APES UNIT 3

Generalist Species

🌍 Definition: Organisms that can thrive in a variety of environments and use a wide range of resources.

✅ Characteristics:

• Use many different resources.

• Adapt to various environments.

• High tolerance for change.

• Advantage when environmental conditions change.

• Less likely to go extinct.

🔹 Example: Humans 👩‍🔬

Specialist Species

🔬 Definition: Organisms with narrow niches, requiring specific environmental conditions and resources.

✅ Characteristics:

• Use a specific set of resources.

• Less adaptable to environmental changes.

• Low tolerance for change.

• Easily affected by environmental disruptions.

• More likely to become extinct.

🔹 Example: Pandas 🐼

r-Strategists

🐭 Definition: Species that reproduce quickly, with many offspring and little parental care.

✅ Characteristics:

• Not endangered

• Many offspring, tend to overproduce

• Low parental care

• Mature rapidly

• Short-lived

• Small in size

• Tend to be prey

• Type III survivorship curve (high infant mortality)

• Wide fluctuations in population density

• Limited by density-independent factors (climate, weather, natural disasters)

🔹 Examples: Insects, algae, bacteria, rodents, annual plants

K-Strategists

🐘 Definition: Species that invest in fewer offspring with high parental care and long lifespans.

✅ Characteristics:

• Most endangered

• Few offspring

• High parental care

• Mature slowly

• Long-lived

• Larger in size

• Tend to be predators (but can be prey too)

• Type I or II survivorship curve (higher survival rates)

• Population size stabilizes near carrying capacity

• Limited by density-dependent factors (competition, predation, parasitism, migration)

🔹 Examples: Humans, elephants, cacti, sharks

Survivorship Curves

📊 Definition: Graphs that show the age distribution of species, reproductive strategies, and life history.

✅ Key Concept:

• Reproductive success is measured by how many organisms survive to reproduce.

• Survivorship curves show the balance between resource limitations, interspecific, and intraspecific competition.

Type I - Late Loss

🧑‍⚕ Characteristics:

• Most individuals survive to old age

• Low mortality at birth, high probability of survival

• Deaths occur mostly at biological lifespan limit

• Advancements in prenatal care, nutrition, and disease prevention improve survival

📌 Examples: Humans, elephants, annual plants, sheep

Type II - Constant Loss

🦜 Characteristics:

• Steady death rate across all ages

• Predation is the primary cause of death

• Organisms reach adult stages quickly

📌 Examples: Rodents, songbirds, perennial plants

Type III - Early Loss

🐢 Characteristics:

• Many offspring, but high early mortality

• Death is high in younger stages due to predation & environmental factors

• Older individuals have higher survival chances

📌 Examples: Sea turtles, trees, fish, oysters, internal parasites

Carrying Capacity (K)

🌱 Definition: The number of individuals that can be sustainably supported in a given area.

Variation in Carrying Capacity

🔄 Species-Specific: Varies from species to species.
📉 Dynamic Over Time: Decreases as the environment degrades.

Regulating Factors

⚖ Purpose: Keep population sizes in balance with carrying capacity.
☀ Sunlight: Amount available for growth.
🍃 Food Availability: Resources to support individuals.
🧪 Nutrient Levels: In soil profiles supporting plant life.
💧 Oxygen Content: In aquatic ecosystems for respiration.
📏 Space: The physical area available for living.

Population Dispersal Patterns

📍 Definition: The way individuals of a species are distributed in a habitat.

• Clumped: Organisms group together in areas with patchy resources.

  • 🐺 Examples: Social animals, prey species, pack hunters.

• Random: Individuals are spaced unpredictably due to uniform environmental conditions.

  • 🌿 Examples: Dandelions, wind-dispersed plants.

• Uniform: Evenly spaced individuals due to competition for resources.

  • 🌵 Examples: Territorial animals, desert plants.

Biotic Potential

🌱 Definition: Maximum reproductive capacity of a species under ideal conditions.

• Increases Biotic Potential: Adaptability, migration, high birth rates, low competition.

