2. What is an example of complete metamorphosis? What is incomplete metamorphosis?

learning target

1. By studying the reproduction and development of frogs, describe the reproduction and development processes and characteristics of amphibians.

2. Pay attention to the relationship between biological reproduction and development and the environment through investigation and practice activities and data analysis.

Self-learning

1. What does a fertilized egg in water develop into first? What are the morphological characteristics of tadpoles? Where to live? What are your living habits? What changes do tadpoles undergo during their development? What did it become in the end?

2. Can all frogs chirp? What is the significance of the croaking of frogs and the hugs of male and female frogs?

3. What is the fertilization method of male and female frogs? Where do egg cells and sperm combine?

reproductive process of frog

1. Can all frogs chirp? What actions occur when a frog croaks?

2. What are the meanings of the croaking of frogs and the hugs of male and female frogs?

3. What is the fertilization method of male and female frogs? Where do egg cells and sperm combine?

The development process of frog

1. What does a fertilized egg in water develop into first?

2. What are the morphological characteristics of tadpoles? Where to live? What are your living habits?

3. What changes occur in tadpoles during their development? What did it become in the end?

1. Reproduction and development of frogs

1. Male frog calls: attracting female frogs

2. Male and female frogs hug each other: increase fertilization rate

3. Reproductive characteristics: sexual reproduction, in vitro (water) fertilization, oviparous

4. Developmental characteristics: abnormal development

Development process: fertilized egg→tadpole→young frog→adult frog or fertilized egg→larvae→adult

Reproductive and developmental processes of frogs:

Male and female frogs hug each other - produce fertilized eggs - tadpoles (first grow two back legs, then stretch out two front legs, and the tail disappears) - young frogs - adult frogs

2. Reproductive development and environment of amphibians

P14-15 Data Analysis: Discussion

1. The above examples illustrate what impact environmental changes have on the reproduction of amphibians?

Environmental changes destroy the environment required for amphibian reproduction and development, making amphibians unable to carry out normal reproductive activities. At the same time, environmental changes also affect the normal development of amphibians, ultimately leading to a decline in the ability of amphibians to reproduce, and the population size and Reduced variety.

2. Deformed frogs appear in some areas. What may be the cause?

Deformed frogs may be caused by water pollution, substances in the water that affect the normal development of frogs.

Section 3 Reproduction and Development of Amphibians

1. Reproduction and development of frogs

1. Song: Male frog - has a song sac; function - to attract female frogs

2. Hug the right person: increase the fertilization rate

3. Reproductive characteristics: sexual reproduction, in vitro (water) fertilization, oviparous

4. Developmental characteristics: abnormal development

Development process: fertilized egg→tadpole→young frog→adult frog or fertilized egg→larvae→adult

2. Reproductive development and environmental conditions of amphibians

Apply what you learn

1. "In the yellow plum season, it rains everywhere, and frogs are everywhere in the grassy ponds." In late spring and early summer, frogs' cries of "croak, croak, croak" are heard one after another. If you look for the sound, you will find that the frogs in the pond are hugging each other. Soon, if you come back, you will see tadpoles in the water. Continuing to observe, you will also see the frog's magical appearance change process. Do you know the reason? Try to analyze the answer:

(1) The male frog calls for _______.

(2) What is the significance of male and female frogs hugging each other? ______________.

(3) The tadpole does not look like "mother", but looks like a small fish. Guess what tadpoles use to breathe in the water? _______.

(4) The tadpole undergoes magical changes and finally becomes the same as its "mother". Can you write down the entire development process of a frog? (please indicate with arrows and developmental stages)___________.

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For more information about the PPT courseware "Reproduction and Development of Biological Reproduction and Development of Amphibians", please click the Reproduction and Development of Biological Things ppt Reproduction and Development of Amphibians ppt tag.

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Update Time: 2024-10-21

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