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BIOA02 Module 3 Lecture Notes

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Biological Sciences

BIOA02 Module 3 Fungi: • Earth’s premiers decomposers • Obtain energy by breaking down organic molecules synthesized by other organisms (heterotrophic) o Saprotroph: decomposers o Symbiont: from living organisms (pathogens or mutalists)  close relationships with each other Categories of Fungi Decomposers: breaking down organic material Pathogen/parasites: (+/-) “infect” living organisms. Take carbon sources directly from host, host is negatively impacted by the interaction. May also act as decomposer after host is dead Mutalists: Take carbon sources directly from host but engages in a mutually beneficial interaction by providing a service in return, usually providing water or nutrients from the soil PLAY CRITICALROLES INALLTERRESTRIALECOSYSTEMS Basic Facts • Some unicellular o Budding yeast: wine, beer, bread (produce asexually and sexually) • Most are multicellular o Mostly composed of mycelium: a mass of hyphae (Mostly underground) o Hyphae: thread like filaments of a fungus (NOT ROOTS) Apical growth: Hyphae grow outward by growth at tips Absorptive nutrition: Fungi secrete enzymes into their environment, breaking down large organic molecules into smaller one that can be absorbed into their cells (hyphae transport water and nutrients through cellular streaming) Hyphae/ mycelia structure • Fungi, like plants have rigid cell walls. Unlike plants, the walls are made of chitin, a nitrogen- cased polysaccharide that is the primary components in insect exoskeletons • Therefore little more closely related to animals • Cross walls (septa) partition some hyphae into cell compartment • Pores in the septa allow the cytoplasm and organelles to move between hyphal cells • Cytoplasmic streaming, allow nutrients to flow through the hyphae Reproduction: • Asexual: hyphae cells can form haploid spores or hyphae detach and form a new clonal individual • Sexual: Three steps o Plasmogamy: the fusion of hyphae between two genetically different individuals (still have two nucleus) o Karyogamy: the fusion of two sexually compatible haploid nuclei (nucleus fuse) o Meiosis: division of the diploid cell to haploid progeny following the two sequential rounds of nuclear and cellular division. The progeny are spores Chytrids: • Most ancient group; paraphyletic • Require moist of aquatic environment for motile spores (flagellated therefore need water) • Most are unicellular saprotrophs Chytridiomycosis is a disease of amphibian species caused by species of parasitic Chytrids. Chytridiomycosis outbreaks are no major cause of amphibian declines in the world Z ygom yc e te s(Z Zygomycetes: c ota ) • Ancient Ancient anand paraphyletic (>1 ancestor) commonancestor)Aseptate hyphae (no cross walls between hypal cells, just one long tube) Aseptatehyphae (oducrsnique zygospores which wallsbetwe•nhypFORMS THE) sporangia FOOD MOULDSspores ProduGlormeromycetesore whichgermi•atesSmall phylum – 160 members sporangia–•roduAll of the “gloms” are mutualistic with Formsther “moulds”wea e familiarwithonfood!rise about hald the fungi in soil –HUGE BIOMASS. They are symbiotic •ith Can increase plant root SA100-1000+ x Fig. 23.8, p. 531 • Comprise the endomycirrhizae or arbuscular mycorrhize • Arbuscular mycorrhize colonize the cells of host plants, forming arbuscles (little trees) which exchange surgar, water and nutrients directly with plants o Plants feed fungi photosynthate (sugar) o Fungai feeds plant water and dissolved minerals Ascomycetes • Sac fungi: named for the sac-like “fruiting body” of the fungus • Extremely numerous -> 30,000 species • Morphologically diverse, multicellular fungi • Many are saprotrophs, but common in mutalisms. Some are pathogens or parasites.A few are predatory – they’re carnivores that trap their prey in noose- like hyphae Basidiomycetes • Most well- known fungi group (mushroom) • Mushroom: fruiting body, basidiocarp, the spore- producing structure of the basidiomycota. • Many mushrooms sprout from one individual – the mycelia can spread of km • Most multicellular – few unicellular • Key decomposers of cellulose and lignin – the most indigestible molecules in plant debris Lecture 2 Population ecology Ecology is the study of: • The distribution and abundance of organisms • The interactions among organisms (biotic interactions) • The interactions between and their non-living environments (abiotic interactions) Levels of Organization Population All the individuals of a single species that live together in the same place and time Characterized by: • Size, the number of individuals in the population • Distribution, or the limits of their geographic range • Dispersion, the distribution of individuals within their range • Age Structure, the relative numbers of individuals in different age groups • Generation Time, the average time between an organism’s own birth and the birth of its offspring • Sex ratio, the relative number of males vs. females • Proportion reproducing, proportion of individuals