How Biological Diversity Evolves CHAPTER 14 How Biological Diversity Evolves

Macroevolution and the Diversity of Life Evolutionary Theory Generates biological diversity (Origin of new species)

What Is a Species? The biological species concept defines a species as a population or group of populations whose members have the potential to interbreed with one another in nature to produce fertile offspring.

Speciation Is the formation of new species; occurs when one or more new species branch from a parent species, which may continue to exist.

Nonbranching evolution Evolution that can transform a population significantly but does not create a new species.

Branching evolution splits a lineage into two or more species, thereby increasing the total number of species. New formations are called speciation.

Reproductive Barriers between Species Prezygotic barriers prevent mating between species. Postzygotic barriers are mechanisms that operate should interspecies occur and form hybrid zygotes. Geographic ranges overlap yet they maintain a species boundary

Reproductive Barriers Gene pools: Prezygotic Postzygotic (Depends when they block interbreeding - before or after formation of zygotes) Figure 14.4

Prezygotic barriers include: Temporal isolation - species breed in different seasons Habitat isolation - species live in same region, different habitats Behavioral isolation - recognizable traits for reproduction Albatross, Giraffe, and Blue-Footed Boobies Courtship Ritual Mechanical isolation - male/female sex organs anatomically incompatible Gametic isolation - copulation but incompatible gametes; no reproduction

Behavioral isolation Traits that enable individuals to recognize potential mates, such as odor, coloration, or courtship ritual, can also function as reproductive barriers. In many bird species, for example, courtship behavior is so elaborate that individuals are unlikely to mistake a bird of a different species as one of their kind. Ex: Courtship ritual - These blue-footed boobies, inhabitants of the Galápagos Islands, will mate only after a specific ritual of courtship displays. Part of the “script” calls for the male to high- step, a dance that advertises the bright blue feet characteristic of the species.

Figure 14.5

Postzygotic barriers Mechanisms that operates should interspecies mating actually occur and form hybrid zygotes. Hybrid Inviability - offspring die before reaching reproductive maturity Hybrid Sterility - offspring fail to develop normally because of genetic incompatibilities between the two species or infertile Hybrid Breakdown - first generation hybrids are viable and fertile, when these hybrids mate with one another or with either parent species, the offspring is sterile and less likely to survive Ex: Hybrid sterility - Horses and donkeys remain separate species because their hybrid offspring, mules, are sterile.

Figure 14.6

Mechanisms of Speciation A key event in the potential origin of a species occurs when a population is somehow severed from other populations of the parent species.

The two modes of speciation are Sympatric speciation Process where new species evolve from a single ancestral species while in the same region. Allopatric speciation (geographic speciation) Occurs when biological population of the same species get isolated from each other preventing interchange.

Figure 14.7

Allopatric Speciation Geologic processes Continuous action, series in a definite manner affecting a specific region. Can be physical or human caused Examples include: Galápagos Islands Overview Grand Canyon

Figure 14.8

(example in next slide) In the both example there is an allopatric scenario but then the top becomes different because it doesn’t go though speciation but creates interbreed species. In the bottom example there is speciation which in time would not create interbreed species

Figure 14.9

Sympatric Speciation When a species is developed or created without any natural/physical barriers, but still within the same population and area Examples include most shrubs, trees and fungi, and some insects E.G. -A fruit fly may lay eggs on a mango, but another variation of fruit fly may lay eggs in oranges causing behavioral differences down the line

Radiometric dating A common way of determining and objects age using knowledge of elements rate of decay and half-lifes. E.G. Uranium-lead dating method Uranium-thorium dating method Radiocarbon dating method Fission track dating method Luminescence dating methods *

Figure 14.17a *

Figure 14.17b *

Classifying the Diversity of Life Systematics The study of the diversity and relationships of organisms, both past and present Taxonomy The identification, naming and classification of species

Some Basics of Taxonomy Carolus Linnaeus A Swedish Physician and Botanist. Her system has two main characteristics, a two-part name for each species and a hierarchical classification of species into broader and broader groups of organisms.

Naming Species This system assigns each species a two part latinized name, or binomial. The first part of the binomial is the genus (plural, general) to which species belong. The second part of a binomial refers to one particular species within the genus.

Hierarchical Classification 1st step of hierarchical classification is built into the binomial. We group the species that are closely related into the same genus. Hierarchical Classification also puts species into broader categories of classification; family into orders, orders into classes, classes into phyla, and phyla into kingdoms and kingdoms into domains.

Figure 14.21

Classification and Phylogeny Phylogeny: the evolutionary history of a species. How an organism is named and classified should reflect its place within the evolutionary tress of life The final product takes place on the branching pattern of a phytogenetic tree.

Figure 14.22

Sorting Homology from Analogy Homologous structures Homologous structures is a source of information about phylogenetic relationships. Homologous structures may look different and function very differently in different species, but they exhibit fundamental similarities because they evolved from the same structure that existed in a common ancestor. The greater the number of homologous structures between two species, the more closely the species are related. An example is, the whale limb is adapted for steering in the water; the bat wing is adapted for flight. There are many basic similarities in the bones supporting these two structures.

Convergent evolution: Species from different evolutionary branches may have certain structures that are superficially similar if natural selection has shaped analogous adaptations Analogy: similarity due to convergence

Molecular Biology as a Tool in Systematics Molecular systematics Comparing the genes and proteins of organisms to find their evolutionary relationships. The more recently two species have branched from a similar ancestor, the more similar their DNA and amino acid sequences will be. Molecular systematics provides a new way to test hypotheses about the phylogeny of species

This slide shows an example of molecular systematics This slide shows an example of molecular systematics. The strongest support for any such hypothesis is agreement between molecular data and other means of tracing phylogeny, such as evaluating anatomical homology and analyzing the fossil record. Some fossils are preserved in a way that it is possible to extract DNA fragments for comparison with modern organisms Figure 14.23

Figure 14.24

Cladistics Scientific search for ‘Clades’ –Consists of ancestral species and all of its descendants; a distinctive branch in the tree of life. Derived from Greek word “Branch” Focuses on evolutionary relationships between organisms rather than Taxonomic

Sometimes it is conflicting to taxonomist because if you go back in time, a bird used to related to a reptile! Figure 14.25

This shows how through time, some organisms are more closely related than you think. Figure 14.26