Evolution PDF

october 9, 2024 intro to evolution: history and evidence evolution explains to similarities, changes over time, and appearances of organisms anatomists in 1500s: they discovered that despite sizes, shapes, and functions, the forelimb of all vertebrates contains - homologous internal bone struct...

october 9, 2024 intro to evolution: history and evidence evolution explains to similarities, changes over time, and appearances of organisms anatomists in 1500s: they discovered that despite sizes, shapes, and functions, the forelimb of all vertebrates contains - homologous internal bone structures - what does homologous structures indicate about vertebrate evolution: share a common body plan and are derived from a common ancestor - humans and other animals are not designed perfect: they contain vestigial structures - appendix, back toes of pig never touch the ground, wisdom teeth, legs in snakes, tail in humans - leclerc: if each species was designed perfectly, then why do they have useless and potentially harmful structures? - must have serve purpose in the past - charles lyell: given enough time, simple, observable geological processes could create the physical world. there is no need to invoke a divine creator - principle stratigraphy: sediments accumulate on top of each other through time, greater depth must reflect greater age - william smith: mapped rocks and fossils in britain in different geological strata, found species that were extinct, failed to find many species that are abundant today - inferred that the history was a series of chapters, each chapter contained a unique collection of species. - jean-baptiste lamarck: first to propose a theory of evolutionary change - it was called the principle of use-and-disuse (or inheritance of acquired characteristics) - ex: the lengthening of a giraffe’s neck - he postulated that body parts or organ systems grow over one’s lifetime in response to use - these change are transmitted to offspring - problem: the available evidence at the time contradicted this theory b/c acquired traits are not transmitted to offspring - thomas malthus: argued that populations grow exponentially and produce more offspring than can survive  - essay on the principle of populations: despite increases in food supplies, man was no better off, because that causes an increase in population size anyways - thus, a large portion of society still faced poverty and famine charles darwin and the voyage of the beagle major discoveries 1. found fossilized glyptodonts in argentina had similar features to living armadillos a. interpretation: armadillos are living relatives of glyptodonts 2. many different species of armadillo in south america, which occupied different habitats, and were different than the ones in europe a. interpretation: different common ancestors 3. south america nutria and european beaver differ in appearance a. interpretation: both species evolved independently from different ancestors, but currently fill a similar ecological niche 4. galapagos finches varied from island to island, different beaks with varying purposes a. interpretation: they all shared a common ancestor b. isolated populations of finches evolved specialized adaptations based on what resources/food was available on their respective islands observations after return to england 1. even closely related organisms exhibited large variations of variation a. ex: puppis from the same litter, kittens from the same liter, large differences in plumage across strains of domestic rock pigeons 2. many traits are heritable, and that humans exploited heritable differences between individuals to selectively breed for individuals with the most desired traits a. ex: quality of crops, selective breeding pigeons to make them fancy b. artificial selection the origin of species charles darwin and alfred russel wallace ach independently proposed a similar mechanism for biological evolution fundamental premise of evolution theory - all living creatures share a common ancestor - we can draw a tree of life to show how all species are related to one another - evolution is a process by which one species movies rise of another, the growth of the tree is ongoing natural selection: darwin hypothesized that an analogous process to article selection occurred in nature. ex: the divergent bill/beak features in the galapagos - human population increases exponentially, while food production increases linearly evolution by natural selection can occur when: a. if a population contains variation for some character b. if that character is at least partially heritable (i.e, differences among individuals are at least partially due to differences in genes they inherited from parents) c. if some variants survive and reproduce at higher rates than others gregor mendel deduced the basic principles of genetics: 1. inheritance involves the passing of discrete units of inheritance, or genes, from parents to offspring 2. during reproduction, the inherited factors (now called alleles) that determine traits are separated into germs cells by meiosis and randomly unite during fertilization 3. genes located on different chromosomes are inherited independently of each other limited of darwin’s work: he did not propose a genetic mechanism for the variation observed julian huxley: modern synthesis october 14, 2024 microevolution microevolution: small-scale changes within populations, often in response to environmental challenges or chance events macroevolution: large-scale evolutionary patterns in the history of life genetic variation 1. qualitative variation: when a trait exists in two or more discrete states in the same species a. ex: snow geese: blue or white, the polymorphism because individuals tend to associate and mate with other geese of the same color, petal shape (pointy vs. curved) 2. quantitative variation: when a trait exists across a continuum of values a. ex: difference in heights, running speed, or body weight b. a histogram (bell curve) is used to show variation in data i. a broad, low curve indicates a lot of variation among individuals ii. a high, narrow curve indicates little variation among individuals evolutionary forces can only act on traits that have a genetic basis, environmentally determined? population genetics gene: a region of dna that encodes for a specific protein or some other “gene product” alleles: alternate versions of the same gene (B or b) - ex: our blood type (A, B, AB, or O) is determined by which alleles of the ABO we have genotype: the genetic makeup, or set of alleles of a diploid organism (BB, Bb, bb) - genotype frequencies: the proportion of individuals possessing each genotype phenotype: observed characteristic of an organism, based on genotype - allele frequencies: the number of times the allele of interest (ex: B or b) is observed in a population divided by the total number of all alleles at that particular genetic locus in the population dominant: B, means that both BB and Bb genotypes will have the same phenotype. Having any B means you have that phenotype recessive: b, only phenotype will display this phenotype codominant: Bb is a blend of the two. for example, B codes for red flowers, b codes for white, Bb result in pink flowers is a population evolving? you can test for changes in allele frequencies (B or b) over successive generations - if allele frequencies change, then you infer that evolution has occurred - a change in allele frequencies is not necessarily beneficial. the change could have a beneficial, neutral, or deleterious effect on the reproductive success of the individuals in that population. hardy-weinberg equilibrium model - permits one to calculate allele frequencies in a population - when a population is in h-w equilibrium, allele frequencies do not change allele frequencies do not change across successive generations - if allele frequencies change across generations, then it demonstrates that the population is evolving hardy-weinberg equilibrium model how do you count alleles with the h-w equilibrium? - assume one gene determines hair color in cats, that there are two alleles for this gene (B and b) - B for black hair, dominant - b for white hair, recessive - frequency of dominant allele = p - frequency of recessive allele = q - because allele frequencies must add to 1: p + q = 1 frequency of homozygous dominant (BB): p x p = p^2 frequency of heterozygotes (Bb): (p x q) + (p x q) = 2pq frequency of homozygous recessive (bb): q x q = q^2 because the frequency of all individuals must add to 1: p^2 + 2pq + q^2 = 1 suppose a population consists of 1000 cats (840 black, 160 white), and that white is the recessive trait genotype frequencies: 0.84 black, 0.16 white (bb) q^2: 0.16, q = 0.4 given that 1 = p + q, 1 = 0.4 + 0.6 how to explain the differences between predicted and observed frequencies? 1. greater immigration and/or survivorship 2. a small percentage of the hybrids (Bb) either emigrated or died 3. most cats with bb have either emigrated or died causes of evolution 1. mutation - factors with uv light and some chemicals cause random and heritable changes (i.e: mutations) to dna - important in that they create new dna sequences for a particular gene, resulting in new alleles - can be beneficial, neutral, or harmful, depending on their context or location, most are harmful - for most multicellular organisms, only those mutations that can occur in germ cells (i.e., sperm and eggs) are transmitted to offspring. mutations in these cells are passed onto offspring - negatively impacts reproductive success (offspring less fit) 2. gene flow: movement of organisms or their gametes (e.g., pollen) from one population to another - dispersal agents (e.g., wind or animals) are responsible for gene flow in plant populations - depends on the degree of genetic differentiation between populations and the rate of gene flow - unpredictable effects on reproductive fitness, may introduce, beneficial, neutral, or negative alleles to a population 3. non-random mating (sexual selection): selection of mates based on their phenotype - often increases reproductive success of individuals with “unusual” traits (e.g., coloration, size, odor or behavior). this process could increase the frequency of alleles with positive, neutral or harmful impacts on reproductive success. 4. genetic drift - founder effect: when a few individuals start a new population, they carry only a small sample of the original population’s genetic variation - population bottleneck: factors like disease, starvation and drought can cause a population’s size to plummet, reducing the number of individuals and hence the genetic variation - genetic drift can also eliminate rare alleles (e.g., red balls in the above example). it can also make the new population genetically distinct from the original population. - is often harmful for reproductive success because of lost genetic diversity 5. natural selection - the process by which heritable traits (e.g., cryptic coloration) enable some individuals to survive and reproduce better than others, and thereby become more common in subsequent generations - it can either cause one allele to replace another or increase allelic variation - what is the effect of natural selection on reproductive success? positive! this is because it can cause the evolution of adaptations to local environmental challenges october 16, 2024 speciation incomplete dominance: blend of the two Bb, red + blue = purple codominance: both traits are expressed (polka dots, stripes) types of natural selection 1. directional selection: shift in population mean in one direction by favoring variants at one extreme of the distribution 2. disruptive selection: favors variance at both ends of the distribution, maintaining allelic diversity 3. stabilizing selection: removed extreme variants and maintain intermediate types constraints on natural selection 1. selection can only act on existing variation 2. evolution is limited by historical constraints: evolution co-opts existing structures and adapts them to novel situations 3. adaptations are often compromises: there are trade offs! speciation: the process of species formation 1. biological species concept species: group whose members have the potential to interbreed in nature and produce viable, fertile offspring, but do not produce viable, fertile offspring, with members of other such groups - although appearances are helpful in identifying members of the same species, it does not define species. strengths: provides an intuitive and testable set of criteria for defining a species, explains why individuals of the same species often look similar weaknesses: it is useless classifying species that reproduce asexually and extinct organisms, impractical to determine whether members of geographically disparate populations are interfertile 2. morphological species concept: species: group of organisms that are morphically similar to one another, but distinct from other similar groups strengths: can be applied to extinct organisms and fossils, permits us to distinguish many species, using measurable external traits weaknesses: some species look similar, but cannot and do not interbreed, species have so much variation, some are polymorphic, some have plastic traits 3. phylogenetic species concept: species: irreducible group whose members are descended from a common ancestor, who share a combination of defining traits, uses morphological and genetic data strengths: no reproductive criteria, can apply to any group or organism, include the history in the formation of species weaknesses: you need detailed morphically, physiological, and/or genetic data, slight differences can be found among individuals -> encourages the division of individual species mechanisms of reproductive isolation (ri) - mechanisms that limit reproduction between members of different species - pre-zygotically: before the formation of the zygote/fertile egg 1. ecological isolation: irrespective of the of whether two species are interfertile, they occult different habitats and thus rarely encounter one another in the wild 2. temporal isolation: species that live in the same area often breed at different times of the day or year 3. behavioral isolation: many males use species-specific signals to attract mates. each species signal has no impact on females of closely related species 4. mechanical isolation: differences in structure of reproductive structures and organs and other body parts can physically prevent successful mating 5. gametic isolation: different species have non-mating receptors on gametes: eggs and sperm are incompatible, and are not fusing to form the zygote - post-zygotically: after formation of the zygote 1. hybrid inviability: some hybrid offspring do not complete development a. they can form the zygote, but the zygote cannot develop fully 2. hybrid sterility: hybrid offspring cannot produce functional gametes a. offspring become sterile 3. hybrid breakdown: interspecific hybrids can be partially fertile, but their offspring are inviable or sterile a. can produce viable hybrids, but the offspring have chromosomal abnormalities * prezygotic barriers have evolved before postzygotic, this is b/c they often require fewer genetic changes, does not waste gametes, postzygotic require gradual genetic mutations types of speciation: allopatric (different, homeland) speciation: sympatric (together) speciation: three main mechanisms for sympatric speciation: 1. polyploidy: a species may originate from an accident during cell division that results in extra sets of chromosomes, preventing it from successfully reproducing with individuals of that species. (for example, plants with 4n rather than 2n) 2. habitat differentiation: subpopulations can use different resources or habitats, thus reducing gene flow between subpopulations, resulting in speciation 3. sexual selection: female preference for male traits can result in the formation of subpopulations with reduced gene flow, resulting in speciation october 21, 2024 macroevolution: broad pattern of evolutionary change across time fossils: remnants, impressions, or traces of organisms that have preserved in the earth’s crust paleogenetics: allows scientists to extract dna fragments from ancient specimens, can be used to date and classify organisms limitations of fossil records: - most organisms decompose quickly - must be quickly covered by sediments and anoxic - geological processes can alter, destroy fossils - hard to find incomplete and biased towards species that were: - abundant and widespread, made of hard materials (shells, skeletons) that fossilized well principle of stratigraphy tells us the sequence not the age radiometric dating: a method of aging fossils that uses the decay of radioactive elements a chemistry primer: - isotopes are atoms with different numbers of neutrons - radioisotopes generally have more neutrons and are often unstable - radioisotopes undergo radioactive decay to a more stable atom with a specific half-life - parent isotope (e.g., c-14) decays at known half life into daughter isotope (e.g., n-14) - half-life is the amount of time for half of the parent isotope to decay into daughter isotope. - by measuring the radioisotope ratio (e.g., c14/c12) in the sample/sediment versus in present similar tissue, we can estimate the age of the fossil. radiometric dating for older fossils - carbon isotopes can be used to date fossils up to 75,000 years old - dating older fossils requires the use of radioactive isotope with longer-half lifes - however, organisms do not use radioisotopes with long half-lives to build bones or shells - older fossils are dated with radioisotopes found in surrounding layers of rock fossil records: - many past organisms were unlike those living today - many organisms once common are now extinct - new groups arose from previously existing ones major transitions:  1. earth formed about 4.6 billion years ago a. 4.6 bya, formed when rocks and dust condensed around a young sun b. rock and ice from newly formed solar system bombarded earth, creating tons of heat and vaporizing all water c. 4 bya, bombardment stopped, and water vapor condensed into oceans d. 3.5 bya, first fossil evidence of bacteria 2. how did life arise? (not going to be asked on an exam) a. abiotic molecules synthesize into small org, such as amino acids and nitrogenous bases b. small organic molecules joined into large molecules, like proteins and nucleic acids c. molecules became packaged in membranes called protocells that maintained an internal chemistry separate from their surroundings d. molecules self replicate, making inheritance possible prokaryotes: do not have distinct nucleus or organelles, most unicellular, but can form colonies, small, reproduce by binary fission, short generation times, rapid adaptation to natural selection 1. first transition: prokaryotes, stromatolites are layered rocks that form when prokaryotes bind thin films of sediment together, fossilized stromatolites dating from 3.5 bya are the earliest evidence of life on earth 2. transition two: great oxygenation event: over 1.6 billion years, photosynthesis arose in prokaryotes, produced oxygen in the sea, dissolved iron reacted with oxygen to precipitate into iron oxide that formed a band of red layers in rock, oxygen dissolved into the sea, once sea was oxygenated oxygen turned the atmosphere from anaerobic to aerobic a. impacts of oxygen revolution: i. oxygen can damage cells and inhibit enzymes = extinction and seeking refuge in anaerobic environments ii. others adapted, used oxygen from cellular respiration single-celled eukaryotes via endosymbiosis - endosymbiosis when a prokaryotic cell engulfed a smaller cell that could use oxygen through respiration - anaerobic cell would have benefitted from a smaller cell that could use oxygen through respiration - over time, the host and endosymbiont would become interdependent, forming a single organism with a mitochondria serial endosymbiosis: - where another bacterial cell capable of photosynthesis was engulfed, cell become a plastid a third endosymbiosis?  - nitrogen fixation? - of marine nitrogen fixing bacteria has created the nitroplast multicellularity: the origins of eukaryotic cells sparked diversification of more complex and multicellular organisms cambrian explosion: animals evolved 700 million years ago, started as sponges, mollusks, and cnidarians - first evidence of predation with adaptations for claws and large bodies as well as defensive adaptations, such as spines and body armor colonization of land: 500 million years ago fungi, plants, and animals, arthropods were first to colonize land, evolution of new adaptations (prevent desiccation, to walk, etc), mutualisms between plants and fungi are found in oldest land plants mass extinction 1. late ordovician, 440 mya a. period of global cooling, massive glaciers, eliminated marine organisms, wiped out more that 60% of all marine invertebrates, but did not dramatically shift ecosystems of the dominant