in a population actually producing offspring Distribution Used interchangeably with range The size of a species range may relate to its rarity • Avery large range may suggest that a species is common and adaptable • Avery small range suggests that a species is locally endemic or specialized to a particular habitat Density • The number of individuals per unit area • Bigger animals have lower population densities Dispersion Distribution of individuals within their range • Clumped • Uniform • Random Sex ratio & proportion reproducing • Sex ratio is the relative proportions of males vs. females in the population • The number of females usually has a larger impact on population growth than the number of males • The proportion reproducing is the actual proportion of males or females contributing to population growth Age structure and generation time • Age structure is the relative numbers of individuals in age groups • Generation time is the average time between an organism’s own birth and the birth of its’offspring (first reproductive event) • Age structure and generation time are related through the study of demography, or the study of the processes that change a population’s size and density through time o Each category in a demographic chart is known as a cohort o Age specific fecundity:  Fecundity is the potential reproductive capacity of an individual or population  Age specific fecundity is the actual number of offspring produced by surviving females in each cohort at a given age level  Age-specific mortality rate is the proportion of individuals that died by the end of a given age interval  Age-specific survivorship rate the proportion of individuals that survived by the end of a give age interval  Proportion of original cohort alive always decreases over time Age specific mortality rate is related to an organism’s life history Life history is the lifetime pattern of growth, maturation and reproduction in a population or species Energy Budget • All individuals have a limited energy budget & time. No individual, genetic or morphological, is immortal • An Individual’s energy budget is determined by its resources, which determine its health and longevity • The energy budget can be determined from the time an organism in conceived, it is usually limited by: o Food o Water o Appropriate space (nesting, foraging, hiding) o Time Energy Expenditures An organism’s energy budget is like a bank account • Checking account: energy being used in the present o Survival o Growth • Savings account: energy that is stored in the body for the future (fat, muscle, larger size) o Future growth and maintenance o Defense o Mating o Parental care An individual must allocate some of its resources to survival and growth and/or maintenance at all times IT TAKES ENERGYAND TIME TOACQUIRE RESOURCES TO MAKE MORE ENERGY Lecture 3 Tradeoffs Energy and time used for one activity cannot be used for anything else; it is an “investment” • Total energy can’t be overdrawn • Energy expended must maximize reproductive fitness • Each species’life history is based on its probability of survival and reproduction over time. These determine the organism’s life history traits o Lifespan o Age of first reproduction o Number of reproductive events o Number of offspring per reproductive event o Investment in parental care Trade-off between fecundity and parental care • Passive parental care before offspring born: o Many young = little care o Few young = more care One reproductive episode vs. several • One reproductive episode o Semelparity o Devotes all stored energy o Individual often dies immediately after o Benefit: maximum fecundity o Risk: zero fitness if organism dies before its reproductive event • Multiple reproductive episodes (spreading the risk) o Iteroparity (=many iterations) o Only some energy devoted o Benefit: fitness is spread out – one failed event doesn’t mean zero fitness! Time reproduction to high resource periods o Risk: smaller reproductive events. Early death = low fitness Selection in Life History • Early reproduction favored o Adult survival rates low o Animals do not grow large with age o Larger size does not increase fecundity • Later reproduction favored o If sexually mature adults likely become older o If organisms grow older with age o If larger organisms have higher fecundity Life History: r vs. k selection • r = ”reproductive” organisms o Short-lived o Few reproductive events o Many offspring o Low parental care • k = “carrying capacity” organisms o Long lived o Several reproductive events o Few offspring per event o High parental care Population dynamics • Populations can grow due to: o Birth o Immigration (from other populations) • Decline due to: o Death emigration (to other populations) • Stay the same (zero change) o New individuals = individuals who die/leave Changes in Population Per Capita Population Growth Amore general way to express population growth is per capita of the population. Per capita birth rate=b=B/N (number of births in a period); per capita mortality rate=d=D/N (death in time period) Ex. In a population of 2000 field