Abiotic Components The word ‘abiotic’ means ‘non-living’. Light, air, water, soil, and temperature are some examples of abiotic components of the environment. Even though these components are themselves non-living, they have an effect on the living organisms, i.e., the biotic components of the environment.
Light Plants use light to prepare their food.
Temperature Temperature is a measure that tells us how hot or cold something is. Earth is the only known planet that has a temperature suitable for life to exist. Even on Earth, the temperature is not uniform all around. It is very hot near the equator, while places near the poles are very cold. Temperature affects the distribution of plants and animals around the planet.
Animals whose body temperature changes with the outside temperature are called cold-blooded animals. Most reptiles, insects, and amphibians are cold-blooded. Animals whose body temperature does not change with the outside temperature are called warm-blooded animals. Most mammals and birds are warm-blooded.
Warm-blooded animals can survive in areas having extreme temperatures like the desert and the Arctic region. Here, cold-blooded animals would have difficulty in surviving. Polar bear is adapted to survive in the harsh temperatures of the Arctic.
Polar Bear
Air Oxygen and carbon dioxide present in air are very important for the survival of organisms. Both plants and animals need oxygen for respiration. Animals and human beings release carbon dioxide during respiration, which is used by green plants for photosynthesis. Carbon dioxide is also released by burning of fuels in vehicles and factories. Plants, in turn, release oxygen into the environment. Thus, green plants play a very important role in maintaining the balance of oxygen and carbon dioxide in the environment. Moving air or wind also helps in the reproduction of plants through pollination and dispersal of certain fruits and seeds.
The balance of oxygen and carbon dioxide in atmosphere
Water Water is very important for living organisms. Plants absorb water through their roots, which is then transported to different plant parts. Water is essential for carrying out photosynthesis in plants. It also plays an important role in the human body. Blood, which transports substances within the human body, is largely composed of water. In fact, 70% of the human body consists of water. Water dissolves vital gases like oxygen and carbon dioxide. This enables living beings to survive in water.
Water is essential for living organisms
Soil Soil is the uppermost layer of the Earth’s crust. It has four sub-layers – topsoil, subsoil, parent material, and the bedrock. It is in the topsoil that plants grow. Soil is very rich in minerals like magnesium, potassium, and phosphorus. Without soil, there would be no plants and thus, no food for us. Plants grow well in loosely packed soil as it allows their roots to grow deeper and also makes it easier for them to absorb water and nutrients. This is why farmers plough their fields before sowing seeds.
Sub layers of soil
Animals like earthworm and snail also make the soil loose by turning it.
Habitat Thus in nature, biotic and abiotic components are closely interrelated. Biotic components (organisms) interact with one another too. A group of interdependent organisms that live in the same region and interact with one anotherform a biotic community. A biotic community includes plants, animals, and microorganisms.
The period of transition from childhood to adulthood is called adolescence. The boys and girls passing through this period are called adolescents. The World Health Organization (WHO) defines adolescence as the period of life between 10 and 19 years of age. Adolescence is characterized by changes like development of breasts in girls and facial hair in boys. As these characteristics help in distinguishing males (i.e., boys) from females (i.e., girls), they are referred to as secondary sexual characteristics. The stage in which secondary sexual characteristics develop is referred to as the stage of maturity or puberty. Puberty is the start of the time when a boy is biologically ready to become a father and a girl is biologically ready to become a mother. Let us discuss the changes that take place when girls and boys reach puberty.
Physical Changes
The following physical changes take place in girls and boys during puberty.
Increase in height and weight Puberty is characterized by a ‘growth spurt’—a rapid increase in height and weight in both boys and girls. The rate of growth may vary from person to person. Generally, girls grow faster than boys initially, but both reach their maximum height around 18 years of age.
Change in body shape In girls, the hips broaden and the pelvic region widens. In boys, muscles develop and shoulders become broader.
Body hair During puberty, hair develop under armpits and in the pubic region in both boys and girls. Boys also develop facial hair (i.e., moustache and beard) and hair on the chest.
Development of reproductive organs In girls, the ovaries enlarge and start producing mature eggs. In boys, testes and penis develop completely and the testes start producing sperms.
Change in voice The voice box or larynx increases in size during puberty, which results in a change in voice. Generally, this increase in size is more in boys and the enlarged voice box can be observed as a prominent lump called Adam’s apple in the neck region. Due to larger voice boxes, boys generally develop a deep voice while girls tend to have a high-pitched voice.Initially, increase in the size of the larynx may cause a boy’s voice to ‘crack’ or ‘break’, but the voice becomes normal after some time.
