Module 4 - Bio1007 - Notes PDF

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Module 4 Understand the links between morphology, physiology and behaviour Appreciate ecological and evolutionary significance of behaviour Understand various behavioural strategies to obtain food, avoid being food, and for reproduction Appreciate the science behind our knowledge and understanding of behaviour 

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Behaviour o Classically, about animals o Coping mechanism = 1. Morphology + 2. Physiology + 3. Behaviour  Behaviour: part of how organism respond to the biotic and abiotic environment o E.g. carnivores differ from herbivores  In skull morphology, guts, gut flora, liver enzymes, metabolism  In behaviours: foraging strategies, social behaviour, communication o E.g. Gelada baboon foraging behaviour is linked to its:  Morphology (teeth, guts)  Physiology (capacity to digest plant cell wall in grass)  Social behaviour (group size, conflict between feeding, safety, mates)  Eats the right kinds of food in the right amounts o Effect of behaviour on fitness  Fitness: an individual’s relative contribution to the next generation’s gene pool  E.g. plant-insect interactions  Insect herbivores consumer vegetative parts of plants  Insects pollinate ~2/3 of all plants; often with food rewards  Together with morphology and physiology – natural selection acts on behaviour  Hence, many behaviours are adaptive o Ecologically significant because it  Links individuals and their behaviour  Affects demographics (population levels outcomes)  Affects interactions among species (community level outcomes) o Evolutionarily significant because it  Has some genetic basis (i.e. nature vs nurture)?  Affects fitness  Can be selected (benefits > costs) o How do we know?  Observations: inter and intra-specific comparisons  Manipulative experiments that test hypotheses Behaviour in relation to: o Abiotic environment: lizard cooling feet on hot sand by raising limbs o Biotic environment: foraging, win/choosing mates, escaping/defending Key aspects of behaviour (1. Obtaining food 2. Avoid becoming food 3. Reproduce) 1. Obtaining food o Foraging strategies are linked with morphology and physiology  Ambush predators: camouflage to increase probability of prey encounter  Active predators: agile and fast to increase probability of prey encounter o Huge variety of foraging strategies defined by:  What they eat: herbivore, insectivore, carnivore, omnivore etc.  How they get it: ambush or active  Diet breadth: specialist  generalist o Common feature of all foraging strategies: non-random  individuals make foraging choice  undertake it to maximise nutrition  Optimal foraging theory  Modelled which food items to eat in a non-depleting environment  Predicts foragers should maximise net rate of food intake  Marginal value theorem  Modelled when to leave a food patch in a depleting environment  Predicts that foragers should leave food patches when capture/harvest rate at patch < average/harvest rate o Patch has marginal value compared to the surroundings  Foraging ecology tests such predictions about foraging behaviour  Net rate model: maximises the quantity of food foraged  Efficiency model: maximises the energy output required per unit food o Note: optimal foraging theory focuses on efficiency of energy gain

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 Sometimes foraging only for nutrients  Behaviours also depends on the nourishment of the forager too  But most foragers are also prey o We should expect that:  Foraging strategies to be linked to predator avoidance strategies  A trade-off between food and fear 2. Avoid becoming food o The dead don’t reproduce, therefore being eaten = ultimate fitness cost  Strategies to reduce predation risk  relevant to most of food chain o Anti-predator strategies include:  Run away  Groups  Hide  Act costly (act dangerous, mimic unpalatable or toxic organisms)  Be costly (sequester toxic compounds, have spines)  Feed in safe places or times (vegetation cover, new moon) o Costs of anti-predator strategies  Missed opportunities to forage in better locations  due to far away from vegetation cover  Competition for food and social aggression  groupings o For anti-predator strategies to evolve benefits > costs 3. Reproduce o No reproduction  fitness = 0 as genes are not passed on o Trade-off costs and benefits o Courtship and mating  Relevant to sexual reproduction  Involves: male-male competition and female choice  Results in non-random mating  sexual selection o E.g. peacock tail  High costs of such tail: energy and maintenance  risk of predation  Benefits  access to mates  Darwin hypothesised peacock tail arises from natural selection o Sexual selection:  Intrasexual selection (usually for males and species where the males are larger than females): competition between genders  facilitates access to mates  Intersexual selection: mate choice  once provided the choice o Parental care  Benefits: increases survivability and growth of offspring  fitness  Costs: missed opportunities to reproduce again  In some species, offspring stay and help parents rear more offspring All organisms show a foraging trade-off between food and fear Plant behaviour o Leaves and stems  Grow towards light  Respond to their environment by moving o Roots  Grow along chemical gradients towards nutrients  Respond to their environment by moving o Plant behaviour? Why not!  Different time frame (plants move slowly)  Different way of moving (plants move parts of themselves (modular))  Similar: all living organisms respond to their environment What is behaviour? o Interaction with environment (abiotic and biotic) o Involves stimulus: response o Sensory? (do you need a brain, or even nerves, or senses to behave?) o Semantics? o Does it matter?

