Chapter 9, Lesson 3 "How Animals Grow and Develop"
Materials:
Objective:
Anticipatory Set: Students will develop two lists. First they have to list five things that are different about themselves now than when they were 1. In the second list they should list at least 5 things that will be different about themselves when they are 50 or 60. A student from each site will then tell one of the things on their list. It must be different from all others. Teacher response: development is a predictable process it happens basically the same in all humans. In all speices of animals. You can expect that one member of a speicies will develop the same as another. Lets start at the beginning.
Teacher Input: All animals start out as a zygote. Show this picture: zygote. Ask students if they remember from chapter 7 what a zygote is. Even though chapter 7 covered plants they too in most instances start out as a zygote. A zygote then divides into two cells, then 4, then 8 and so on until it is millions of cells. How many times would a cell have to divide to become a million cells? Have the students try to quickly figure it out. It ends up being around 20.
Show Cell differentiation. Although the cells originally look the same over time and after a number of divisions the cells begin to look and act differently. this is known as cell differentiation. (Have a student define cell differentiation)
Cell differentiation leads to development of an organism. What is development? Discuss these examples of development: Grasshopper, discuss the word nymph, butterfly, fish, humans.
Many animals produce hundreds or thousands of offspring. Why? Give me some examples. Many other animals produce few offspring. How is it that that species survives? give me some examples. What do most mammals do produce hundreds or just a few? Most mammals give birth to live offspring can you name the two that lay eggs. platypus, and spiny anteater. There also is a type of mammal that gives birth to offspring that are not well developed can you name that type of mammal? Here are some pictures of them. kangaroo, koalas, opossums. Do you know the name of this type of animal? Define Marsupial.
Compare a fish embryo to a mamal embryo. Fish embryos are very small, little food in the egg. Mammal embryos are huge because they recieve nutrition from their mother thoughout their development. How? What is the place called where a mammal embryo develops. What is the name for the tissue that provides the embryo with food and oxygen from is mother's body? Show uterus and placenta. Most fish are also on their own for food when they hatch from the egg. Mammals are nurished by there mother even after they are born. The mothers mammary glands provide the offspring with millk until the offspring are developed enough to eat other types of food. Even the egg laying monotreams nurish their young with milk. dogs, bears, gorillas.
How long does a mammal keep its embryo inside it while it develops? Is it the same for all mammals? What is this time period called? Define Gestation time.
Guided Practice: Give the students the names of several different types of animals and have them guess wether it will have a long or short gestation time. Find out why they are putting the anmimals in the different catagories.
Help students answer the questions at the end of the section on page 225.
Independent Practice: Students will complete the animal development worksheet.
Check for Understanding: Students will take the quiz for Chapter 9 lesson 3.
Conclusion: Have the students get a map of the world. On the map list at least five animals from that part of the world and then guess whether they produce a lot of spring or few offspring and whether the parents care for the offspring once it is born.
Duration:
30 minutes + 10-15 for Independent Practice (Could be longer if taken for homework).
Alaska Content Standards Addressed in this lesson:
