Unit 5 - Population Dynamics

Question 1

crude density (D)

Answer 1

takes into account all the area

D = N ÷ S
crude density = # ÷ area

Question 2

ecological density (D)

Answer 2

takes into account only the habitable area of the species

D = N ÷ S
ecological density = # ÷ habitable area

Question 3

dispersion patterns of wild populations

Answer 3

• clumped; most common (e.g. fish)
• uniform (e.g. lions)
• random (e.g. trees)

Question 4

quadrat analysis

Answer 4

ideal for stationary and small organisms (e.g. plants)

average sample density = total number of individuals ÷ total sample area

Question 5

mark-recapture sampling

Answer 5

• 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)

Question 6

technological tracking of populations

Answer 6

• radio collars
• sattelite-linked monitors decipher migration patterns
• microcomputer tags; geographical information system (GIS) mapping is used to determine dispersion patterns and migration activities

Question 7

ethics of technological tracking (the 3 R’s)

Answer 7

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)

Question 8

factors affecting population growth

Answer 8

• natality (birth rate)
• mortality (death rate)
• immigration and emigration
• human actions and natural factors

Question 9

formula for population size

Answer 9

(births + immigration) - (deaths + emigration)

Question 10

formula for population change

Answer 10

([(births + immigration) - (deaths + emigration)] ÷ initial population size)) × 100

Question 11

populations vs. communities

Answer 11

• Populations are one species.
• Communities are many species co-existing (e.g. the different organisms in a pond).

Question 12

closed populations vs. open populations

Answer 12

• 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).

Question 13

fecundity vs. fertility

Answer 13

• 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.

Question 14

patterns in survivorship of species

Answer 14

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)

Question 15

carrying capacity (K)

Answer 15

• 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

Question 16

biotic potential (r)

Answer 16

the maximum growth rate that a population exhibits under ideal environmental conditions

Question 17

modelling population change

Answer 17

• geometric growth (J-shaped)
• exponential growth (J-shaped)
• logistic growth (S-shaped; sigmoidal)

Question 18

geometric growth

Answer 18

• 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

Question 19

formulas for geometric growth (λ)

Answer 19

λ = N(t+1) ÷ N(t)
rate_geometric = population at interval ÷ initial population

N(t) = N(0)λ^t
rate_geometric = (initial population)(geometric rate)^time

Question 20

exponential growth

Answer 20

• 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

Question 21

formulas for exponential growth (dN/dt)

Answer 21

dN/dt = rN
rate_exponential = (intrinsic growth rate)(population)

t_d = 0.69 ÷ r
doubling time = 0.69 ÷ intrinsic growth rate

Question 22

logistic growth rate

Answer 22

• 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

Question 23

formula for logistic growth (dN/dt)

Answer 23

dN/dt = r_maxN × [(K - N) ÷ K]

rate_{instantaneous} = (maximum growth rate)(population) × [(carrying capacity - population) ÷ carrying capacity]

Question 24

density-dependent factors

Answer 24

• 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)

Question 25

density-independent factors

Answer 25

extreme weather, natural disasters, human impact, etc.

Question 26

r-selected strategies

Answer 26

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

Question 27

K-selected strategies

Answer 27

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

Question 28

predator-prey interactions

Answer 28

* 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

Question 29

ecological niche

Answer 29

* the role of an organism in a community * either **fundamental** (theoretical) or **realized** (realistic; with competition)

Question 30

inter-specific competition

Answer 30

**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

Question 31

passive defense mechanisms

Answer 31

**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)

Question 32

interspecific interactions

Answer 32

**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)

Question 33

estimated human population on Earth

Answer 33

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

Question 34

human population projections

Answer 34

* 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)

Question 35

ecological footprint

Answer 35

* 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)

Question 36

biomagnification

Answer 36

* 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

Question 37

biomass

Answer 37

the renewable organic material from plants and animals

Question 38

energy transfer

Answer 38

as the trophic level increases, only 10% of energy is passed on

Question 39

bioremediation

Answer 39

* 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

Question 40

limiting wastes

Answer 40

* 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

Question 41

ecological effects caused by human activity

Answer 41

**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