chapter 5 evolution - biology 20hillabybiology20.yolasite.com/resources/chapter 5 evolution...

1

Nelson pages 132 – 173

BIOLOGY 20 - CHAPTER 5

EVOLUTION

CHAPTER 5.1

CLASSIFICATION OF ORGANISMS

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Nelson Reference: Pages 132-139

5.1 CLASSIFICATION OF ORGANISMS

10 million different species

Biological diversity is a sign of a healthy ecosystem

Why?

Higher chance that some organisms will survive changes in ecosystem

3

TWO LEVELS OF BIOLOGICAL DIVERSITY

1. Species diversity

# of different species

2. Genetic diversity

Amount of variation in inherited traits between individuals of same species

4

TAXONOMIC SYSTEMS

Taxonomy

Science of classification according to inferred (presumed) relationships among organisms

2 purposes

1. Identify organisms

2. Provide a basis for recognizing natural groupings of living things

5

CARL LINNEAUS

Created biological system of classification

Based on organisms’ physical and structural features

The more features in common, the closer the relationship among organisms

6

BINOMIAL NOMENCLATURE

Developed by Linnaeus

A method of naming organisms by using 2 names

Genus name – may appear alone

Species name – never appears alone

To hand write – genus name is capitalized, species name is not; both are underlined

To type – genus name is capitalized, species name is not; both are italicized

7

ADVANTAGES TO BINOMIAL

NOMENCLATURE:

Indicates similarities in:

Anatomy

Embryology

Evolutionary ancestry

8

9 Levels of Classification

Dandelion Housefly Human

kingdom Plantae Animalia Animalia

phylum Tracheophyta Arthropoda Chordata

class Angiosphermae Insecta Mammalia

order Asterates Diptera Primates

family Compositae Muscidae Hominidae

genus Taraxacum Musca Homo

species offincinale domestica sapiens

•7 major taxa

•Categories used to classify organisms

KINGDOMS

• The most common system of classification used today divides living organisms into five or six kingdoms

• We will look at the six kingdom system where Prokaryote is split into two separate kingdoms

• Prokaryotes or Monerans

• Eubacteria

• Archaebacteria

• Protista

• Fungi

• Plantae

• Animalia

11

12 Kingdom General

characteristics

Cell wall Representative organisms

1. Eubacteria Simple organisms lacking nuclei (prokaryote)

Either heterotrophs or autotrophs

All can reproduce asexually

Live nearly everywhere

Often present (contains peptidoglycan – made of carbohydrate and protein subunits)

Bacteria, cyanobacteria

13 Kingdom General

characteristics


2. Archaebacteria

Prokaryotic

Heterotrophs

Live in salt lakes, hot springs, animal guts

Present (does not contain peptidoglycan)

Methanogens, extreme thermophiles, extreme halophiles

14 Kingdom General

characteristics


3. Protista Most are unicellular (single – celled); some are multicellular; eukaryotic

Some are autotrophs; some heterotrophs; some both

Reproduce sexually and asexually

Live in aquatic or moist habitats

Absent Algae; protozoans

15 Kingdom General characteristics


4. Fungi Most are multicellular

All are heterotrophs


Most are terrestrial

Present (made of chitin)

Mushrooms, yeasts, bread molds

16 Kingdom General characteristics


5. Plantae All are multicellular

All are autotrophs


Most are terrestrial

Present (made of carbohydrates)

Mosses, ferns, conifers, flowering plants

17 Kingdom General

characteristics


6. Animalia All are multicellular

All are heterotrophs

Most reproduce sexually

Live in terrestrial and aquatic habitats

Absent Sponges, worms, lobsters, starfish, fish, reptiles, birds, mammals

PHYLOGENY

History of evolution of a species or a group of organisms

18

PHYLOGENETIC TREE O’ LIFE 19

DICHOTOMOUS KEY

A two – part key used to identify living things

A series of choices must be made

Each choice leads to a new branch of they key

20

DICHOTOMOUS KEY EXAMPLE:

