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 Chapter 19: History of Evolutionary Thought Discuss the 5 scientists who influenced Darwin’s development of ideas 1) Aristotle+Plato: ladder 2) Linnaeus: taxonomy Percieved natural world as imperfect Taxnomy and binomial naming system representations of a per...

 Chapter 19: History of Evolutionary Thought Discuss the 5 scientists who influenced Darwin’s development of ideas 1) Aristotle+Plato: ladder 2) Linnaeus: taxonomy Percieved natural world as imperfect Taxnomy and binomial naming system representations of a perfect world Focused on grouping and naming, whereas Introduced scala naturae, a ladder Darwin argued classification should be of life forms arranged by complexity based on evolutionary relationships 3) Cuvier: fossils Observed fossils in strata Noticed emergence/disappearance and proposed catastrophism Catastrophism suggests that local species were destroyed by events, leaving their fossils as snapshots to when they were alive 4) Lamarck: use and disuse Studies fossils and found lines of descent Principle #1: use and disuse Principle #2: inheritance of acquired characteristics Argued that evolution happens because organisms have an inane drive to become more complex Darwin disagreed with this argument, however agreed with the idea of inheritance of acquired characteristics 5) Hutton Proposed idea of gradualism; variation in The Earth must be very old landforms can be explained by slow, gradual Slow and subtle biological change processes over long periods of time 6) Lyell Darwins biological Geological processes have not changed and are uniformitarianism. uniform through time Evolution took place from The rates at which these forces operate are the one generation to the next same today as there were in the past before our very eyes, he The forces that form a mountain and then erode argued, but it worked too it are the same now an then slowly for us to perceive Descent with Modification: summarized Darwins ideas, organisms descend from ancestors, develop adaptations, and pass them on. Descent - shared ancestry relating in shared characteristics Modification - the accumulation of differences Natural Selection: is differential success in reproduction, AKA results from the interaction between inidvuals that vary in heritable traits and their environment Role of limited resources: Role of heritable variation: organisms produce more offspring than survivors who reproduced pass on their the environment can support, so only traits, making it more likely to appear at those with advantageous traits will survive greater frequency in future generations What observations and inferences did Darwin make? Observation 1: members of a population vary in their inherited traits Observation 2: all species produce more offspring than the environment can support, many die Inference 1: individuals who inherited traits give them an advantage in a given environment tend to reproduce more than other individuals Inference 2: this unequal ability to survive and reproduce leads to the accumulation of favorable traits in a population over generations Anagenesis and Cladogenesis: two patterns of evolutionary change Anagenesis: linear progression Cladogenesis: branched path Ancestral species appearance Population experiences a mutation that leads changes over time to advantageous trait Replaces species instead of Over time a new species develops; the other creating more species doesn’t necessarily go extinct Usually due to mating preferences but can also be caused by food resources and geographic isolation ****Darwin did NOT observe that survival depends on inherited traits  Chapter 20: Evolution of Populations Genetic variation is the differences among individuals in the composition of their genes Heritable vs Non Heritable Variations a) Non heritable variation: means that a specific phenotype is not inherited consistently (example is number spots on a lady bug offspring; the dots are inherited but the number is not; depends on season they were born in) b) Heritable variation: mutations and sexual recombination that produce variation in the gene pool; only mutations in cell lines that can produce gametes can be passed on to offspring The Gene Pool: the total aggregate of genes in a population Consist of all gene loci (alleles) in all individuals Sexual recombination (crossing over + fertilization) is more important than mutation in producing the genetic differences that make adaptation possible Evolutionary impact of natural selection is seen in how a population changes over time 3 main mechanisms to change… natural selection, genetic drift, and gene flow Gene flow: the transfer of alleles between populations Natural Selection: only this improves degree to which organisms are well suited to life Genetic drift: describes how allele frequencies can fluctuate unpredicted from one generation to the next Chance events that alter allele