Unit 3: Reproduction, Heredity and Evolution How does life on Earth continue and adapt in response to environmental change?

All living things: Are composed of cell(s) Have different levels of organization Use energy Respond to the environment Grow Reproduce Adapt to the environment

Cells Are the basic unit of structure and function of living things (all the “work” in an organism takes place in the cells). Contain the genetic material (in the nucleus) that provides the instructions to direct all the activity (life functions) in an organism.

What is genetic material? Chromosomes are the keepers of the genetic material in eukaryotic (with a nucleus) cells. An organism has the same chromosomes for its entire life. The chromosomes are located within each cell nucleus. Each somatic (body) cell in an organism has the same chromosomes. Chromosomes provide the directions for how the cell is supposed to function and determine some characteristics about how the individual looks. Each chromosome contains a very complex molecule called DNA. The DNA molecule contains genes, which direct how an organism’s body is built and maintained.

Human Chromosomes

Drosophila (Fruit Fly) Chromosomes Female Male

Summary Different species have different numbers of chromosomes (humans have 46 while fruit flies have 8). Chromosomes are homologous (They come in matched pairs of approximately the same size and shape, with each one containing slightly different information).