The trickle buds

Chapter 1.4 Environmental variation: Variation among individuals due to environment Genetic Variation: Variation when genes passed on Chapter 19 Hierarchical control of development Gene regulation during development is hierarchical; genes expressed at each stage control genes that act later on Humans gastrulation forms in 3 germ layers; ectoderm, endotherm, mesoderm Oocyte: unfertilized egg cell produced by mother Maternal-effect genes: Bicoid and nanos that are expressed by mother but affect phenotype of the offspring mRNA for nanos is synthesized by mothers cell, imported into oocyte Like mRNA for bicoid/nanos, mRNA for caudal/hunchback are transcribed by mothers genome and transported into egg Bicoid protein represses translation of caudal and nanos represses hunchback Caudal concentrated at posterior, hunchback=anterior Homeotic genes determine where diff body parts develop in an organism Homeotic genes: genes which regulate the development of anatomical structures Homeotic genes encode transcription factors DNA binding domain in homeotic proteins=sequence of 60 amino acids (homeodomain) Evolutionary conservation of key transcription factors in development Molecules that are similarly in sequenced= evolutionarily conserved Eyes evolved independently of one another All eyes contain same molecule, but as time went on the diverged from one another Loss of function mutation: gene products having less or no function Pax6: induces development of the eye almost anywhere Gain of function mutation: Gene expressed In the wrong place or time Transcription factors like pax6 interact w/ target genes by binding w/ short dna sequence adjacent to the gene (usually at 5’ end) this is called cis-regulatory elements Chapter 20 Genetic variation Gene pool: All the alleles present in all individuals of a species Somatic Mutation: Occuring in the bodies tissues Germline mutation: Occurs in reproductive cells, therefore passed on Measuring Genetic Variation Allele frequency: Rates of occurences of alleles in a population When population exhibits only one allele at particular gene, population is fixed for that allele Evolution & Hardy Weinberg Hardy Weinberg equilibrium: Evolution doesn’t occur, allele and genotype doesn’t change No diff in surivival and reproductive success of individuals No migration No mutation Very big population Mating is random Natural Selection Natural selection results in allele freq changing from gen to gen Competitive advantage: Function of how well an organism adapted to its environment Better adapted=more fit Fitness: measure of the extent to which indiv genotype is represented in next gen Modern synthesis= current theory of evolution Positive selection: Increases favourable allele Artificial selection: Successful genotype picked by the breeder Sexual selection: promotes traits that increase individuals access to reproduce Intrasexual selection is when individuals of one sex interact and compete for a mate usually happens when they fight one another Intersexual selection happens when they compete for the attention so the mate picks the better male Migration/Mutation/Genetic drift Gene flow: Movement of alleles from one population to another, migrating Non-random mating alters genotype frequencies without affecting allele frequencies Inbreeding depression: Reduction in childs fitness by homozygosity of deleterious recessive mutations Molecular Evolution Mutation has 1 of 3 fates: Goes to fixation It is maintained at intermediate frequencies Its eliminated When populations diverge genetically it is evidence of molecular evolution Molecular clock: Time two species have been evolutionarily apart and the amount of genetic divergence between them Pseudogene: gene that us no longer functional Chapter 21 Biological Species Concept BSC: Species are groups interbreeding populations, reproductively isolated from other such groups Morphospecies concept: Members of the same species usually look alike Members of a species may not look alike but show diff phenotypes called polymorphisms BSC doesn’t apply to asexual/extinct organisms Ecological species concept: One to one correspondence between a species and its niche Phylogenetic species concept: Members of a species all share a common ancestry/fate Reproductive Isolation Prezygotic isolation: act before fertilization of egg Indiv only mate with others based on specific songs, rituals, etc Gametic isolation: Genetalia fit only with those of same species Trying to mate with members of diff species prevented by mechanical incompatibility Postzygotic isolation: Come into play after fertilization Ex. Diff number of chromosomes Sometimes produces offspring but not favoured by natural selection Speciation Partially reproductively isolate: not yet separate species but if produce offspring=lower fertility Allopatric: populations that are