• Decreases Biotic Potential: Specialized niches, high competition, disease, unfavorable habitat.

📈 J-Curve (Exponential Growth)

Rapid increase in population until resources are depleted, leading to a crash.

📊 S-Curve (Logistic Growth)

• Slow initial growth, rapid increase, then stabilization at carrying capacity (K).

Feedback Loops

🔄 Positive Feedback Loop: Amplifies change (e.g., population booms).
⚖ Negative Feedback Loop: Stabilizes systems (e.g., predator-prey balance).

Limiting Factors

🚧 Definition: Resources or conditions that restrict population growth.

• Density-Dependent: Affected by population size (e.g., food, disease, predation).

• Density-Independent: Unaffected by population size (e.g., climate, natural disasters).

Rule of 70 (Population Doubling Time)

🧮 Formula: Doubling Time (years) = 70 / Growth Rate (%)

• Larger growth rate → Faster doubling time.

• Populations cannot grow indefinitely.

Important Population Formulas

📝 Birth Rate (%) = (Total Births / Total Population) × 100
📝 Death Rate (%) = (Total Deaths / Total Population) × 100
📝 Doubling Time = 70 / % Growth Rate
📝 Population Density = Total Population / Total Area

Impacts of Population Growth

🌍 Biodiversity: Habitat destruction reduces species survival.
🌊 Coastlines & Oceans: Overfishing, habitat loss.
🌲 Forests: Deforestation exceeds sustainable use.
🍽 Food Supply: Malnutrition increases with population growth.
💧 Freshwater: Rising demand, limited supply.
🔥 Climate Change: More greenhouse gases → Rising temperatures.
🏥 Public Health: Pollution and disease worsen with high populations.

Age-Structure Diagrams

📊 Definition: Graphical representations of population distribution by age and sex.

• Determined by:

  • 📈 Birth Rate

  • 🕰 Generation Time

  • ⚰ Death Rate

  • ⚥ Sex Ratios

Types of Age-Structure Diagrams

1⃣ Pyramid-Shaped 🔺

• Characteristics:

  • High birth rates 📈

  • Majority in pre-reproductive & reproductive age groups

  • Indicates a growing population

• Example: Developing countries 🌍

Types of Age-Structure Diagrams

2⃣ Bell-Shaped 🔔

• Characteristics:

  • Pre-reproductive & reproductive age groups nearly equal

  • Post-reproductive group smallest due to mortality

  • Indicates a stable population

• Example: Developed countries with stable birth rates 🏙

Types of Age-Structure Diagrams

3⃣ Urn-Shaped ⚱

• Characteristics:

  • Post-reproductive group largest

  • Pre-reproductive group smallest

  • Birth rate lower than death rate

  • Indicates a declining population

• Example: Countries with aging populations (e.g., Japan 🇯🇵, Italy 🇮🇹)

Total Fertility Rate (TFR)

🍼 Definition: The average number of children a woman will have during her lifetime.

Factors Leading to a Decline in TFR

1⃣ Healthcare & Family-Planning 🏥

• Increased access to primary healthcare and family planning services in developing countries transitioning to developed countries.

2⃣ Female Education 🎓

• More educational opportunities for females, leading to delayed childbearing.

3⃣ Career Prioritization 💼

• Millennials are delaying marriage to focus on career and personal goals.

4⃣ Desire for Higher Standard of Living 💸

• Many individuals and families want to improve their standard of living, often by having fewer children.

5⃣ Increased Female Workforce Participation 👩‍💼

• More women are joining the workforce, leading to fewer children per family.

6⃣ Contraception Acceptance 💊

• Greater acceptance of contraception by individuals and governments, enabling family planning.

7⃣ Urbanization 🏙

• In urban areas, the cost of living rises, reducing the need for extra children to assist on farms.

Factors Reducing Human Death Rates

1⃣ Increased Food & Distribution 🍞

• Improved nutrition from increased food production and efficient distribution.

2⃣ Medical & Public Health Advancements 💉

• Better access to anesthetics, antibiotics, and vaccinations.

