This document provides an overview of chapter 10 from an introductory biology textbook. It covers the origin of life from non-living materials, the earliest cells, the definition and classification of species, mechanisms of speciation, and evolutionary trees. Key points include: life likely originated from organic molecules formed on the early Earth; the first cells developed membranes, allowing metabolism; species are defined by the ability to interbreed; speciation occurs through geographic isolation or polyploidy; and evolutionary trees reveal ancestral relationships between organisms.

1. The Origin
and
Diversification
of Life
on Earth
BIOL 108
Intro to Bio Sci
Chapter 10 pt 1
Rob Swatski
Assoc Prof Biology
HACC-York1

2. Learning Goals
Life on earth
most likely
originated from
nonliving
materials.
Species are the
basic units of
biodiversity.
Evolutionary
trees help us
conceptualize
and categorize
biodiversity.
Macroevolution
and the
diversity of life.
An overview of
the diversity of
life on earth.
2

3. 3

4. 10.1 Complex organic
molecules arise in non-living
environments.
4

5. Phase 1: The Formation of Small Molecules
Containing Carbon and Hydrogen
5

6. 6

7. 7

8. The Urey-Miller Experiments
The first demonstration that complex organic
molecules could have arisen in earth’s early
environment
8

9. Why is it important that Urey and Miller’s
experiment produced amino acids?
1. Because they are the building blocks of
DNA
2. Because they are the building blocks of
RNA
3. Because they are the building blocks of
protein
4. Because they are the building blocks of
triglycerides
9

10. Take-Home Message 10.1
Under conditions similar
to those on early earth,
small organic molecules
form which have some
chemical properties of life.
10

11. Life on earth most likely originated from
nonliving materials.
10.2 Cells and self-replicating systems
evolved together to create the first
life.
11

12. - RNA appears on the scene
- RNA can catalyze reactions necessary for
replication
Phase 2: The Formation of Self-Replicating,
Information-Containing Molecules.
12

13. The “RNA World”
Hypothesis
A self-
replicating
system
A precursor
to cellular
life?
RNA-based
life and DNA-
based life
13

14. 14

15. Life Is Defined by Two Characteristics:
1) the ability to replicate
2) the ability to carry out some sort of
metabolism
15

16. Phase 3: The Development of a
Membrane, Enabling Metabolism,
and Creating the First Cells
Membranes make numerous aspects of
metabolism possible.
16

17. How Did the First Cells
Appear?
Spontaneously?
Mixtures of
phospholipids
Microspheres
Compartmental-
ization within
cells
17

18. 18

19. Take-Home Message 10.2
The earliest life on earth
appeared about 3.5 billion
years ago, not long after
earth was formed.
Self-replicating molecules—
possibly RNA—may have
formed in earth’s early
environment and later
acquired or developed
membranes
Membranes enabled these
self-replicating molecules to
replicate and make
metabolism possible, the
two conditions that define
life.
19

20. 20

21. 10.3 What is a species?
21

22. Biological Species Concept
 Species: different kinds of organisms
 Species are natural populations of organisms
that:
• interbreed with each other or could possibly
interbreed
• cannot interbreed with organisms outside their
own group (reproductive isolation)
22

23. 23

24. Two Key Features of the Biological
Species Concept:
1) Actually interbreeding
or could possibly
interbreed
2) “Natural” populations
24

25. The biological species concept is not easily applied to
bacteria and fossils. What other characteristics could we
use to decide whether two different bacteria are two
different species?
1. Observe asexual reproduction.
2. Measure the size of each bacteria.
3. Compare the sequences of specific
genes in the bacteria.
4. All of the above.
25

26. Barriers to Reproduction
1) Prezygotic barriers
2) Postzygotic barriers
26

27. 27
Prezygotic
Barriers
Make it impossible for
individuals to mate
with each other
OR
Make it impossible for
the male’s
reproductive cell to
fertilize the female’s
reproductive cell

28. Examples of
Prezygotic
Barriers
Courtship systems
Physical
differences
Physical or
biochemical
factors involving
gametes
28

29. 29
Postzygotic Barriers
Occur after
fertilization
Generally
prevent the
production of
fertile offspring
Hybrids

30. Which answer below is considered to be a
postzygotic barrier to reproduction?
1. Two species of frogs mate at different times in the
spring.
2. Birds about to mate need to go through specific
courtship rituals.
3. The male gamete (pollen) of one flower is not
compatible with the female organs of another
flower.
4. Fertilization occurs, but the embryo dies before it is
born.
5. There is a mechanical isolation that prevents
fertilization.
30

31. Take-Home Message 10.3
Species are generally
defined as populations of
individuals that interbreed
with each other or could
possibly interbreed.
Species cannot interbreed
with organisms outside
their own group.
This concept can be
applied easily to most
plants and animals, but for
many other organisms it
cannot be applied.
31

32. 10.4 How do we name species?
We need an organizational system!
32

33. Carolus Linnaeus and
Systema Naturae
A scientific name consists
of two parts:
1) Genus
2) Specific epithet
33

34. Hierarchical System
Inclusive categories at the
top…
…leading to more and
more exclusive categories
below.
34

35. Take-Home Message 10.4
Each species on earth is
given a unique name,
using a hierarchical
system of classification.
Every species on earth
falls into one of three
domains.
35