Increased activity of sweat and oil glands During puberty, sweat and oil glands in the body become very active and cause increased sweating. Increased activity of these glands may also cause acne or pimples in adolescents. In addition to the above, the following physical changes are observed in girls.
Enlargement of breasts During puberty, breasts increase in size and milk-producing glands called mammary glands develop inside them.
Beginning of the menstrual cycle From the onset of puberty, the two ovaries inside a girl’s body take turns to produce an egg or ovum (plural ova), and one ovum is released every 28 days. The process of release of an ovum by an ovary is called ovulation.
The cycle of producing and releasing mature ova is called the menstrual cycle (menstrual means month in Latin). The start of the menstrual cycle indicates that the girl has now acquired the ability to have a baby. During the menstrual cycle,
Different parts of the body release hormones to prepare the body for pregnancy. The pituitary gland secretes a hormone that stimulates the ovary to release a mature ovum. The ovaries release two important hormones, oestrogen and progesterone, which change the lining of the uterus. The ovum then begins its journey through the fallopian tube.
Ovum, fallopian tube, and uterus
In case the ovum is not fertilized by a male sperm, it dies and starts disintegrating and the hormonal levels drop. The lining of the uterus starts breaking down and is shed, accompanied by a loss of blood. This phase, which usually lasts 4-6 days, is called a girl’s period or menstruation. Figure shows the various changes occurring during the menstrual cycle.
Changes occurring during the menstrual cycle
Emotional Changes
One may experience various emotional changes during puberty. Due to an increase in the hormonal level, mood swings may occur. One may become conscious of the changes occurring in one’s body and feel awkward or embarrassed. During this phase one may also develop attraction towards the opposite sex. All these changes are normal and are a part of growing up. Puberty is also the phase during which one has a great capacity to learn and one’s way of thinking matures.
Role of Hormones During Puberty
The changes experienced during adolescence are brought about by hormones. In girls, a hormone released by the pituitary gland stimulates the ovaries to produce female sex hormones called progesterone and oestrogen. Oestrogen is responsible for the production of ova and development of secondary sexual characteristics in girls. In boys, a hormone released by the pituitary gland stimulates the testes to produce the male sex hormone called testosterone. Testosterone is responsible for the production of sperm cells and the development of secondary sexual characteristics in boys.
Nutritional requirements and personal hygiene
During adolescence, there is rapid physical and mental growth and, as a result, the nutritional requirements of the body increase tremendously. It is, therefore, important to consume a balanced diet at this stage. Consuming too much junk foods should be avoided as these are deficient in important nutrients like proteins, vitamins, and minerals. Milk, green- leafy vegetables, and fruits are some examples of food items that are good for adolescents. Since girls start menstruating at this stage, they need to consume foods rich in iron, calcium, and zinc.
Personal hygiene is also very important during adolescence. Sweating may become a major problem at this stage. Bacteria multiply rapidly in sweat and cause bad odour. One can manage these odours by bathing daily and wearing clean clothes.
It is also very important to keep the genital areas clean. Girls should be aware of supplies like sanitary pads and tampons and their usage during menstruation. A large number of adolescents are affected by acne or pimples.
One should wash the face with a mild non-oily soap to keep it clean. In some cases, acne may require medical attention.
Drug abuse and AIDS
Drug abuse is a common problem among adolescents all over the world. Drugs are chemical substances that produce physical, mental, behavioural, or emotional changes in the user. Use of a drug for purposes other than medicinal use is called drug abuse. Drug abuse harms the body seriously. Once a person starts taking drugs, he/she develops physical and/or psychological dependence on them. This dependence, commonly termed as addiction, makes it difficult for people to stop taking drugs. It is, therefore, important to say no to drugs and avoid them at all costs. Alcohol, nicotine (present in tobacco products like cigarettes, gutka, and pan masala), cocaine, and marijuana are examples of drugs.
People who use drugs are also at risk of being infected with HIV, the deadly virus that causes AIDS. This virus can spread by sharing syringes used for injecting some drugs. It also spreads through sexual contact with an infected person.
All living things depend on their surroundings for food, water, and shelter. All that surrounds living things and affects their growth and development is called their environment. Both living and non-living things form the environment. Thus, we can say that the environment is made up of two parts or components – biotic and abiotic.
Components Of Environment
Living things like plants and animals are called biotic components.
Non-living things like air, light, water, soil, and temperature are called abiotic components.
