LESSON # 23

THE OUTCOMES OF EVOLUTION:

Macroevolution

A change of allele frequencies in a population over a relatively short period of time. No new species are originated.

EVOLUTIONAny genetically based phenotype change in a population

of organisms over successive generations.

Evolution that results in the formation of new species.

MICROEVOLUTION MACROEVOLUTION

How Do New Species Arise?One specie can be transformed into another in the process called speciation. The development of new species through evolution.

What brings this branching evolution?

Speciation:

Common ancestor

Microevolution

Macroevolution

Microevolution: A change of allele frequencies in a population over a relatively short period of time.

After enough time, should the two population find them- selves geographically reunited, they may no longer freely interbreed. At that point, they are separated species. Speciation has occurred.

What Could Drastically Reduce Interbreeding?

Geographical separation is the most important factor in getting speciation going.

When geographical barriers divide a population and the resulting populations then go on to become separate species, what has occurred is Allopatric Speciation.

Allopatric Speciation

Sympatric Speciation

Speciation

Examples of Allopatric Speciation

The east and west population came back together in Southern California, but could no longer interbreed

(or produce infertile hybrid offspring).

Millions of years ago

Geographical separation can not produce speciation by itself.

Following geographic separation, the two populations of the same species must then undergo physical or behavioral changes that will keep them from interbreeding, should they ever be reunited.

Geographic Separation by itself

InterbreedingNo interbreeding

Geographic Separation +Reproductive isolating mechanisms

no speciation Speciation

Reproductive Isolating MechanismsAny factor that, in nature, prevents interbreeding between individuals of the same species or of closely related species.

IntrinsicExtrinsic1- Ecological Isolation2- Temporal isolation3- Behavioral Isolation4- Mechanical Isolation5- Gametic isolation6- Hybrid Inviability (Infertility)

Geographic Separation

Intrinsic Isolating Mechanisms

Intrinsic Reproductive Isolating Mechanisms can develop between two populations in the absence of any geographic separation of them.

Sympatric Speciation: Any speciation that does not involve geographic separation.

Allopatric Speciation: When geographical barriers divide a population and the resulting populations then go on to become separate species.

Sympatric: “of the same country”

Allopatric: “of other country”

The Categorization of Earth’s Living Things

How many species are in the earth?The lowest estimate: About 4 million species

The higher end estimate: From 10 to 15 million species.

Every species may have different common names in different places.

To prevent the confusion that can result from having several common names, species are not named by their common names but by scientific names.

Scientific names for species has two parts: 1- The first part is the genus, which designates a group of individuals who are closely related but still are separated species

BINOMIAL NOMEMCLATURE

Felis is a genus of cats. The second name is the species of cat.

Chinese Mountain Cat, Felis bieti Jungle Cat, Felis chaus Pallas's Cat, Felis manul Sand Cat, Felis margarita Black-footed Cat, Felis nigripes Wildcat, Felis silvestris Domestic Cat, Felis silvestris catus

2- The second part designates species

Canis adustusCanis aureus (jackal)Canis dirus (extinct)Canis latransCanis lupus (wolf, domestic dog)Canis mesomelasCanis rufusCanis simensis

Genus canis

Canis lupus

Canis lupus familiaris

Canis aureus

Taxonomic ClassificationA method of classifying organisms based on 8 categories called taxons.

1- Domain

2- Kingdom3- Phylum4- Class5- Order6- Family7- Genus8- Species

BacteriaArchaea

Eukarya PlantaeFungiAnimaliaProtista

1- Domain

2- Kingdom3- Phylum4- Class5- Order6- Family7- Genus8- Species

BacteriaArchaea

Eukarya PlantaeFungiAnimaliaProtista

Species are named and classified according to how closely they are related.Systematics:

It is the field of Biology that is concerned with the diversity and relatedness of organisms.Systematics tries to establish the truth about who is more closely related to whom by studying the evolutionary history of organisms.

1- Classical Taxonomy

2- Cladistics

Classification of Living Things

1- Classical TaxonomyIt is based in the physical form or “morphology” of the animals in questions, as preserved by fossil record, and comparing it to the morphology of modern animals.

2- CladisticsIt is based in the differences between ancestral characters and derived characters.

- Ancestral characters: Characters existing in a common ancestor

- Derived characters: Characters which are unique to the organisms descended from a common ancestor

Classical Taxonomic Classification

Cladistic Taxonomic Classification

It is based in the physical form or “morphology” of the animals in questions, as preserved by fossil record, and comparing it to the morphology of modern animals.

It is based in the differences between ancestral characters and derived characters.