Population Ecology, Species Interactions, and Indian Demography

Comprehensive flashcards covering population biology concepts, growth models, survivorship curves, ecological interactions, succession mechanisms, and demographic patterns of India.

What is the etymological origin and ecological definition of a population?

The term originates from the Latin word 'Populus', meaning 'people'. Ecologically, it is defined as the grouping or sum of similar individuals of the same group or species living in a particular geographical area or space at a particular time, having the capability of reproduction.

How does a local population (deme) differ from a metapopulation?

A local population (or deme) refers to the different populations of the same organism present in particular geographical areas, whereas a metapopulation is a complex of local populations connected by dispersing individuals.

How is demography defined in biological and ecological contexts?

Demography is the scientific study of biological populations. It is a general science applied to any dynamic population that changes over time or space, encompassing the study of population size, structure, distribution, and spatial or temporal changes resulting from birth, death, migration, and ageing.

What are the three main patterns of population distribution, and what ecological conditions drive each?

1. Clumped: Organisms cluster in groups due to patchy resource distribution (the most common pattern; e.g., elephant herds, wolf packs). 2. Random: Unpredictable distribution typical of species with weak individual interactions (e.g., wild flowers, fungal spores). 3. Uniform: Organisms are evenly spaced due to competition for scarce environmental resources, such as water in a desert (e.g., desert shrubs, nesting penguins).

How is population density defined?

Population density is a measurement of population per unit area or unit volume.

How are maximum natality and ecological natality differentiated?

Maximum natality is the absolute or theoretical maximum production of new individuals under ideal conditions. Ecological natality is the realized population increase observed under actual environmental conditions.

What is the distinction between minimum mortality and ecological mortality?

Minimum mortality represents the theoretical loss of individuals under ideal conditions, whereas ecological mortality represents the actual loss of individuals under a given set of environmental conditions.

What mathematical equation and graphical curve characterize exponential population growth?

Exponential growth occurs when resources are effectively unlimited and environmental resistance is minimal. It is described by the differential equation $\frac{dN}{dt} = rN$ (where $N$ is population size, $t$ is time, and $r$ is the intrinsic rate of natural increase) and produces a characteristic J-shaped curve.

What is logistic population growth, and what does the symbol $K$ represent?

Logistic growth is a pattern of restricted population increase where growth rate accelerates, slows down, and eventually levels off as environmental resources are depleted. It produces a sigmoid or S-shaped curve that stabilizes at the carrying capacity ($K$), which is the maximum sustainable population size an environment can support.

What are the four successive stages of logistic population growth?

1. Lag phase (population establishes and grows slowly); 2. Exponential phase (resources are abundant and growth accelerates rapidly); 3. Deceleration phase (competition and resource limitations increase, slowing growth); 4. Equilibrium phase (births balance deaths, and population stabilizes around carrying capacity $K$).

How do density-dependent limiting factors differ from density-independent limiting factors?

Density-dependent factors are biotic mechanisms whose effects intensify as population density rises (e.g., competition, predation, disease, parasitism, overcrowding stress). Density-independent factors are typically abiotic or catastrophic events that affect populations regardless of their size or density (e.g., floods, droughts, wildfires, volcanic eruptions, pollution).

What physiological and behavioral responses are triggered by overcrowding stress?

Overcrowding triggers endocrine stress responses where hormone levels rise, immunity weakens, and aggression increases, leading to lower reproduction and survival (observed in laboratory rat colonies through fighting and decreased fertility, and in wild bird colonies through nest abandonment).

How do biotic potential and environmental resistance interact to regulate population size?

Biotic potential is the maximum reproductive capacity of a population under ideal, unconstrained conditions that pushes numbers upward. Environmental resistance encompasses all abiotic and biotic limiting factors (e.g., temperature extremes, drought, disease, predation) that restrict population growth. Actual population growth is the outcome of these opposing forces.

What are the three general models of survivorship curves, and what reproductive strategies do they reflect?

Type I (Late Loss): Low infant mortality and high survival through early/middle life followed by steep mortality in old age; typical of K-selected species with high parental care (e.g., humans, elephants). Type II (Constant Loss): Constant mortality rate throughout lifespan (e.g., birds, rodents, reptiles). Type III (Early Loss): Very high juvenile mortality with high longevity for surviving adults; typical of r-selected species producing massive offspring with zero care (e.g., fish, oysters, insects).

How do r-selected species differ from K-selected species across key life-history traits?

r-Selected (Opportunistic): Focus on exponential replication; short lifespan; rapid maturation; numerous offspring with zero active parental care; volatile population with booms and crashes; Type III survivorship (e.g., mosquitoes, dandelions, mice). K-Selected (Competitors): Focus on carrying capacity; long lifespan; slow development; few offspring with intensive parental care; stable population near $K$; Type I or II survivorship (e.g., elephants, humans, redwoods).

