APES Unit 3

Name:____________________________________________ 3.1 Specialist vs. Generalist

  • Specialist: Species that thrive in specific, narrow environmental conditions. They have specialized traits that make them suited to particular habitats or food sources.
    • Example: Koalas, which depend on eucalyptus trees for food.
  • Generalist: Species that can thrive in a wide range of environmental conditions and can use a variety of resources.
    • Example: Raccoons, which can live in diverse environments and eat many types of food.    Similarities and Differences:
  • Similarities: Both are adapted to their environment and have evolved over time to survive.
  • Differences: Specialists have a narrow range of tolerance, while generalists can survive in a broader range of conditions. This means generalists often have a higher chance of survival under changing conditions.

Ecological Niche: The role of a species within its environment, including how it gets its food, where it lives, and how it interacts with other species.

Thrive in Different Environments:

  • Specialists thrive in stable, predictable environments with limited competition.
  • Generalists thrive in variable or unpredictable environments where they can adapt to many different conditions.

Examples:

  • Specialist: Panda (depends on bamboo).
  • Generalist: Coyote (can eat a variety of foods and live in diverse habitats).

 K-selected vs. R-selected Species

  • K-selected Species: Species that produce fewer offspring but invest more in raising them. They typically live in stable environments and have longer lifespans.
    • Characteristics: Long lifespan, low reproductive rates, high parental investment, larger size.
    • Example: Elephants, humans.   
  • R-selected Species: Species that produce many offspring with little investment in each. They are typically found in unstable environments.
    • Characteristics: Short lifespan, high reproductive rates, minimal parental care, smaller size.
    • Example: Mosquitoes, dandelions.

Differences:

  • K-selected species are typically larger, longer-lived, and invest more in fewer offspring.
  • R-selected species produce many offspring with little parental investment, often in unpredictable environments.

K and R-selected individuals in the same species: Some species can show both strategies depending on environmental conditions. For example, a species may produce fewer offspring in a stable environment (K-selected) or more offspring in a disturbed or changing environment (R-selected).

Environmental Influence:

  • K-selected species are more affected by changes that reduce competition or habitat stability.
  • R-selected species may thrive after disturbances or changes that open up opportunities for rapid reproduction.

 3.2 Survivorship Curves

  • Purpose: To show how the number of individuals in a population changes with age and to understand the likelihood of survival at different life stages.

Types of Survivorship Curves:

  • Type I: High survival rate in early and middle life, but a steep decline in survivorship in old age (e.g., humans, elephants).
  • Type II: A constant mortality rate throughout life (e.g., birds, rodents).
  • Type III: High mortality early in life but those that survive early stages tend to live longer (e.g., fish, many insects).

Environmental Factors Affecting Survivorship Curves:

  • Disease, predation, food availability, and environmental stress can shift the curve (e.g., an outbreak of disease may reduce survivorship).

 3.3 Carrying Capacity

  • Overshoot: When a population exceeds its carrying capacity, leading to resource depletion.
  • Die-off: A sharp decline in population size after overshoot, often caused by resource scarcity.

Factors Regulating Carrying Capacity:

  • Density-dependent factors: Factors that depend on the population size, such as food availability, disease, and competition.
  • Density-independent factors: Factors that affect populations regardless of size, such as natural disasters, climate change, or habitat destruction.

Bottleneck Event: A sharp reduction in the size of a population due to environmental events (e.g., natural disasters, overhunting). This can reduce genetic diversity and lower the carrying capacity for future generations.

 3.4 Population Growth and Resources

Population Characteristics:

  • Size: The total number of individuals in a population.
  • Density: The number of individuals per unit area.
  • Distribution: How individuals are spaced across the environment (random, uniform, or clumped).
  • Sex Ratio: The ratio of males to females in a population.

Density-dependent vs. Independent Factors:

  • Density-dependent: Affect populations more as density increases (e.g., competition, predation).
  • Density-independent: Affect populations regardless of density (e.g., weather events, natural disasters).

Population Size Equation:

  • Population growth = (Birth rate + Immigration) - (Death rate + Emigration)

 3.5 Age Structure Diagrams

  • Shape and Interpretation:
    • Pyramid-shaped (Expansive): Rapid population growth (high birth rates, low death rates), common in developing countries.
    • Bell-shaped (Stable): Birth rates roughly equal to death rates, common in developed countries.
    • Inverted Pyramid (Constrictive): Declining population, higher proportion of older individuals, common in countries with low birth rates.

Prediction of Population Growth or Decline:

  • The shape of the age structure diagram helps predict future population trends (e.g., a wide base indicates potential for rapid growth).

 3.6 Total Fertility Rate (TFR)

  • TFR: The average number of children a woman is expected to have during her lifetime.
  • Replacement Level Fertility: The TFR required to replace the population without growth or decline, usually around 2.1 children per woman.

Influence of IMR on TFR:

  • High Infant Mortality Rate (IMR) often correlates with higher TFR, as families may have more children to compensate for expected deaths.

TFR in Developed vs. Developing Countries:

  • Developed countries tend to have lower TFR due to factors like better healthcare, contraception, and education for women.
  • Developing countries typically have higher TFR due to limited access to healthcare, high infant mortality, and cultural factors.

Government Influence:

  • Governments can influence TFR through policies like family planning, healthcare access, education, and economic incentives or disincentives.

 3.7 Human Population Dynamics

  • Malthusian Theory: The idea that populations grow exponentially while resources grow linearly, leading to eventual scarcity and collapse.    Evolution of Society:
  • Technological advances, agricultural improvements, and public health measures have helped societies avoid the collapse predicted by Malthus.

Global Population Growth Rate:

  • Calculated using the formula: (CBR - CDR)/10

Rule of 70:

  • Used to estimate the doubling time of a population: 70/growth rate

National Population Growth Rate Equation: [(CBR + immigration) - (CDR + emigration)]/10

Factors Affecting Population:

  • Birth rates, death rates, immigration/emigration, healthcare, education, economic factors, and social norms.

Indicators of Living Conditions:

  • Life expectancy, literacy rate, GDP per capita, and infant mortality rate.

 3.8 Demographic Transition

  • Level of Development: Determined by factors like GDP, literacy rates, access to healthcare, and life expectancy.

Stages of Development:

  1. Pre-industrial Stage: High birth and death rates, little population growth.
  2. Transitional Stage: High birth rates, declining death rates, population grows rapidly.
  3. Industrial Stage: Birth rates begin to fall, population growth slows.
  4. Post-industrial Stage: Low birth and death rates, population stabilizes or declines.

GDP, TFR, and Life Expectancy: As countries move through the demographic transition, their GDP increases, TFR decreases, and life expectancy rises.

Population Growth Rate: As countries industrialize, population growth slows due to better living conditions, healthcare, and education.

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Specialist vs. Generalist

Specialist Species Species that have a smaller range of tolerance (narrower ecological niche) Limited diet and lives only in a narrow range of environmental conditions. Restricted Habitat Less able to adapt to varying environmental conditions Prone to extinction

Generalist Species Species that have a larger range of tolerance (broader ecological niche) Broad diet and live in a wide range of environmental conditions. Able to adapt to varying environmental conditions Less prone to extinction

Reproduction Patterns

K-selected - Carrying Capacity (quality) Babies are entering the competitive world at or near carrying capacity Carrying Capacity - the population size in which a habitat can support. Few babies with a lot of parental care Multiple reproduction Long Lifespan Long time to sexual mature → low biotic potential → Slow population growth

r-selected - reproduction (quantity) Many babies with very limited parental care May have limited amounts of reproduction (many times only once) Shorter Lifespan Short time to sexual mature → high biotic potential → fast population growth

Invasiveness and Disturbances

Recover from disturbance? K selected slow reproduction rate → slow population recovery → greater risk of extinction R selected high reproductive rate → fast population recovery → low risk of extinction Adaptivity? R - selected highly adaptive due to its high reproductive rate → increase in genetic diversity Higher chance of becoming invasive Survival? r-selected: Less parental care → less emotional and needs attachment → More independence K-selected: high parental care → Early Parental death = offspring death

(It screams “I’m Creative”)

Survivorship Curves Line that shows survival rates of a cohort (same-aged individuals) in a population from birth to death Faster drop in line = quicker die-off of individuals Slower drop in line = longer life expectancy

Types I, II, and III Type I Mostly K-selected species High survivorship in early life due to high parental care High survivorship in mid life due to size and defensive behaviors Rapid die-off due to old age

Types I, II, and III Type II Species in between r and K Steady rate of survivorship

Type III Mostly r-selected species Rapid die-off in early life due to lack of parental care Low to steady survivorship in mid-life Few survive to adulthood, slow decline in survivorship in old age

Carrying Capacity The maximum number of individuals in a population that an ecosystem can support (limited by the amount of resources).

Overshoot and Die-off Overshoot: Reaching populations over the carrying capacity of the ecosystem. can result in resource depletion resulting in die-off and/or population crash. Population sometimes don’t always fluctuate around the carrying capacity. If resources are severely depleted, total population die-off/crash can occur.

Predator-Prey There is an increase and decrease in amounts of predator/prey within the ecosystem. Increase in prey → increase in predator Decrease in prey → decrease in predator

Population Characteristics Size (N): total number of individuals in a given area at a given time. Density: Number of individuals per area Distribution: How individuals in a population are spaced out compared to each other Random (trees and plants) Uniform (territorial plant/animals) Clumped (herds/groups of animals)

Population Characteristics Sex Ratio: ratio of males to females. 50:50 ratios are ideal for breeding and population growth. Die-off or bottleneck disaster can lead to limited population growth.

Density-Dependent Factors: Factors that influence population growth based on size of population. Food, habitat competition, water, light, disease, etc.

Density-Independent Factors: Factors that influence population growth independent of the size of population. Natural Disasters

Biotic Potential vs. Environmental Resistance Biotic Potential (exponential growth): Maximum potential growth rate, with no limiting resources Environmental Resistance (logistic growth) = initially rapid growth, them limiting factors limit population to carrying capacity (K)

Age Structure Diagram Diagrams that displays the dispersion of a population due to age.

Age Cohort Age cohorts & growth = groups of similarly aged individuals

0-14 = Pre reproductive 15-44 = reproductive age group 45+ = post reproductive age group

Size differences between pre reproductive and reproductive age groups indicated the growth rate of the population

Extreme Pyramid Shape: Rapid growth Less Extreme Pyramid Shape: slow, stable growth House Shape: stable, little to no growth Narrow Base Shape: Declining population

Total Fertility Rate (TFR) TFR: The average number of offsprings a women will have in a lifetime. Higher TFR = higher birth rate (higher population growth)

Replacement Level Fertility: the TFR required to offset deaths in a population and keep population size stable. Developed countries: 2.1 → country stays at a constant population size Higher in less developed countries

Infant Mortality Rate (IMR): number of deaths of children under the age of 1 years per 1,000 people in a population. Higher in less developed countries due to lack of access to resources and health care.

Infant Mortality and TFR Globally, IMR has been declining due to: Access to cleaner water, health care, and food supply

Factors that Affect TFR Affluence (Development): More developed, or wealthy countries have a lower TFR than less developed countries. Education access for women Economic opportunities for women More family planning education and contraceptives Older first pregnancy Less child labor

Factors that Affect TFR Government Policies: Role in fertility by coercive or non coercive policies. (usually to slow pop. growth) Sterilization (snip-snip or tie) Tax incentives → fewer kids, pay less taxes Microcredit or loans for women with no children → used to start business Limit on number of children High tax for multiple children (China)

The reverse could happen too due to slow population growth.

Human Population Dynamics Earth’s Human carrying capacity (CC) is based on food supply Human population growth overshooting food production limits (of the time)

Technological Advancement Humans can alter CC by increasing food production Invention and production of synthetic fertilizers (haber-bosch reaction; synthetic nitrogen fixation) → increases food production Malthusian Theory

Birth Rate, Death Rate, and Growth Rate Growth Rate (r) = Percentage increase in a population (per year) Crude Birth Rate & Crude Death Rate (CBR and CDR) Births and Deaths per 1000 people in a population

Factors Affecting Human Population Growth Factors that increase population growth: Higher Birth Rates High infant mortality → drives higher TFR High immigration Access to health care and resources (lower death rates)

Factors Affecting Human Population Growth Factors that decrease population growth: Higher Death Rates High infant mortality Increased education and contraceptives Later life first pregnancy Later life marriage

Standards of Living Indicators Gross domestic product (GDP) = key economic indicators of standard of living Total value of the goods and services produced Per capita  total GDP/total population Life Expectancy = key health indicators of standards of living Average age a person will live to in a given country Increase with access to health care and resources

Demographic Transition

Industrialization Industrialization: The process of economic and social transition from farming (agrarian) economy to an manufacturing (industrial) one.

Stage 1 - Preindustrial Country has not yet made the transition from farming to manufacturing. Low GDP (poor) High death and Infant mortality rates Due to lack of resources and health care High TFR (replacement children) and child labor (agriculture) CBR and CDR are about equal/balanced → no population growth

*No Country is in phase 1

Stage 2 - Industrializing Going through transition Decreasing Death and Infant mortality rates Modernization and access to health care and resources (clean water, food, etc.) TFR remains high Lack of education (women, contraceptives, family planning) Need for child agricultural work Generational Lag (time for infrastructure and systems to develop) Rising GDP (as a country) but low per capita GDP Rapid Population growth due to high CBR and decreasing CDR.

Stage 3 - Industrialized Completed transition from farming to manufacturing. Modernization of economy → higher family income → TFR to decrease High per capita GDP Low death and infant mortality rates More access to health care and family planning Delayed marriage and later life pregnancy (first child) Higher literacy rate and life expectancy Slowing population growth rate as CBR is near the CDR

Stage 4 - Post-Industrialized Highly affluent and modernized countries TFR very low → more time spent on education and careers Increased family planning Very high per capita GDP Longer life expectancy due to high availability of healthcare. CBR drops lower than CDR → population decline

Stages 1 = pre-industrial 2 = developing 3 = developed 4 = highly developed *5 = future

  • don’t worry too much about stage 5