Q1:

List the attributes that populations possess but not individuals.

1. Conceptual Foundation: Individual vs. Population

In ecology, a biological population is defined as a group of individuals of the same species living in a specific geographical area, sharing or competing for similar resources, and potentially interbreeding. [Per fundamental ecological hierarchy], while an individual organism interacts with its environment, it is the population that exhibits emergent properties—characteristics that arise from the collective dynamic of the group, which a single individual cannot possess.

2. Birth Rate (Natality) vs. Birth

An individual possesses the attribute of being born (a singular, discrete event). Conversely, a population possesses a Birth Rate or Natality. This represents the per capita births within the population over a specific period.

• Mathematical Representation: If $N$ is the initial population size and $\Delta N_b$ is the number of births in time $\Delta t$, the per capita birth rate $b$ is expressed as:
  
  $b = \frac{\Delta N_b}{N \cdot \Delta t}$
• Significance: It indicates the rate at which new individuals are added to the population, driving population growth [Per the Malthusian growth model].

3. Death Rate (Mortality) vs. Death

An individual can only die (a definitive, singular event). A population, however, exhibits a Death Rate or Mortality, which is the per capita death of individuals within the group over time.

• Mathematical Representation: If $\Delta N_d$ is the number of deaths in time $\Delta t$, the per capita death rate $d$ is:
  
  $d = \frac{\Delta N_d}{N \cdot \Delta t}$
• Significance: Mortality rates determine population decline and are critical for plotting survivorship curves.

4. Sex Ratio vs. Sex

An individual organism has a specific biological sex (e.g., male or female). A population possesses a Sex Ratio, which is the proportional distribution of males and females within the entire group.

• Measurement: It is typically expressed as the number of females per 1,000 males, or as a percentage (e.g., a population consisting of $60\%$ females and $40\%$ males).
• Significance: The sex ratio directly dictates the reproductive potential of the population. A heavily female-skewed ratio in polygynous species can lead to rapid population expansion.

5. Age Distribution and Age Pyramids vs. Age

An individual has a specific age (e.g., 5 years old). A population possesses an Age Distribution, which is the proportion of individuals at different developmental stages or age cohorts.

Ecologically, a population is divided into three functional ecological age groups: Pre-reproductive, Reproductive, and Post-reproductive. When these proportions are plotted geometrically, they form an Age Pyramid.

6. Population Density and Population Size ($N$)

An individual has a specific spatial location and biomass. A population has Population Density, which is the number of individuals of a species per unit area or volume at a given time.

• Mathematical Representation: Density ($D$) is calculated as:
  
  $D = \frac{N}{S}$
  
  Where $N$ is the total number of individuals in the population, and $S$ is the total space (area for terrestrial, volume for aquatic species).

Summary Comparison Table

Final Solution: The distinct attributes possessed by a population—but absent in an individual organism—are Birth Rate (Natality), Death Rate (Mortality), Sex Ratio, Age Distribution (and subsequent Age Pyramids), and Population Density.