BIO1022 Notes Part 1: Natural Selection, Artificial Selection, and Speciation, Lecture notes of Biology

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• BIO1022 NOTES PART

BIO WEEK 1

21.4 NATURAL SELECTION & ARTIFICIAL SELECTION

Explain the main requirements for natural selection to occur, and compare with artificial and sexual selection

**- Describe the biological species concept and its limitations

• Explain the two general types of reproductive isolation
• Describe the processes by which new species can form There are 3 reqs for natural and artifical selection:**

1. Heritable variation of traits
2. Overproduction of offspring
3. Selection of some individuals over others Artificial: humans engineering the process not natural Result: +ve traits become more common in population Natural selection:
   • Brings about adaptations
   • Darwin used the term “natural selection” for the filtering process that acts against deleterious alleles and in favor of advantageous ones.
   • Competitive advantage - how well an organism is adapted to its environment. A desert plant that is more efficient at minimizing water loss than another plant is better adapted to the desert environment
   • Fitness , is a measure of the extent to which the individual’s genotype is represented in the next generation o Survives longer, greater opportunity to reproduce
   • Natural selection that increases the frequency of a favorable allele is called positive selection.
   • Natural selection that decreases the frequency of a deleterious allele is called negative selection. o b lethal only as a homozygote, bb, and has no effect as a heterozygote, Bb ). When it first arises, all other alleles in population are B. o first b allele that appears in the population must be paired with a B allele = Bb heterozygote. Natural selection does not act against heterozygotes in this case, the b allele may increase in frequency by chance alone o Only bb homozygote appearance causes natural selection to rid population of allele.

• carefully controlled by the breeder, artificial selection is astonishingly efficient at genetic change. Disruptive selection: Favour of extremes and against intermediate forms Can produce two genetically distinct populations of apple maggot fly, each one coordinated with fruiting times of two different species of tree. Sexual selection , acting in opposite direction promotes traits that increase an individual’s access to reproductive opportunities. Intrasexual selection compete with one another for access to the other sex intersexual selection focuses on interactions between females and males

Species are reproductively isolated from other species. The distances between the dots within a cluster reflect variation from one individual to another within a species Species are groups of actually or potentially interbreeding populations that are reproductively isolated from other such groups. Mo rphospecies concept The idea that members of the same species usually look like each other more than like other species.

• Barcode of Life has established a database linking DNA sequences to species. Biological Species Concept = defines species as members of populations that potentially interbreed in nature, not similarity of appearance. o Although appearance is helpful in identifying species, it does not define species. Problems of the BSC: Animals of same species may not always be similar to be part of same species o Young vs old; caterpillar vs butterfly  members of the same species but different in appearance thru their lifespan o Does not apply to asexual (bacteria) or extinct organisms o Ring species n hybridization complicate BSC  Ring : contain populations reproductively isolated from each other but can exchange genetic material through linking populations.  Hybridization : Interbreeding between two different varieties or species.

Mechanical incompatibility Structural configuration of the genitalia that prevents mating with another species Temporal isolation Pre-zygotic isolation between individuals that are reproductively active at different times. Ecological isolation Pre-zygotic isolation between individuals that specialize ecologically in different ways Post-zygotic isolating factors occur after egg fertilization. genetic incompatibility Genetic dissimilarity between two organisms, such as different numbers of chromosomes, that is sufficient to act as a post-zygotic isolating factor. 22.3 SPECIATION Speciation is a by-product of the genetic divergence of separated populations. Partially reproductively isolated populations not yet diverged as separate species

• genetically different enough that hybrid offspring produced have reduced fertility or viability compared with offspring produced by crosses between individuals within each population. (horses and donkeys) Genetic drift if alone  changes in the allele frequencies of the population
• For gene pools of 2 closely related species to remain distinct must be reproductive isolation

Allopatric speciation is speciation that results from the geographical separation of populations. Speciation is the process by which two groups of organisms become reproductively isolated from each other Allopatric = different place How do populations become allopatric? Dispersal The process in which some individuals colonize a distant place far from the main source population. Vicariance The process in which a geographic barrier arises within a single population, separating it into two or more isolated populations. Peripatric speciation A specific kind of allopatric speciation in which a few individuals from a mainland population disperse to a new location remote from the original population and evolve separately. Adaptive radiation A period of unusually rapid evolutionary diversification in which natural selection accelerates the rates of both speciation and adaptation in a single lineage. Adaptive radiation is more likely to occur in a population produced by a dispersal event than in a long-established population on a continent.

• Eg: Volcanic island are dependent on process of colonization. Only some plants and animals can get there.
• Absence of competitors on these islands = many available ecological opportunities for colonizers. o May be no insect-eating birds on the islands, providing an ecological niche to be filled. Co-speciation is speciation that occurs in response to speciation in another species. Co-speciation  Two groups of organisms speciate responding to each other + producing matching phylogenies. When host species speciates, the parasite will also speciate. Sympatric populations—those not geographically separated—may undergo speciation. sympatric populations in same geographic location.

BIO WEEK 2 FOSSILS AND THE TREE OF LIFE

Reading a phylogenetic tree node = common ancestor which descendant species diverged + branch point. In plants, the point on a shoot where one or more leaves are attached. Taxa: tips of the branches are groups of organisms Phylogenetic trees provide hypotheses of evolutionary relationships. Taxonomic ranks—Domain, kingdom, phylum, class, order, family, genus, species Did Katy Perry Come Over For Good Sex Phylogenetics – Pattern of evolutionary relatedness among groups of species or other groups by comparing anatomical or molecular features + depict relationships as phylogenetic tree