1. Animal is taller than 1.5 meters ……………….. Go to 2

Animal is smaller than 1.5 meters …………….. Go to 3

2. Animal is black and white …………………….. cow

Animal is brown ………………………………… horse

3. Animal has feathers ……………………………. Chicken

Animals is pink with curly tail …………………… pig

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Determine the names for each of the organisms:

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1. Has green colored body ......go to 2 Has purple colored body ..... go to 4

2. Has 4 legs .....go to 3

Has 8 legs .......... Deerus octagis 3. Has a tail ........ Deerus pestis

Does not have a tail ..... Deerus magnus

4. Has a pointy hump ...... Deerus humpis Does not have a pointy hump.....go to 5

5. Has ears .........Deerus purplinis

Does not have ears ......Deerus deafus

C

B

A

F

D

E

TASKS TO BE COMPLETED:

Read Chapter 5.1 in your textbook – pages 132-138

Complete Chapter 5.1 Questions: Page 139- #1-3, 5-7

Using a Classification Key – Investigation 5.1 – Textbook pages 162-163 – complete procedure 1-2, and analysis a-d.

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CHAPTER 5.2

EVIDENCE OF A CHANGING EARTH

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5.2 EVIDENCE OF A CHANGING EARTH

Types of evidence include:

Fossil records

Geographic distribution of species

Comparative anatomy

Embryology

Behavior

Plant and animal breeding

Biochemistry

Genetics

25

I.) EVIDENCE FROM FOSSILS

Paleontology

Study of fossils

250 000 fossil species discovered

Fossilized:

Burrows, footprints, chemical remains

However, most organisms do NOT leave any evidence

26

FORMATION OF FOSSILS

Hard parts of organisms

Teeth, shells, and bones

Resist action of weathering for long periods of time, in dry environments

Insects may become entrapped in amber (hardened gum given off by trees)

27

SOFT PARTS OF ORGANISMS

Impressions or imprints of plants and animals

Tracks made in soft mud, and fecal material of animals

Intracellular spaces of skeletal material of animals or plants

Replaced with mineral matter

Silica, calcite, or iron compounds

“Petrified forests” – have turned to stone

28

FINDINGS FROM FOSSIL EVIDENCE

1. Different species lived on Earth at various times in past

Very few of today’s species were alive 1 million years ago

Almost all are now extinct

2. Complexity of living organisms generally increases from most distant past to present

Progression from very simple organisms to species of complexity

3. Living species and their closely related matching fossils live in same geographic region

29

DATING THE PAST

Lyell (1830s)

Most geological change was slow and gradual

Had been going on over vast expanses of time

Based on:

Fossil deposits

Geological processes of erosion and sedimentation

30

KELVIN - LORD THOMSON, WILLIAM

(1824-1907)

Disagreed with Lyell

Earth was gradually cooling

Disproved by discovery of radioactive decay

Source of heat energy generated within Earth

31

RADIOACTIVE DECAY

Allows scientists to precisely determine Earth’s age

Changes a particular atom (parent isotope) into a daughter isotope of the same or different element

32

33

Half – life for any particular isotope is a constant

Unaffected by temperature, moisture, etc.

COMMON RADIOACTIVE ISOTOPES

RADIOMETRIC DATING

Technique used to determine age of a rock or fossil

Oldest fossil is ~ 3.8 billion years old

Age of Earth is ~ 4.6 billion years old

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4.6 BILLION YEARS IN ONE HOUR! 35

Fossil Record and Geological Time:

A closer look...

Due to the gradual formation of sedimentary rock and the steady accumulation of the remains of organisms, the deepest sedimentary layers are usually the oldest

Geologists have developed a relative time scale for dating rocks and fossils

The geologic time scale is a series of major and minor divisions that correspond to major evolutionary events

Geologic Time Scale

The divisions are:

Eras

– Precambrian (pre-life) – life begins, simplistic organisms

– Paleozoic (ancient life) –first fish, land plants, amphibians and reptiles

– Mesozoic (age of reptiles) – first dinosaurs, mammals, birds,

– Cenezoic (age of mammals) – end of dinosaurs, mammals dominate, humans appear

Periods

Epochs (Cenezoic Era only)

Absolute Dating

Exact age of an object or event (example – your

birthdate!)