players 2. late devonian, 360 mya a. oceanic volcanism, global cooling, declines in sea level and increased ocean anoxia, about 50% of all genera of animals went extinct over a period of several million years 3. permian extinction, 250 mya a. high volcanic activity, atmospheric co2, global climate warmed, ocean acidification, eutrophication, multiple meteor impacts b. the great dying, 70% of terrestrial species, 10 millions for life to recover from this calamity 4. late triassic, 200 mya a. climate change, volcanic eruptions, asteroid impacts, 50% of all animal species went extinct 5. late cretaceous, 66 mya a. volcanos, meteor strike in yucatan peninsula 6. evidence for asteroid impact hypothesis: rock samples, crater, had iridium, extremely rare metal on earth october 23, 2024 phylogeny and systematics taxon: a group at any level of hierarchy is called a taxon phylogenetic trees show presumed evolutionary relationships between different organisms - they are inferred by identifying traits or characters that vary across species and are heritable - physiological, anatomical, and behavioral - molecular, biochemical - often reflect a shared ancestry reading phylogenies: common ancestor shown by branch point sister taxa are groups that share a common ancestor that is not shared by any other group hatch mark: represents a character shared by the groups up until that mark vertical and diagonal trees construct a table of characters that distinguishes the vertebrates in the different taxa, select the outgroup, a taxon very different that the others but still share an essential traits with the organisms, construct a phylogenetic tree that depicts the hypothesized lines of evolutionary descent from a common ancestor, principle of parsimony: the simplest plausible explanation for a phenomenon is usually the best, the “best” tree is the one that require the smallest number of evolutionary changes, assuming it is unlikely that the same trait evolved twice in the same lineage cladistics: classifying organisms based on common ancestry a. monophyletic group i. includes an ancestral species and all its descendents b. paraphyletic group i. includes an ancestral species and some of its descendants c. polyphyletic group i. includes distantly related species but not their more recent common ancestor ancestral vs. derived traits  - shared ancestral traits: trait that originated in an ancestor of the taxon - shared derived trait: trait that is shared by all members of a taxon but not the ancestor the phylogenetic relationship between taxa is determined by the number of derived traits they share homology: phenotypic and genetic similarities due to shared ancestry. these are what we want to use for our trees analogies: similarities between organisms that are due to similar environmental or selective pressure (convergent evolution), not due to shared ancestry convergent evolution: the independent evolution of similar features in different lineages october 28, 2024 the diversity of life i molecular approaches dna: from our dna we get a dna sequence, specific base pairs, specific order - every base pair can serve as a separate, independent character for analysis - molecular dna can be used to compare distantly related organisms that do not share any morphological characters - many bacteria and viruses lack easily identifiable morphological characters -> therefore, dna approaches prokaryotes: no distinct nucleus or organelles (no mitochondria, no chloroplasts), mostly unicellular, but can form colonies, really small, reproduce by binary fission, can reach high densities, short generation times, rapid adaptation to natural selection autotrophs manufacture energy and o2 from inorganic sources and uses co2, phototrophs obtain energy from light chemotrophs obtain energy from chemicals heterotrophs obtain energy from consuming organic matter and produce co2 mixotrophs obtain energy in both ways motility: 50% of prokaryotes exhibit taxis, the ability to move toward or away from a stimulus - chemotaxis - movement towards/away from a chemical stimulus flagella are common structures used for movement, they can be in one place or scattered throughout surface of the cell prokaryotic diversity - today we use metagenomics to obtain entire prokaryotic genomes from environmental samples (many of these cannot be cultured), soil samples can contain 10,000 species domain bacteria (prokaryotic) - metabolic diversity - consumers or decomposers - some aerobic, other anaerobic - diverse range of environments, h.pylori - some move via flagella 1. gram-positive bacteria, gram-negative bacteria  - gram-negative bacteria have cell walls: a plasma membrane, and then peptidoglycan layer, and outer membrane - gram-positive bacteria: inner plasma members, thick ass layer of peptidoglycan - beneficial bacteria - autotrophic prokaryotes, use photosynthesis, is the basis of the food web - nitrogen-fixing bacteria, transform atmospheric nitrogen into forms available to other organisms - form mutualistic and symbiotic relationships - gut health! - human intestines are home to about 500-1000 species of bacteria - intestinal bacteria cells collectively outnumber all human cells in the body by a factor of ten - bacteroides thetaiotaomicron has genes