Topic: Evidence for Macroevolution

Macroevolution = evolutionary changes over long time spans involving many traits and large genetic changes. The derivation of a new group above the species level (ex., genera or family)

In contrast to Microevolution ~ Evolution at the population level up to the level of species that occurs through changes in allele frequencies (and likely genotypes) within a population over time ~ across generations.

Topic: Evidence for Macroevolution

A. Biogeography

Biogeography = patterns of species distribution.

Taxa on islands more similar to nearest continent.

Example: Galapagos finches

Continental Drift - time of separation between land masses linked to species similarities.

Figure Biogeographical areas

Figure The history of continental drift

B. Taxonomy

Carl Linneaus recognized the organism diversity could be organized into groups depending on the traits expressed.

Kingdom, Phylum, Class, Order, Family Genus, species

Darwin ‘s interpretation?

Figure Classifying life

C. Fossil Record

Fossils = transformed remains of organisms.

More fossil evidence today.

Radioisotope dating provides age of fossil.

Evidence exists for progressive evolutionary change.

Fossils are not equally present for all groups of organisms.

Half-life = length of time required for 50% of the parent material to decay into daughter product.

• Uranium 235 to Lead 207 (half-life = 710,000,000 years)

• Uranium 238 to Lead 206 (half-life = 4,500,000,000 years)

• Thorium 232 to Lead 208 (half-life = 14,000,000,000 years)

• Rubidium 87 to Strontium 87 (half-life = 47,000,000,000 years) - most common system used for dating rocks older than 100 million years.

• Potassium 40 to Argon 40 (half-life = 1,300,000,000 years) - this method is very often used to date rock less than 60 million years old.

Carbon 14 dating:• Carbon 14 to Nitrogen 14 (half-life = 5,570 years)---

• There are 3 forms (isotopes) of carbon occuring in nature: Carbon 12 (accounts for 99%)

• Carbon 13 (accounts for 1%)

• Carbon 14 (accounts for less than 1%).

• While alive, plants and animals incorporate these isotopes of carbon into their tissues at the ratio found in the atmosphere.

• Upon death, the Carbon 14 in their tissues begins to decay. By measuring the remaining amount of Carbon 14, the age of the fossil can be determined. This method can be used to date material ranging in age from a few hundred years to about 50,000 years. The use of Carbon 14 permits the determination of age directly a fossil. For fossils greater than 50,000 years old, the age of the fossil is found indirectly by determining the age of the rock associated with the fossil. Carbon 14 dating has a dating range of several hundred years before present to 50,000 years before present.

http://snakefly.tripod.com/Date.html

Figure The fossil record is one type of historical documentation that chronicles evolution: Archeopterex

Figure Fossil of a fish: perch

Figure A gallery of fossils

Figure Earth’s crustal plates and plate tectonics (geologic processes resulting from plate movements)

D. Homologous Structures

Homologous = traits developed from a common ancestor.

Environment-genotype interactions ~ adaptations

Thus homologous traits may function differently.

Example: Mammalian forelimbs

Figure   Homologous structures: anatomical signs of evolution

Figure   Transitional fossils linking past and present

E. Development

von Baer noted: related species most resemble each other in the juvenile stage.

Hackel noted:

“Ontogeny recapitulates Phylogeny”

Ontogeny= embryonic development

Phylogeny= evolutionary history

~Successive stages of individual’s development corresponds with successive adult ancestors. Ex.’s

Developmental embryology

Developmental Embryology

Humans repeat evolutionary history in utero:

-Possess tail ~ fish, it develops into our tail bone

-Possess fine fur from about 5 mo. Gestation

-Gill like stage in early gestation

Human tail in utero

http://embryology.med.unsw.edu.au/wwwhuman/stages/Images/CSt15.gif

http://www.palaeos.com/Vertebrates/Bones/Gill_Arches/Images/Meckel4.jpg

Figure Some properties of life: Development: tad pole – frog metamorphosis

Timing of development is important:

• Heterochrony = a change in timing of trait development.

• Ex., bones of forelimb

• Allometric Growth:

• same character either grows faster OR for a longer period of time and this changes its shape.

• Change in duration OR rate of development of a trait.

Figure   Homologous structures: anatomical signs of evolution

Timing of developmental change:

Peramorphosis = adult trait expressed in juvenile

(ontogeny does recapitulate)

Two ways:

a) acceleration of development

b) increased duration of development

Ex.,

Hypermorphosis ~ gigantism

Timing of developmental change:

Paedomorphosis = juvenile traits expressed in mature reproducing adult

Two ways:

a) retardation of development

b) decreased duration of development

Ex., neotonic salamanders

domesticated animal playfulness

***Large changes in morphology can occur through relatively simple changes in rates or timing of development***

F. Vestigial Structures

Vestigial = structures with no apparent current function, resembling presumed ancestors.

Consistent with predictions from Natural Selection, that leftovers of change can be found.

Ex.’s

http://www.gutenberg.org/files/20417/20417-h/images/image258.jpg

G. Molecular Record

Natural Selection results in the accumulation of genetic changes, reflected in the DNA.

Compare degree of similarity in DNA sequences among organisms.

Example: human hemoglobin peptide

Figure   Molecular data and the evolutionary relationships of vertebrates

Now onto Systematics and Phylogenies