The Endocrine System

The endocrine system is a network of glands that produce and release

hormones, which help regulate various bodily functions, such as metabolism,
growth, development, mood, and homeostasis. Unlike the nervous system,
which uses electrical impulses, the endocrine system relies on chemical
signaling via hormones.

Endocrine vs. Exocrine Glands

The body has two main types of glands:

1. Endocrine Glands – These glands secrete hormones directly into the

bloodstream. They are ductless and play a major role in regulating
physiological functions. Examples: Thyroid, Pancreas (endocrine part),
Pituitary, and Adrenal glands.
2. Exocrine Glands – These glands release their secretions through ducts
onto body surfaces or into body cavities. They do not release hormones
but rather substances like sweat, saliva, or digestive enzymes. Examples:
Salivary glands, Sweat glands, and Pancreas (exocrine part).

Feature Endocrine Glands Exocrine Glands

Secretion Hormones Enzymes, sweat, saliva
Mode of Transport Directly into the bloodstream Through ducts
Target Distant organs and tissues Localized effect
Example Pituitary, Thyroid, Adrenal Sweat glands, Salivary glands

Location and Shape of Endocrine Glands

1. Adrenal Glands – Located on top of each kidney, pyramid-shaped.

2. Pancreas – Located behind the stomach, elongated and somewhat J-
shaped.
3. Thyroid Gland – Found in the neck, butterfly-shaped, positioned in front
of the trachea.
4. Pituitary Gland – Located at the base of the brain, pea-sized, attached to
the hypothalamus.

Hormones Secreted by Major Endocrine Glands

1. Pancreas (Both Endocrine and Exocrine)

  Insulin: Lowers blood glucose levels by facilitating glucose uptake by
cells.
 Glucagon: Raises blood glucose levels by promoting glycogen
breakdown in the liver.

2. Thyroid Gland

 Thyroxine (T4): Regulates metabolism, growth, and energy production.

3. Adrenal Gland

 Cortical Hormones (Cortisol, Aldosterone, Androgens):

o Cortisol: Helps manage stress and metabolism.
o Aldosterone: Regulates salt and water balance, affecting blood
pressure.
o Androgens: Contribute to secondary sex characteristics.
 Adrenaline (Epinephrine): Prepares the body for "fight or flight"
response, increasing heart rate and energy supply.

4. Pituitary Gland (Master Gland)

 Growth Hormone (GH): Regulates growth and development of bones

and muscles.
 Tropic Hormones: Stimulate other glands to release their hormones.
Examples:
o TSH (Thyroid-Stimulating Hormone) – Stimulates the thyroid to
produce thyroxine.
o ACTH (Adrenocorticotropic Hormone) – Stimulates the adrenal
cortex to produce cortisol.
o FSH & LH – Regulate reproductive functions.
 ADH (Antidiuretic Hormone): Regulates water balance by acting on the
kidneys.
 Oxytocin: Triggers uterine contractions during childbirth and milk
ejection during lactation.

Effects of Hormone Hyposecretion and Hypersecretion

Hyposecretion
Gland Hormone Hypersecretion (Excess)
(Deficiency)
Diabetes mellitus (high Hypoglycemia (low blood
Pancreas Insulin
blood sugar) sugar)
 Hyposecretion
Gland Hormone Hypersecretion (Excess)
(Deficiency)
Hypothyroidism (slow Hyperthyroidism (high
Thyroid Thyroxine metabolism, weight gain, metabolism, weight loss,
fatigue) restlessness)
Addison’s disease (fatigue, Cushing’s syndrome (weight
Adrenal Cortisol
low blood pressure) gain, high BP)
Excessive stress response
Adrenal Adrenaline Reduced stress response
(high BP, rapid heartbeat)
Growth Gigantism (in children) /
Pituitary Dwarfism (short stature)
Hormone Acromegaly (in adults)
Diabetes insipidus
Pituitary ADH Fluid retention and swelling
(excessive urination)

Feedback Mechanism (Example: TSH and Thyroxine)

The endocrine system works through feedback loops to maintain hormonal

balance. A negative feedback loop regulates thyroid function as follows:

1. The hypothalamus detects low thyroxine levels and releases TRH

(Thyrotropin-releasing hormone).
2. TRH stimulates the pituitary gland to release TSH (Thyroid-
Stimulating Hormone).
3. TSH signals the thyroid gland to produce and release thyroxine (T4).
4. Once thyroxine levels are adequate, it inhibits further secretion of TSH
and TRH to maintain balance.