involved in synthesizing carbohydrates, vitamins, and other important nutrients - bacterial fermentation, bacteria break down carbohydrates and amino acids to obtain energy for growth exotoxins and endotoxins - causes disease by releasing exotoxins and endotoxins - exotoxins are proteins secreted by bacteria that can cause disease even if bacteria is no longer presence - diarrheal disease, accumulation of toxins - endotoxins are lipopolysaccharide components of the outer membrane of gram-negative bacteria, they are released when the bacteria die and cell walls break down - salmonella causes food poisoning, then releases endotoxins antibiotics - minor differences in dna replication, transcription, and translation between eukaryotes and prokaryotes - bacterial cells walls: peptidoglycan - eukaryotic cell walls: cellulose and chitin - these difference allow antibiotics to kill bacterial cell growth without harming human cells antibiotic resistance: because… 1. large population sizes 2. rapid growth 3. incorrect antibiotic usage and overuse  4. horizontal gene transfer: is the movement of genetic material between organisms other than transmission of DNA (vertical transmission) from parent to offspring (reproduction) a. for every antibiotic now in use, at least one species of bacteria has developed to it domain archaea (prokaryotic) - share molecular and cellular traits with both bacteria and eukarya extremophiles: live in extreme environments that are uninhabitable to most organisms - what you should know ^^^ - desert, nuclear contamination, acid mine, salt lakes, deep sea, anoxic lakes, permafrost, volcanoes, etc. - methanogens: break down organic carbon into methane which is also a major greenhouse gas - found in digestive tracks of humans and ruminants - can be used for biogas production and sewage treatment domain eukaryotes ancestral cell -> heterotroph (cellular respiration) mitochondria, engulfed photosynthetic bacteria - > early photosynthetic eukaryotes (plastid) protists: all eukaryotes that are NOT fungi, plants, or animals - are not monophyletic, are paraphyletic (no common ancestor) 4 supergroups 1. excavata - generally have an “excavated” groove on one side of the body (just need to know this) - diplomonads: giardia, waterborne pathogen eek - euglenozoans: sleeping sickness caused by trypanosoma 2. SAR a. stramenopiles have characteristic flagella with numerous fine, hairlike projections, some are most important photosynthetic organisms on the planet 1. specifically: diatoms - unicellular algae (phytoplankton) - glass like wall made of silica - cell walls consists of two parts, like a shoe box, that provides protection against crushing jaws of predators - fossilized diatom walls create sediment called diatomaceous earth - diatoms as a co2 sink for the ocean  - during diatom blooms, dad diatoms sink to ocean floor, where it takes decades to decompose -> effective co2 sink, “pumping” co2 to the ocean floor - iron is a limiting nutrient for diatoms in the ocean - some scientists advocate fertilizing the ocean with iron to cause diatom blooms to capture/store mor eco2 and store it in the ocean floor - fertilize ocean with iron, have the blooms, fall to the ground, stores co2 2. brown algae are multicellular marine photosynthetic organisms - unlike plants, they lack true tissues and organs - brown and olive color comes from carotenoids in their plastids 3. alveolates have membrane-enclosed sac (alveoli) just under the plasma membrane a. dinoflagellates - abundant components of marine and freshwater phytoplankton - they have two flagella housed in the grooves of armor-like cellulose plates that surround the cell - beating of the spiral flagella causes dinoflagellates to spin as they move through the water - causes red tides and toxic algal blooms - massive die-offs - in this case, these species produce allelopathic toxins that are used to kill off competing algal species. however, in high densities, they can have lethal effect on other creatures as well - these blooms can also cause anoxia (Via bacteria growth) further exacerbating marine mortality - water appears brownish red or pin dye to the carotenoids present in their plastics - zooxanthellae are dinoflagellates! - apicomplexans: nearly all are parasites of animals - apex contains a complex of organelles specialized for penetrating host cells and tissues - plasmodium evades the host immune system by living inside cells and continually changing its surface proteins (don’t need to know the life cycle) 3. archaeplastida - plastids arose when a heterotrophic protist acquired a cyanobacterial endosymbiont  - the photosynthetic descendants of this ancient protist evolved into red algae and green algae - plants are descended from the green algae - red algae and not green - accessory pigment called phycoerythrin masks the green of chlorophyll giving red algae its color 4. unikonta - fungi and animals! very diverse clade - amoeba: slime molds - produce fruiting bodies that aid in spore dispersal, just like fungi, fruiting bodies have independently evolved in both lineages - convergent evolution, analogous - dictyostelium: a cellular slime mold - study evolution of multicellularity - what you need to know: all of these individual