3⃣ Sanitation & Hygiene 🚿

• Enhanced sanitation and personal hygiene practices.

4⃣ Safe Water Supply 💧

• Improvements in the safety of water supplies.

Human Population Growth Surges

1⃣ Use of Tools 🛠 (3.5 million years ago)

• Early humans started using tools for survival.

2⃣ Discovery of Fire 🔥 (1.5 million years ago)

• Fire discovery allowed better survival and food processing.

3⃣ First Agricultural Revolution 🌾 (~10,000 B.C.E.)

• Shift from hunting and gathering to crop growing.

4⃣ Industrial & Medical Revolutions 🏭💊 (~200 years ago)

• Industrial and medical advancements spurred population growth.

Human Population Growth Stages

Before Agricultural Revolution

👥 Population: ~1-3 million
🌍 Lifestyle: Hunter-gatherer
💡 Earth Wisdom: Natural cycles can guide human behavior.

8000 B.C.E. to 5000 B.C.E.

👥 Population: ~50 million
🌱 Advances: Agriculture, domestication of animals, settling down
💡 Earth Wisdom: Natural cycles continue as models for behavior.

5000 B.C.E. to 1 B.C.E.

👥 Population: ~200 million
📉 Growth Rate: 0.03-0.05% (compared to today's 1.3%)
🌍 Worldview: "Frontier Worldview" - viewed land as to be exploited for resources.

0 C.E. to 1300 C.E.

👥 Population: ~500 million
⚔ Factors: Famines, wars, disease slowed growth
🌍 Worldview: Frontier mindset persists.

1300 C.E. to 1650 C.E.

👥 Population: ~600 million
💀 Plagues: Significant loss of life, plagues caused up to 25% mortality rates.

1650 C.E. to Present

👥 Population: ~7.5 billion
🌱 Growth Rate: Increased to ~1.2%
🏥 Factors: Healthcare, hygiene, medical advances, education
🌍 Worldview: "Planetary Management" - Humans are in charge of Earth, resources are virtually unlimited.

Present to 2050 C.E.

👥 Estimated Population: ~9.8 billion
🌱 Worldview: "Earth Wisdom" - Resources are finite, and we must promote sustainable growth and learn from nature.

Demographic Transition

• Transition from high birth and death rates to lower birth and death rates as a country or region develops from pre-industrial to industrialized economic systems.

Stage 1: Pre-Industrial (High Stationary)

1⃣ Characteristics:

• Poor agriculture, pestilence, and living conditions cause food scarcity and poor medical care.

• High birth rates replace high mortality, resulting in low population growth.

• Example: Sub-Saharan Africa, with 54% of the world’s AIDS-HIV cases but only 6% of the population.

• Since 2010, drug therapy has reduced new infections by 28% and death rates by 44% in the region.

Stage 2: Transitional (Early Expanding)

2⃣ Characteristics:

• Occurs after industrialization begins.

• Hygiene, medical advances, sanitation, cleaner water, vaccinations, and higher education lower death rates.

• Rapid population increase as death rates drop.

Stage 3: Industrial (Late Expanding)

3⃣ Characteristics:

• Urbanization reduces economic incentives for large families.

• Families in urban areas are increasingly discouraged from having large families as costs rise.

• Female education and employment lower birth rates.

• Leisure and food are less prioritized.

• Retirement safety nets reduce the need for more children.

• Economic pressures lower birth rates until they approach death rates.

Stage 4: Post-Industrial (Low Stationary)

4⃣ Characteristics:

• Population growth is zero when birth rates and death rates are equal.

• Higher standard of living leads to low birth and death rates.

• In some countries, birth rates fall below mortality rates, leading to population losses.

Stage 5: Sub-Replacement Fertility (Declining)

5⃣ Characteristics:

• Some theorists believe this is needed to represent countries with sub-replacement fertility.

• Death rates exceed birth rates in most European and East Asian nations.

• Without mass immigration, countries in this stage face population aging and decline.