Be able to describe and understand exponential and logistic models of population growth Define instantaneous growth rates in discrete and continuous exponential growth models Become familiar with demographic rates and how they are measured Understand what a stage/age structure model is Understand what a spatially structured population is Understand the principles and implementation of population viability analysis 

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Groups: multiple organisms (can be singular or multiple species) occupying a common space o Can be ephemeral or consistent o Can be social (positive or negative), indirect (sharing common resource) or accidental (random chance) Populations: a number of organisms of the same species in a defined geographical area o Definition encounters issues for highly migratory groups of individuals o Composition and structure are influenced by life history, mobility and habitat o Properties of populations include:  Number of individuals or population size  Area they occupy  Age structure  Sex ratio o Play a central role in our understanding of the factors that shape and drive the diversity of life Populations are essential for: o Ecology:  Distribution and abundance of individuals  Density o Evolution:  Populations of organisms evolve, not individuals  Gene flow o Conservation and management:  Invasive species  Defined threat status of taxa  Translocations and restoration Groups vs Populations o Dynamics: populations are more cohesive through time Individuals: populations consist of a number of individuals that grow, survive and reproduce  individuals may be unitary or modular o Unitary:  Develop from zygote: genetically distinct  Form to determinate  Development and growth predictable o Modular:  Grow by addition of modules (e.g. leaves or lengths of stems): genetically identical (clones)  Individuals are highly variable in the number of modules (e.g. some plants, aquatic invertebrates)  Modular ‘individuals are often difficult to count  Look at the percentage of space covered Importance of population biology o Understand temporal dynamics of populations o Understand spatial distribution of populations o Natural selection occurs within populations Population growth o Populations change in numbers over time o Change can be positive or negative o Rate (r): change/unit time  Populations grow at different rates Demographic rates o Variables that drive changes in population size: (first 4 affect the population numbers, last 3 affect rates)  Birth  Death  Emigration (number leaving population)  Immigration (number entering population)  Growth (individual)  Age at maturity  Sex ratio

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Birth and death o Fundamental to population growth  balance of the birth versus death o Measured in changes of individuals per yea o Balance between additions (births) and losses (deaths) determines growth rates o Inherent to all types of population growth models Population growth in ‘closed’ systems o The population growth rate is the change in numbers of individuals over time o Where there is no emigration or immigration, the population is ‘closed’ e.g. isolated areas, islands, mountain tops o Nt = number of individuals in the population at time t  Nt+1 = Nt + Births – Deaths  Number next year (t+1) = Number (N) this year (t) after accounting for changes in births and deaths Exponential growth o Geometric growth is exponential: a population’s per capita growth remains the same irrespective of population size; thus, populations grow faster as they get bigger o Dynamic over time depends on life history of organism  Discrete: reproduction occurs periodically  Continuous: reproductions occur year-round

Estimating birth rates o Common methods:  Histology of reproductive organs  Capture/counting of fertilised gametes  Counting of newly born individuals Resource limited growth o Population growth is often resource limited (e.g. food, space, water, nesting sites etc.) o Numbers cannot increase without bound