amoeba, slime olds, and then form a fruiting body - a stalk, the fruiting body that disperse spores - some have cheat mutation, you never form the stalk only fruiting bodies heheh - why don’t we all cheat? and then no one forms the stalk, then essentially there would be lower fitness - cheating cells lack a specific surface protein, non-cheater can tell who is a cheater, and therefore would not form a stalk - recognition system! the ecological role of protists (takeaways) - 30% of the world’s photosynthesis comes from protists - key symbiotic partner for coral reefs - responsible fo massive fish kills via red tides - protist parasites cause massive human health impacts october 28, 2024 the diversity of life ii plants (archaeplastida) what to know: for the different taxa about, what supergroup they are in (ex: what group are diatoms in?) - evolved from green algae around 470 million years ago - not descended from modern charophytes, but share the same common ancestor - charophytes inhabit shallow waters around ponds and lakes where they are adapted to survive occasional drying - a durable polymer called sporopollenin prevents zygotes from drying out - a similar polymer is found on plant spores - these adaptations allowed the first plants to live permanently above the waterline - novel challenges to land: - pro: lots of new habitats to colonize with no competition - con: - scarcity of water/drying - lack of structural support against gravity - evidence of mutualistic fungi associated with the first plants on land, helped them acquire nutrients and water just like mycorrhizal fungi do today key derived traits of plants (no need the details of them, but the three derived traits) 1. they evolved this novel cycle of alternation of generations a. know that where they got one stage where with a gametophyte (n) (one copy of the chromosome), produce gametes and sperm, when they come together, they form a zygote (2n), produce a sporophyte which produce spores (n) 2. walled spores produced in sporangia a. the sporophyte produces spores in a multicellular organs called sporangia b. spore walls contain sporopollenin, which makes them resistant to harsh environments 3. apical meristems a. local regions of cell division at the tips of roots and shoots are called apical meristems b. these cells divide continuously, enabling elongation of roots and shoots for better resource acquisition early plants lacked structural support (nonvascular plants) - liverworts, hornworts, mosses (ground cover, but no verticality) plants evolve vascular tissue, facilitating larger and taller plant structures, is paraphyletic vascular plants (425 mya ago) - vascular tissue is a derived trait of vascular plants - are cells joined into tubes that transport water and nutrients throughout the body and give plants structures  - this allows plants to grow taller, outcompeting nonvascular plants for light - > leading to the first forests in 385 million years ago - early vascular plants lacked seeds consequences of vascular plants - atmospheric co2 declines as plants took it up for photosynthesis - roots broke down rocks, which released chemicals that reacted with co2 - together, this led to global cooling and glaciation due to the drop in atmospheric co2 seed plants evolved 360 million years ago key adaptations: pollen, ovules, seeds - ovules produce eggs - pollen produce sperm and are protected from desiccation which allows pollen grains to - travel long distances by wind or pollinators - fertilized eggs without water - a seed consists of an embryo (fertilized egg) and its food supply, surrounded by a protective coat - when mature, seeds are dispersed from their parents by wind or other means, enabling them to colonize distant locations - the hardiness of both pollen and seeds explains the success of this evolutionary clade * main difference: gymnosperms are not enclosed in chambers, angiosperms do have chambers (FLOWERS) gymnosperms angiosperms - the flower is a angiosperm structure specialized for sexual reproduction - in many species, insects or other animal transfer pollen from one flower to the sex organs of another - some angiosperms are wind pollinated, particularly occurs in high density plants, such as grass - as seeds develop, the ovary walls thickens and other ovary matures into a fruit - for example, a pe pod is a fruit with seeds (mature ovules, peas) encased in a ripened ovary (the pod) - fruits protect seeds and aid in their dispersal (wind and animal) fungi (unikonta) - evolved from a unicellular, flagellated protist - fungi were among the earliest colonizers of land - fossil evidence support the early mutualistic relationship between fungi and plants structure and function of fungi - hyphae go into the soil, excrete enzymes that break down organic matter and absorbs the nutrients from the soil - decomposers break down and absorb nutrients  - parasitic fungi absorb nutrients from living hosts - mutualistic fungi absorb nutrients from hosts and reciprocate with actions that benefit the host - have specialized hyphae used to exchange nutrients with their plant hosts ascomycetes - includes plant pathogens, decomposers, and symbionts - more than 25% of all ascomycete species form lichens, symbiotic associations with