Unit Two: ReproductionScience 9

Cellular Processes

• Students will be expected to: •Recognize that the nucleus of a cell contains genetic information and determines cellular processes

First Five Minutes

• Look around the classroom and observe, note and report differences and similarities among members of the class•Physical traits such as hair and eye colour, attached/detached ear lobes, tongue rollers/non-rollers

“What causes people to be the same and yet different?”“Are there similarities and differences in other species?”

Who started describing cells and a nucleus?

• The cell was first described by Robert Hooke in 1665 while he was looking at cork under a microscope•He was really looking at cell walls, not cells

• Anton van Leeuwenhoek observed living cells in blood, bacteria and single-celled organisms• Robert Brown was the first to

describe a nucleus in plant cells (1820); it was also discovered in animal cells a few years later

What are cells?

• Schwann and Schleiden concluded that plants and animals are composed of cells• All living things are composed of one

or more cells• The cell is the functional unit of life• Most cells have to be seen with the

aid of a microscope

Light Microscopes

•Uses light and multiple lens to see small organisms and cells

Light Microscopes

Electron Microscopes

•Uses beams of electrons, limited to only looking at a single layer of cells but with much more magnification than light telescopes• Only dead cells can be observed

Transmission Electron Microscope

Scanning Electron Microscopes

•Uses reflection by electrons hitting the surface of the cell•Produces a three dimensional image

Scanning Electron Microscope

Images of Cells

• What we can see under a microscope as far as the cell goes has helped us to create a model of what a cell looks like with all its parts. This is a plant cell.

Animal Cells

What is common among all cells?

• The entire cell is covered with a cell membrane which controls what goes into and out of the cell

• The nucleus acts as a control centre, directing the cell’s activities•Genetic information is organized into threadlike structures called chromosomes•Each chromosome contains different genes•Genes are units of genetic information that determines the specific characteristics of an individual

Continued…

• The cytoplasm is the area where work is done•Nutrients are absorbed, transported and processed

• It contains many different organelles, which is a specialized structure inside the cell