Module 2: Evidence for Evolution

Evolution

• descent with modification

• a change in population allele frequencies

Homology

similarity resulting from common ancestry (same origin) often despite differences in function

analogy

similarity in function, but not having the same evolutionary origin

phylogentic analysis unambigously shows that are descended from

wolves (Canis lupus)

selective breeding shows us that

biological change is possible and it can occur quite rapidly

scientific evidence supports three different types of evolutionary change

1. microevolution

2. speciation

3. macroevolution

Microevolution

small evolutionary changes within species or populations

Speciation

the splitting and divergence of lineages, an ancestral species can give rise to two or more descendent or daughter species

Macroevolution

refers to larger phenotypic changes sufficient to place an organism in a different higher level taxon (e.g phylum).

over time, microevolution results in both speciation

as well as macroevolutionary differences

one powerful line of evidence for evolution is that

we can observe it directly in a wide variety of settings

Incipient species

two populations that have been nearly completed the process of becoming seperate species

host plant shifts have been an important factor that induces

speciation in insects

vestigial structures

body parts that are useless, or rudimentary in one or more organisms, but have an important function in related organisms

species is difficult to define bc

hard to come up w a definition that encapsulates the tremendous biological diversitybio

biological species concept

species are groups of interbreeding natural populations that are reproductively isolated from other groups

key operational criterion of biological species concept

reproductive isolation

biological species concept can only be applied to

species that are sexually reproducing

the fossil record

the entire collection of fossils that we have globally

in 1801, Georges Cuvier

published a list of 23 species that he believed to be extinct

treating evolution as a hypothesis and testing it with a fossil record

h: evolution has occured, we should see changes in the organisms that have inhabited the planet over the course of time throughout the fossil record and it that there should be strong geographic patterns with respect to the similarity of the organisms that within the fossil record, and those that exist today

law of succession

states that fossils in a given geographic region are more closely related to the extant fauna of that region than they are to organisms in a different geographic region

extant is

the opposite of extinct

phylogenetics is the study of

ancestor-descendant relationships p

phylogeny is

a hypothesis of ancestor-descendant relationships and we must always think of phylogenies as being hypotheses

phylogentic tree consts of

taxa or terminal nodes, internal nodes which represents ancestors, root of the tree which is the most recent common ancestor shared by all of the taxa within our phylogenetic tree

sister taxa

two taxa which are each other’s closest relatives

transitional forms

if later life forms are descended from earlier ones, the fossil record should contain organisms with intermediate or a mixture features between them

ex of homology problems

similar to fish, when males are first developed, their gonads are relatively close to their heart, this can later cause a hernia that needs to be surgically fixed

principle of superposition

younger geological layers sit on top of older layers

principle of original horizontality

lava and sedimentary rocks were originally laid down in a horizontal position

the combination of geological data sets with biological data sets and fossils provide us with

very powerful evidence for evolution and it also allows us to trace the history of life on Earth

plate tectonics

holds that the continents move around over the course of time

continental drift

laurasia and gondwana started shifting away from each other