krit.club logo

Biology - Population

Grade 10ICSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

•

Demography: The statistical study of human population, including its size, structure, and distribution.

•

Population Explosion: The rapid and exponential increase in the human population size, primarily due to improved medical facilities, better food security, and a decrease in infant mortality rates.

•

Natality (Birth Rate): The number of live births per 10001000 people in the population per year.

•

Mortality (Death Rate): The number of deaths per 10001000 people in the population per year.

•

Growth Rate: The net increase in the population per 10001000 individuals per year, calculated as (Birth Rate−Death Rate)(\text{Birth Rate} - \text{Death Rate}).

•

Population Density: The number of individuals of a species per unit area (e.g., individuals per km2km^2).

•

Immigration and Emigration: Immigration is the entry of individuals into a population from outside, while Emigration is the departure of individuals from a population to settle elsewhere.

•

Contraception: Methods used to prevent pregnancy. These include Barrier methods (Condoms, Diaphragms), Chemical methods (Spermicides), and Hormonal methods (Oral pills containing estrogenestrogen and progesteroneprogesterone).

•

Intra-Uterine Contraceptive Devices (IUCD): Devices like the Copper−TCopper-T that are inserted into the uterus to prevent implantation. CopperCopper ions (Cu2+Cu^{2+}) released suppress sperm motility.

•

Surgical Methods (Sterilization): Vasectomy is the surgical cutting and ligation of the Vas deferensVas\ deferens in males. Tubectomy is the surgical cutting and ligation of the Fallopian tubesFallopian\ tubes in females.

•

Malthusian Theory: Thomas Malthus proposed that the human population grows in a geometric progression (1,2,4,8...1, 2, 4, 8...), while food production grows in an arithmetic progression (1,2,3,4...1, 2, 3, 4...).

📐Formulae

Birth Rate (Natality)=Total number of live births in a yearTotal population at mid-year×1000\text{Birth Rate (Natality)} = \frac{\text{Total number of live births in a year}}{\text{Total population at mid-year}} \times 1000

Death Rate (Mortality)=Total number of deaths in a yearTotal population at mid-year×1000\text{Death Rate (Mortality)} = \frac{\text{Total number of deaths in a year}}{\text{Total population at mid-year}} \times 1000

Growth Rate=Birth Rate−Death Rate\text{Growth Rate} = \text{Birth Rate} - \text{Death Rate}

Population Density=Total Number of Individuals (N)Total Area (S)\text{Population Density} = \frac{\text{Total Number of Individuals (N)}}{\text{Total Area (S)}}

Percentage Growth Rate=Births−DeathsTotal Population×100\text{Percentage Growth Rate} = \frac{\text{Births} - \text{Deaths}}{\text{Total Population}} \times 100

💡Examples

Problem 1:

In a specific town, the total population is 2,00,0002,00,000. During a single year, the number of live births recorded was 4,0004,000 and the number of deaths was 1,5001,500. Calculate the Birth Rate and the annual Growth Rate.

Solution:

Birth Rate =4,0002,00,000×1000=20= \frac{4,000}{2,00,000} \times 1000 = 20. Death Rate =1,5002,00,000×1000=7.5= \frac{1,500}{2,00,000} \times 1000 = 7.5. Growth Rate =20−7.5=12.5= 20 - 7.5 = 12.5 per thousand.

Explanation:

The Birth Rate (Natality) is calculated per 10001000 members of the population. The Growth Rate is the difference between the Natality and Mortality rates.

Problem 2:

Identify the surgical procedure where a small part of the sperm duct is removed and the cut ends are tied. Explain its effect on fertility.

Solution:

The procedure is called Vasectomy. It involves the ligation of the Vas deferensVas\ deferens.

Explanation:

By cutting and tying the Vas deferensVas\ deferens, the path of the spermsperm from the testes to the urethra is blocked. Therefore, while semen is still produced by accessory glands, it contains no spermsperm, preventing fertilization.