Unit 3 - Population

3.1 Generalist & Specialist Species

some species (generalist feeders) adapt to environmental changes %%better%% than other species (specialist feeders)
^^generalist species^^: thrive in dynamic environments; can adapt well (broad niche) * can live in a variety of environments * %%broad%% range of ecological tolerance (no specific diet or habitat) * usually known for being $invasive species$ * ex. raccoons, mule deers, rats, bald eagles
^^specialist species^^: thrive in stable environments; easily struggle or succumb to changes in habitat (narrow niche) * only live in specific conditions * %%narrow%% range of ecological tolerance (limited diet, conditions, and habitat) * ex. giant pandas, mountains gorillas, osprey

3.2 K-Selected & r-Selected Species

^^K-selected species^^: large, quality > quantity in offspring, long life spans, late maturation can reproduce multiple times, specialists, large body types, strong competition in their particular environments * %%high levels of competition%% for resources in the habitat * %%more prone%% to the colonization of invasive species * can %%maintain the population%% at carrying capacity (adjusting population to utilize resources efficiently) * ex. giant pandas, elephants
^^r-selected species^^: small, quantity > quality in offspring, early maturation, reproduce only once, generalists * %%low competition%% for resources in the habitat * prone to %%overpopulation%% by exceeding the carrying capacity * can experience %%population dieback%% due to overpopulation * ex. mosquitos, invasive species
^^biotic potential^^: max ideal reproductive rate of a population (measurement of growth capacity in populations) * ex. 1-2 cubs for giant pandas
many species have characteristics of both K-selected and r-selected species * ex. osprey, frogs, sea turtles

3.3 Survivorship Curves

^^survivorship curve^^: displays the relative survival rates of a group of same-age individuals in a population * ^^x-axis^^: max lifespan of organisms from birth to death * ^^y-axis^^: percent of surviving organisms in a population (logarithmically)

Types of Survivorship Curves

==Type I==: late loss * a %%large number%% of the population survives throughout their lifespan, reaching old age * dies at the end of their lifespan * adequate care → increasing chances of survival to maturation * represents many ^^K-selected species^^ * ex. mountain gorillas
==Type II:== constant loss * death rate %%constant%% from birth to death * organisms die throughout their lifespan * ex. birds, squirrels
@@Type III@@: early loss * surviving rate %%drops immediately%% after birth; few organisms survive to adulthood * little to no care → high infant mortality * represents many ^^r-selected species^^ * ex. monarch butterflies

3.4 Carrying Capacity

>= carrying capacity → resource depletion → famine, disease, and conflict
^^carrying capacity^^: max number of organisms the environment can support without resource degradation * represented as a horizontal dotted line at the top of the graph labeled K
^^population dieback^^: decrease in population as a result of resource degradation caused by overpopulation in species * exceeding carrying capacity → population dieback → within carrying capacity * ex. reindeer of st. matthew island

3.5 Population Growth and Resource Availability

^^environmental resistance^^: factors that limit population growth * emerges after the population goes over carrying capacity
%%exponential growth%% = unlimited resources * occurs in all populations below carrying capacity (competition does not greatly affect population growth)
%%logistic growth%% = limited resources * occurs in populations at or above carrying capacity when competition is a dependent variable
^^fecundity^^: ability to produce offspring * including factors such as maturation age, reproductive rate, biotic potential, and reproductive strategy

Types of Environmental Resistance Factors

^^density-dependent resistance factors^^: biotic, affects organisms when population density is ==high== * ex. competition, predation, parasitism
^^density-independent resistance factors^^: abiotic, affects all populations ==regardless of size or density== * ex. natural disasters or droughts

3.6 Age Structure Diagrams

another name for %%population pyramid%% * shows the $distribution of ages$ in a population divided by males and females * shapes represent trends within the population
@@x-axis@@: # of individuals (left side male right side female)
@@y-axis@@: center of the diagram showing age groups * ^^reproductive^^: 0-14 years * ^^reproductive^^: 15-45 years * ^^post-reproductive^^: 46-100+ years
higher proportion of young people = rapid population growth (bottom heavy) * wide base, pyramid shape * indicates %%developing nation%% * ex. india, brazil, nigeria, mexico
higher proportion of middle-aged people: stable population growth (middle heavy) * rectangular shape * similar percentages throughout all age groups * indicates %%more developed nations%% * ex. united states, sweden, canada, austrailia
higher proportion of elder people: declining population growth (top heavy) * inverted pyramid shape * many people in the post-reproductive stage * %%more economic and social development%%, higher education common * long-term impact on social services * ex. japan, germany, italy, russia

3.7 Total Fertility Rate

%%TFR%%: avg # of children a woman has during her childbearing years (15-49) * been lowering in recent years depending on the country * ex. world avg = 2.5
developing countries: ^^TFR > 2.1^^ * rapid population growth * ex. niger, congo, uganda
developed countries: ^^TFR <= 2.1^^ * stable/declining population growth * ex. united states, japan, united kingdom

@@Societal Factors@@

age of first pregnancy
educational opportunities for women
family planning resources
governmental regulations
access to healthcare resources

3.8 Human Population Dynamics

%%thomas malthus%% → all populations have a carrying capacity
humans are limited by density-independent & density-dependent factors * ^^density-independent factors^^: affects population regardless of size or density * ex. storms, fire, heat waves, droughts * ^^density-dependent factors^^: affects population based on size or density * arises during overshoot and dieback → decreasing overpopulation * ex. disease transmission, territory size, food availability, access to clean air and water
^^doubling time^^: the amount of time a population takes to double at a constant growth rate * calculated using rule of 70 * @@rule of 70@@: 70/r = doubling time * r = growth rate of population (%)

Environmental Problems

density-independent factors * hurricanes → drop in population due to property damage, economic loss, and better opportunities elsewhere
more years a woman is in school = lower TFR

Societal Factors

%%birth rates%%: * high rate = rapid population growth * low rate = slow population growth
^^death rates^^: * high rate = slow population growth * low rate = rapid population growth
^^education of women^^: * high rate = slow population growth * low rate = rapid population growth
i^^nfant mortality^^: * high rate = slow population growth * low rate = rapid population growth
%%age of marriage%%: * early - rapid population growth * late - slow population growth
%%nutrition%%: * better = rapid population growth * worse = slow population growth

3.9 Demographic Transition

%%demographic transition%%: model that shows trends in CBR, CDR, and total population * derived from historical data * moving towards industrialization from agricultural-based economies * development shown in 4 stages
^^Stage 1^^: high infant mortality, child labor → low growth (preindustrial)
^^Stage 2:^^ improved resources → very high growth (transitional) * the gap between birth and death rate widens * less developed countries (LDC)
^^Stage 3^^: high education amongst women, low infant mortality → slower growth (industrial) * less developed countries (LDC) * birth and death rate are almost @@equal@@
^^Stage 4^^: stage 3 + aging population + tax burdens for senior citizen care → zero or negative growth (post-industrial) * more developed countries (MDC)