Form 4 Biology – GROWTH AND DEVELOPMENT 2

SIGNIFICANCE OF MITOSIS

• It is the basis of asexual reproduction
• It maintains the diploid state of the organism
• It is the basis of growth i.e it brings about growth in terms of increase in number of cells.
• It help to recovery of dead worn out cell

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DIFFERENCE BETWEEN MEIOSIS AND MITOSIS

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GROWTH AND DEVELOPMENT IN HUMAN BEING.
Human beings like other animals show growth and development. Human beings show diffuse growth where growth occurs all over the body.
– Development is an increase in the complexity of an organism. It includes growth, differentiation, wound healing, tissue regeneration, ageing and death.
– Growth and development in humans can be;-(i) Pre-natal or (ii) Post-natal.

(i) Pre-natal growth and development takes place in the womb before a body is born.

(ii) Post-natal growth and development occurs after the body is born.

HUMAN POST-NATAL GROWTH AND DEVELOPMENT.
The human beings post-natal growth and development comprises of five main stages. These stages are;
(1) Childhood
(2) Adolescences
   (3) Adulthood
(4) Old age (senescence)
(5) Death

• 1) CHILDHOOD (Infancy stage).
  – Is the period from the time the body is born up to sexual maturity (about 11 years).
  – Childhood stage has several stages. These stages are;
  Neonatal
  Older baby
  Toddler
  Early childhood
  Late childhood, and
  Pre-adolescence NEONATAL STAGE
  Is the from birth up to 5 months. New babies are also called neonates.

  Changes
  – The following are the physical, physiological, behavioral and psychological changes which occur at this stage of growth and development.
  i) The baby can lie on its back and tries to roll over. It can do a number of things such as crying, moving their arms, legs, heads, swallowing and sucking.

  ii) Babies at this stage suck anything and put in their mouth.

  iii) Neonates can see but only a short distance of about 20cm. They can also hear, smell and feel. They spend most of their time sleeping.

  iv) Babies at this stage express their feelings mainly through crying. They cry to show hunger, thirst, pain, tiredness, fear and discomfort such as wet nappies, cold and lot of heat and sickness.

  v) The immune system is immature and the baby depends on the immunity from his or her mother through breast-feeding.

  Advantages of breast-feeding.
  The milk produced by mother in the first days after delivery is called colostrum. The colostum is usually sticky and yellow and contains more proteins and antibodies than white milk produced later.
  – Mother milk contains nearly all the nutrients needed for growth and development of the body. The following are the advantages of breast feeding.
  (i) Breast-feeding creates a special bond between the mother and the baby. i.e it has psychological benefits.
  (ii) Breast milk is at the right  temperature for the baby.
  (iii) Breast milk is well balanced. i.e it contains nearly all nutrients needed for normal functioning.
  (iv) Breast feeding (milk) does not require preparation.
  (v) Breast milk is safe and free from contamination.
  (vi) Colostrum contains a lot of antibodies needed to protect the baby against infection.

  Reasons for substitution of Mothers milk with others foods like cows milk.
  (i) Death of Mother.
  (ii) Inability of the Mother to produce enough milk.
  (iii) In case of multiple births e.g twins, triplets etc.
  (iv) In case the Mother has easily transmitted diseases like tuberculosis.

   OLDER BABY STAGE
  This is the stage from 6 to 12 months.

  Changes
  (i) At six months, a baby can completely control his/her head and sit without support.
  (ii) At 7 months the baby learn to crawl.
  (iii) He or She can hold and drop objects and stand while holding things like tables or chairs.
  (iv) Teething occurs at this period.
  (v) From 9 to 12 months the baby start to walk.
  (vi) The baby responds to his or her own name and other words that are familiar to him.

   TODDLER STAGE
  This is the age between 1 to 3 years.