This prevents overproduction or underproduction of hormones, ensuring

homeostasis.
The Reproductive System
The reproductive system in humans is responsible for producing, maintaining, and
transporting reproductive cells (sperm and egg), as well as facilitating fertilization,
implantation, and the development of a fetus. It consists of male and female reproductive
organs, each playing a crucial role in reproduction.

1. Functions of Male and Female Reproductive Organs & Male Accessory Glands

Male Reproductive System

The male reproductive system includes organs and glands that produce sperm and deliver it to
the female reproductive tract.

Main Organs:

 Testes: Primary male sex organs responsible for sperm production and secretion of
testosterone.
 Scrotum: A sac that holds the testes outside the body, maintaining an optimal temperature
for sperm production.
 Epididymis: A long coiled tube where sperm matures and is stored.
 Vas Deferens: A muscular tube that transports sperm from the epididymis to the urethra.
 Urethra: A shared passage for both urine and semen, leading to the external environment.
 Penis: An organ that facilitates the transfer of sperm into the female reproductive tract.

Male Accessory Glands:

 Seminal Vesicles: Produce seminal fluid rich in fructose to nourish sperm.

 Prostate Gland: Secretes an alkaline fluid to protect sperm from acidic vaginal conditions.
 Bulbourethral (Cowper’s) Glands: Secrete mucus-like fluid to lubricate the urethra.

Female Reproductive System

The female reproductive system is responsible for producing eggs, facilitating fertilization,
and supporting the growth and development of the embryo.

Main Organs:

 Ovaries: Primary female reproductive organs that produce eggs (ova) and secrete estrogen
and progesterone.
 Fallopian Tubes: Tubes connecting the ovaries to the uterus where fertilization occurs.
 Uterus: A muscular organ where the fertilized egg implants and the fetus develops.
 Cervix: The lower part of the uterus that opens into the vagina and facilitates childbirth.
 Vagina: A muscular canal that receives sperm during intercourse and serves as the birth
canal.
2. Secondary Sexual Characteristics

Secondary sexual characteristics develop during puberty due to hormonal changes.

In Males (Due to Testosterone):

 Growth of facial, chest, and pubic hair.

 Deepening of voice due to the enlargement of the larynx.
 Increased muscle mass and body size.
 Growth of reproductive organs and sperm production.

In Females (Due to Estrogen & Progesterone):

 Development of breasts.
 Widening of hips for childbirth.
 Growth of pubic and underarm hair.
 Regulation of the menstrual cycle.

3. Structure and Functions of Sperm and Egg

Sperm (Male Gamete)

Sperm is a microscopic, motile cell designed to fertilize the egg.

Structure:

 Head: Contains genetic material (haploid nucleus) and an acrosome with enzymes to
penetrate the egg.
 Midpiece: Packed with mitochondria to provide energy for movement.
 Tail (Flagellum): Enables movement toward the egg.

Function:

 Carries paternal genetic material to fertilize the egg.

 Actively moves through the female reproductive tract.

Egg (Female Gamete)

The egg is a large, non-motile cell that provides genetic material and nutrients for the
developing embryo.

Structure:

 Nucleus: Contains maternal genetic material.

 Cytoplasm: Provides stored nutrients for early embryo development.
 Zona Pellucida: A protective layer that prevents multiple sperm from entering.
Function:

 Combines with sperm during fertilization to form a zygote.

 Provides initial nutrition for the developing embryo.

4. Explanation of Key Terms

Fertilization

The process where a sperm cell fuses with an egg cell to form a zygote. This usually occurs
in the fallopian tube.