36. 10.5 Species
are not always
easily defined.
36

37. Difficulties in Classifying
Asexual Species
 Doesn’t involve fertilization or even two
individuals
 Does not involve any interbreeding
 Reproductive isolation is not meaningful
37

38. Chihuahuas and Great Danes
generally can’t mate.
Does that mean they are different
species?
38

39. Difficulties in Classifying Ring Species
 Example: insect-eating songbirds called
greenish warblers
 Unable to live at the higher elevations of the
Tibetan mountain range
 Live in a ring around the mountain range
39

40. Difficulties in Classifying Ring Species
 Warblers interbreed at southern end of ring.
 The population splits as the warblers move north
along either side of mountain.
 When the two “side” populations meet at
northern end of ring, they can’t interbreed.
 What happened?!
40

41. Difficulties in Classifying Ring Species
 Gradual variation in the warblers on each side
of the mountain range has accumulated…
 …the two populations that meet have become
reproductively incompatible…
 …no exact point at which one species stops
and the other begins
41

42. Difficulties in Classifying Hybridizing
Species
 Hybridization
• the interbreeding of closely related species
 Have postzygotic barriers evolved?
 Are hybrids fertile?
42

43. Morphological Species Concept
 Focus on aspects of organisms other than
reproductive isolation as defining features
 Characterizes species based on physical
features such as body size and shape
 Can be used effectively to classify asexual
species
43

44. Which answer below would require
the morphological species concept to
delineate between the two species?
1. Dog and cat
2. Salmonella and E. coli
3. Cow and goat
4. Donkey and horse
44

45. Take-Home Message 10.5
The biological species concept
is useful when describing most
plants and animals.
It falls short of representing a
universal and definitive way of
distinguishing many life forms.
Difficulties arise when trying to
classify asexual species, fossil
species, speciation events that
have occurred over long periods
of time, ring species, and
hybridizing species.
In these cases, alternative
approaches to defining species
can be used.
45

46. 10.6 How do new species arise?
46

47. Speciation
 One species splits into two distinct species.
 Occurs in two distinct phases
 Requires more than just evolutionary change in
a population
47

48. Allopatric Speciation
 Speciation with geographic isolation
48

49. 49

50. 50

51. Speciation without Geographic Isolation
51

52. Polyploidy
 Error during cell division in plants
 Chromosomes are duplicated but a cell does
not divide.
 This doubling of the number of sets of
chromosomes is called polyploidy.
52

53. Polyploidy
 The individual with four sets can no longer
interbreed with any individuals having only
two sets of chromosomes
 Self-fertilization or mating with other
individuals that have four sets can occur.
 Instant reproductive isolation, considered a
new species.
53

54. 54

55. Take-Home Message 10.6
Speciation is the process
by which one species
splits into two distinct
species that are
reproductively isolated.
It can occur by polyploidy
or by a combination of
reproductive isolation
and genetic divergence
together.
55

56. 56

57. 10.7 The history of life can be
imagined as a tree.
57

58. Systematics and Phylogeny
 Systematics names and arranges species in a
manner that indicated:
• the common ancestors they share
• the points at which they diverged from each other
58

59. Systematics and Phylogeny
 Phylogeny
• evolutionary history, of organisms
 Nodes
• The common ancestor points at which species diverge
59

60. 60

61. Take-Home Message 10.7
The history of life can be
visualized as a tree; tracing
from the branches back
toward the trunk follows the
pathway of descendant back
to ancestor.
The tree reveals the
evolutionary history of
every species and the
sequence of speciation
events that gave rise to
them.
61

62. 10.8 Evolutionary trees show
ancestor-descendant relationships.
62

63. 63

64. 64

65. 65

66. Monophyletic Groups
 a group in which all of the individuals are
more closely related to each other than to any
individuals outside of that group
 determined by looking at the nodes of the
trees
66

67. 67

68. Which animals are represented in a
monophyletic group indicated by the red
arrow?
1. Fish, bird, human,
rat, and mouse
2. Bird, human, rat
and mouse
3. Human, rat, and
mouse
4. Rat and mouse
68

69. Constructing evolutionary trees
requires comparing similarities
and differences between
organisms.
69

70. 70

71. 71

72. Below are genetic sequences for a gene found in
four different species. Which species are the
most closely related?
Species A: AGT-CTA-CTT-ACT-ATC-CTA
Species B: AGT-CTA-CTT-ACC-ATC-CTA
Species C: AGT-AAA-CTT-ACC-ATC-CTA
Species D: AGA-CTA-TTT-ACC-ATG-CTA
1. Species A and B
2. Species A and C
3. Species A and D
4. Species B and D
72

73. Take-Home Message 10.8
Evolutionary trees
constructed by biologists are
hypotheses about the
ancestor-descendant
relationships among species.
The trees represent an
attempt to tell us which
groups are most closely
related to which other groups
based on physical features,
usually DNA sequences.
73