Evolution and Natural Selection Unit 7a Evolution and Natural Selection

Charles Darwin Traveled on board the HMS Beagle 1831-1836 Using observation and insight, proposed the theory of evolution by natural selection (gradualism) Organisms will change genetically over time Suggests that present day organisms descended from a common ancestor

Evolution Definition: The process of cumulative change in the heritable characteristics of a population Changes must be passed on genetically from one generation to the next Can result in a new species Cannot interbreed with ‘old’ species Heritable – the changes mused be passed on from one generation to the next, does not happen overnight Cumulative – one change is usually not enough to have a major impact on the species Population – changes do not effect just one individual

Speciation Rates How fast/when evolution occurs Punctuated Equilibrium: Step-like pattern of gradual changes that occur

Evidence of Evolution Fossil Record Artificial Selection The remains or impression of a prehistoric organism preserved in petrified form or as a mold or cast in rock Evidence of the appearance, change, and disappearance of species Artificial Selection Selective breeding allows breeders to create unique combinations of characteristics Homologous anatomical structures Similar in form and function Found in seemingly dissimilar species

Mechanism for Evolution Natural Selection Example: antibiotic resistance in bacteria Due to too many offspring/not enough resources Results in competition for key resources Those organisms with favorable traits survive and reproduce These traits get passed on to the next generation “Survival of the fittest” Concept of natural selection is not always true Example: Extinction of the dinosaurs

Causes of Variety Choice of mate Mutations in DNA Sexual reproduction Can lead to disease Can produce an advantageous characteristic Example - Slightly faster growing tree Sexual reproduction Powerful source of variation in a population Thousands of genes are mixed and combined Meiosis / Fertilization

Allele frequency and gene pools Definition: all of the genetic information present in the reproducing members of a population at a given time Allele frequency Definition: a measure of the proportion of a specific variation of a gene in a population Example: 25% of all chromosomes in a population have a certain allele ¼ of the loci for that gene are occupied by that allele

Evolution and Alleles After many generations, allele frequency changes due to: Immigration Emigration Mate choice (reproduction) Advantageous alleles are more frequent Disadvantageous alleles are not passed on No change in allele frequency = no evolution Big change in allele frequency = evolution has occurred

Barriers between Gene Pools Geographical isolation Physical barriers prevent males and females from finding each other Temporal isolation Incompatible time frames Behavioural isolation Lifestyle and habits of on population is not compatible with another Hybrids Most are infertile

Unit 7b Classification

Classification Putting living organisms into groups Purpose Trying to make sense of the biosphere Showing evolutionary links Predicting characteristics shared by members of a group

Modern Classification Compares External/internal structures Geographical distribution Genetic make-up Feeding habits Habitat Daily activity Risk Anatomy

All organisms results from a common ancestor Domains There are 3 domains Bacteria / Archaea / Eukarya All organisms results from a common ancestor

Five Kingdoms Animalia Plantae Fungi Protista Eubacteria 76% of all species Plantae 15% of all species Fungi 5.6% of all species Protista 2.8% of all species Eubacteria 0.3% of all species Archeabacteria 0.03% of all species

Binomial Nomenclature Consolidated and popularized by Carl Linnaeus (1735) System of names organisms using two names ‘Bi’ means two / ‘nomial’ means name ‘nomenclature’ refers to a system used to name things First name Capitalized Refers to the genus Second name Begins wish a small letter Refers to the species Written in italics when typed Underlined when written by hand Most are of Greek or Latin origin

Taxonomy Branch of Biology that groups and names organisms based on studies of their different characteristics (living and extinct) Example: Bangle Tigers and Saber-tooth tigers Taxon(singular)/Taxa (plural) Seven taxa Domain / kingdom / phylum / class / order / family / genus / species

Taxonomic Rankings Taxa range from wide-ranging to narrow There are more organisms found in KINGDOM than in PHYLUM Wide-ranging taxa include: general characteristics more species Ex. The phylum chordata contains any creature that has a backbone Narrow taxa include: Specific characteristics Fewer species Ex. The species, Cardinalis cardinalis, will only contain Cardinals

Dichotomous Keys Method of classification Used to reveal the identity of an organism based on certain characteristics