Population

Population: Group of organisms of same species living in particular area at particular time.

Population Ecology: Study of populations and factors affecting their size and distribution.

Characteristics: (1) Birth rate, (2) Death rate, (3) Age distribution, (4) Sex ratio, (5) Population density.

Population Dynamics: Changes in population size due to births, deaths, immigration, emigration.

Carrying Capacity: Maximum population size that environment can sustain indefinitely.

Diagram Importance: Population growth curves and age pyramids are essential for understanding.

Population Growth: Increase in population size over time.

Growth Rate: (Birth rate + Immigration) - (Death rate + Emigration).

Types of Growth: (1) Exponential growth (J-shaped curve), (2) Logistic growth (S-shaped curve).

Exponential Growth: Unlimited growth when resources abundant. Seen in bacteria, algae in favorable conditions.

Logistic Growth: Growth slows as population approaches carrying capacity. S-shaped curve.

Factors Affecting Growth: (1) Natality (birth rate), (2) Mortality (death rate), (3) Immigration, (4) Emigration.

Population Explosion: Rapid increase in human population. Currently over 8 billion.

Diagram Importance: J-shaped and S-shaped growth curves are crucial for ICSE.

Population Density: Number of individuals per unit area. Formula: Density = Total population / Total area.

Types: (1) Crude density, (2) Ecological density (per habitable area).

Distribution Patterns: (1) Uniform (even spacing), (2) Random (no pattern), (3) Clumped (grouped).

Factors Affecting Distribution: (1) Resources availability, (2) Climate, (3) Topography, (4) Competition, (5) Predation.

Human Population Density: Varies globally. High in India, China; low in deserts, mountains.

Age Structure: Proportion of different age groups in population. Shown in age pyramids.

Age Pyramids: Graphical representation. (1) Expanding (broad base, high birth rate), (2) Stable (uniform), (3) Declining (narrow base, low birth rate).

Sex Ratio: Number of females per 1000 males. Normal: 1000:1000. In India: 940:1000 (2011 census).

Factors Affecting Sex Ratio: (1) Female infanticide, (2) Better healthcare for males, (3) Migration.

Importance: Indicates population growth potential and social structure.

Diagram Importance: Age pyramids for different countries are frequently asked.

Demographic Transition: Model describing population change over time as society develops.

Stages: (1) High birth and death rates (pre-industrial), (2) High birth, falling death rates (industrial), (3) Falling birth and death rates (post-industrial), (4) Low birth and death rates (developed).

India: In stage 3. Death rate decreased, birth rate still high.

Implications: Population growth, aging population, resource strain.

Diagram Importance: Demographic transition model diagram is important.

Need for Control: Population explosion causes poverty, pollution, resource depletion, unemployment.

Methods: (1) Education, (2) Family planning, (3) Women's empowerment, (4) Government policies.

Family Planning: Use of contraceptives, sterilization, abortion.

Government Programs: (1) National Population Policy (2000), (2) Reproductive health programs, (3) Awareness campaigns.

Success Stories: China (one-child policy), Kerala (education and healthcare).

Challenges: Religious beliefs, poverty, lack of education.

Impact of Population on Environment: (1) Habitat destruction, (2) Pollution, (3) Resource depletion, (4) Biodiversity loss, (5) Global warming.

Sustainable Development: Development that meets present needs without compromising future generations.

Carrying Capacity: Earth's carrying capacity for humans is debated (4-16 billion).

Optimum Population: Population size that maximizes welfare.

Measures: (1) Reduce consumption, (2) Sustainable agriculture, (3) Renewable energy, (4) Conservation.

Census: Official count of population. Conducted every 10 years in India. Last: 2011 (1.21 billion).

Key Findings: (1) Population growth rate: 1.64% (2011), (2) Literacy rate: 74%, (3) Sex ratio: 940, (4) Density: 382 per sq km.

Trends: Decreasing growth rate, increasing urbanization, aging population.

Challenges: Overpopulation in urban areas, rural-urban migration, regional imbalances.

Policies: (1) National Health Mission, (2) Education for All, (3) Skill development programs.