[Biology Class Notes] on Human Life Cycle Pdf for EXAM [2024]

Human life cycle is the cycle that occurs in human beings and involves a time period for different stages of life. The ideal nutrition and physical well-being ensures prosperity of each stage and helps humans to live more. The major six stages of the human life cycle are known that starts with the prenatal stage where fertilisation takes place and foetal development occurs inside a mother and then ends with the death of human beings. Therefore, old age is the final stage of the life cycle and death is the end of the human life cycle.

Human life cycle biology chapter is there in the books for students and it is easy to understand. In this we’ll talk about the human life cycle and the various stages of the human life cycle.

What are the Six Stages in the Human Life Cycle?

The Human Life Cycle consists of various stages that include foetus, baby, childhood, adolescence, adulthood and elderly; these are discussed in detail as follows:

Stage 1:

Foetus- It is a creation called zygote with the fusion of an egg from the mother and a sperm from the father. Zygote looks like a bundle of cells that divides rapidly and turns into an embryo after about 2-4 weeks inside the mother’s womb. It takes about 8 weeks for the embryo to turn into a human body shape and it is called the foetus.

Stage 2:

Baby- After nine months in the mother’s womb, a baby is born. Babies under 1 year of age are called infants and are fed on mother’s milk. Newborn babies are able to suck, breathe, swallow and cry when they feel hungry/cold/hot or any other uncomfortable situation. This is the way of expressing themselves as they cannot talk at this stage.

Stage 3:

Childhood- This among the various stages of human life can be divided into 3 sub stages, namely-

Toddler: It is a child who is a grown up baby and is between the ages of 1-3 years. Here, a child slowly learns crawling, walking, talking, running, jumping, identifying things and eating by themselves.
Preschooler: It is a child who is between the ages of 3-5 years. At this sub-stage of childhood, the child can communicate properly, read, write, make friends and indulge in various childhood activities.
Primary School Kid: It is a child who is between the ages of 5-12 years. At this stage, a child or primary schooler has developed good muscle control and coordination, eye-hand coordination, personal habits, thinking patterns, awareness of safety issues and personal habits and choices.

Stage 4:

Adolescence- In this human life cycle stage, a child grows into an adolescent through puberty period. Puberty is the process of physical changes where a child’s body matures into an adult body that is capable of sexual reproduction. It starts from the age of 13 years and continues up to 19 years of age. Adolescents are also called teenagers as they belong to thirteen to nineteen years of age range. Many hormonal changes in the body take place that appear externally too. Some of the changes taking place in boys and girls include turning taller, heavier and stronger, getting hair under arms, on arms and legs and around genitals, oily skin and more sweating. Boys’ specific changes are deep and rough voice, hair on face, broader chests, shoulders and muscles and girls’ specific changes include development of breasts, bigger hips and start of menstruation cycle. It is considered that the adolescence stage is difficult to manage for parents as there are behavioural and attitudinal changes in teenagers and they find more comfortable in being independent in their day-to-day activities.

Stage 5:

Adulthood

This stage comprises people who fall in the range of ages between 20 -65 years and they are called adults. This is the right age for the process of reproduction and making babies. Adults can be young adults i.e. 20-36 years, middle-aged adults i.e. 36-55 years and older adults i.e. 55-65 years.

Stage 6:

Elderly

A person who reaches 65 years of age generally belongs to the elderly group. The average life expectancy of a person can range from 70-85 years. It also depends on the overall health and fitness of a person. The healthier a person is, their life expectancy is more.

So, these were the six different stages of the human life cycle explained above that include fetus (pregnancy), birth of a baby (infant), toddler or preschooler, teenager, adult man/woman and old person.

Characteristic Developmental Features

In all the six stages of the human life cycle, the developmental period shows certain peculiar features of internal growth and external social skills. These are stated below:

The Neonatal stage

In these first few weeks of life, a new born adjusts to the outside world. The head of the neonate is disproportionately larger than the rest of its body. All other body parts are small, soft and tender.
During this short period, the baby spends most of its time asleep., which is broken by short waking periods (usually every 2-3 hours) on account of any discomfort or for feeding.
They lack neuromuscular control and have underdeveloped organ systems. Their tender bodies and an absolute lack of defense mechanisms make it imperative to closely protect the neonate at this stage.
They are highly vulnerable to diseases and improper nutrition or unhygienic conditions can quickly elevate the susceptibility.

The Infancy period

This is the stage of one of the most rapid periods of growth in the human life cycle.
The metabolic activity increases; there is a higher rate of neuromuscular development. The infant gains some muscle control and shows several body movements such as movement of the eye, swallowing, smiling, moving arms and legs, etc.
It is during this period the child learns to sit and then starts crawling, creeping, standing and finally is able to walk (first with support and then on its own).
They also show psychological development. They can recognise family members and differentiate them from strangers. Withdrawal from strange people, places and things is usually seen.
Finally it gains the concept of “Object permanence” (that is, objects do exist even after they are removed from immediate view sight).

The Childhood period

The childhood years can be further divided into early childhood and late childhood. During this transitional period from infancy, the growth rate slightly slows down. Now the child mainly grows in height and weight relative to each other.
The child shifts from solitary play to parallel play and seeks companionship from children of the same age. They often engage in cooperative play and like to imitate people and their behaviour.
Their vocabulary skills increase and become curious, often asking many questions to their caretakers. They also seek active approval of parents and adults around them
By the age of 9 or 10, girls show rapid growth than boys. In their late childhood, both boys and girls show separate interests which may be common in earlier stages.

The Adolescence

This is again one of the rapid growth periods. They will reach their adult height. Girls often reach their maximum height by their menarche.
Secondary sexual characteristics develop in both boys and girls.
Psychologically, adolescents enter into a period of identity crisis, where they actively seek their purpose in life and develop ideas and beliefs around who they are. They seek individuality as well as approval and being part of a peer group.
There is moral and psychosocial development and proper timely counselling becomes necessary to understand and appreciate their growth.

Adulthood

The adolescent has now transitioned into a full grown adult. There is a marked difference in the understanding of the self and world around them.
They now establish themselves through their careers and relationship with other beings.
They now seek a marriage partner, build a family and gain status in the society.

Late Adulthood/ Old age (Senescence)

There is loss of several bodily functions gradually
The adult has now retired from its social responsibilities and challenges fully or partially. They however seek delight in helping their children by co-parenting their grandkids.
Sometimes they may feel lonely as children move away for educational and professional reasons. They may find themselves frustrated for being unable to execute many day to day activities without assistance.
Health declines and one may be plagued with many metabolic disorders.
They seek solace in the younger generation or in divine activities (prayers, pilgrimage, etc.).