A chem review of isotopes: yay!

– Isotopes are elements that have the same atomic number (#

p+ and e-) but different atomic masses (n 0 vary). Recall that

the mass of an atom is due to the p+ and n 0

– Example carbon-13 , carbon-14, carbon-15 are 3 isotopes for C

– If isotopes are unstable (too few/many neutrons) they naturally

break down --- radioactive --- by changing into atoms of other

kinds

– Radioactive isotopes (aka radioisotopes) gain stability when

they spontaneously decay into stable, non-radioactive

elements

Absolute dating continued…

Radioisotopes decay at a constant rate in which radiation is given off --- known as radioactive decay

Within a rock sample that we want to determine the absolute age of (or fossil within the rock sample), if we know how much of the radioisotope elements within the rock has decayed, and we know the time period for the half-life, then we can determine the absolute age of the rock

Radioisotopes can be used to estimate the age of rocks and archeological artifacts.

A half-life is the time required for half of an element's atoms (parent material) in a sample to change to the decay product (daughter material)

In each half-life only half of the remaining radioactive atoms decay, no matter how large the sample is

What is a Half-life?

Like popcorn, some atoms decay right away, while others survive much longer than the average

Half-lives vary from fractions of seconds to millions of years, giving each radioisotope specific applications in dating

Look at the diagram which represents the radioactive decay of uranium-238. The shaded area represents the decay product which is lead-206. The half-life of uranuim-238 is 4.5 billion years, since this object has gone through two half-lives it is 9 billion years old.

1st half life 2nd half life 3rd half life 4th half life

½ parent ¼ parent parent parent

½ daughter ¾ daughter daughter daughter

Lets Review half- life:

Radioactive Parent Half-life (in billion

years) Stable Daughter

Product

Uranium 238 4.5 Lead 206

Uranium 235 0.71 Lead 207

Thorium 232 14.1 Lead 208

Rubidium 87 47.0 Strontium 87

Potassium 40 1.3 Argon 40

Common Radioactive Isotopes

Radioactive Decay Calculations:

If we know the ratio of parent to daughter material, we can calculate the number of half-lives elapsed

From this info, the age of the sample can be calculated from the known length of the half-life of the radioisotope

Remember this chart:

# of Half-lives

O 1 2 3 4

% Parent

% Daughter

Examples:

1. What % of carbon-14 would be left after 3 half-lives?

2. A rock sample weighs 250 g. If it undergoes 2 half-lives of time, what mass of carbon will it contain?

Parent Isotope Half Life (yrs) Daughter Isotope (decay product)

Carbon-14 5730 Nitrogen-14

3. How old (approx.) is a sample if it contains 75 g of carbon-14 and 350 g of nitrogen-14?

II.) EVIDENCE FROM BIOGEOGRAPHY

Biogeography

Study of geographic distribution of life on Earth

47

CONTINENTAL DRIFT

Explains changes in position of continental land masses

Theory of plate tectonics Explains how Earth changed from a

single supercontinent (225 million years

ago), Pangea, to present continents

Species older than 150 million years old were on same continents

Species younger than 150 million years old were on separate continents

Thus, they developed AFTER break up of Pangea

48

PANGEA EXAMPLES:

Limited distribution of marsupials in Africa, Australia, and

South America

Limited distribution of mammals

Amphibians and reptiles

Exception

Moose found in both Europe and North America

Land bridges - narrow strips of land that

connected certain continents

Arose during time of supercontinent - are widely

distributed on practically all continents

49

ISLANDS

Islands have fewer species than their mainland counterparts

“How do organisms get to islands?” – animals may fly, “hitch a ride”, swim, cross ice and landbridges, or “raft” on vegetation and ice floes (large mass of ice)

Island immigration explains presence or scarcity of organisms in various parts of Canada

Ice rafts, ice bridges, timber rafts, and ice floes provide methods of transportation

