Themes in the Study of Life

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4

Fig. 1-6c

(c) Neurons

100 µm

Slide 41

Fig. 1-6d

Infoldings of

membrane

Mitochondrion

(d) Mitochondria

0.5 µm

Slide 42

Theme: Cells are an organism’s basic units of structure and function

The cell is the lowest level of organization that can perform all activities required for life

All cells:

Are enclosed by a membrane

Use DNA as their genetic information

The ability of cells to divide is the basis of all reproduction, growth, and repair of multicellular organisms

Slide 43

25 µm

Fig. 1-7

Slide 44

A eukaryotic cell has membrane-enclosed organelles, the largest of which is usually the nucleus

By comparison, a prokaryotic cell is simpler and usually smaller, and does not contain a nucleus or other membrane-enclosed organelles

Bacteria and Archaea are prokaryotic; plants, animals, fungi, and all other forms of life are eukaryotic

Slide 45

1 µm

Organelles

Nucleus (contains DNA)

Cytoplasm

Membrane

DNA

(no nucleus)

Membrane

Eukaryotic cell

Prokaryotic cell

Fig. 1-8

Slide 46

Theme: The continuity of life is based on heritable information in the form of DNA

Chromosomes contain most of a cell’s genetic material in the form of DNA (deoxyribonucleic acid)

DNA is the substance of genes

Genes are the units of inheritance that transmit information from parents to offspring

Slide 47

DNA Structure and Function

Each chromosome has one long DNA molecule with hundreds or thousands of genes

DNA is inherited by offspring from their parents

DNA controls the development and maintenance of organisms

Slide 48

Nuclei

containing

DNA

Sperm cell

Egg cell

Fertilized egg

with DNA from

both parents

Embryo’s cells with

copies of inherited DNA

Offspring with traits

inherited from

both parents

Fig. 1-9

Slide 49

Each DNA molecule is made up of two long chains arranged in a double helix

Each link of a chain is one of four kinds of chemical building blocks called nucleotides

Slide 50