green algae or cyanobacteria - often called sac fungi, named for the saclike asci, in which spores are produced genus penicillium - decomposer mold - commonly found as a decomposer of food - some species produce penicillin, discovered by alexander fleming basidiomycetes - including mushrooms, puffballs, and shelf fungi - some are mutualists that form mycorrhizae - others are destructive plant parasites: rusts and smuts animals (unikonta) features that all animals share - eukaryotic, multicellular - cells lack cells walls - heterotrophic, don’t make their own energy - use oxygen to metabolize food - motile at some times in their lives - specialized tissues and organ systems deliver nutrients to cells, and carry away wastes - most have sensory and nervous systems that allow them to receive, process, and respond to information phylum porifera, sponges - lack true tissues (ex: nervous system) - to move to a new location, flagellated larvae are released and attack to substrates and undergo metamorphosis into sessile adults - filter feeders - waterborne food particles flow into spongocoel through pores, and get trapped and ingested by specialized cellsongo evolution of tissues: tissues are collection of specialized cells that act as a functional unit - phylum cnidarians - hydra, coral, sea anemones, and jellyfish - simplest animals with specialized tissues - radially symmetrical - lack a brain: instead, they have a diffuse nervous system (nerve net) permits coordination of simple movements  - their gastrovascular cavity has a single opening (the mouth), which serves digestive, circulator, and locomotory functions (in hydra) - gas exchange and excretion occur by diffusion evolution of bilateral symmetry and three germ layers - symmetry of body form - most animals are radially or bilaterally symmetrical - three germ layers: ectoderm, endoderm, and mesoderm - allowed for body cavity formation and organs lophotrochozoa phylum platyhelminthes (flatworms) - planara, cestodes, trematodes, and monogeneans - lack an internal body cavity, and any form of circulatory or respiratory system - have a primitive brain - parasitic clades: tapeworms, schistosome, monogenean phylum mollusca - mostly marine (clams, snails, octopuses) - visceral mass contains digestive, excretory, reproductive systems, and heart - the muscular headfoot permits locomotion and escape - the mantle folds of body that enclose the viscel mass, may secrete a calcium carbonate shell phylum annelida (Segmented words) - bobbit words, earthworms ecdysozoa phylum arthropoda - includes more than half of the animal species on earth - insects, spiders, crustaceans, millipedes, centipedes,and beetles - segment body is encased in exoskeleton that is shed - head, thorax, abdomen - highly organized central nervous system, with a wide array of sensory systems deutermonia - chordates - have a notochord that supports the embryo from head to tail (primitive backbone) tunicates - sessile as adults, swim around as larvae - has notochord as larva, but not as adults - filter feeders, pulling water in and getting nutrients vertebrae subphylum vertebrata - have internal body skeleton that provides structural support and protection for the nervous system and other organs - only animals that have bones - muscles attach to bones, and permit rapid movement - birds, mammals, bony fish, reptiles, amphibians class chondrichthyes (cartilaginous fishes) - lost bones, lost the traits, entirely composed of cartilage (skates, rays, shark) - more lightweight and flexible bony fish - teleosts are the most diverse and successful bony fish - they have modifications in their jaw and jaw musculature for predation - gas-filled swim bladder that increases buoyancy evolution of limbs of digits - class amphibia (frogs, salamandersm caecelians) - this moist skin that has gas exchange occurring - eggs are laid in water, they hatch into larvae, which metamorphose into adults evolution of a amniotic egg - class reptilia - three adaptation help reptiles conserve water, and hence in dry habitats 1. tough,a waterproof skin containing keratins and lipids, which prevents dehydration 2. amniote eggs, which can survive and develop on dry land 3. use uric acid as the waste product to nitrogen metabolism - class aves (birds) - feathered reptiles without teeth - diverse adaptations for flight - hollow bones so they are lighter - reduced number of bone elements - big flight muscles for strength - feathers that streamline the surface of the body to help with flight - class mammalia - four key adaptations 1. high metabolic, 4-chamber heart, and high-pressure circulatory system 2. specializations of jaw, teeth, and respiratory system to eat variety of different foods 3. mammary glands produce an energy-rich milk for offspring***** what defines 4. complex brain permits higher-level information processing and learning three different types of mammals - marsupial: young crawl out of the mother’s uterus, locate a teat in the abdominal pouch, there they complete embryonic development - monotreme: leathery shelled egg, once young hatch, they lap up milk secreted form glands in the mother's abdominal skin - placental young complete embryonic development in the mother’s uterus, nourished by the placenta