frequencies More significant in small population Can cause allele frequencies to change at random Can lead to loss of genetic variation within populations Can cause harmful alleles to become fixed & Founder effect: occurs when a few individuals become isolated and establish a new population with a differing gene pool; accounts for high Lecture Example: a blind colonist entered an isolated frequency of inherited disorders among isolated African gene pool populations and made blindness more common Genetic drift cont. The Bottleneck effect: a catastrophic event/sudden change in the envrionment may drastically reduce the size of the population The gene pool of the survivors is unpredictable; by chance alleles may be over or underrepresented in subsequent generation; lower genetic variation The gene pool may no longer be reflective of the original populations Example of genetic drift event Example from lecture is the prairie chickens: Environment changed —> population reduced to 50 individuals —> survivors had low genetic variation —> only 50% of eggs would hatch The data suggests that the genetic drift during the bottleneck may have led to a loss of genetic variation and an increase in the frequency of harmful alleles. Diploidy: recessive alleles preserve genetic variation in a population DDT Resistance: allele provides pesticide resistance, becomes more frequent in populations exposed to pesticides over time— by favoring some alleles over others, natural selection occurs and can cause adaptive evolution: process in which traits that enchance survival or reproduction tend to increase in frequency over time Selection: Favors certain genotypes by acting on the phenotypes 1. Directional Selection: favors phenotype at one end of range 2. Disruptive Selection: favors phenotypes at both extreme ends 3. Stabilizing Selection: favors intermediate phenotypes Frequency Dependent Selection: Left and right Predominate phenotypes oscillates between generations mouthed fish Sexual Selection: natural selection for mating success Intersexual vs. Intrasexual 1. Intersexual: females are choosy; even if the trait is unfavorable for envrionment it may give mating advantage 2. Intrasexual: males compete to mate, through violence or showy features Biological Species Concept: defines a species as a population whose members have the potential to interbreed and produce viable, fertile offspring Reproductive Isolation: biological factors that impede members of two species from producing viable, fertile offspring; there are prezygotic and post zygotic barriers Prezygotic Barriers: barriers to fertilization Post-zygotic Barriers: impaired hybrids (isolations) 1. Reduced hybrid viability — the genes of 1. Habitat isolation — geographically different parent species may interact seperated or not, species in different and impart the hybrids development; habitats rarely interact salamanders in overlapping zones 2. Temporal isolation — different breeding produce weak hybrid offsprings seasons 2. Reduced hybrid fertility — hybrids may 3. Behavioral isolation — different courtship be vigorous but will be sterile; ex rituals horses and donkeys have different 4. Mechanical isolation — morphological number of chromosomes, mules are differences that prevent mating; snails sterile shells and location of reproductive 3. Hybrid breakdown: some first gen organs hybrids are viable and fertile, but the 5. Gametic isolation — sperm of one 2nd gen will not be; explained by species cannot fertilize egg of another; mDNA not being compatible with sea urchins and binding proteins organelles Limitations of the biological species concept: cannot be applied to asexual organisms, fossils, or organisms which little is known about their reproduction Why natural selection cant fashion perfect organism: 1. Selection can only act on existing variations 2. Evolution is limited by historical genetic constraints of ancestral 3. Adaptations are often compromises 4. Chance, natural selection, and the environment interact Speciation: can take place with or without geographic separation Sympatric Speciation: populations not geographically isolated A subset of a population forms a new population without geographic separation 1. Habitat differentiation — occurs when subpopulation exploits new different habitat or resource, example is apple flies and hawthorn flies; some hawthorn found a new food source, started to law their eggs there, becomes new species 2. Sexual selection — choosing mate based on appearance; several cichilid species exist due to sexual selection, leading to reproductive isolation and speciation. If the water is murky however and females cant tell males apart, they can mate successfully with either species. Allopatric Speciation: populations geographically isolated A population forms a new species while geographically S If reunited they isolated from its parent population probably wouldn’t Geographic isolation