Biology'1B'Notes,'Fall'2013'

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Biology'1B'Notes,'Fall'2013'

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Biology'1B'Notes,'Fall'2013'

PART%2:%ECOLOGY%SECTION%%People%• Ernst Haeckel – defined ‘ecology’ as: the comprehensive science of the relationships

of the organism to the environment • Charles Elton – 1927 – ecology is a new name for a very old subject – it means

scientific natural history • Herbert Andrewartha – ecology is scientific study of distribution and abundance of

organisms • Alexander von Humboldt – father of biogeography – inspiration to Darwin and many

others – a naturalist, Renaissance thinker – monitored and mapped vegetation changes with elevation

• Thomas Malthus – theories about change of population – dangers of population growth

• Tansky – defined ecosystem as: the whole system, including not only the organism-complex, but also the whole complex of physical factors forming what we call the environment

• Raymond Lindeman – seminal studies in field of ecosystem ecology 'Ecology%• Working definition of Ecology – interaction among organisms; relationship between

organisms and environment • Species distribution – the manner in which a biological taxon is spatially arranged. • Population size – N – is dynamic • Population density – the number of individuals per area (or volume) • Estimation of N – Direct

o Counting individuals, quadrants and transects • Estimation of N – Indirect

o Tracks and signs o Special case – associated species (i.e. peregrine falcons and red-breasted geese) o Mark-Recapture technique – estimates how many individuals are in a

population o Tracking distribution o Telemetry - highly automated communications process by which measurements

are made and other data collected at remote or inaccessible points and transmitted to receiving equipment for monitoring.

o PIT Tags – Passive integrated Transponder o Camera Traps – voyeuristic (spying)

• Population Distribution Patterns o Random – rare in nature o Uniform – more common – even distribution – territoriality o Clumped – pack hunting animals, environmental abilities

• Dispersion Patterns are dependent on spatial scale • Absolute Estimates of Population Size – provide quantitative numerical estimates

Biology'1B'Notes,'Fall'2013'

• Relative Estimates of Population Size – identify populations as relatively larger or smaller than some baseline

• Extrapolation – using quadrants/ transects to estimate the number of individuals per area

• Quadrats and Transects – look at relative abundance in an area - Transect lines can be purchased commercially, made from measuring tape or rope marked off at regular intervals. A quadrat is a framed area.

• DBH – diameter at breadth height • Safety in Numbers

o Does flocking/schooling behavior have anti-predator benefits? o Thermoregulation – the maintenance of internal body temperature within a

tolerable range o Group Foraging – seeking and obtaining food o Many Eyes Hypothesis – in a group, there are more individuals to sense threats

• Principle of Allocation – resources that are used towards survival cannot be simultaneously to an organism for reproduction - determined by the number of resources, stressful condition

• Resource Acquisition – how does one collect resources? Has to do with niches and competition

• Life-History Tradeoffs o Growth vs. Reproduction o Survival vs. Reproduction

• To flock or not to flock? o Conspicuousness o Increased vigilance o Locating food o Securing prey o Competition o Disease o Cheating o Thermal advantage

• Fecundity – reproductive output of an organism • Evolution of Life History Traits

o Number of reproductive events during life o Age at first reproduction o Clutch size o Developmental stage of young at birth

! Precocial – hatched with eyes open, covered with down, leave nest within two days

! Altricial – hatched with eyes closed, little or no down, cannot depart from nest

• Cohort – a group of individuals in a sample (often of the same generation) • Annual Plants – put everything into single reproduction, then die • Pioneer plants – plants that arrive in a disturbed area quickly (i.e. after a fire) • Semelparity – one reproductive episode before death (often are annular)

Biology'1B'Notes,'Fall'2013'

• Iteroparity – multiple reproductive episodes before death • Big Bang Reproduction – plant puts everything into reproduction once a century, then

dies • Survivorship Curve – a plot of the number of members of a cohort that are still alive at

each age; one way to represent age-specific memory • How many individuals are in a population?

o Birth and immigration add individuals to a population, death and emigration remove individuals

o Population growth: BD Model ! Nt+1 = N1 + (B+I) – (D+E)

Nt-1 = N1 + B-D Nt-1 – N1 = B-D

! (B-D) = per capita birth rate • Fixed Interval Growth • Instantaneous Growth • Exponential Growth • Population Regulation – biotic and abiotic factors that determine population size over

time • Carrying Capacity (K) = maximum population size an environment can contain or

sustain o dN = rN k-N

dt k • Population Dynamics

o Fluctuations o Cycles o Can be overshooting (time lag)

• Sunspot Activity, when low, causes: o Ozone produced decreases o Plants invest UV blocking chemicals increases o Plants investing herbivore defenses decreases

