The History of Evolutionary Thought

Biological definition of a species

• A group of populations whose members are capable of interbreeding and producing fertile offspring.

Isolating Mechanisms

•Behavioral

•Geographic

•Temporal

THE PROCESS OF SPECIATION

Sciurus aberti kaibabensis Sciurus aberti aberti

Allopatric speciation – Geographic Isolation

Sympatric speciation (not geographically isolated)

These 2 species of toads are similar but are (somewhat) reproductively isolated by different mating seasons.

Fowler’s toad(Bufo fowleri)

American toadBufo americanus

Pre-or postzygotic???

Sympatric Speciation These 2 species of meadowlarks look alike but do not

sing the same song

Eastern Meadowlark(Sturnella magna)

Western Meadowlark (Sturnella neglecta)

Pre- or Postzygotic?

Aristotle (384-322 B.C.)

• Ladder of Life» 2 types of animals –

those w/ blood & those w/o

• Animals classified by their way of life

• Plants by structure

• Observation of various marine life anatomy was remarkably accurate

• Distinguished whales from dolphins

•Linnaeus was classifying organisms based on what they looked like.

•This made it difficult to classify organisms that seemed to share characteristics with both kingdoms that Linnaeus proposed, Plants and Animals.

• For example, fungi including mold and mushrooms do not move (or do they?) so they seem to be plants but, unlike plants…..?????

Lion Cat Dog Man Catbird

Phylum Chordata Chordata Chordata Chordata Chordata

Class Mammalia Mammalia Mammalia Mammalia Aves

Order Carnivora Carnivora Carnivora Primata Passeriformes

Family Felicidae Felicidae Canidae Hominidae Minidae

Genus Felis Felis Canus Homo Dymetella

Species leo domesticus carolinensis sapiens familiaris

            

                     

           

Homologous Structures

• Structures that have different mature forms in different organisms but develop from the same embryonic tissues.

BATWHALE

HORSE

CAT

MAN

Analogous Structures

• Structures that have same function in different organisms but the organisms are not closely related and the structures are not closely derived.

Chordate Characteristics

1.Dorsal hollow nerve cord2.Notochord3.Postanal tail4.Pharyngeal pouches (Gill slits)

Plica luminaris

Arrector Pili

coccyx

Human Vestigial Stuctures

Classifying organisms often starts at the cellular level

Cladistics (phylogeny)

A system of classification based on the study of evolutionary relationships/ history of groups of organisms.

legs

internal fertilization

produce milk

placenta

An Example of Cladogram Construction for VertebratesOutgroup(lobed-finned fish)

Trait Turtle Kangaroo Mouse Human

Dorsal Nerve Cord

Yes Yes Yes Yes Yes Yes

Legs NO Yes Yes Yes Yes Yes

Nature of Egg

Requires water

Requires water

Hard shell prevents drying

Develops inside the

mother

Develops inside the

mother

Develops inside the

mother

Nature of development

In egg In egg In egg Marsupial Placental Placental

Hair No No No Yes Yes reduced

Presence of pouch

No No No Yes No No

Bipedal posture

No No No Yes No Yes