BIOS1301 Lecture notes PDF

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BIOS The distribution and abundance of organisms Distribution: - Where organisms are found, why they live where they do and the factors that limit their distribution Abundance: - How many are found in a given area, how dynamic their populations are, the factors which regular their numbers    The ...

Description

BIOS The distribution and abundance of organisms Distribution: -

Where organisms are found, why they live where they do and the factors that limit their distribution

Abundance: -

How many are found in a given area, how dynamic their populations are, the factors which regular their numbers

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The distribution and abundance of species changes over time Some species decline in abundance and range Other species increase in abundance and expand in range

Why is it important? -

Conservation, Management and policy, economic (pest species, resources, farming) Climate change Future developments

Two different approaches: -

Species level approach Ecosystem approach Changing climate  changing distribution and abundance  multidisciplinary approach

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The basic problem of ecology is to determine the causes of distribution and abundance of organisms Niche: each species occupies a niche in the community, including where it lives, what it eats, where it reproduces and its relationship to other species. The physical and biological variables that affect an organism’s well-being (n-dimensions hyper volume) Total set of environmental factors that determines a species distribution Generalists – Broad Niche, Specialists – Narrow Niche

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Organism’s Niche: -

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Single dimension Two dimension More than one dimension Factors interact (additives, multiplicative) A single factor may limit success Genetic variation Dynamic environments Lags in response

Key factors affecting the distribution and abundance of organisms: -

Abiotic (light, fire, pH, geology, isolation)

Temperature     

Explains distribution of many organisms, depending on temporal and spatial scales Affects biological processes/rates Affects regulations of body temperatures Interactions with other factors Extremes important (heat and cold)

Moisture-water    

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90-98% of protoplasm consists of water Distribution of water important in determining organism distribution Temporal and spatial scale of water availability critical Climatic warming in this century will have major impacts on the geographical ranges of species that are currently limited by temperature and moisture Polar, temperature (seasons), arid, tropical and Mediterranean Mountains

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Evolutionary history (looking at past adaptability for future range) Biotic factors Competition between species Predation (structure of trophic food levels) Mutualism: Symbiosis, commensalism, parasitism Succession

Keystone species: -

Species or group whose impact on its community and ecosystem is much larger and influential than rest (large predators, critical food organism bogong moth)

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Human impacts Habitat loss fragmentation degradation pollution overharvesting indirect impacts – feral predation

Ecological Succession: -

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Process of ecological modification by organisms Primary succession: a community develops on a site previous unoccupied by living organisms (pioneer species) Secondary succession: an existing community is disruopted and a new one subsequenty develops at the site Constantly changing with different disturbances

Biodiversity What is biodiversity? -

The variety of all living things; plants, animals, micro organisms, the genetic information they contain and ecosystem they form Explored at 3 levels: genetic, species and ecosystem

Why is biodiversity important? -

Boosts ecosystem productivity where each species, no matter how small all have an important role to play A larger no. plants = great variety of crops Ensures natural sustainability Healthy ecosystems can better withstand and recover from a variety of disasters Technology: infrared technology (zoology), sonar technology, solar panels (photosynthesis), hearing technology (insects), artificial intelligence (worm nervous systems), computer and microchip (mammalian brain)

Australia’s unique biodiversity: -

Endemic families: exclusively native to a place or biota, in contrast to cosmopolitan or introduced Biodiversity of endemic vertebrates (not fish) in 17 highest ranked countries Biodiversity of vascular plants in highest ranked countries: have specialized tissues for conducting water, include ferns, gymnosperms, flowering plants, conifers In Australia: 47% invertebrates, 42% fungi, 9% plants, 1% vertebrates