What do the shapes of age structure diagrams reveal about population growth?

A pyramid shape with a broad base reflects positive/rapid growth (e.g., Kenya, Nigeria). A steep pyramid with narrower taper reflects slow growth (e.g., United States, Australia). Straight, vertical edges indicate zero population growth (ZPG; e.g., Denmark, Italy). An inverted pyramid with a narrow base indicates negative population growth (e.g., Germany, Hungary).

What is mutualism, and how are obligate and facultative mutualisms distinguished?

Mutualism ($+/+$) is an interspecific symbiotic interaction that benefits both interacting species. Obligate mutualism is strictly necessary for the survival of one or both species, whereas facultative mutualism allows species to survive independently in the absence of the other partner.

What are the respective roles of the partners in a lichen mutualism?

A lichen is a mutualistic association between an algal partner (phycobiont) and a fungal partner (mycobiont). The algae synthesizes carbohydrates and organic nutrients via photosynthesis, while the fungus absorbs and retains water and minerals.

How do Rhizobium bacteria and leguminous plants interact mutualistically?

Rhizobium bacteria infect the root hairs of legume seedlings to form root nodules, where they fix atmospheric nitrogen ($N_2$) into ammonia ($NH_3$) for plant use. In exchange, the host legume supplies the bacterial bacteroids with carbohydrates, amino acids, and other nutrients.

What is commensalism, and how do epiphytes and lianas differ in their commensal habits?

Commensalism ($+/0$) is an association where one organism benefits while the other experiences neither benefit nor harm without physiological exchange. Lianas are vascular woody plants rooted in the soil that use trees purely for structural support. Epiphytes (e.g., orchids) grow on other plants to access light and moisture but are not rooted in the soil, utilizing specialized aerial roots to absorb moisture and nutrients from humid air.

What is allelopathy, and what are two specific plant examples?

Allelopathy is a biological phenomenon in which an organism releases biochemicals (allelochemicals) that influence the growth, survival, and reproduction of nearby competing organisms. Examples include Black Walnut trees, which release chemicals from roots and decaying leaves to inhibit surrounding plant growth, and desert Sagebrush, which leaches chemicals into the soil to secure space.

What are exploitation competition and interference competition, and what are the three possible outcomes of competition?

Exploitation competition occurs when a shared resource is in short supply and its use by one individual deprives another. Interference competition occurs when an individual directly harms or impedes another through physical action or toxic secretions. The three outcomes are: competitive exclusion (one wins, the other loses), coexistence (neither wins), and mutual extinction (both lose).

How does predation differ among classic predators, grazers, and insectivorous plants?

Classic ('true') predators kill their prey shortly after capture and typically consume it entirely (e.g., sharks, cheetahs). Grazers consume only parts of a prey organism without immediately killing it. Insectivorous plants (e.g., Nepenthes, Drosera) capture insects and secrete proteolytic enzymes from foliar appendages to digest them for supplemental nutrients.

What distinguishes endoparasites from ectoparasites, and what specialized organ does Cuscuta use?

Endoparasites live inside the host's body (e.g., Trypanosoma), whereas ectoparasites live and feed on the external surface using hooks or suckers (e.g., ticks, mites). The parasitic plant Cuscuta develops specialized absorbing structures called haustoria to penetrate host tissues and extract food.

What are three forms of positive intraspecific interactions?

1. Colonization: Cooperative grouping for survival (e.g., elephant herds positioning young calves in the center, females in the middle ring, and adult males on the outer protective ring). 2. Aggregation: Clustering for mating or thermoregulation (e.g., mayfly swarms; honeybees clustering below $14^\text{o}\text{C}$ to generate mass warmth). 3. Social organization: Division of labor for communal defense, feeding, and reproduction (e.g., honeybees).

How did Robert Smith (1965) define ecological succession?

Smith (1965) defined ecological succession as 'an orderly and progressive replacement of one community by another till the development of a stable community in that area.'

What are the six recognized steps in the process of ecological succession?

1. Nudation (creation of a barren area by disturbances like volcanoes or drought); 2. Invasion (dispersal and arrival of propagules like seeds or insects); 3. Establishment (germination and multiplication of the pioneer community); 4. Competition (competition for space and nutrients as density rises); 5. Reaction (environmental modification by inhabitants making it unsuitable for themselves and favorable to seral invaders); 6. Stabilization (establishment of a final stable climax community).

How do primary and secondary succession differ in origin and trigger?

Primary succession begins on completely lifeless, barren substrates where no soil or previous community existed (e.g., newly formed volcanic islands, bare rock colonized first by lichens). Secondary succession develops in areas where a pre-existing community was partially or completely destroyed by disturbances such as forest fires, floods, or agricultural abandonment, retaining residual soil and nutrients.

