Unit 5 - Population Dynamics Flashcards
crude density (D)
takes into account all the area
D = N ÷ S
crude density = # ÷ area
ecological density (D)
takes into account only the habitable area of the species
D = N ÷ S
ecological density = # ÷ habitable area
dispersion patterns of wild populations
- clumped; most common (e.g. fish)
- uniform (e.g. lions)
- random (e.g. trees)
quadrat analysis
ideal for stationary and small organisms (e.g. plants)
average sample density = total number of individuals ÷ total sample area
mark-recapture sampling
- ideal for mobile wildlife populations (e.g. fish, polar bears)
- often demonstrate clumped dispersion
total # marked (M) ÷ total population (N) = # of recaptures (m) ÷ size of second sample (n)
technological tracking of populations
- radio collars
- sattelite-linked monitors decipher migration patterns
- microcomputer tags; geographical information system (GIS) mapping is used to determine dispersion patterns and migration activities
ethics of technological tracking (the 3 R’s)
replacement (trapping with computer models), reduction (reducing the number of animals used), and refinement (adjust techniques to minimize pain/stress); suggested by the Canadian Council on Animal Care (CCAC)
factors affecting population growth
- natality (birth rate)
- mortality (death rate)
- immigration and emigration
- human actions and natural factors
formula for population size
(births + immigration) - (deaths + emigration)
formula for population change
([(births + immigration) - (deaths + emigration)] ÷ initial population size)) × 100
populations vs. communities
- Populations are one species.
- Communities are many species co-existing (e.g. the different organisms in a pond).
closed populations vs. open populations
- Closed populations are stationary and are not affected by migration (e.g. fish in an aquarium).
- Open populations are affected by migration (e.g. ants at a picnic).
fecundity vs. fertility
- Fecundity is the theoretical maximum number of offspring that could be produced by a species in one lifetime.
- Fertility is the actual number of offspring produced by an individual during its lifetime, and is affected by food supply, disease, and mating success.
patterns in survivorship of species
Type I
- low mortality
- high life expectancy
- small number of offspring (e.g. mammals)
Type II
- uniform risk of mortality
- constant proportion of individuals dying at each age interval (e.g. songbirds)
Type III
- high mortality
- low life expectancy
- large number of offspring (e.g. sea turtles)
carrying capacity (K)
- the maximum number of organisms that can be sustained by available resources over a limited period of time
- is dynamic; environmental conditions are always changing
biotic potential (r)
the maximum growth rate that a population exhibits under ideal environmental conditions
modelling population change
- geometric growth (J-shaped)
- exponential growth (J-shaped)
- logistic growth (S-shaped; sigmoidal)
geometric growth
- organisms reproduce at a constant rate during fixed intervals
- births take place at one time of the year (i.e. breeding season); population grows rapidly during breeding season, and declines throughout the year until the next breeding season
- an annual growth rate can be determined
- e.g. seals, deer, salmon
formulas for geometric growth (λ)
λ = N(t+1) ÷ N(t)
rategeometric = population at interval ÷ initial population
N(t) = N(0)λt
rategeometric = (initial population)(geometric rate)time
exponential growth
- organisms reproduce at a constant rate continuously
- slope of the tangent increases over time
- reproduction is continuous throughout the year (i.e. no breeding season)
- an instantaneous growth rate can be determined
- e.g. yeast, bacteria, humans
formulas for exponential growth (dN/dt)
dN/dt = rN
rateexponential = (intrinsic growth rate)(population)
td = 0.69 ÷ r
doubling time = 0.69 ÷ intrinsic growth rate
logistic growth rate
- population size grows until it levels off, as it approaches its carrying capacity
- most common among wild populations
- includes a lag phase (lowest growth; flattest slope), log phase (highest growth; steepest slope), and a stationary phase (zero growth; slope = 0)
- e.g. sheep, harbor seals
formula for logistic growth (dN/dt)
dN/dt = rmaxN × [(K - N) ÷ K]
rateinstantaneous = (maximum growth rate)(population) × [(carrying capacity - population) ÷ carrying capacity]
density-dependent factors
- intra-specific competition; within the same species (e.g. food, mating)
- inter-specific competition; amongst different species (e.g. predation)
- Allee effect; population is not viable due to a small size, because there’s a smaller chance of reproduction (e.g. passenger pigeon)
density-independent factors
extreme weather, natural disasters, human impact, etc.