  Changes
  (i) Brain develops by 90%
  (ii) The child is able to control micturition and defaecation as urinanry and anal sphineter control become possible.
  (iii) The baby can see everything that an adult can see.
  (iv) All the 20 milk teeth appear by the age of 2.5 to 3 years.
  (v) Immune system becomes mature.
  (vi) Hearing has developed well.
  (vii) At 12 to 14 months, the child uses gestures to express his or her feelings. For example raising arms when he/she wants to be picked up.
  (viii) At 15 months, the child copies what adults do .
  For example, a child may imitate “cooking” by taking a spoon and “stirring” it in a bowl.
  (ix) At 15 to 18 months a child feeds him or herself.
  (x) A t 19 to 24 months a child likes to play with others (socialization), likes to dress and undress himself or herself. He mimics social behaviours such as holding and feeding a toy.
  (xi) At 25 to 36 months, emotional children may feel jealousy, for example toward a new born baby. They also show fear for particular things like fear of some insects, scary noise.

   EARLY CHILDHOOD
  This is the age from 4 to 6 years. At this stage children go to kindergarten.

  Changes
  (i)A child has good appetite and therefore grows rapidly, Good appetite is important as children at their stage are very active and play a lot.
  (ii) Motor coordination has developed well and therefore the child can walk, jump and skip.
  (iii) The child becomes curious and imaginative.
  (iv) He or she understands right and wrong.
  (v) He or she becomes curious.

   LATE CHILDHOOD
  This is the age from 7 to 9 years. At this stage children are in primary school.

  Changes
  (i) Children become very active.
  (ii) The child can assume simple responsibilities like looking after the house when parents are not at home.
  (iii) The child is very social and likes to socialize and belongs to groups.
  (iv) He or she can help with household chores like washing dishes, setting the table, fetching water.
  (v) The child likes to associate with peers of similar interest.
  (vi) This is the time children have friends and best friends. However they  prefer friends of the same sex.
  (vii) Children at this stage can listen to peers opinion but still value opinions of their parents.

  * PRE – ADOLESCENCE
  This is the age from 10 and 11 years

  Changes
  (i) Growth starts to increase
  (ii) Appetite increase
  (iii) Secondary sexual characteristics start to show. For example growth of breast and growth of public hair and hair under armpits.
  (iv) Children still prefer  friends of the same sex.
  (v) Children are very social and tends to value peers opinion.

  Common problems in Infancy (Childhood)
  i) Constipation
  This is the difficulty in passing out faeces. This can be solved by giving fruit juice,vegetables and by increasing the baby’s intake of water.

  ii)Excessive crying
  It indicates illness, pin, hunger, thirst, need for love and attention or the baby may be uncomfortable due to excessive heat or wetness.

  iii) Heat rash
  Heat rash results to a roughing itching skin, which may be painful caused by excessive heat. Putting the baby in a cooler place and loosening the tight clothes may relieve this.

  iv)Nappy rash
  The nappies should be changed frequently to avoid the nappy rash. The baby’s skin should be kept clean, dry and well oiled. Use of powder on the skin is recommended.

  v) Diarrhoea
  Diarrhoea may be a symptom of a disease or may be caused by overfeeding, infection or reaction to particular kind of food.
  – The baby should be given plenty of liquid to avoid dehydration.
  – In case of excessive diarrhoea, the baby should be taken to the nearest health center for treatment.

  vi) Colic
  – A baby is said to have colic if it seems to be uncomfortable from pain in its abdomen. This causes the baby to cry out loudly.
  – The pain is caused by airs swallowed at feeding time.
  – The baby should be held up with its abdomen leaning on the mothers shoulder to force the air out gently a condition known as winding up.

  Services required to meet the needs of children
  The services required to meet the needs of a child can be categorized into two;-
  (a) Essential (basic) services
  (b) Supportive services

  (a) Essential (basic) services are necessary for baby’s survival. Basic services include;-
  – Healthy.
  – Warms.
  – Shelter.
  – Clothing.
  – Protection against illness and injury.
  – Excessive and rest.

  (b) Supportive services are services that will help a child to grow well socially, emotionally and mentally. Supportive services includes;-
  – Love
  – Care and comfort
  – Security
  – Training of habits and skills
  – Older children need to be disciplined
  – Trained to independent and useful to others and be responsible.