What is the difference between autotrophic succession and heterotrophic succession?

Autotrophic succession begins predominantly in inorganic environments and is characterized by the initial and sustained dominance of autotrophic green plants. Heterotrophic succession begins in organic-rich environments and is dominated by heterotrophic organisms (animals and decomposers).

What are the three competing theoretical concepts of the climax community?

1. Monoclimax theory (proposed by Clements): Each climatic region possesses only one single climax community controlled solely by climate. 2. Polyclimax theory (proposed by Tansley): A region can support multiple climax communities governed by local factors like soil moisture and nutrients. 3. Climax pattern theory (proposed by Whittaker, 1953): Climax communities form a continuum determined by total environmental factors involving nine major variables.

What environmental conditions define xerarch, hydrarch, and mesarch successional series?

Xerarch (xerosere) begins in dry, moisture-deficient environments such as bare rock with lichens as pioneers. Hydrarch (hydrosere) begins in open bodies of water like ponds with plankton as pioneers. Mesarch (mesosere) occurs in intermediate environments characterized by adequate moisture conditions.

When were the first census and the first complete census conducted in India?

The first population census in India was conducted in 1872, but the first complete census was conducted in 1881. Decennial censuses have occurred every $10\,\text{years}$ since.

What was the total population and average population density of India according to Census 2011?

According to the 2011 Census, India's total population was $1,210.19\,\text{million}$ ($1,210,193,422$ persons), and the average population density was $382\,\text{persons per sq km}$ (an increase from $117\,\text{persons per sq km}$ in 1951).

Which Indian administrative divisions recorded the highest and lowest population densities in 2011?

Among states and Union Territories, the National Capital Territory of Delhi recorded the highest density with $11,297\,\text{persons per sq km}$, while Arunachal Pradesh recorded the lowest density with $17\,\text{persons per sq km}$. Among Northern states, Bihar ranked highest with $1,102\,\text{persons per sq km}$.

How are physiological density and agricultural density calculated?

Physiological density is calculated as $\frac{\text{total population}}{\text{net cultivated area}}$. Agricultural density is calculated as $\frac{\text{total agricultural population}}{\text{net cultivable area}}$, where agricultural population includes cultivators, agricultural laborers, and their family members.

What characterized Phase I and Phase III of India's population growth over the last century?

Phase I (1901–1921) was a stagnant/stationary phase with high birth and death rates resulting in low growth, including an absolute negative growth rate of $-0.31\%$ during 1911–1921. Phase III (1951–1981) was a period of population explosion caused by rapid medical improvements lowering mortality while fertility remained high, yielding an average annual growth rate as high as $2.2\%$.

What proportion of India's 2011 population was comprised of adolescents, and how does the National Youth Policy (NYP–2014) define youth?

Adolescents (ages 10–19) constituted $20.9\%$ of India's population in 2011 (comprising $52.7\%$ male and $47.3\%$ female adolescents). The National Youth Policy (NYP–2014) launched in February 2014 defines 'youth' as persons aged 15–29 years.

What was the rural-urban population distribution of India in 2011?

In 2011, $68.8\%$ of India's population resided in rural villages ($597,608$ inhabited villages out of $640,867$ total villages), while $31.16\%$ resided in urban centers.

What are the four major language families of India and their respective speaker shares?

1. Indo-European (Aryan): $73\%$; 2. Dravidian (Dravida): $20\%$; 3. Austric (Nishada): $1.38\%$; 4. Sino-Tibetan (Kirata): $0.85\%$.

What was the percentage breakdown of major religious communities in India according to Census 2011?

Hindus: $79.8\%$ ($966.3\,\text{million}$); Muslims: $14.2\%$ ($172.2\,\text{million}$); Christians: $2.3\%$ ($27.8\,\text{million}$); Sikhs: $1.7\%$ ($20.8\,\text{million}$); Buddhists: $0.7\%$ ($8.4\,\text{million}$); Jains: $0.4\%$ ($4.5\,\text{million}$); Other Religions and Persuasions (ORP): $0.7\%$ ($7.9\,\text{million}$); Religion Not Stated: $0.2\%$ ($2.9\,\text{million}$).

How does the Indian Census classify working individuals into Main Workers and Marginal Workers?

A Main Worker is defined as a person who works for at least $183\,\text{days}$ (or six months) in a year. A Marginal Worker is defined as a person who works for less than $183\,\text{days}$ (or six months) in a year.

What are the four occupational categories recognized by Census 2011, and how was the Indian workforce sectorally distributed?

The four categories are: 1. Cultivators, 2. Agricultural Labourers, 3. Household Industrial Workers, and 4. Other Workers. Sectorally, the Primary sector accounted for $54.6\%$ of workers, the Secondary sector accounted for $3.8\%$, and the Tertiary sector accounted for $41.6\%$.