Speciation SJCHS

Evolution Microevolution: Change in a population ’ s gene pool from generation to generation Speciation: When one or more new species branch from a parent species Evolution does not always result in new species

Species

Definition Species Concepts Biological: A group of organisms that can interbreed and produce fertile offspring Morphological : Classified on shape, size, other features Phylogenic: Species who share common ancestor/ evolutionary history

Definition Different species are determined by considering all definitions

Phylogenic Tree Phylogenics/Cladistics: Search for clades (group that consists of ancestral species and all its descendants) Branch points: New species Common Ancestor: Not necessarily a known organism; characteristics hypothesized based on traits of descendents Branch: History of species

Phylogenic Trees Species in clades share primitive characters Sequence of branch points are defined by derived (evolutionary innovative) characters Changing field

Evolution Convergent evolution: Characteristics shared by species because of similar environments or ecological roles- NOT due to a close common ancestor

Evolution Coevolution: When 2 species reciprocally affect the evolution of each other

Speciation Event Speciation event: A series of genetic changes in a common ancestor that produces two or more separate species

Speciation Event Reproductive barrier: Biological features that prevents interbreeding Prezygotic Barrier: Prevents mating or fertilization

Speciation Event Postzygotic Barrier: Prevents the development of fertile adults

Speciation Event Barriers occur due to changes in the gene pool of a separated part of a population

Speciation Event Allopatric speciation: Geographic isolation of a population Different environments may result in different evolutionary adaptations due to natural selection

Speciation Event Parapatric speciation Species are not geographically isolated but are spread over a large, differentiated geographic area Natural selection can result in speciation due to different environments

Speciation Event Sympatric speciation Species are geographically close and a speciation event occurs

Pace Evidence for speciation events comes from fossil record Can use fossils to determine how quickly speciation can occur No one pace is correct- can differ depending on species

Pace Punctuated Equilibria: Long periods of little change followed by abrupt (1000 ’ s to 10,000 ’ s of years) episodes of speciation

Pace Gradualism: Species diverged over large periods of time (100,000 ’ s or millions of years)

Pace A major mutation can “ instantaneously ” result in a speciation event Rare

Evidence Historically: Fossil and geologic record can be used to determine when species diverged

Evidence Differences in RNA/DNA/protein sequences can be used to determine evolutionary relationships

Bioinformatics Bioinformatics: Using math, computers, and biology to store and analyze data from sequenced genomes

Molecular Clocks Molecular Clock: Using DNA/RNA/proteins sequences to determine when two or more species diverged

Molecular Clocks Assumptions- The rate of mutation in a gene is: similar in different species occurs at a constant speed (graphs of mutations versus time should be a straight line) Not true for all genes/species fibrinopeptide Cytochrome C

Molecular Clocks Calibrating a molecular clock: To use molecular clocks you must use the fossil or geologic record to determine the rate of mutation