  ADOLESCENCE
  – Is a period in human developed between childhood and adult hood.
  – It generally occurs between the ages of 12 and 18 years.
  – At adolescence boys and girls attain sexual maturity (puberty),puberty is a term used to refer to the period when secondary sexual characteristics develop.
  – Girls attain puberty at the ages of 11- 13, boys attain puberty at the age of 12-14.
  – During adolescence, an individual experiences a lot of changes which includes emotional, social and physical changes. These changes occur in both boys and girls to prepare their bodies for parenthood.
  – At puberty the boys secrete the male sex hormone known as androgen that brings about the development of male secondary sexual characteristics.
  – The girls secrete the female hormone called oestrogen that brings about development of female secondary sexual characteristics.

  Changes in Boys only at Puberty.
  (i) Shoulders and chest become broader (wider).
  (ii) Muscles get stronger.
  (iii) Beard grow.
  (iv) The voice breaks (becomes deep).
  (v) Enlargement of sex organs and they occasionally emit some fluid from the penis at night (wet dream).
  (vi) Sperm production starts.

  Changes in Girls only at Puberty.
  (i) Enlargement of breasts.
  (ii) Widening of pelvic girdle (leads to enlargement of hips).
  (iii) Ovulation starts.
  (iv) Menstruation begins.
  (v) Enlargement of uterus and vulva.

  Changes in both Boys and Girls at Puberty.
  (i) Hairs grow in public region and under the armpits.
  (ii) Sex hormones are secreted.
  (iii) The skin sweats more often.
  (iv) Attraction by members of the opposite sex.
  (v) Pimples may appear on the face but later disappear.
  (vi) Body increases in size due to rapid growth.

  Personal Hygiene during Adolescence.
  Puberty is a period of rapid growth with so many changes occurring in the body. As a result the body produces a lot of waste products such as sweat, wet dream in boys and menses in girls.
  – Adolescence should therefore maintain high level of cleanlines to avoid stinking and infections.
  – It is important that they should bathe daily and change into clean clothes.
  – When bathing, one must pay extra attention to genitals, armpits and areas between the toes.
  – If the armpits sweat a lot shave the public hair to reduce warmth and sweating.
  – After bathing apply deodorant to kill germs and prevent foul smell.
  – For sweaty feet, clean between the toes, dry well and if it can be afforded, dust the areas with talcum powder. The powder absorbs the sweat, prevents bad smell and athletes foot.
  – In case acne (pimples) strikes, it should not worry anybody. Avoid breaking the pimples, just keep the face clean, avoid applying oily creams, avoid diet that has a lot of oil.
  – Boys need to keep their beards trimmed or well styled.
  – Girls need to bathe more than once during the menstruation flow to avoid foul smell of blood.
  – Girls needs to wear sanitary towels (pad) to avoid staining their clothes with blood. The sanitary towels (pads) must be changed regularly to avoid development of foul smell.
  – If commercial sanitary towels cannot afforded, home made pads can be prepared by folding clean cotton cloth to make pads.

  Services required to meet the needs of Adolescence
  Adolescence require;
  – Healthy food for their growing bodies.
  – Peaceful home
  – Security emotional support.
  – Cancelling
  – Physical exercise
  – Social skills

  3. ADULTHOOD
  Adulthood starts at 20-55 years. Adults are physiologically, Psychological and Physical mature to make families.

  Changes
  (i) Growth has stopped, only maintenance of body parts, for example repair of worn out cells taken place. A person may gain weight due to deposit of facts but not due to growth and development.
  (ii) At this stage people are in their best physical conditions that is very strong, energetic, have good memory capacity, sharp senses and stamina.
  (iii) People at this stage are very ambitious and want to succeed. They work hard to meet their goals, for example to finish studies, get a job, start a family.
  (iv) They have the desire to be socially independent.
  (v) In the late forties or early fifties, the rate of deterioration becomes significant.
  (vi) The ability to do tasks that require a lot of energy and high speed decrease, sharpness of vision decreases and memory loss may occur.
  (vii) Hair starts to turn grey, skin starts to loose elasticity.
  (viii) Women reach menopause and their desire to have sex is reduced.

  4. OLD AGE 
  Old age starts from 56years and over. This is the age of senescence simply after menopause in women. Men tend to diminish their sexual activity but their are not actually sterile.

