Chapter 25 - Phylogenies and History of Life

patterns of evolution over large time scales (mya)

evolution that occurs quickly

• ex - antibiotic resistance

indicates that insufficient data were available to resolve which taza is more closely related; DNA sequences are identical

• “many splits”

an ancestral population and all of its descendants

trait unique to a monophyletic group. (hair)

similarity among organisms of different species due to shared ancestry

• organisms may be similar for other reasons

taxon that is not part of the group being studied

1. identify taza of interest (ex - lizard, dog, human)

2. select useful traits or characteristics

3. define character states (1 = present, 0 = absent)

4. add an outgroup

5. use data to construct the tree

similarity among organisms of different species due to reasosn other than common ancestry, such as convergent evolution

share similarities, but not a common ancestor

• ex - dolphin and ichthyosaur

independent evolution of similar traits in distantly related organisms due to adaptation to similar environments and lifestyles

a scale bar can indicate number of base substitutions per site, years, etc

the interval between the formation of Earth and the appearance of most animal groups

• formation of earth

• first oceans

• origin of life (without oxygen)

• presence of oxygen in atmosphere

• eukaryote fossils and photosynthetic eukaryotes

• sexual structures in eukaryotes

4.6 billion years ago

3.5 billion years ago

began 541 million years ago (following the precambrian)

interval between 541 mya and present

• paleozoic era

• mesozoic era

• cenozoic era

major animal lineages appeared

• transition to land

diversification of dinosaurs and gymnosperms

diversifiation of birds, mammals, and angiosperms

• humans evolved

rapid evolutionary diversification within a lineage, producing numerous species with a wide range of adaptive forms

• ecological opportunity

• morphological, physiological, or behavioral innovation

the availability of more resources or new types of resources

ex - hawaiian silverswords

1. immigration of a single species to hawaii (5 mya)

2. dispersal and colonization of different habitats (few competitors; empty ecological niches)

3. genetic divergence (selection, genetic drift, and mutation)

• ex of allopatric speciation by dispersal

1. the species involved form a monophyletic group

2. speciation occurred relatively radpidly compared with other groups

3. the species diversified ecologically (occupy many niches)

an adaptive breakthrough

ex - angiosperm vs gymnosperms

• angiosperms have flowers, which are more efficient movement of pollen

• gymnosperms have no flowers/ fruits and rely on wind to transfer pollen from the male to female flowers

produced all of the major animal phyla existing today

1. higher oxygen levels - larger bodies, more movement

2. evolutioon of predation - arms race between predators and prey

3. explotation of new niches - more movement

4. duplication and diversification of Hox genes

an unusual event splitting a habitat, like a hurricane will NOT trigger adaptive radiation

• causes genetic drift

a large-scale, sudden (within 1 mil years) extinction event that is geographically and taxonomically widespread

involves routine/typical ecological events (predation, competition, diseases) and gradual environmental change

• reflects action of natural selection

• giant volcanic eruptions

• extreme global warming

• low oxygen in atmosphere and oceans

• acidic oceans and drop in sea levels