Biogeography: -

Study of patterns of distribution of plants and animal in time and spaces Due to plate tectonics: continental drift, Gondwanaland linked continents Wallace’s line: separates oriental biota from Australia biota Flightless birds prove the Gondwana countries being joined Divergence of mammals: marsupials and monotremes compared with the placentals Indomalayan-Australian: distinct species’ distribution, reflect continental processes, , , 20% mammal fauna shares, shared bats and murids (mice) Southern beech tree (Nothofagus): ancient relic trees, appeared about 84 million years ago, links southern continents, indicative of Gondwana past

Evolutionary changes in Australia: -

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Cretaceous: angiosperm (flowering plant) diversity increased, including the southern beech Nothofagus, dinosaur diversity

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Cainozoic: about 24-11 million years ago drier rainforests displaced nothofagus, appearance of eucalyptus, megafauna (diprotodons), high rainfall followed by increasing aridity

Evolutionary History: -

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Pollination of plants by birds in Australia is common (1000 plants and 100 birds) Lack of diversification by social bees in Australia compared to Europe

Origin of Marsupials: -

Living marsupials occur in North, Central and South America and Australasia Marsupial originated in North America (oldest fossil 100 million years ago) Panamanian land bridge developed 2-5 million years ago, major interchange of fauna 65 million years ago, marsupials moved from South America to Antartic and Australasia Australia marsupials evolved in relative isolation from eutherians

Marsupials: -

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7 orders and 18 families, 260-280 species characterisated by marsupium (pouch) Litters weight 1% of mother’s body mass compared to about 50% for eutherians (placental mammals) Offspring (no more than 1g) climb and attach to a teat

Adaptive Radiation of Marsupials: -

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Diprotodonts: possums, kangaroos, koalas Polyprotodonts: numbats, thyalcine, quoll

Diversity of Marsupials: -

Polyprotodonts: long mandible, lower incisors, small and unspecialized Diprotodonts: short mandible with first pair of lower incisors enlarged to meet upper incisors

Monotremes: -

Two fams: platypus and echidna Monotrema: “one opening” Retention of various reptilian features (rubbery-shelled eggs permeable) Young have well-developed forelimbs

Climate: -

Most arid inhabited continent, high variability in rainfall, considerable difference in climate between tropical and temperate regions Distribution of eucalypts and acacias in different bioregions: 13% of vascular plants dominated by two genera: Eucalyptus and Acacia Desert habitats: extraordinarily diverse and abundant lizard fauna, most herbivory in Australia by ants and termites  most are invertebrates with highly diverse communities of social insects

Key threats to biodiversity: -

Altered fire regimes Land clearing Fragmented habitats Weeds Salinity areas Altered hydrology

Extinct species: -

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Desert bandicoot Desert rat kangaroo Thylacine Lesser Bilby

Disturbance Ecology Population or ecosystem dynamics -

dN/dt = r N (where r is rate of increase) as time passes, more individuals added to the population number of individuals added is a function of the population size Logistic curve K: carrying capacity (no. individuals)

Population ecology: -

Predation, competition, disturbance, availability of resources (food, breeding) is the plateau in the graph

Balance of Nature: -

Historically ecological theory based on assumptions of equilibrium (steady state) Concept of plenitude: ‘that all potential niches were filled at all times’ Competition between organisms dominant

Successional theory (understanding how ecosystems change) -

Succession of ecosystems considered the primary process until the 1960s Increased understanding of the role of disturbance Involve biotic and physical processes creating patches at different spatial scales Succession not necessarily predictable Human disturbances increasingly important

Succession and disturbance -

Succession describes directional change in an ecological community structure and composition over time Succession follows disturbance and colonization All biotic (microorganism’s plants and animals) are affected by physical and biotic disturbances

Primary/Secondary Succession: -

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Ecological succession: process of ecological medication by organisms Primary: a community develops on a site previously unoccupied by living organisms; can occur after severe human disturbance (i.e. mining and pollution)  pioneer species Secondary: an existing community is disrupted and a new one subsequently develops at the site (i.e. forestry)

