Themes in the Study of Life

Page
7

Fig. 1-15d

Protists

Slide 71

Fig. 1-15e

Kingdom Fungi

Slide 72

Fig. 1-15f

Kingdom Plantae

Slide 73

Fig. 1-15g

Kingdom Animalia

Slide 74

Unity in the Diversity of Life

A striking unity underlies the diversity of life; for example:

DNA is the universal genetic language common to all organisms

Unity is evident in many features of cell structure

Slide 75

Fig. 1-16

Cilia of

Paramecium

Cross section of a cilium, as viewed

with an electron microscope

Cilia of

windpipe

cells

15 µm

5 µm

0.1 µm

Slide 76

Charles Darwin and the Theory of Natural Selection

Fossils and other evidence document the evolution of life on Earth over billions of years

Slide 77

Fig. 1-17

Slide 78

Charles Darwin published On the Origin of Species by Means of Natural Selection in 1859

Darwin made two main points:

Species showed evidence of “descent with modification” from common ancestors

Natural selection is the mechanism behind “descent with modification”

Darwin’s theory explained the duality of unity and diversity

Slide 79

Fig. 1-18

Slide 80

Fig. 1-19

Slide 81

Darwin observed that:

Individuals in a population have traits that vary

Many of these traits are heritable (passed from parents to offspring)

More offspring are produced than survive

Competition is inevitable

Species generally suit their environment

Slide 82

Darwin inferred that:

Individuals that are best suited to their environment are more likely to survive and reproduce

Over time, more individuals in a population will have the advantageous traits

In other words, the natural environment “selects” for beneficial traits

Slide 83

Fig. 1-20

Population