7th science … · unit 1 lesson 1 the characteristics of cells •robert hooke (1665) - first to...

7th Science

Cells and Heredity (Module A)

Unit 1: Cells

Lesson 1: Characteristics

of Cells

Copyright © Houghton Mifflin Harcourt Publishing Company

What is a cell?

• A cell is the smallest functional and structural unit of all living organisms.

• Organism - any living thing that carries out its own life processes.

Unit 1 Lesson 1 The Characteristics of Cells

Cell size

All cells are small - size is limited by their outer surface area.

• If too large, can’t take in enough nutrients or get rid of enough wastes.

• The surface area-to-volume ratio: ratio of the outer surface to the cell’s volume. • The smaller the cell, the greater this ratio.



Cell theoryThree basic components:



1. All organisms are made up of one or more cells.

2. The cell is the basic unit of all organisms.

3. All cells come from existing cells.



•Robert Hooke (1665) - first to describe cells. He looked at the bark of a cork tree under a microscope (that he built).

• Thought that cork cells looked like cells in monastery

Cell Hall of Fame

• Anton van Leeuwenhoek (1673) made first microscope, described “wee beasties” in pond water.

• Matthias Schleiden (1838) said all plants are made of cells.

• Theodor Schwann (1839) said all animalstissues are made of cells.

• Rudolf Virchow (1858) said cells divide to form new cells



Cell Hall of Fame (con’t) read pg. 8-9

A few more important cell theory things:

• Unicellular organisms: Organisms made up of just

one cell

• One cell has to carry out ALLlife functions.

• multicellular organisms: Organisms made up of more than one cell

• Cells have specialized functions.



• Prokaryotes - No nucleus or membrane-bound

organelles

• All are single-celled

• DNA is in the cytoplasm

• Have ribosomes to make proteins

• Some have flagella to help move

• Smaller than eukaryotes

• Examples: bacteria, archaeaCopyright © Houghton Mifflin Harcourt Publishing Company

Unit 1 Lesson 1 The Characteristics of CellsTwo types of cells

Bacteria Flagella



• Eukaryotes - have DNA in a nucleus

• Have other membrane-bound organelles

• Most are multicellular

• Also have ribosomes (not membrane bound)

• Examples: animals, plants, protists, fungi

• Do page 11


• cell membrane – protective outer layer • controls materials moving into and out of the cell.

• cytoplasm - region inside the cell that includes the fluid and all the organelles except for the nucleus.• organelle - small body in the cytoplasm

• specialized to perform a specific function

• DNA (deoxyribonucleic acid)- genetic material that provides instructions for all cell processes

Do page 10

Unit 1 Lesson 1 The Characteristics of CellsAll cells have…

What parts do all cells have in common?

• How many parts of a cell can you name?



7th science … · unit 1 lesson 1 the characteristics of cells •robert hooke (1665) - first to...

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