51

REMOTE ISLANDS

Islands that have always been isolated from mainland (e.g., Newfoundland)

Home to unique or endemic (found only in one location) organisms

Porcupine, gray squirrel and raccoon are absent from N. American islands

52

TASKS TO BE COMPLETED:

Read Chapter 5.2 in your textbook: Pages 140-143

Complete 5.2 Questions – Page 143 # 1-2

Radioactive Decay Calculations Practice Problems - Workbook

M&M Lab – A sweet simulation of radioactive decay – optional - workbook

Mini Investigation: Page 140 (optional) – Puzzling over the evidence

Case Study – Finding Fossils and Famous Footprints – Page 142 (optional)

Optional - Evolution and Time Interactive Web Activity – PBS website

http://www.pbs.org/wgbh/evolution/educators/lessons/lesson3/act1.html

53



5.3 EVIDENCE OF EVOLUTION

FROM BIOLOGY

54


5.3 EVIDENCE OF EVOLUTION FROM

BIOLOGY

Includes physical anatomy and genetic makeup of organisms

55

I.) EVIDENCE FROM ANATOMY

A comparison of anatomies of various organisms suggests that organisms with similar structures evolved from a common ancestor

56

HOMOLOGOUS STRUCTURES

Have similar origin but different uses in different species

Example:

Front flipper of a dolphin and forelimb of a cat

57

ANALOGOUS STRUCTURES

Are similar in function and appearance but not in origin

Example

Wing of an insect and wing of a bird

58

CONVERGENT EVOLUTION

Associated with

analogous structures

Refers to development of similar forms from unrelated species

Due to adaptation to similar environments

59

60

An example of convergent evolution of 4 different animals Look similar Are not because close relatives Evolved similar adaptations Occupy similar niches Dine on ants, hunt in high grass, or swim in dark Evolutionary origins are different

EMBRYONIC DEVELOPMENT

During late 1800s

Scientists noted striking similarity between embryos of different species

Many structures in an embryo are similar to those found in common ancestors

61

View video clip – Common Pasts, Different Paths

62 Can you identify which embryo is the human, chicken, fish,

tortoise, hog, calf, salamander, or rabbit?

VESTIGIAL FEATURES AND ANATOMICAL

ODDITIES

Vestigial features

Rudimentary structures with no useful function

Perhaps were once functional in an ancestor

64

• Dogs, pigs, and horses

have at least one

vestigial toe

65

•Whale skeletons have vestigial hip and leg bones

From an old science text (now out of

print). This shows that tail on a human

baby.

This is not common but also not rare. The

tail is removed surgically.

• vestigial features are useless or harmless parts of the body

• eg. human appendix, coccyx (tail bone), muscles which move the

ears

• some snakes still have leg bones

• Are we descended from animals in which these structures were

useful?

VESTIGIAL FEATURES CONTINUED… 66

II.) EVIDENCE FROM BIOCHEMISTRY

All organisms share similar DNA molecules and certain proteins, such as cytochrome C

Analysis and comparison of proteins and DNA from different organisms

Similar organisms also have similar chemical structures

67

Example: amino acid sequencing between human, macaque, dog, bird, frog, and lamprey

Differences reflect degree of similarity

DNA SEQUENCES

Deoxyribonucleic acid

Hereditary material in cells

Each DNA molecule contain many different genes

Gene – a segment of DNA that performs a specific function

68

DNA

Composed of 4 nucleotide bases arranged in different sequences

Adenine (A), thymine (T), cytosine (C), guanine (G)

DNA sequences from different species that code for the same protein vary in # and order of nucleotides

Geneticists have found homologous and vestigial genes in DNA in virtually all species

69

•DNA PROTEIN SEQUENCE EXAMPLE

Cow milk protein

AGTCCCCAAAGTGAAGGAGA CTATGGTTCCTAAGCACAAG GAAATGCCCTTCC

70

III.) EVIDENCE FROM ARTIFICIAL SELECTION

Process of humans selecting and breeding individuals with desired traits

Dramatic changes are produced in a species over a relatively short period of time

71

TASKS TO BE COMPLETED

Read pages 144-149 of your textbook

Complete Chapter 5.3 Questions – Page 149 - #1-3

Optional: Mini Investigation – Variations of a Theme – Page 145

Optional: Lab Exercise 5.A – Evidence from Genetics – Page 147 – complete letters

Optional: Case Study – Were Neanderthals Humans?