• Herbivory – an interaction in which an organism eats parts of a plant or alga • Parasitism – one or few hosts, rarely lethal (i.e. tapeworm, brown headed cowbird) • Mutualism – a symbiotic relationship in which both participants benefit

o Obligate – participants require each other for survival/ fitness o Facultative – organisms benefit from other organisms but do not require them

for survival/ fitness • Mycorrhizae- plant roots and fungi – a majority of plants on earth have fungi with

their roots to help them better gain nutrients • Predation – ‘true predators’ – have many hosts, relationship always lethal • Parasitoids – one host, always lethal • Predator/prey dynamics – Lotka-volterra equation – describes dynamics of biological

systems in which two species interact, one as predator and one as prey • Gut symbionts – allow termites to digest wood • Lichen – symbiosis between fungi and algae (or cyanobacteria)

Biology'1B'Notes,'Fall'2013'

• Nitrogen fixation – plants and bacteria – nitrogen in atmosphere is converted to ammonia

• Cultivation of crops – ants and fungi • Cultivation of livestock – ants and aphids (ant is the boss) • Hunting association • Competition – the use of a shared, limited resource (you can only compete for

something if it is in a limited supply) • Exploitative Competition – a form of competition in which one species either reduces

or more efficiently uses a resource and therefore depletes the availability of the resource for the other species

• Interference Competition – involves direct interactions between individuals such as fighting over limited resources

• Resource Partitioning – the division of environmental resources by coexisting species such that the niche of each species differs by one or more significant factors from the niches of all coexisting species

• Competitive Exclusion Principle – Two species competing for the same resource cannot coexist indefinitely o If two competing species coexist in a stable environment, they do so as a result

of ecological differentiation. If there is no such differentiation, then one species will eliminate or exclude the other.

o Gause • Niche – Joseph Grinnell – the role or function of an organism or species in an

ecosystem • Fundamental Niche – where an organism can live • Realized Niche – where living when competing

o Realized almost always < fundamental • Niche partitioning – differences that allow coexistence - The process by which natural

selection drives competing species into different patterns of use for food, shelter, or other assets

• Ecomorph – an ecological specialism • Ecological Character Displacement - differences among similar species whose

distributions overlap geographically are accentuated in regions where the species co-occur, but are minimized or lost where the species’ distributions do not overlap.

• Exponential Growth Curve – increases exponentially forever • Logistic Growth Curve – tapers off • Density Dependent Factors – increase in population density intensifies limiting factor

effect (disease, competition, predation, parasites) • Density independent factors – liming factor is unrelated to population density (fire,

landslides) • Interspecific Interactions:

o Commensalism – a symbiotic relationship in which one organism benefits but the other in neither helped nor harmed

o Amensalism – A symbiotic relationship between organisms in which one species is harmed or inhibited and the other species in unaffected

Biology'1B'Notes,'Fall'2013'

o Competition - an interaction between organisms or species, in which the fitness of one is lowered by the presence of another ! Exploitative – when consumption of a limiting resource by one species

makes that resource unavailable for consumption by another ! Interference – two species physically interfere with one another

o Consumer Resource interactions – food chain - n umbrella term for a variety of more specialized types of biological species interactions including prey-predator), host-parasite, plant-herbivore and victim-exploiter systems.

o Mutualism • Disturbances – natural or anthropogenic – can occur on hugely varied spatial scales –

a natural or human-caused event that changes a biological community and usually removes organisms from it – play a pivotal role in structuring many communities

• Intermediate Disturbance Hypothesis – intermediate levels of disturbance correlate to high levels of diversity

• Fire – large disturbance – can help maintain a forest by killing pathogens, opening pine cones

• Succession – the non seasonal, directional and continuous pattern of colonization and extinction on a site by species populations

• Vernal Pool – non-successional seasonal change • Types of Ecological Succession:

o Primary – the gradual growth of an ecosystem over a longer period – substrate that was devoid of vegetation

o Secondary – occurs on preexisting soil whereas primary succession usually occurs in a place lacking soil

o Degredative – occurs on dead organic matter over a relatively short time-scale (months to years)

• Mechanisms of Succession o Facilitation o Inhibition o Tolerance

• Primary Succession – concerns successional process that starts at an abiotic condition o Life is stubborn, and hard to kill off o Starts from clean slate

• Secondary succession – substrate is full of organisms o Fires (medium intensity) o Glacier Bay Example

• Degradative Succession – carcasses – assess when the individuals dies • R-selected – selection for life history traits that maximize reproductive success in

uncrowded environments; density-independent selection • K-selected – selection for life history traits that are sensitive to population density;

density-dependent selection • Wallace Line – biological difference between Australasia and Indonesia • Biogeographic Realms – Nearctic, neotropic, afrotropic, palearctic, indomalayan,

Australasian, Antarctic • Latitudinal Diversity Gradients – groups of organisms are more diverse closer to the

equator