  Changes
  (i) The ability to focus on objects, smell and hear decreases.
  (ii) Hair turns grey as a result of reduced production of hair pigment. Some men may develop a bald head.
  (iii) Loss of memory due to death of  brain cells.
  (iv) Kidney functioning slows down and the frequency of urination increases.
  (v) Decreases blood flow to the brain and death of nerve cells.
  (vi) Elasticity of the skin decreases. The skin gets looser and wrinkles develop.
  (vii) Bones may become weak especially for those who have been taking food with less calcium in young age.
  (viii) By the age of 70, about two thirds of taste buds in the month die, making a person feel like food in tasteless.

  – The above features do not apply to all aged people. Healthy life style during young age may delay occurrence of the above features and make a person lead a normal life even in older age.
  – A healthy life style is achieved by eating healthy food, avoiding smoking, alcoholism, overeating, drug abuse and inactivity.

  5. DEATH
  This is the end of life. The cells and all body processes stop to function.

  FACTORS AFFECTING THE RATE OF DETERIORATION OF THE HUMAN BODY
  Some people may live a happy health life up to their old age and until they die. Others get very old while they are still very young.
  – Factors affecting the rate of deterioration of the human body have been categorized into;-
  a. Psychological factors
  b. Environmental factors
  c. Genetical factors

  a) PSYCHOLOGICAL FACTORS

  (i) Smoking
  Smoking reduces life span by 12 years. Smokers suffer more illnesses such as cancer than non-smokers. Smokers leads to permanent building, skin wrinkling.

  (ii) Alcoholism
  The ability to metabolize alcohol decrease with age. Prolonged use of alcohol leads to damage of the central nervous system and brain and increase the risk of heart stroke and breast cancer for women.

  (iii) Drug abuse
  Drug abuse weakness the immune system and causes premature ageing. It thus reduces life span.

  (iv) Stress
  Stress may cause heart problems and high blood pressure. It also causes impairment of the immune system, thus making a person sick often.
  – Other problems that may result from stress are failure to sleep (insomnia), fatigue, headache and migraine.

  (v) Inactivity
  Sedentary work and inactivity such as spending a long time watching TV or doing office work that involves sitting most of the time results in being overweight and its associated risks.
  – People who are inactive have more changes of developing health problem such as obesity and high blood pressure than those who are active.

  b) ENVIRONMENTAL FACTORS.

  (i) Poor diet
  Poor diet includes both underfeeding and over-feeding. Under-feeding cause malnutrition which reduces life spar over-feeding leads to obesity and diabetes obesity cause premature age.

  (ii) Diseases  and infections
  Pathogens produce toxins that accelerates deterioration. They also deprive our bodies the necessary nutrients needed for good health.

  (iii) Chemical and radiations
  Some chemicals such as those found in cosmetics, medicines, insecticides, pesticides, foodstuffs and sprays may have adverse effects in the human body.
  – These chemicals speed up deterioration or shorten life span.
  – Some radiations for example x-rays may affect our lives by killing body cells or causing deadly diseases like cancer.

  C) GENETIC FACTORS
  A small number of individual carry a defective gene that causes Werner syndrome.
  – Werners syndrome is a very rare diseases that causes premature ageing. It causes a 20 or 30 years old person may look several decades old.

  SOCIO-CULTURAL FACTORS THAT AFFECT GROWTH AND DEVELOPMENT.

  (i) Trading beliefs
  They affect the kind of food one should eat. For example in some tribes pregnant women are not supposed to eat eggs, which contain proteins needed for growth and development of the unborn baby.

  (ii) Poverty
  People having low income may fail to provide the basic needs for proper growth. Poor or insufficient diet and lack of medical care result into poor growth and even death especially at infancy.

  (iii) Religion
  Some religious sects bar certain groups of people e.g pregnant women from eating certain food. For example Muslims do not eat pork on religious ground.
  – Some religious sects do not allow their followed to go for treatment in hospital resulting to poor health and even death.

  (iv) Ignorance
  Lack of knowledge about proper diet, proper medical care and education contribute to poor health. Most people do not know how to care for themselves, and do not know what is good and bad for them.

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