Page 149

Optional: Internet Web Quest Assignment – Evidence of Evolution


72



5.4 THE MAKING OF A THEORY –

ACCOUNTING FOR THE EVIDENCE

73

5.4 THE MAKING OF A THEORY – ACCOUNTING

FOR THE EVIDENCE

Scientific theory

A model that accounts for all of the known scientific evidence

Plausible explanation

May be altered or modified as new data is gained

74

BUFFON (18TH CENTURY)

Species can change over time

Changes could lead to new organisms

75

I.) LAMARCK’S THEORY

Presented 1st theory of evolution that included a mechanism

New, simple organisms were created by spontaneous generation

Living things arose from non – living things

Organisms gradually became complex

76

LAMARCK’S THEORY

Organisms had a “desire” or “force” that led them to change for the better

Organisms can produce new parts or get rid of unwanted parts

Use and disuse of certain structures would be passed on to offspring

Organisms eventually adapted to their environment

77

LAMARCKISM

Describes “inheritance of acquired characteristics”

False concept of inheritance of features acquired during an individual’s life

78

II.) DARWIN’S THEORY

In 1831, a five – year voyage on the ship, Beagle

Provided Darwin with opportunity to study diverse life forms

From South America to South Sea Islands

79

80

Darwin – mid 1800’s

Published the Origin of Species by Means of Natural Selection based on his investigations while on board the 5 year world voyage aboard the Beagle

Much of his evidence for the theory of natural selection was his studies of the finches of the Galapagos Islands (1000 km west of Ecuador)

DARWIN’S OBSERVATIONS

1. S. America – unusual fossil species

Resembled sloths and armadillos living in same region

Living forms descended from fossilized species

81


2. Species living in S. American tropics did not resemble those in African tropics

Landmass isolated species

Thus, species evolved independently

82


3. Galapagos islands

Home to 13 very similar species of finches

Found nowhere else on Earth

Birds most closely resembled species living on mainland coast of S. America

Islands finches evolved from a single species that arrived from S. America

83


4. Andes mountains

Fossil deposits of corals at an elevation of 3 000 m

Geological forces and time accounted for location of fossils and mountains

84

DARWIN AND OTHER CONTRIBUTING SCIENTISTS

Malthus’ essay on population

All species produce more offspring than are able to survive

Thus, Darwin realized that competition exists

Wallace’s paper sent to Darwin

Wallace traveled extensively

Independently arrived at the same conclusions as Darwin

85

NATURAL SELECTION

Result of differential reproductive success of individuals

Caused by variations in their inherited characteristics

86

87 The Theory of Evolution by Natural

Selection

Observation 1 Individuals within any species

exhibit many inherited variations

Observation 2 Every generation produces far more

offspring than can survive to

reproduce

Observation 3 Populations of species tend to

remain stable in size

88

Inference 1 Individuals of same species are in a

constant struggle for survival

Inference 2 Individuals with more favorable variations

are more likely to survive and pass these

variations on. Survival is not random. This

is natural selection.

Inference 3 Since individuals with more favorable

conditions contribute proportionately more

offspring to succeeding generation, their

favorable inherited variations will become

more common. This is evolution.

The Theory of Evolution by Natural Selection

2. Theory of Evo lut ion by Natura l Se lect ion Five main components:

1. Overproduction

Number of offspring produced by a species is greater than can survive and reproduce

2. Struggle for existence

Organisms of the same species (and other species) must compete for the same limited resources

3. Variation

Differences among traits occurs by chance ---> no two individuals are exactly alike.