occurs, populations change, gene choose to mate or flow is disrupted over time. may be incompatible Example is one pond becomes two; fish in pond 1 with to mate predators have strong body type, those in pond 2 without predators have slimmer, faster body type Hybrid Zones: form when allopatric populations come back into contact together, forming zones where members of different species meet and mate and potentially produce viable offspring of mixed ancestry Possible outcomes of hybrid zones: reinforcement, fusion, stability 1. Reinforcement — reinforces reproductive barriers (usually prezygotic) preventing fertilization or making hybrids weak and sterile 2. Fusion — weakens barriers to reproduction creating viable hybrids 3. Stability — offspring who aren’t really viable or reproducing Examples of each: Reinforcement: pied and Stability: toads were Fusion: cichlid collared fly catches separated and then females cant tell the reunite and when mating reunited without any species difference produce weak and sterile barriers, but hybrid in murky water so offspring weren’t fertile they mix back again  Chapter 20: Phylogeny and Systematics Systematists use morphological, biochemical, and molecular data to infer evolutionary relationships Binomial Nomenclature: format of the scientific name of an organism (Linnaeus) domain —> kingdom —> phylum —> class —> order —> family —> genus —> species Taxon: unit at any level of the hierarchy Phylogenetic Trees Can conclude that animals closer together are closer related Represents hypothesis of how a change occured Includes common ancestors BUT cannot show which species evolved earlier/how long it took Keep in mind that… 1. Trees show patterns of descent, not phenotypic similarity 2. We cannot necessarily infer the ages of branch points in a tree 3. We should not assume that a taxon on a tree evolved from the taxon next to it (i.e. dont assume humans evolved from monkeys or vice versa) Important Terms Branch (node): represents the common ancestor of the two evolutionary lineages diverging from it Sister Taxa: groups of organisms that share an immediate common ancestor that is not shared by any other group Out group: the group that shares an even more common ancestor with the group you are making a tree for; useful for inferring which character traits are ancestral Homology: shared traits between Example — The forelimbs of humans, bats, and species that were inherited from a whales are homologous structures. Even though common ancestor, that may have they perform different functions, they all inherited similar or different functions the same bone structure from a common ancestor Convergent evolution: the process where unrelated species independent evolve similar traits as a result of adapting to similar environments. Example is sharks and dolphins, who both developed streamlined bodies and fins independent for a similar environment in water Example is American moles (mammal) and Australian moles (marsupial) who developed similar traits like long claws to adapt to a similar environment L Analogy: Similar traits/characteristics between species that evolved independently to share the same function being a product of convergent evolution; example is wings on birds and bats, who do not share a recent common ancestor with wings Homoplasy: the analogous structures/sequences that evolved independently TLDR; homology is same trait from shared ancestor, analogy is same trait/ function as result of independently adapting to their environment, homoplasy is broader term of analogy Cladistics: like tree, but primarily focuses on common ancestry to classify organisms Clades: groupings of species, each of which includes an ancestral species and all of its descendants; can be nested inside larger/smaller clades Other uneven toed (deer) Monophyletic, paraphyletic, and polyphyletic clades · Hippo Mono — consists of an ancestral species and all of its · Para descendants (true clade) Cetaceans Para — consists of ancestral species and some of its Mono descendants · Y Bears Poly — includes distantly related species but does not ⑨ Poly include their most recent common ancestor Other carnivores (wolf) Shared ancestral character: trait present in a Shared derived character: group of organisms but also in their common trait present in group of ancestor (mammals have backbones but so do organisms not present in all vertebrates & the common ancestor) common ancestor  Chapter 28: Plant Growth, Structure, and Development Vascular plants have three organs: roots, stems, and leaves The Root System A root… 1. Is an organ that anchors the vascular plant in the soil 2. Does water and mineral absorption/uptake 3. Stores organic materials like carbs Root hairs are found at the tips of the roots, made of epidermal (outer skin) cells. They do the majority of nutrient absorption and water uptake, and greatly increase surface area There are two main types of roots: taproots