mice, if 1000 mice are born and 200 mice die in one month then: B=1000/2000=0.5 D=200/2000=0.1 r=(b-d)=0.4, therefore population is growing • When r is a constant the population grows exponentially • Even through the per capita growth rate is constant, there is an increase in the overall population growth rate because more individuals are reproducing each period Exponential Growth Model Assumptions made • Unlimited food and water • Unlimited space • No predators • No parasites, pathogens • No immigration or emigration • All deaths occur due to old age If we make these assumptions, we can calculate the population’s intrinsic rate of increasmax therefore exponential growth model is: Larger, longer-lived animals have lower rmax But the resources in the environment are limited • Resources in the environment may, however, be renewed, or made available • The max number of individuals of any species that an environment can support indefinitely (meaning resources are renewed at a constant rate) is called the carrying capacity, k • K is defined for each population, not each species. This is because K Is a property defined by the resources in the environment in which population lives • The environment’s resources, and therefore its ability to “carry” a population, can vary over time and space • Therefore 2 populations of the same species living in different environments ay have different k • R declines as resources are used up Logistic Model The logistic population growth model assumes that r approaches 0 as the population approaches k Models of Population Growth • Exponential model: o “Ideal” conditions: no limiting resources o Population growth stays the same for each generation (ex population doubles) • Logistic model o Includes effect of resource limitations o Individuals compete for resources (intraspecific competition) o Population growth goes to zero when resources are “maxed out” Lecture 4 Carrying Capacity is an Example of Population Regulation • Many factors regulate populations: change the size and growth of populations • Some factors are density dependent factors: the importance of the factor in changing the population depends on the density of the population, usually: o ↑ density = ↑ impact o Resource consumption o Predation o Health: starvation, disease spread, parasites o Territoriality/ mating o Waste accumulation o Intrinsic (behavioral) factors • Some factors in the environment are density-independent: they are external to the population and the impact doesn't depends on the size of the population o Availability of many resources o Climate variation o Natural disaster Escaping regulation – how some species boom • Invasive species are organisms that are able to spread uncontrollably. They do not experience adequate population regulation o Invasive species are usually introduced from their native range to a new area. In its new habitat, we call the species non-native, exotic, or alien o When they are introduced, non-native species sometimes escape their predators, pathogens, and parasites. These forms of regulation are not transferred or cannot survive in the new habitat o Nonnative species may also adapt to acquire more resources or utilize new habitats Invasive Species Often Share Some Common Traits • Few predators (or herbivores, for plants). These may be left behind in the native range • Adaptable. Population bottlenecks and strong selection pressures in the new range select robust, adaptable phenotypes • Reproduce quickly. Akey trait of invasive species: they have higher fecundity than co-occurring native species • Thrive in disturbed ecosystems. Invasive species are often human adapted; they thrive under condition of human disturbance. They also tend to acquire resources quickly and use them quickly, which take advantages of the resources released by the disturbances • Out-compete native species for resources. All the above traits combine to make highly competitive species who suffer fewer population regulations and acquire a larger share of resources than their neighbors Population Regulation Can Have Large Scale Consequences • The Mountain Pine beetle is a bark beetle native throughout NorthAmerica • The MPB normally, helps remove weak, old, or diseased pine trees, aiding forest regeneration • When trees are overcrowded, they compete for water and are weakened by drought • Fire suppression was the primary approach to forest management throughout most of the last century o Clears dead and dying trees/Stimulates crops to release seeds • Both fire and pine beetles are forms of density-dependent population regulation in pine trees o High densities of pine trees increase intraspecific competition for water o Trees become drought-stressed making them vulnerable to beetle attack o Beetles and drought increase mortality, making lots of standing dry fuel for fires o Fire has so much fuel that it burns insanely o Pine tree population declines as well as the beetle population Exponential growth in human populations • Past 200 years: human’s overcame usual density-dependent population regulation mechanisms • Our population now