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It is constantly changing with different disturbances: through succession (orderly replacement of one plant community by another) Succession (traditional view): proceeds in a predictable manner from disturbance through changes to reach a climax It is primary autogenic (driven by changes caused by plants and other organisms in the community) Failure of a community to reach the climax is a result of temporary obstacles

Non-Equilibrium response: -

Communities can get stuck Thresholds stop succession Maybe multiple climax states Outside forces may affect trajectory Physical or biotic controls exists Physical or biotic controls may be under human influence

Ecological Climax: -

Notion of ‘climax’ concept is largely dead Communities are constantly changing and environmental heterogeneity and disturbance regimes rarely lead to a pre-determined ‘equilibrium’ community

Disturbance ecology: -

Any relatively discrete event that disrupts ecosystem, community or population structure and changes resources, substrate availability or physical environment Biotic (microorganisms, plants and animals) or abiotic (physical or chemical) Types: weather, fire, floods, droughts…. Disease, insections, burrowing animals, predators

Weather disturbance: Cyclones are influential in tropical Australia, cutting swathes through forests and creating patches -

Wind may affect individual trees, patches or forests Allow successional growth Low pressure systems over warm tropical water: gale force winds Cyclone Yasi (200km/hr) ; February 2011 Cyclones significant disturbances (i.e. great barrier reef, rainforests, floods) Example: The Pink Pigeon in Mauritius depleted due to forest destruction and rats down to 60 birds, however through recovery in captive breeding their numbers have increased again

Volcano and earthquake disturbance cause significant impacts -

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Mt. St Helen destroyed 16km squared of forest Primary succession follows over lava flows

Landslide disturbance -

Laconchita landslide of March in Ventura country along California coast Followed by colonization of ecosystem

Fire disturbance -

Critical for structure and composition of many plant communities in Australia Many species depend on fire during their life cycles Fire disturbance regimes have changed with fire suppression and burning

Water disturbance -

Floods cause erosion and changes in geomorphology Constantly destroying and repairing floodplain and wetland areas Heavy rainfall followed by flooding can cause landsides Many plants and animals depend on varying flood regimes

Drought disturbance -

Many animals and plants require a dry phase Allows for the buildup of nutrients and organic matters Colonization by dryland plants and animals

Biotic disturbance -

Insects, disease (bird flu, H5N1), burrowing animals and large animals

Human disturbance: -

Habitat loss, forestry, river regulation, altered fire regimes, overharvesting, climate

Disturbances create patches: -

Open spaces: gaps in forests created by lightening or old age of trees More resources Patchiness: relatively discrete spatial patter; not necessarily internally homogenous; has relationships to matrix around it and other patches

Disturbance regimes: -

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Characteristics: timing, size or area, frequency and return period and intensity Can apply to a range of different disturbances (i.e. fire, floods, droughts and storms) Disturbances operate at different spatial and temporal scales Intermediate disturbances associated with high diversities

Fire Ecology -

Fossil charcoal indicates that wildfires began soon after the appearance of terrestrial plants (420 mYa) O2 levels correlate with fire activity (13% atmospheric O2 required from combustion) Ignition from lightning, volcanoes and humans Fire activity is correlated with net primary productivity Climate is also a key driver of fire activity  in high rainfall areas lots of biomass, limited ignition  in low rainfall, lots of fire but minimal fuels

Australian Plants: Adaption to fire -

Many Australian plants have characteristics that promote fire (i.e. flammable resins and oils in leaves) The seed life history stage (species only germinate in response to fire cues)

Main strategy of fire response by plant species: Seeders: adults killed by crown fire and regenerate from seed Sprouters: mature plants survive fire; regenerate from buds underground (stem or crown) - Recovery after fire: 1) Resprouting after fire from lignotubers 2) Eucalyptus: Resprouting from epicormics buds 3) Banksia: often killed by fire germination from seeds, cones open after fire

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Serotiny: seed release occurs in response to an environmental trigger