and lateral roots 1. Taproots: tall erect plants have main vertical root for stability While expensive, it gives more favorable light conditions and may provide advantage for reproduction. In taproot plants, the role of absorption is largely restricted to the tips of lateral roots, which branch off from the taproot 2. Fibrous Roots: thin, interweaving roots spread out beneath surface Found in small plants or those with trailing growth plants who are susceptible to grazing (grass etc) Each root forms its own lateral roots, which form their own lateral roots, creating a thick mat Anchoring combats erosion Many plants also have modified roots (lecture examples!!) Buttress roots: some tropical trees have treetops that go above the general canopy, so buttress roots give support to them by attaching to the sides of the trunk Prop roots: looks like the plant is walking, support tall top heavy plants like maize Storage roots: beets store food and water in their roots Pneumatophores: mangrove roots, in watery/muddy environments these grow up towards the sky, allowing them to get oxygen Strangling roots: aerial roots wrap around the tree, shading it and preventing water uptake so the tree dies. What’s left is a shell of roots The Shoot System: consists of stems and leaves… Stems: Organ bearing leaves and buds Main function is to elongate/orient shoot to maximize photosynthesis by leaves Also elevates reproductive structures for dispersal of pollen and fruit Sa Each stem consist of nodes Apical Axillary bud: formed by each (the points at which leaves leaf at every node, can become are attached) and · lateral branch, thorn, or flower # internodes (the stem Apical bud: most of the growth of · Axillary segments between the a young shoot is concentrated near & nodes) the tip, aka apical bud Some plants also have modified stems for storage or reproduction (lecture examples!!) Rhizomes: grows a horizontal shoot beneath the surface, vertical shoots emerge from axillary buds on the rhizome Bulbs: short stem for storage and reproduction; onions for example Stolons: grows horizontally above the surface “runners” that enable asexual reproduction; plantlets grow from axillary buds along runners; strawberries Tubers: enlarged ends of rhizomes or stolons specialized for storing food; the eyes of potatoes are clusters of axillary buds Leaves: The main photosynthetic organ Consist of flattened blade and stalk; the petiole joins the lead to the stem at a node Primary function is photosynthesis, but also intercept light, enhance gases with the atmosphere, dissipate heat, and defend from herbivores and pathogens. Some plants have modified leaves (lecture examples!!) Tendrils: long shoots on pea plants that coil around something for support Spines: spines on cacti are “leaves”; the lead dies and becomes spiky for protection; hairy spines protect cacti from the sun Storage leaves: bulbs, succulents, plants in dry/salty areas; short stem and leaves that store food Mother of millions: tissue grow on side of leaves, eventually fall off becoming own plant (cloning) Bracts: red leaves surrounding flowers to attract insects Three different types of tissue: ground, dermal, and vascular 1. Ground Tissue Ground tissue is a “filling tissue” which fills up space between the other tissues, but also will differentiate. It is the main photosynthetic tissue. Mainly does photosynthesis, also does storage, support, and short distance transport; found sandwiched in mesophyll region Tissue internal to vascular tissue is “pith” Tissue external to vascular tissue is “cortex” Ground tissue cell differentiation: Parenchyma (living) metabolism and photosynthesis; dermal and ground Collenchyma (living) provide flexible support; beneath epidermis in petioles Sclerenchyma (dead) rigid support in regions that have stopped lengthening 2. Dermal Tissue Plants’ outer protective covering, like skin. Prevents against damage, water loss Epidermis: Single layer of packed cells in non-woody plants Cuticle: Waxy coating on top of the epidermis that most stems and leaves have Peridem: Protective tissues that replace older regions of epidermis in woody plants The epidermis can be specialized. Root hair: an extension of an epidermal cell near the tip of a root Trichomes: hairlike outgrowths of shoot epidermis; can reduce water loss and reflect light, but usually defend; also secrete sticky liquid to catch bugs Stomata (pores): allow for gas exchange and water release 3. Vascular Tissue Main functions are to facilitate transport of materials & to provide mechanical support. Composed of two types of transport tissues called xylem and phloem Xylem: water and mineral uptake from roots to shoots Water conducing Phloem: transports organic nutrients (rna, proteins, etc) and sugars from where they are made (leaves) to where they are needed or stored, usually roots and sites of growth S cells of xylem Sugar conducting cells of phloem Arrangement