Offspring inherit most of parent’s traits, but not all of them. Some traits arise randomly (eg. by genetic mutation)

4. Survival of the fittest

The environment acts to select favorable traits (not create them). Those with an advantage survive and reproduce, increasing their numbers. This is selection by nature, hence natural selection

5. Speciation

Individuals do not change, populations change over time. Accumulation of new traits over a long period of time ---> population so different ---> new species.


Read Chapter 5.4 in Your textbook – Pages 150-152

Section 5.4 Questions – Page 152 - #1-2

Peppered Moth Case Study – Workbook

Optional: Survival of the Sneakiest Cartoon

Optional: Who was Charles Darwin? Internet Assignment http://www.pbs.org/wgbh/evolution/educators/lessons/lesson2/index.html

90

http://www.pbs.org/wgbh/evolution/educators/lessons/lesson2/index.html

http://www.pbs.org/wgbh/evolution/educators/lessons/lesson2/index.html

5.5 SOURCES OF INHERITED VARIATION

Darwin’s book “On the Origin of Species” did not answer the question:

Where does the sources of variation of individual traits come from?

91

I.) MUTATIONS

DNA

Found in chromosomes of all cells

Composed of long sequences of 4 nucleotide bases:

Adenine, guanine, thymine, cytosine

Sequence of bases codes for specific inherited traits

Genes are segments of DNA that code for specific traits

92

MUTATIONS

Random changes in DNA sequence in a chromosome

Provide a continuous supply of new information

Caused by:

Environmental factors

Errors while cell is making copies of DNA

Relatively rare in individuals

93

TYPES OF MUTATIONS

Neutral mutation

No immediate effect on an individual’s fitness or reproductive success

Most common

Harmful mutation

Reduces an organism’s fitness

Beneficial mutation

Enhances an organisms’ fitness

Provides a selective advantage of others

94

95 Mutation Misconceptions and Accepted

Understandings

Misconception Accepted Understanding

Mutations occur when “needed”,

in response to environmental

changes.

Mutations occur at random, with

harmful mutations being more

common than beneficial ones.

There is no design to it.

Since harmful mutations are

more common than beneficial

mutations, they can accumulate

and the species will steadily

degrade.

Harmful mutations are selected

against and thus, do not

accumulate over generations.

The environment favor the fittest

organisms. Harmful mutations

can reduce or even eliminate the

individual’s chance of

reproductive success.

96 Mutation Misconceptions and Accepted Understandings

Misconception Accepted Understanding

Since mutations are random or

chance events, then evolution is

just pure chance.

Although beneficial mutations are

rate, they are selected for and

may accumulate over the

generations. Beneficial

mutations often give individuals

improved survival and

reproductive success.

II.) SEXUAL REPRODUCTION AND VARIABILITY

Asexual reproduction

Production of offspring form a single parent

Offspring inherit genes of that parent only

Very little inherited variability

Mutations may still occur

97

SEXUAL REPRODUCTION

Production of offspring by the union of sex cells from two different parents

Offspring inherit a combination of genes from both parents

98

•3 REASONS FOR VARIABILITY AMONG SEXUALLY

– REPRODUCING INDIVIDUALS

1. Sexually reproducing species have 2 copies of each gene

Both parents contribute one copy of each gene to the offspring

Offspring has a different combinations of genes from either parent

Unique set of traits

99

2. ASSORTMENT OF GENES AN OFFSPRING

INHERITS FROM EITHER PARENT IS RANDOM

The greater the # of genes a species has, the larger the # of combinations and the greater variability of the species as a whole

100

3. SEXUALLY REPRODUCING SPECIES CHOOSE

DIFFERENT MATES

Each combination of parents will give rise to different combinations of genes and traits in the next generation