Biotic and abiotic components of the environment
1. Biotic Components The word ‘biotic’ means ‘living’. Biotic components are those that have life. Plants, animals, scavengers, and decomposers are biotic components. Plants Most plants have green leaves. Leaves are green because they contain a green pigment called chlorophyll (<chloro, green; phyll, leaf). Chlorophyll gives plants the special ability to make their own food using light, water, and carbon dioxide. The process by which green plants make their food using carbon dioxide and water in the presence of light and chlorophyll is called photosynthesis (photo, light; synthesis, production).
Diagrammatic representation of photosynthesis
Animals Animals cannot make their own food, as green plants do, thus they are called heterotrophs. Both animals and plants need substances called nutrients in order to grow. Plants absorb nutrients like nitrogen, phosphorus, and calcium from the soil. These nutrients enter the bodies of animals when they eat plants or the flesh of other animals. After these plants and animals die, their bodies decompose and nutrients reach back to the soil.
Scavengers and Decomposers Some organisms feed on the bodies of dead plants and animals and release the nutrients trapped inside them. Animals that feed on the dead bodies of other animals are called scavengers. For example, hyena and vulture.
vulture
Tiny organisms that feed on the remains of dead plants and animals to break them down into simpler substances are called decomposers. Bacteria and fungi are common decomposers.
fungi
The nutrients released from the dead bodies by the action of scavengers and decomposers get mixed with the soil and are again absorbed by plants. This process is called recycling of nutrients.
Scavengers and decomposers play two important roles in the environment because:
They keep the environment clean by removing the bodies of dead plants and animals.
They help in the recycling of nutrients in the environment.
Interactions Among Biotic Components Plants and animals depend on each other for various needs. Animals mainly depend on plants for food and shelter. Animals in turn help plants by pollinating flowers, dispersing seeds, etc.
A bee pollinates flowers while collecting nectar
In nature, the following relationships are observed among plants, animals, scavengers, and decomposers.
Plants (called producers) utilize sun’s energy and manufacture their own food through photosynthesis.
Herbivores (called primary consumers) like rabbit and deer feed on plants.
Carnivores (called secondary consumers) like tiger and lion feed on herbivores.
Omnivores (called secondary consumers) like human beings and bear feed on both plants and flesh of other animals.
Scavengers and decomposers feed on dead plants and animals and release the nutrients trapped inside their bodies into the soil. These nutrients are then absorbed by plants, which helps them to grow and manufacture their food.
The endocrine system consists of a collection of bag-like structures called glands. These glands are located at specific places inside our bodies and release chemical substances called hormones. These hormones travel inside our bodies and act like chemical messengers.
The major glands that make up the human endocrine system are pituitary, thyroid, adrenals, pancreas, ovaries, and testes. The pituitary gland, located at the base of the brain, is called the master gland of the endocrine system because its hormones control the activities of many of the other endocrine glands. The adrenal gland is called the gland of emergency because it helps the body respond to emergency situations. Epinephrine or adrenaline, a hormone secreted by the adrenal gland, is known as the fight or flight hormone because it prepares the body to act when we are in a stressful or potentially dangerous situation. It is because of this hormone that the body experiences emotional states like anger and excitement. The changes brought about by adrenaline are widespread, very rapid, and last a very short time. Some of the changes brought about by adrenaline are listed below.
It increases the heartbeat.
It increases the blood sugar level.
It results in an overall increase in the body’s energy level.
A diagrammatic representation of the human endocrine system is shown in Figure.
Role of some of the key hormones is given in Table.
Table Hormones and their role in the body
Hormone
Role in the body
Thyroid stimulating hormone (TSH)
TSH stimulates the growth and functions of the thyroid gland.
Growth hormone (GH)
GH stimulates the growth and development of the body.
Insulin
It regulates the blood sugar level. Inability of the body to produce insulin in sufficient quantity may result in a disease called diabetes.
Thyroxine
It regulates body temperature and plays an important role in growth and development. Inability of the body to produce this hormone may result in a disease called goitre, which causes swelling of the neck.
Adrenaline
It helps in the defence of the body in emergency situations.
Oestrogen
It controls the development of secondary sexual characteristics, like development of breasts, in females.
Testosterone
It controls the development of secondary sexual characteristics, like facial hair, in males.
Hormones play an important role in the growth and development of the body, especially during a period known as adolescence.
Most clothing materials or fabrics we use in our day-to-day lives are made from thin, thread-like fibres. Fibres can be either natural or artificial. Natural fabrics have been used for clothing since ancient times. But nowadays, synthetic fibres are largely used for clothing and other purposes.