Estimating death rates (mortality) o Common methods  Tagging  Follow individuals (for sessile organisms)  Probability based (for more motile organisms)  Changes in size structure (how many organisms caught are young versus old) o Very challenging – how can you know for sure an individual has died unless you see it happen or sample the entire population? Population growth in ‘open’ systems o The population growth rate is the change in numbers of individuals over time o Nt = number of individuals in the population at time (t) o If the individuals move in and out of the populations then it is ‘open’  Nt+1= Nt + Births – Deaths + immigrants – emigrants Estimating demographic rates o Relatively easy for individuals which do not move o Movement  Tagging and recapture

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 Physical  GPS  Radio telemetry  Acoustic  Genetics  Genetic similarity occurs with only very low levels of interbreeding between populations o i.e. individuals move far o if they are genetically distinct, it means that the demographic is enclosed  Genetic differences = no movement between populations  Genetic analysis of microsatellites Spatially structured populations o Metapopulations  Local populations, but individuals move  Demographic rates vary spatially  Large-scales dynamics dependent on local demographics and connectivity  Can prevent global extinction o Glanville Fritillary butterfly  Periodic local extinctions  Recolonization from nearby populations  Metapopulation level extinction prevented o Mayfly  Larval stages mature in local pools  Adults disperse between pools  Mortality variable from pool to pool  Some pools are sources (low mortality) while others are sinks (high mortality) Estimating population size o Common tools  Counts  Visual  Auditory  Acoustic  Mark-release-recapture (MRR)  Estimates the total population size from a sample proportion of a mobile species  Use the proportion of recaptures to estimate whole population size  Assumptions often are hard to satisfy: o Closed population (no immigration, no emigration) o All individuals equally likely to be marked o Marked individuals do not lose their mark  Technique has been used successfully on many animals, including whales, lizards, small animals Demographic rates: growth (individual), age at maturity, sex ratio o Estimating growth and age  Trees: tree rings  dendrochronology  Perennial plants: rings in the tap root  Mammals: counting rings in teeth e.g. grey-headed flying fox  Fish: otoliths (ears which provide fish balance) Understanding age and size-structured population dynamics o Age and/or size of an individual affects:  Fecundity (probability of giving birth)  Survival o Treating all members of a population as identical  unrepresentative of natural population structure o Imbalanced initial age structure  age and number cycles o Life tables: show survivorship probability at each age o Long-term studies: key to understanding population dynamics Australia’s human population dynamics o Changes in human population size: mostly due to behavioural changes o Economists need to know the future age structure to plan: more infrastructure o The current trend: ageing population o Growth rate of many western countries:  Below replacement rate

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 Population numbers will level out then fall Extinction: loss of all populations of a species o Processes of chance that contribute to an extinction event  Genetic stochasticity (small populations)  Demographic stochasticity (random nature of births and deaths)  Environmental stochasticity (variability)  Catastrophes (cyclones, epidemics, fire)  Human impacts (habitat loss, fragmentation, over-exploitation, hunting, pollution, introduction of new pest species, other environmental changes e.g. climate change) Population viability analysis (PVA) o Toll used to model population dynamics over time o Uses basic population data o Includes environmental variation in these values o Can change values to reflect human impact o Key information needed:  Population size/carrying capacity (K)  Fecundity  Mortality: adults and juveniles  Inter-annual variation in parameters Model sensitivity o A tool which enables you to enter all data significant to measure population dynamics o PVA only as good as the data o Test the robustness of conclusions using sensitivity analysis of parameters based on known or hypothesised variance in the data used to estimate the parameters o Fundamental to PVA o Allows estimation of what could occur if certain changes occur Summary o Populations are groups of organisms of the same species in a defined area o Biotic and abiotic factors can influence the processes of population change: birth, death, immigration and emigration o Populations can be ‘closed’ if they primarily change only by birth and death processes or ‘open’ if immigration and emigration are also important in affecting changes in numbers o Populations may grow exponentially at first but as resources become limiting, growth slows until they may reach the carrying capacity  such growth is typically described by a logistic curve o The age/stage structure of a population affects population growth o Population viability analysis is a toll that can be used to determine the long-term vulnerability of species to extinction under a variety of scenarios