Implantation

The attachment of the fertilized egg (blastocyst) to the uterus lining, where it begins to grow.

Placenta

A temporary organ that forms in the uterus to provide oxygen and nutrients to the developing
fetus.

Gestation

The period of fetal development from fertilization to birth (approximately 9 months in

humans).

Parturition

The process of childbirth, where the baby is delivered from the mother's womb.

5. Role of the Placenta

The placenta is crucial in supporting fetal development. It is attached to the uterine wall and
connects to the fetus via the umbilical cord.

Functions:

1. Nutrition: Transfers oxygen and nutrients from the mother's blood to the fetus.
2. Respiration: Facilitates gas exchange, providing oxygen and removing carbon dioxide.
3. Excretion: Removes fetal waste products into the mother’s bloodstream.
4. Endocrine Function: Produces hormones (HCG, estrogen, and progesterone) to maintain
pregnancy.
6. Functions of Fetal Membranes & Amniotic Fluid

 Amnion (Fetal Membrane): Forms a protective sac around the fetus.

 Chorion: Involved in forming the placenta.
 Amniotic Fluid:
o Cushions the fetus from mechanical shocks.
o Maintains a stable temperature.
o Allows fetal movement for muscular development.

7. Menstrual Cycle

The menstrual cycle is a monthly cycle that prepares the female body for pregnancy. It lasts
around 28 days and has four phases:

1. Menstrual Phase (Days 1-5): Shedding of the uterine lining if no fertilization occurs.
2. Follicular Phase (Days 6-13): Growth of ovarian follicles and an increase in estrogen levels.
3. Ovulation (Day 14): Release of a mature egg from the ovary.
4. Luteal Phase (Days 15-28): Formation of the corpus luteum, which secretes progesterone to
maintain the uterine lining.

If fertilization does not occur, hormone levels drop, leading to menstruation.

8. Role of Sex Hormones

Testosterone (Males):

 Produced by the testes.

 Stimulates sperm production.
 Responsible for secondary sexual characteristics.

Estrogen (Females):

 Produced by the ovaries.

 Develops secondary sexual characteristics.
 Regulates the menstrual cycle.

Progesterone (Females):

 Secreted by the corpus luteum and placenta.

 Prepares the uterus for implantation.
 Maintains pregnancy.

9. Identical and Fraternal Twins

Identical Twins:
  Formed from a single fertilized egg that splits into two embryos.
 Genetically identical and always the same sex.

Fraternal Twins:

 Result from two different eggs fertilized by two different sperm.

 Genetically unique and can be of different sexes.
Population and Population Control

Population Explosion in India and the Need for Control Measures

Population explosion refers to a rapid and unchecked increase in the population of a region.
India, with a population of over 1.4 billion, is the second-most populous country in the world.
The rising population has put immense pressure on natural resources, infrastructure, and
economic development. As a result, it is crucial to implement effective population control
measures to ensure sustainable growth and development.

Main Reasons for the Sharp Rise in Population

1. Improved Medical Facilities: Advances in healthcare have significantly reduced the

mortality rate, leading to longer life expectancy.
2. Decline in Death Rate: Improved sanitation, better nutrition, and medical
advancements have contributed to a decline in the death rate.
3. High Birth Rate: Social and cultural factors encourage large families, leading to a
high birth rate.
4. Lack of Education: Low literacy rates, especially among women, result in a lack of
awareness about family planning and contraception.
5. Religious and Social Beliefs: Many communities believe in having large families due
to traditional and religious practices.
6. Early Marriages: In many rural areas, early marriages lead to longer reproductive
lifespans and higher fertility rates.
7. Poverty: Poor families often have more children to ensure financial security through
labor and old-age support.