Synthetic fibres
Fibres that are made by human beings are called synthetic fibres. Most synthetic fibres are obtained from coal, petroleum, and natural gas. A synthetic fibre consists of multiple units (each of which is a chemical substance), which are joined together to form a single unit called a polymer (poly: many; mer: unit). The structure of a polymer can be described as resembling numerous beads on a string, with the beads representing the individual units that are joined together. Rayon, nylon, polyester, acrylic, and spandex are examples of synthetic fibres.
Polyamides and polyesters are two groups of synthetic fibres with high strength, not easily stretched and used as textile.
Nylon is an example of polyamide polymers. Terylene is an example of polyester polymers.
Nylon and terylene are produced through condensation polymerisation.
Nylon (a) Nylon is a general term given to the synthetic polymer made from two types of monomer, diamine molecules and diacid molecules. (b) A diamine molecule has two -NH2 groups and a diacid has two -COOH groups. (c) Diacid molecules and diamine molecules undergo condensation reaction to form nylon and water. (d) Nylon-6,6 is manufactured from polymerisation of hexane-1,6-diamine and hexane-1,6-dioc acid. (e) Nylon-6,6 is a strong, tough and waterproof polymer and can be easily made into fibres. (f) Nylon is used to make toothbrushes, ropes, fishing lines, parachutes, carpets, textile, threads and electrical insulators.
Terylene (a) The monomers used to make polyester are diol molecules and diacid molecules. (b) A diol molecule has two -OH groups and a diacid molecule has two -COOH groups. (c) When many diacid molecules condense with diol molecules, a polyester and water are formed. (d) Terylene for example, is manufactured from ethane-1,2-diol and (benzene)benzoic- 1,4- dicarboxylic acid. (e) Terylene is suitable for making textile, stocking, parachutes and fishing nets because it is elastic, chemically inert, can be coloured and easily made into fibre.
Rayon, also called artificial silk, is prepared from cellulose (which comes from wood pulp).
Properties
It absorbs sweat. Rayon clothes are, therefore, preferred over other synthetic fibres in summer.
It is shiny and lustrous and resembles silk in appearance.
Uses
Rayon is used for making shirts, ties, home furnishing (bed sheets, curtains, tablecloths, sofa covers, etc.), and bandages.
Rayon Ties
Nylon
Nylon was the first true synthetic fibre. It was first produced in the early 1930s by the scientists at the DuPont Company from coal, water, and air.
Properties
It is elastic and does not lose strength even after repeated use.
It is lustrous and easy to wash.
Uses
Nylon is used for making saris, socks, stockings, tents, umbrellas, parachutes, and tarpaulins.
Nylon fibres are used for making toothbrush bristles.
Due to their high strength and elasticity, nylon threads are used for making fishing nets, climbing ropes, and strings of badminton and tennis racquets.
Strings of a tennis racquet are made of nylon.
Polyester
Polyester is of different types. The most commonly used polyester is Terylene. It is blended with natural fibres to improve its properties. Terrycot, a blend of Terylene and cotton, has better absorbing power as compared to Terylene. Terylene is blended with wool to make Terrywool, which is warm in addition to all the characteristics observed in polyesters.
Properties
It is strong, lightweight, and has good elasticity.
It resists wrinkling and springs back into shape when creased.
Polyester fabrics can be washed and dried easily and quickly.
Note: Elasticity Ability of a material to return to its original shape after it has been stretched or compressed
Uses
Polyester is used for making lightweight sails.
Sails made of polyester
Polyester films (commonly known as Mylar) are used for making magnetic recording tapes in audio cassettes, video cassettes, and floppy disks.
Terylene is used for making conveyor belts as it is very elastic. Terrycot is commonly used for making shirts, skirts, and other dress materials.
Terrywool is used for making formal suits.
Acrylic
Acrylic fibres, also known as Orion and Acrilan, closely resemble wool.
Properties
It is warm, soft, light, and flexible.
It is resistant to moths and chemicals.
Uses
Acrylic is used for making sweaters, socks, shawls, carpets, and blankets.
Spandex
Spandex, also known as Lycra, was invented by the DuPont chemist Joseph Shivers in 1959.
Properties
It has excellent elasticity, which makes it suitable for use in clothes that require snug fitting.
Uses
Spandex is used for making swimming costumes. It is often mixed with other fibres, like cotton, to get stretch fabrics, which are used for making caps and T-shirts.
Initially, increase in the size of the larynx may cause a boy’s voice to ‘crack’ or ‘break’, but the voice becomes normal after some time.
