EvolutionEvolution

Chapter 4Section 2

Evolution by Natural SelectionEvolution by Natural Selection Organisms tend to be well suited to where they

live and what they do. How do they become so well suited? Charles Darwin observed that organisms in a

population differ slightly from each other in form, function and behavior

New genes/traits arise from _________________ Most are either neutral (no effect), or

disadvantageous (decrease an organism's chance for survival).

Natural SelectionNatural Selection

Darwin’s term to describe the __________ ____________________________________________________________________ Over many generations natural selection

causes the characteristics of populations to change.

__________________: change in genetic characteristics of a population from one generation to the next

Darwin & Natural SelectionDarwin & Natural Selection

•Darwin was a Naturalist aboard an exploration ship called the __________________________.•Collected and catalogued biological specimens for return to England.

Darwin & EvolutionDarwin & Evolution Natural selection:

Based on following premises: _____________________________________

_____________________________________ Some organisms are more "fit" to survive. Fitness refers to: The ability of an organism to survive in its

environment. _____________________________________

_____________________________________ Natural pressures "weed-out" those

individuals "less fit" to survive. Thus changing a species over time.

Natural Selection : The Peppered Moth:Natural Selection : The Peppered Moth:

The peppered moth is a species of moth which uses camouflage against tree bark to avoid being eaten by birds. It is normally a light grey color.

During England's industrial revolution, pollution caused a darkening of the bark of the trees.

There was a natural variation in moth coloration with some being darker than others.

Those moths of a lighter color, were easier to spot and eat by birds. And were eaten at a faster rate.

The survivors tended to be darker, and when they mated, their offspring tended thus to be darker also.

Over time, this resulted in the species becoming darker in color.

Nature SelectsNature Selects

Darwin proposed that nature selects for certain traits that are more favorable to survival and reproduction ___________________: an inherited trait that

increases an organism’s chance of survival and reproduction in certain environment.

Directional Selection:Directional Selection:

_______________________________________________________________________________________________________________

Stabilizing Selection:Stabilizing Selection:

__________________________________________________________________________ Results in an increase in individuals exhibiting an intermediate phenotype.

Disruptive SelectionDisruptive Selection

____________________________________________________________________________

How evolution worksHow evolution works

1. Organisms produce more offspring than can survive

2. The environment is hostile and contains limited resources

3. Organisms differ in the traits they have

4. Some inherited traits provide organisms with an advantage

5. Each generation contains proportionately more organisms with advantageous traits.

Sunday Monday Tuesday Wednesday Thursday Friday Saturday

1 Significant oxygen atmosphere begins to develop on Earth.

2 3 4 5 Extensive vulcanism and channel formation on Mars.

6

7 8 9 10 11 12 13

14 15 16 First Worms.

17 Precambrian ends. Paleozoic Era and Cambrian Period begin. Invertebrates flourish.

18 First oceanic plankton. Trilobites flourish.

19 Ordovician Period. First fish, first vertebrates.

20 Silurian Period. First vascular plants. Plants begin colonization of land.

21 Devonian Period begins. First insects. Animals begin colonization of land.

22 First amphibians. First winged insects.

23 Carboniferous Period. First trees. First reptiles.

24 Permian Period begins. First dinosaurs.

25 Paleozoic Era ends. Mesozoic Era Begins.

26 Triassic Period. First mammals.

27 Jurassic Period. First birds.

28 Cretaceous Period. First flowers. Dinosaurs become extinct.

29 Mesozoic Era ends. Cenozoic Era and Tertiary Period begin. First cetaceans. First primates.

30 First evolution of frontal lobes in the brains of primates. First hominids. Giant mammals flourish.

31 End of Pliocene Period. Quaternary (Pleistocene and Holocene) Period. First humans.

DECEMBERDECEMBER

December 31

Origin of Proconsul and Ramapithecus, probable ancestors of apes and men ~ 1:30 p.m.

First hominids A. afarensis~ 10:30 p.m.

Widespread use of stone tools by Homo habilis 11:00 p.m.

Domestication of fire by Homo erectus 11:46 p.m.

Beginning of most recent glacial period. Homo Neanderthalis & Homo sapiens evolve 11:56 p.m.

Seafarers settle Australia 11:58 p.m.

Extensive cave painting in Europe 11:59 p.m.

Invention of agriculture11:59:20 p.m.

Neolithic civilization; first cities. Colonization of North and South America across Bering straits11:59:35 p.m.

First dynasties in Sumer, Ebla and Egypt; development of astronomy11:59:50 p.m.

Invention of the alphabet; Akkadian Empire11:59:51 p.m.

Hammurabic legal codes in Babylon; Middle Kingdom in Egypt11:59:52 p.m.

Bronze metallurgy; Mycenaean culture; Trojan War; Olmec culture; invention of the compass11:59:53 p.m.

Iron metallurgy; First Assyrian Empire; Kingdom of Israel; founding of Carthage by Phoenicia11:59:54 p.m.

Asokan India; Ch'in Dynasty China; Periclean Athens; birth of Buddha11:59:55 p.m.

Euclidean geometry; Archimedean physics; Ptolemaic astronomy; Roman Empire; birth of Christ11:59:56 p.m.

Zero and decimals invented in Indian arithmetic; Rome falls; Moslem conquests11:59:57 p.m.

Mayan civilization; Sung Dynasty China; Byzantine empire; Mongol invasion; Crusades11:59:58 p.m.

Renaissance in Europe; voyages of discovery from Europe and from Ming Dynasty China; emergence of the experimental method in science

11:59:59 p.m.

Widespread development of science and technology; emergence of global culture; acquisition of the means of self-destruction of the human species; first steps in spacecraft planetary exploration and the search of extraterrestrial intelligence

Now: The first second of New Year's Day

CoevolutionCoevolution _________________

____________________________________________________________________

Artificial SelectionArtificial Selection _________________________________

of organisms by humans for specific characteristics Examples: fruits, grains, vegetables, domestic

dogs and other animals

Evolution of ResistanceEvolution of Resistance

Sometimes humans cause populations of organisms to evolve unwanted adaptations. Resistance: ___________________________

__________________________________________________________________________