Key Terms Explained

1. Demography: The statistical study of human populations, including their size,

structure, and distribution.
2. Population Density: The number of people living per unit area of land, usually
expressed as people per square kilometer.
3. Birth Rate: The number of live births per 1,000 people in a given year.
4. Death Rate: The number of deaths per 1,000 people in a given year.
5. Growth Rate of Population: The rate at which the population increases, calculated
as the difference between birth and death rates, including migration.
Problems Faced Due to Population Explosion

1. Unemployment: The growing population leads to a lack of job opportunities,

resulting in high unemployment rates.
2. Over-Exploitation of Natural Resources: Increased demand for water, land, and
energy leads to resource depletion.
3. Low Per Capita Income: More people mean a division of resources, reducing per
capita income and affecting the standard of living.
4. Price Rise: Increased demand for goods and services leads to inflation, making
essential commodities expensive.
5. Pollution: Overpopulation leads to air, water, and land pollution, adversely affecting
health and the environment.
6. Unequal Distribution of Wealth: Economic disparity increases as a large population
puts strain on the economy, leading to social inequalities.

Methods of Population Control

1. Family Planning Programs: Governments promote contraceptive use, awareness

campaigns, and incentives for smaller families.
2. Education and Awareness: Educating people, especially women, about reproductive
health and family planning helps control population growth.
3. Government Policies: Policies like the two-child norm and incentives for smaller
families help in controlling the birth rate.
4. Encouraging Late Marriages: Delaying marriage reduces the reproductive span,
leading to fewer children per couple.
5. Surgical Methods of Contraception:
o Tubectomy: A permanent surgical method of sterilization in women, where
the fallopian tubes are cut or blocked to prevent pregnancy.
o Vasectomy: A permanent surgical method of sterilization in men, where the
vas deferens (sperm-carrying tubes) are cut or sealed to prevent the release of
sperm.
Human Evolution

Introduction to Human Evolution

Human evolution refers to the lengthy process of change by which modern humans
developed from early hominins. This transformation took millions of years and involved
various anatomical, physiological, and behavioral adaptations. The study of human evolution
incorporates findings from paleontology, anthropology, genetics, and archaeology to
understand how Homo sapiens emerged as the dominant species on Earth.

Theories of Evolution

Several theories have been proposed to explain the process of evolution. Two prominent
theories are Lamarck’s Theory of Inheritance of Acquired Characteristics and Darwin’s
Theory of Evolution by Natural Selection.

Lamarck’s Theory of Inheritance of Acquired Characteristics

Jean-Baptiste Lamarck (1744–1829) proposed that organisms could pass on characteristics

acquired during their lifetime to their offspring. According to Lamarck:

 Organisms change over time in response to their environment.

 Traits that are frequently used become more developed, while those not used
diminish.
 These acquired traits are inherited by future generations.

Examples:

1. Giraffe’s Neck: Lamarck suggested that giraffes originally had short necks but
stretched them to reach high leaves. Over generations, this led to longer necks.
2. Vestigial Organs in Humans: Lamarck’s theory can be linked to the presence of
vestigial structures in humans, such as the wisdom teeth, vermiform appendix, and
pinnae. These organs were once functional but diminished in importance due to
changes in lifestyle and diet.

Darwin’s Theory of Natural Selection

Charles Darwin (1809–1882) proposed that evolution occurs through natural selection, where
individuals with favorable traits are more likely to survive and reproduce. His theory is based
on the following principles:

 Variation: Individuals within a species exhibit differences in their traits.

 Overproduction: Organisms produce more offspring than can survive.
 Competition: Limited resources lead to competition for survival.
 Survival of the Fittest: Individuals with advantageous traits have a higher chance of
survival and reproduction.
 Inheritance: Favorable traits are passed down to the next generation.
Example: Peppered Moth

 Before industrialization, light-colored moths were more common as they blended with
tree bark.
 With pollution darkening the trees, darker moths became more camouflaged, leading
to an increase in their population.
 This adaptation showcases how natural selection favors traits that enhance survival.

Human Ancestors and Their Characteristics

Human evolution involved a gradual transition from early hominins to modern Homo
sapiens. Some of the major ancestors include:

1. Australopithecus (4 – 2 million years ago)

 Early bipedal hominins found in Africa.

 Small cranial capacity (~400-500 cc).
 Large face and prominent brow ridges.
 Lived in open grasslands and adapted to upright walking.