Fire regime: the pattern, frequency and intensity that prevails in an area -

Dictated by many things including climate, vegetation and human land-use Most Australia plant species can persist under the fire regimes they have experiences over millennia Changing the fire regime can influence the biota through fire functioning as a biological filter Made up of 3 components: frequency, severity and season

What happens if fire regime changes? -

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Effects of fire frequency the most well studied

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How can changes to fire frequency affect persistence  banksia do it by having primary juvenile period, seed bank Too frequent can reduce species diversity and abundance

Why fire severity and season? -

Increase in managed fire: HR’s focused on protection, conservation/ecological burns Climate change shifts fire season To manage for biodiversity, need to understand the ecological consequences

Fire driven plant dynamics: -

How can other aspects of the fire regime affect plants? Majority of species recruit only after fire Seeds banks maintain seeds between fires Dormancy/germination cues ensure emergence at the right time (seed ecology)

Why is seed ecology important? -

Lots of crop/agricultural studies same needed in our natural system

Can fire severity affect physically dormant species? -

Heat and physical dormancy change to response with severity Lab studies show 80C even sometimes 60 breaks dormancy for many species 120C kills seeds Soil seed bank: temperature regulates dormancy; increased heat = increased loss of dormancy

Cool burns: -

Much cooler soil temperatures Patchy heating Co-occurring species can have different thresholds for breaking dormancy Range of temperature thresholds – adaptation to inherent fire variation Different severity selects for lower threshold species

How does change to fire season affect plant recovery? -

Physiological dormancy means post-fire flush is seasonal Studies winter vs summer fire seedling performance Delayed emergency post-winter fire – high mortality

Positive or negative on biodiversity? -

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Positive on systems evolved with fire, but shifts in fire regime may be negative Introduction of fires into area with little or no fire history negatively impact it

Invasive Species Case Study 2: Last Northern White Rhino dies            

Environmental problem Rhino poaching Medicines and daggers One horn in china Effect on environment Large herbivore removed from ecosystem Estimate one rhino a day in south Africa Kruger 90 rhinos in 2011 Role of environmental science Document long term trends Provide advice about management Management Reducing poaching Tracking poisoned horns Indelible dyes Remove horns

Definitions: Pest: an animal that causes more harm than good to a value resource Alien species (exotic): occurs outside its natural range and dispersal potential Invasive species: an alien species whose establishment and spread threaten ecosystems, habitats, or species with economic or environmental harm Characteristics: -

Species enter an area not previously occupied Irruption of irregular occurrences of organisms outside their normal range Population advances in waves into areas of lower density Population dynamics is described by dispersal, migration, colonization, epidemic, range expansion

Population Ecology of pest species: -

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Escape native biotic constrains: competitors, predators, resources, parasites Little population control allows alien species to increase until carrying capacity is reached

Dispersal of Invaders: -

May be linear or irregular (e.g. along watercourses) Favourable habitat is occupied first, followed by unfavourable habitat Biological diffusion is enhanced by ‘bridgeheads’ ahead that serve as nuclei for shotdistance diffusion Populations proceed by dispersal, settlement and extinction

Causes of invasions: African land snail, cattle egret, mosquito fish -

Passengers Sport hunting Utilitarian Fishing Biological control Natural dispersal

Successful invaders:    

Behaviorally and physiologically adaptable Can change behaviour with changing environment and invade habitat of other animals Aggressive (i.e. indian mynah) outcompete for nesting sites and food resources Tolerant of wide range of conditions High rates of reproduction (e.g. rabbits) Large populations of invaders species results in more success

Habitats vulnerable to invasion: -

Habitats that are fragmented or disrupted are vulnerable (e.g.) European starlings invasion of farmland Communities with few species and not adapted to predators are particularly vulnerable (e.g. islands)

Disturbance/land transformation: -

Human activities have simplified and fragmented original landscapes Dispersal foci of invading species often associated with human activities (e.g. horticultural, agricultural) Fragmentation process may decrease competitive ability of natives and enhance performance of pre-adapted invad...