Define the biological species concept and interspecific hybrids Provide arguments in the debate about the species problem Describe what is known about the number of species and how this varies globally, by region and by group Use methods for counting and estimation of the number of species Variation within species  Groups within a species can be defined as being of a taxon hierarchically lower than a species  In zoology only, the subspecies is used  In botany the variety, subvariety, and form are used  In conservation biology, the concept of evolutionary significant units (ESU) is used, which may define either species or smaller distinct population segments  In horticulture there are cultivars  There are also breeds of domesticated animals such as dogs, cats, cattle, sheep What do we mean by a species?  Definitions: in biology, a species is one of the basic units of biological classification and a taxonomic rank o Can be genotypically similar but completely different species  A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring  Biological species concept o Ernst Mayr’s definition of a species as: ‘groups of actually or potentially interbreeding natural populations, which are reproductively isolated from other such groups’ Limitations of the biological species concept  This concept may not be relevant to organisms that are capable of asexual reproduction (e.g. many types of bacteria)  If the definition of a species requires that two individuals are capable of interbreeding, then an organism that does not interbreed is outside of that definition o Fossils o Clonal species o Asexual species  Organisms may also breed beyond the notional definition of species o Interspecific hybrids o Ring species Other species concepts  Ecological species (lives in the same space)  Biological/isolation species  Genetic species (look at the genetic differences)  Cohesion species  Evolutionary significant unit (ESU) (preserve their species separate from other species)  Phenetic species  Microspecies  Recognition species  Mate-recognition species Interspecific hybrids  Another difficulty that arises when defining the term species is that some species are capable of forming hybrids Hybridisation – why does it occur?  1) breakdown of reproductive isolating barriers which usually prevent gene flow between closely related species o Separation of geographical location or intrinsically genetically different  2) potential causes of hybridisation in Lomatia include: Habitat disturbance Species in closer proximity Secondary contact Increased migration distances (pollinator change, or dispersal) – through vectors Altered phenology Leading to overlap in flowering time (and pollen transfer) Altered genetics Breakdown in the pollen incompatibility system  3) potential evolutionary outcomes: o Sterile (F1) o Speciation – new species o Enhancing variation

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Ring species arises when a parental population expands around an area of unsuitable habitat in such a way that when the two fronts meet they behave as distinct species while still being connected through a series of intergrading populations o Further away you get – the lesser possibility of interbreeding

Species problem – review of ideas  The difficulty of defining species is known as the species problem  Differing measures are often used, such as similarity of DNA, morphology or ecological niche  Presence of specific locally adapted traits may further subdivide species into ‘infraspecific taxa’ such as subspecies  Many organisms do not conform to the reproductively isolated criteria  Not possible to test this for fossil taxa Vascular Plant Flora of Australia Native Species 15 638 Species – how many species are there? Naturalised Species 1 952 Number of species – Mammals NSW Total Species 17 590 Monotremes 2 Presumed Extinct 83 Marsupials 46 Described Species 19 324 Rodents 17 % world described 6.9% Bats 37 Estimated species ~21 645 Total 102 Percentage endemic 91.8% Species numbers  Insects comprised about 57% of all named species  Beetles comprised 25%  Most non-insects have probably been discovered and described o Most insects never will Methods of counting the amount of insect species in a tropical rain forest 1) Method: counting the number of beetles on one tree species  Knockdown method: insecticide fog in the canopy, insects die and fall onto collecting devices  Sample: 19 individuals of a leguminous tree o Luehea seemannii at different seasons  Results: 9000 beetles from 1200 beetle species  Comparison: 2800 species of Arthropods from the canopies of 10 trees belonging to 5 species in the Bornean rainforest  Based on extrapolations: o 13.5% of beetles live only on this one tr...