geographically isolated Peripatric speciation: Indiv from mainland pop disperse to new location and evolve separately When separated but no fully speciated=subspecies ptive radiation: rapid evolutionary diversitification, natural selection accelerates both rates of speciation and adaptations. Co-speciation: 2 groups of organisms speciate in response to each other and at the same time Sympatric: Same geographical area Natural selection must act strongly Instantaneous speciation: hybridization b/w two species in which the offspring are reproductively isolated from both parents Polyploidy: creation of species with multiple chromosome sets Allopolyploids: Produced from hybridization of 2 diff species Autopolyploid: Derived from unusual reproductive event b/w members of single species Speciation and selection Speciation can occur with or without natural selection Natural selection can enhance reproductive isolation Reinforcementd: diverging populations undergo natural selection in favour of traits that enhance pre-zygotic isolation, preventing production of less fit hybrid offspring Chapter 22 Reading a phylogenetic Tree Node is where the tree splits, represents common ancestor Phylogenetic tree: hypothesis of the evolutionary history Sister groups: 2 organism groups that are more closely related than any other species Monophyletic group: has a common ancestor and ALL of its descendants Paraphyletic group: Incudes some but not all descendants of a common ancestor Polyphyletic group: Do not include last common ancestor of all members Doman Kingdom Phylum Class Order Family Genus Species Building a Phylogenetic Tree Homology is similarity by common descent Character states: observed conditions of characters Homologous: Characters similar b/c of common descent Analogous: Similarities due to independent adaptations Synapomorphies: Homologies that are shared by some but not all members of the group Cladistics: Phylogenetic reconstruction on the basis of synapomorphies Parsimony: Choosing simpler table out of the bunch Fossil record Fossils provide unique info, our only source of extinct species Trace fossils: Tracks and trails but not actual sedimentation Molecular fossils: organic molecules derived from dead animals Burgess Shale: accumulated on deep seafloor covering what is now british Columbia during Cambrian period Mesel Shale: In Germany, toxic gases suffocated local animals, carcases settled on the oxygen poor muds on lake floor Geological timescale: series of time divisions that mark earths history Radiometric dating: radioactive decay of C14 to date wood and bone Comparing Evolutions 2 great patterns Only fossils can show extinct species relatedness to modern species It can show animals who lived in the past and where/how they lived Chapter 25 -876300215900 -723900207010 Eukaryotes: Review  Endomembrane system: Endoplasmic reticulum, golgi apparatus, plasma membrane  Engulfing molecules=endocytosis   Eukaroytes can replicate multiple DNA at once  Eukaryotes have “junk genes” but some of them function for gene regulation  Sex promotes genetic variation in 2 ways:  Meiotic cell division results in gametes=genetically unique  In fertilization: new combos of genes are brought together by fusion of gametes  Some eukaryotes= horizontal gene transfer  Eukaryotic Origin Symbiont: organism that lives in closely evolved association with another species Association called symbiosis Endosymbiosis: Living inside another organism Chloroplast have their own DNA , single circular chromosome like bacteria Mitochondria came from bacteria, eukaryotic cell engulfed it Eukaryotes w/out mitochondria once had them but they lost it 2 hypothesis regarding endosymbiosis theory: Eykaryotic cells evolved from ancestral archaea, later took up mitochondrial bacteria Eukaryotic cells evolved froma symbiosis b/w archea and mitchodondria bacteria Eukaryotic Diversity Opisthokonta: Animals/Fungi/Some protists Movement by a single flagellum Heterotrophic but some photosynthesize Chaoanoflagellates: Close relation to animals, ring of microvilli projections form a collar around cells flagellum Amoebozoa: Amoeba like cells, pseudopods to move. Amoebas/slime moulds Movement by pseudopodia Heterotrophic usually Archaeplastids: Photosynthetic organisms Descended from protists w/ photosynthetic bacteria (cyanobacterium) Red algae, green algae, viridiplantae Stramenopila: Unicellular and gian kelps, algae and protozoa, freeliving cells and parasites Unusual flagellum, bearing 2 rows of stiff hairs Most have second smooth flagellum Most photosynthetic Alveolata: Photosynthetic and heterotrophic species. Have small vesicles (cortical alveoli) Store calcium ions for use by the cell Rhizarians: Amoeba like, form shells Protozoa: heterotrophic protists (single celled almost all) Fossil record of protists Not all algae and protozoa fossilize easily