r-selected strategies
life strategies used by populations that live close to their biotic potential
- have a short life span
- become sexually mature at a young age
- produce large broods of offspring
- provide little or no parental care to their offspring
- e.g. insects, annual plants, algae
K-selected strategies
life strategies used by populations that live close to their carrying capacity
- have a relatively long life span
- become sexually mature at a later age
- produce few offspring per reproductive cycle
- provide a high level of parental care to their offspring
- e.g. mammals, birds, humans
predator-prey interactions
- predators limit the population of the prey by weeding out the weak (natural selection), and prey provide food for the predators
- populations never reach 0; the relationship between predator and prey is sustainable
- sinusoidal growth is a wave-like oscillating pattern that is typical of predator-prey interactions
1. less predator = more prey
2. more prey = more predator
3. more predator = less prey
4. less prey = less predator
ecological niche
- the role of an organism in a community
- either fundamental (theoretical) or realized (realistic; with competition)
inter-specific competition
interference
- “default” competition; traditional
- aggression between members of different species who fight over the same resource
- e.g. tree swallows and bluebirds fight over birdhouses
exploitation
- consumption of a shared resource by individuals of different species in which consumption of a resource limits the other species
- e.g. arctic foxes and snowy owls prey on the same population of arctic hares
passive defense mechanisms
protective structures
- e.g. thorns
chemical
- taste
- toxins
- smell
protective colouration
- camouflage; involves the surrounding environment (e.g. chameleons)
- mimicry; an organism imitates the physical appearance of a more dangerous organism (e.g. viceroy butterflies mimic monarch butterflies)
- warning colouration; usually red and black (e.g. poison dart frogs)
interspecific interactions
competition
- competitive (-/-): both populations are negatively affected (e.g. cheetahs and lions)
predation
- predator-prey or herbivore-plant (+/-): one population gains at the expense of the other (e.g. hawks and rabbits)
- herbivore-plant (+/-): one population gains at the expense of the other (e.g. antelopes and grass)
symbiosis
- parasitism (host-parasite) (-/+): one population gains at the expense of the other (e.g. deer and tapeworms)
- mutualism (mutualistic) (-/-): both populations are positively affected (e.g. algae and coral)
- commensalism (+/0): one population gains, while the other is unaffected (e.g. suckerfish and sharks)
estimated human population on Earth
7.6 billion (2018) → 8.1 billion (2024)
- doubling time of humans have changed drastically over time; 600 years (in antiquity) → 60 years (today)
- carrying capacity of humans is currently unknown
- dip in population in the 1300s, due to the bubonic plague
- population skyrockets in the 1900s due to the discovery of antibiotics by Alexander Fleming (i.e. penicillin), and refrigeration increased sanitation techniques
human population projections
- positive growth (rapid growth or slow growth): more young people, less old people (higher natality, lower mortality)
- zero growth: equal amount of young and old people (equal natality and mortality)
- negative growth: less young people, more old people (lower natality, higher mortality)
ecological footprint
- the total amount of land needed to support one person
- includes cropland, grazing land, fishing grounds, forest land, carbon absorption land, and building area
- industrialized countries (e.g. U.S., Australia, Canada) have a greater footprint than developing countries (e.g. Egypt, China, India)
biomagnification
- the increasing concentration of toxic substances that enter the food chain or food web at low levels
- e.g. methylmercury increases in concentration in organisms as the trophic level increases
biomass
the renewable organic material from plants and animals
energy transfer
as the trophic level increases, only 10% of energy is passed on
bioremediation
- the use of organisms, usually bacteria, to detoxify polluted environments such as oil spill sites or contaminated soils
- e.g. chlorinated organic solvents like trichloroethene (TCE) and perchloroethylene (PCE or PERC) are commonly used in paint thinners, antifreeze, dry-cleaning, and industrial processes that involve grease removal
limiting wastes
- prevent, reduce, or eliminate the production of pollutants by use of such cleaner, nonpolluting technologies (e.g. wind power, solar photovoltaic systems, microturbines)
- cleaning up the pollutants after they have been produced
- the development of eco-cities: urban centres that are planned to minimize their impact on the local and regional environments and to foster sustainable lifestyles
ecological effects caused by human activity
excessive use of fertilizers
- inorganic fertilizers allow for the production of much more food on the same land base
- excessive use may result in the release of nitrous oxide from soil, cause water pollution, and reduce soil fertility after extended
- alternative cultivation practices can reduce fertilizer demand without reducing productivity.
deforestation
- growing populations (especially equatorial regions) often cut down lots of trees for new farmland and housing
- trees purify air, regulate water flow, influence climate, provide habitats, and support food webs and energy flow
loss of biodiversity
- humans have degraded 40%-50% of Earth’s land surface via deforestation
- many species become extinct or endangered due to displacement
ozone (O3) depletion
- a layer of ozone in the lower stratosphere shields the Earth from 95% of the Sun’s radiation
- ozone layer depletion is the result of many chlorofluorocarbons (CFCs) and other ozone-degrading chemicals being released in the air; the sources of these emissions is mostly from highly industrialized populations
pesticides
- pesticides have increased harvests of crops, by kill many insects that compete with humans
- pesticides pose a risk to territorial and aquatic ecosystems
- the risk of long-term exposure to trace pesticide residues in food, water, and air is unknown
widespread pollution
- air, water, and soil pollution are all the result of regular human activity (e.g. oil spills)
- pollution is most severe in larger urban populations, where more waste is generated