2. Homo habilis (2.4 – 1.4 million years ago)

 Known as “Handy Man” due to tool usage.

 Increased brain size (~600-700 cc).
 Reduced size of canine teeth.
 Developed primitive stone tools for hunting and scavenging.

3. Homo erectus (1.9 million – 110,000 years ago)

 Larger brain (~900-1100 cc) and more developed tools.

 First hominin species to use fire.
 Taller stature and robust body structure.
 Spread from Africa to Europe and Asia.

4. Neanderthals (400,000 – 40,000 years ago)

 Stocky build with large cranial capacity (~1600 cc).

 Adapted to cold climates.
 Skilled hunters and used complex tools.
 Evidence of burial rituals and possible speech ability.

5. Cro-Magnon (40,000 – 10,000 years ago)

 Early modern humans with advanced tool-making skills.

 High forehead, reduced brow ridges, and prominent chin.
 Created cave paintings and sculptures.
 Social organization and language developed.
6. Homo sapiens sapiens (Modern Humans, ~300,000 years ago - Present)

 Large brain (~1350 cc) and complex cognitive abilities.

 Highly developed culture, language, and technological advancements.
 Minimal body hair, fully upright posture, and refined motor skills.

Evolutionary Trends in Humans

Several key characteristics have evolved over time:

1. Bipedalism:
o Australopithecus exhibited early bipedal traits.
o Freed hands for tool use and improved endurance for long-distance travel.
2. Increasing Cranial Capacity:
o Brain size increased from ~400 cc (Australopithecus) to ~1350 cc (modern
humans).
o Enhanced problem-solving, communication, and social interaction.
3. Reduction of Canine Teeth Size:
o Early hominins had large canines for defense and competition.
o Dietary changes reduced the need for large canines.
4. Forehead and Brow Ridges:
o Early hominins had prominent brow ridges.
o Modern humans have a high forehead and reduced brow ridges for increased
brain volume.
5. Development of Chin:
o Unique to Homo sapiens.
o May aid in speech and jaw reinforcement.
6. Reduction in Body Hair:
o Helped in thermoregulation and reducing parasite load.
o Allowed for better endurance running and adaptation to hot climates.
7. Height and Posture:
o Early hominins were shorter and more robust.
o Modern humans have a taller, more slender build suited for endurance
activities.
Pollution
(i) Types and Sources of Pollution; Major Pollutants

Pollution is the introduction of harmful substances into the environment, which can
negatively impact living organisms and ecosystems. The major types of pollution include:

1. Air Pollution

Air pollution occurs due to the release of harmful gases and particulate matter into the
atmosphere. Sources:

 Vehicular emissions: Exhaust from cars, buses, and motorcycles contains carbon monoxide
(CO), nitrogen oxides (NOx), and particulate matter.
 Industrial emissions: Factories release sulfur dioxide (SO₂), nitrogen oxides (NOx), and
volatile organic compounds (VOCs).
 Burning of garbage: Open burning releases dioxins, furans, and particulate matter.
 Brick kilns: These contribute significantly to air pollution by emitting soot, carbon monoxide,
and other harmful gases.

2. Water Pollution

Water pollution occurs when harmful substances contaminate water bodies, affecting aquatic
life and human health. Sources:

 Household detergents: Contain phosphates and chemicals that lead to eutrophication.

 Sewage: Untreated wastewater can introduce harmful bacteria and viruses.
 Industrial waste: Heavy metals such as mercury and lead contaminate rivers and lakes.
 Oil spills: Oil leaks from tankers and pipelines can devastate marine ecosystems.

3. Thermal Pollution

This occurs when industries discharge hot water into water bodies, leading to increased water
temperatures that can disrupt aquatic life.

4. Soil Pollution

Soil pollution results from the deposition of harmful chemicals and waste materials. Sources:

 Industrial waste: Heavy metals and toxic chemicals seep into the soil.
 Urban commercial and domestic waste: Non-biodegradable materials like plastics
contaminate the soil.
 Chemical fertilizers and pesticides: Excessive use can deplete soil fertility and enter the food
chain.