grows exponentially o Expanded into most terrestrial habitats o Increased resource availability and consumption o Reduced death rates with improved medical care and sanitation o Increased carrying capacity Humans are subject to ecological laws • We have escaped a major population crash • Technology cannot reduce resource limitation and disease forever Steps Toward Sustainability • Family planning o Create voluntary measures to reduce extreme fertility— Raise low birth rates but curb high birth rates o Birth control: available and socially acceptable • Educate women and support equality o Has the duel benefit or lowering birth rate and increase socioeconomic status in countries with gender equality • Consume sustainably o Reduce our eco footprint o Support political and social change for sustainable practices • Conserve the environment for the future Lecture 5 Animal Behavior The “Selfish” or (‘Immortal’) Gene • Organisms are vehicles for genes which “seek” to replicate themselves • Purpose of life is reproduction • Individuals who do not reproduce drop out of gene pool • Species that do not reproduce would cease to exist • Reproduction is the basic requirement for continuation of life and diversity at both genetic and species scales • Natural selection operates on the phenotypes of individuals; more successful phenotypes = more off-springs  evolutionary win Meaning of Life • High relative fitness o Individuals that produce the most off-spring who survive to sexual maturity themselves will contribute the most genes to the next generation relative to the other individuals of the same species o Compared to relative individuals of the same species, usually in the same population o Meaning of life: having healthy babies Study of Animal Behavior – Ethology • Basic mechanistic of behavior (chemical, anatomical, physiological) • Influence of development on behavior • Evolutionary history of behavior • Behavior and its relationship to survival and reproduction Organismal Behavior Must Ultimately Maximize Reproductive Fitness • Survival • Growth and maintenance • Defense • Mating • Parental care Always Under Pressure To Obtain and Maximize Limiting Resources • Limiting resources: factors in an environment essential for an organism’s survival, growth and/or reproductive success which are limited in availability o Food o Water o Space (nesting, foraging, hiding etc.) o Mates o Time Nature vs. Nurture • Instinctive behaviors • Learnt behaviors Behaviors develop through complex interactions between genes and the environment • Feedback loops occur between the potential behavior, encoded in genes and factors in the environment (food, danger, parental rearing) Instinctive Behaviors • Can be performed without prior experience • Basic necessities for survival and reproductive success • Adaptive under strong natural selection • Strong genetic basis • May involve Fixed Action Pattern (FAP): sequence of unlearned, innate behaviors that is unchangeable o Usually carried to completion once initiated o Triggered by an external sensory stimulus (=a releaser or sign stimulus) • Kinesis: a simple change in activity or tuning rate in response to a stimulus o Ex. Pilli bugs go under a leaf in dry conditions • Taxis: a more or less automatic, oriented movement toward or away from a stimulus • Fixed action o Herring gull chicks respond to sign stimulus of an adult break with a dark or red spot on the bottom o Chicks peck the spot to beg for food o Parents signaled to feed Learned Behaviors • Cannot be performed accurately or completely the first time in response to a stimulus from the response. Experience is required o Imprint learning: occurs during a critical period during early development.Animals learn to identify caregivers and suitable mates • Classical conditioning o Mental association between unrelated phenomena o Pavlov’s dog • Operant conditioning o Link voluntary operant with favorable reinforcement o Trial-error • Insight learning o Uses true problem solving o “Ah-hah!” experience; a mental process marked by a sudden and unexpected solution to a problem o Solutions can be passed through teaching others • Habituation o Lack of response to unimportant stimuli o Saves energy Survival, Growth and Maintenance • Survive juvenile years • Finding limiting resources (food) • Habitat choice • Social interactions Migration • The predictable, seasonal movement of animals from an area where they were born to a distant initially unfamiliar destination • They always return to natal site • Escape stressful, low resource seasons to seek food in less-stressful, high-resource conditions • Special requirement for unique breeding or offspring rearing conditions How Do Species Migrate? • Piloting: using familiar land marks to guide the way • Compass Orientation: moving in a particular compass direction (N or S) based sensing of the sun or earth’s magnetic field • True Navigation: Organisms nay use a combination of a compass orientation with a mental map, recognizing local cues from the environment (smell or landmark)
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