101

102 Genetic Mechanisms and Darwin’s Theory

Darwinian Evolution Genetic Mechanisms

1. Inherited characteristics Are determined by genes

• Organisms possess

thousands of genes

2. Population variability Individuals of same species

differ from one another

partly due to different

combinations of genes

• Gene pool – all the

genes in a certain

population



3. Source of new variations New traits may arise when

genes are mutated

4. Natural selection Some genes determine

traits that make the

individual better suited for

survival and reproductive

success

• These individuals will

produce more offspring,

some of which will have

advantageous genes



5. Evolutionary change Over many generations,

individuals carry genes that

determine the most

favorable traits for survival

and reproductive success

will become more common

in the population

• Evolution is this change

in the population’s gene

pool

Tasks to be Completed For Chapter 5.5

Read Pages 153-156 of your Text book

Complete #1-3 on page 156

Optional: Investigation 5.2 – Measuring Inherited Variation- Human foot length – Page 164-165

CHAPTER 5.6

SPECIATION AND EVOLUTION

106

5.6 SPECIATION AND EVOLUTION

I.) Speciation Formation of new species

Species

A population of individuals who are reproductively isolated

Not capable of breeding with individuals of other species under natural conditions

107

ALLOPATRIC SPECIATION – SPECIATION BY

REPRODUCTIVE ISOLATION

1. A physical barrier separates a single interbreeding population into 2 or more groups

Groups are isolated from each other

Any mutations that occur in these groups are not shared with other populations

From large to small physical barriers

Mountain ranges, oceans, river channels, canyons, dams, canals

108

2. NATURAL SELECTION WORKS ON SEPARATED

GROUPS INDEPENDENTLY

Results in inherited differences in the 2 populations

I.e., populations evolve independently

Differences in selective pressures will be greater the more pronounced the environmental differences

109

If reunited, individuals of these 2 groups are not sexually compatible

Thus, the formation of two or more distinct species

110 3. In time, accumulated physical and / or behavioral populations are pronounced that groups cannot reproduce with each other

EXAMPLE: PLANT SPECIATION

A single population splits into distinct breeding populations in a single geographic region

Sudden process

Mutation results in a double # of normal chromosomes

Polyploids

Healthy, vigorous individuals

Reproductively isolated from rest of population

http://bcs.whfreeman.com/thelifewire/content/chp24/2402001.html

http://www.nodvin.net/snhu/SCI219/demos/Chapter_4/Chapter_04/Present/animations/23_2_2_1.html

111





II.) RATE OF EVOLUTION

Theory of gradualism

Speciation takes place slowly

However, distinct species often appear abruptly in fossil record

Little further change is seen over very long periods of time

112

THEORY OF PUNCTUATED EQUILIBRIUM

Proposed by Eldridge and Gould

3 assertions:

1. Many species evolve rapidly in evolutionary time

2. Specially usually occurs in small isolated populations

Intermediate fossils are rare

3. After an initial burst of evolution, species are well adapted to their environment

They do not significantly change over long periods of time

113

GRADUALISM VS. PUNCTUATED

EQUILIBRIUM 114

III.) MACROEVOLUTION:D IVERSIFICATION AND

EXTINCTION

Earth has experienced an increase in diversity of living things

Interrupted by “extinction” events

Example: Burgass Shale

Canada’s Rocky Mountains

515 million year old fossils

120 species

Evidence for divergent evolution

Evolution into many different species

115

CAUSES OF MASS EXTINCTION

Cataclysmic events

Tectonic movements

End of Permian era

Asteroid impact (= 100 million nuclear bombs)

End of Mesozoic era

Fireball killed many species

Tsunamis devastated coastal lines

Atmospheric debris blocked out sun for years

116

SPECIES EXTINCTION

Most are caused by ongoing competition and environmental change

“Background” rate of extinction is slow

Average species exists for 1 million years

117

III.) PUTTING THE THEORY OF EVOLUTION TO

WORK:PREDICTIONS

Because evolution is a slow process, it is difficult to witness evolutionary changes directly

Thus, difficult to test predictions about future evolution of a species

118


Read Pages 157-161 in your textbook

Complete Section 5.6 Questions – Page 161 #1, 4-5

Optional: Web Activity – Lactose Intolerance and Evolution – Page 158 Text

Web Activity – Peppered Moth Simulation – Page 161

Prepare for a Unit Exam!!!

Chapter 5 Review: Page 168-169 # 1-10

Unit B Review Pages 170-173 #2-3, 12-14, 36-37

119

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