5. Biomedical Waste Pollution

Medical waste poses significant health risks when improperly disposed of. Sources:

 Used and discarded needles and syringes

  Soiled dressings and contaminated medical equipment
 Expired medicines and chemical disinfectants

6. Radiation Pollution

Radiation pollution occurs due to excessive exposure to harmful ionizing radiation. Sources:

 X-rays: Overexposure can cause health issues.

 Radioactive fallout from nuclear plants: Can lead to radiation sickness and genetic
mutations.

7. Noise Pollution

Noise pollution is excessive and disruptive sound that affects human well-being. Sources:

 Motor vehicles
 Industrial establishments
 Construction sites
 Loudspeakers and urban activities

(ii) Biodegradable and Non-Biodegradable Wastes

Biodegradable Wastes

Biodegradable wastes decompose naturally by the action of microorganisms. Examples:

Paper, vegetable peels, food waste, cotton, wood.

Non-Biodegradable Wastes

Non-biodegradable wastes do not decompose easily and persist in the environment.

Examples: Plastics, glass, Styrofoam, metals, pesticides like DDT.

(iii) Effects of Pollution on Climate, Environment, Human Health, and Other Organisms

1. Climate Effects

 Greenhouse Effect and Global Warming: Increased CO₂ and other greenhouse gases trap
heat in the atmosphere, leading to rising temperatures and extreme weather patterns.
 Acid Rain: Emission of sulfur dioxide (SO₂) and nitrogen oxides (NOx) leads to acid rain,
which damages crops, soil, and aquatic systems.
 Ozone Layer Depletion: Chlorofluorocarbons (CFCs) break down the ozone layer, increasing
exposure to harmful UV radiation.

2. Environmental Effects

 Deforestation and loss of biodiversity

  Water body contamination leading to loss of aquatic life
 Soil degradation reducing agricultural productivity

3. Human Health Effects

 Respiratory diseases: Asthma, bronchitis, lung cancer due to air pollution.

 Waterborne diseases: Cholera, typhoid due to contaminated water.
 Neurological disorders: Lead and mercury poisoning affect brain function.
 Hearing loss: Due to prolonged exposure to noise pollution.

4. Effects on Other Organisms

 Decline in fish populations due to water pollution

 Poisoning of birds and animals by consuming plastic waste
 Habitat destruction affecting biodiversity

(iv) Measures to Control Pollution

1. Air Pollution Control

 Use of unleaded petrol and CNG in vehicles.

 Encouraging public transport and carpooling.
 Switching off vehicle engines at traffic signals to reduce emissions.
 Implementation of Euro Bharat Vehicular Standards to regulate emissions.

2. Water Pollution Control

 Establishing sewage treatment plants.

 Regulating industrial waste discharge into water bodies.
 Preventing oil spills by enforcing safety measures on oil tankers.

3. Soil Pollution Control

 Reducing chemical fertilizers and pesticides by promoting organic farming.

 Proper disposal and recycling of urban and industrial waste.
 Banning polythene bags and plastics to reduce land contamination.

4. Biomedical and Radiation Pollution Control

 Safe disposal and incineration of biomedical waste.

 Strict regulation of nuclear plant emissions and proper disposal of radioactive waste.

5. Noise Pollution Control

 Strict regulations on loudspeakers and industrial noise levels.

 Establishing soundproofing measures in industries and urban areas.
 Promoting green belts and tree plantations to absorb noise.
(v) National Initiatives: Swachh Bharat Abhiyan

Swachh Bharat Abhiyan (Clean India Mission) is a nationwide campaign launched by the
Government of India to clean streets, roads, and infrastructure.

Key Objectives:

 Eliminate open defecation by constructing toilets.

 Improve waste management by promoting segregation and recycling.
 Encourage cleanliness awareness among citizens.
 Develop sustainable sanitation practices.

By implementing these pollution control measures and fostering awareness, we can create a
healthier and more sustainable environment for future generations.