depends: in angiosperm roots it forms vascular cylinders, in shoots it forms vascular bundles (called veins in leaves) Vascular tissue cont Water conducting cells of the xylem: tracheids and vessel elements They are both tubular, elongated elements that are dead at maturity. When living cellular contents of either cell disintegrate, it leaves behind the walls, allowing water to flow through. Pits (thinner, primary wall) interrupt the thick secondary wall making it easy for water to flow between cells Tracheids: Vessel Elements: Long, thin cells with Wider, shorter, thinner walled and less tapered tapered ends Aligned end to end forming long pipes, aka vessels. Water moves from cell Contain perforation plates: end walls of cell that through mainly pits enables water to flow freely Sugar conducting cells of the phloem: sieve tube elements and companion cells Alive at functional maturity Sugars and organic nutrients are transported through long, narrow cells called sieve cells and companions cells Sieve tube elements: Transports nutrients Long chains of sieve cells Lack nucleus, ribosomes, distinct vacuole and cytoskeletal elements; allows nutrients to pass through easily Sieve plates - end walls between sieve tube elements, have pores that facility de flow of fluid from cell to cell Companion Cells Connects via plasmodesmata, like gap junction that allows exchange of large materials Run alongside each sieve tube element All of its organelles serve the sieve tube and itself Can help load sugars into sieve tube element Plant Growth and Meristems Plants grow their entire lives, a This is because they have unspecialzed process called indeterminate tissues that perpetually divide, called growth. meristems (like stem cells) **However, some plant organs such as leaves, thorns, and flower undergo determinate growth, where they stop growing after reaching a certain size There are two main types of meristems: apical and lateral 1. Apical Meristems: primary growth (lengthening + leaves) Located at the tips of roots and shoots, and in axillary buds of shoots Allows roots to extend into soil and for shoots to increase their exposure to light In non-woody plants, primary growth produces all/almost all of the plant body 2. Lateral Meristems: secondary growth (thickening) Woody plants grow in circumference in parts of stems and roots that have stopped growing in length Two types of lateral meristems include the vascular cambium and cork cambium a) Vascular Cambium Adds layers of vascular tissues called secondary xylem; secondary vascular tissue (wood) and secondary phloem Is a cylinder of meristematic cells one cell thick Develops from parenchyma cells (ground tissue) b) Cork Cambium Replaces the epidermis with the ticker, tougher periderm Single cell layer around the stem in a cylinder way Periderm (outer layer) consists of cambium and the cell layers produced by it Bark Everything externally from the vascular cambium On a tree technically you are looking at cork Includes secondary phloem and periderm ** The evolution allowed the production of novel plant forms ranging from massive forest trees to woody vines. Primary Growth (lengthening) of Roots Root Cap: Covers tip of root, protects the apical meristem as the root pushes through rough soil Secretes slime that lubes the surrounding soil Root growth occurs just behind the tip, three overlapping zones of stages of primary growth: cell division, elongation, and differentiation 1. Zone of Cell Divison Includes the root apical meristem ↳ New root cells produced cell, including root cap cells **Apical meristem keeps adding new 2. Zone of Elongation cells to younger end of elongation zone Just a few mm behind the cell division zone, this is where most of the growth occurs as cells elongate Before cells even finish lengthening, many begin specializing in structure and function 3. Zone of Differentiation Aka zone of maturation, where cells complete differentiation and become distinct cell types The primary growth of a root produces it epidermis, ground tissue, and vascular tissue OTHER: Heartwood & Sapwood Heartwood Stomata: Older and deeper In leaves, epidermis is interrupted by Darker from oxidation pores called stomata, allowing for gas Non functioning, dead material exchange Sapwood Regulate CO2 uptake and major Younger, more external avenue for evaporation Humid Flanked by two specialized epidermal Replaces heartwood cells called guard cells which regulate Fresh xylem the opening and closing of the pore More liquid/humid During the early stages of secondary growth, the epidermis is pushed outward, causing it to split, dry, and fall off the stem or root. It is replaced by tissues produced by the first cork cambium, a cylinder of dividing cells that arises in the outer cortex of stems and in the outer layer of the pericycle in roots. The cork cambium gives rise to cork cells that accumulate to the exterior of the cork cambium.