Chapter 9 "Where Life Comes From"

Materials:

• Worksheet: "That's Life"
• Students will need a notebook for notes.

Objective:

• .Students will define spontaneous generation.
• Students will recognize the importance of DNA in reproduction.
• Students will describe how spontaneous generation was proved to be untrue.
• Students will explain the importance of diversity in a population.

Alaska Content Standards:

• SCI A-10 Students will understand that living things are made up mostly of cells and that all life processes occur in Cells (Cells)
• SCI A-12 Students will distinguish the patterns of similarity and differences in the living world in order to understand the diversity of life and understand the theories that describe the importance of diversity for species and ecosystems.

Anticipatory Set: Introduce the students to a question posed by one of the students last week, "How does a person get lice even if they are not around anyone that has lice?" Students will each jot down an answer to this question, "Where does life come from?" After students have been given some time a student from each site will read their explanation. Students will keep there explanation until the end of the period then re-read it and see if it still fits.

Teacher Input: Show this picture of Francesco Redi or this one and tell the story how long ago (1690's) people thought that organisms were created from non-living things some examples include: mud created frogs, rotten meat created maggots, flour created meal worms, water created fish, and soils created crop pests(worms and locust). This idea that living things can come from nonliving things was called spontaneous generation. Redi did a famous experiment which went a long way to disprove that theory. Here is the experiment. P210. Later after 100's of experiments showing spontaneous generation as untrue have led us to believe that living things have to come from other living things.

Show a cell. Remind students that in chapter 1 they learned that living things are made of cells. Each cell has a nucleus which contains the information for what the cell is to do. It also has all the information for what our physical appearance is going to be. This information is contained in this: Show this DNA strand. Explain how DNA deoxyribonucleic acid contains all the information in how it is arranged. An identical twin (or clone) would have the same DNA as you unless there were small mistakes or mutations as the chains were duplicated. The brain however would have many different connections based on many, many factors.

In reproduction parents pass on their DNA to there offspring. Where there is only one parent such as bacteria and most one celled organisms exact copies are passed on. This is asexual reproduction. In humans and other organisms two sets of DNA are combined to make the offspring. Sexual reproduction.

Look at this picture of diversity and Ask the question, "Why does it help us as a species to be so diverse?" "What causes diversity. Show this picture of animals and ask, "How come we have such a diversity of animal species?" "How does it help an animal population to be diverse" Don't choose one particular answer as right or wrong. These are questions we want students pondering over the next quarter.

Guided Practice: Have the students look at the headings in the chapter and on the same piece of paper where they wrote down where life comes from have them look at the headings of the chapter, "Spontaneous Generation", "DNA", "DNA and Reproduction", "Diversity" Have them write down a question they still have about one of those topics. Then have the students exchange questions with a partner and see if the partner can answer the question. If they can't see if anyone in the room can answer it or find an answer. If they can't and Mr. Marley can't maybe that could be a basis for some future investigation of their own.

Independent Practice: Students should complete the worksheet 34, "That's Life" Then take the quiz on Lesson 1, "Where Life Comes from"

Duration:

30 minutes + 10-15 for Independent Practice (Could be longer if taken for homework).