science 6 BYME
Descripción: Activity book de 6º...
1 Read and discover. We perceive the world through our senses. Sight, touch, smell, hearing and taste allow us to explore the environment around us. All the information received by our senses is processed by our most important organ, the brain. The brain is home to the conscious and unconscious mind, as well as our emotions and memory. It controls our involuntary actions, such as breathing, or digesting our food, as well as our thinking and decision making. What other types of involuntary actions do we have?
hy is the brain so important? What information does 2 W it process? 3 What are feelings and emotions?
hy are our senses important? What would happen 4 W if we lost the use of one or more of them? hich body parts or organs do you associate with the 5 W function of interaction? • brain
• sense organs
ur body moves in response to the information sent from 6 O the brain. Which system enables us to move? hat is the difference between a voluntary and involuntary 7 W muscle? Give an example of each. hy is it important to keep fit and healthy? What happens 8 W if we do not look after our bodies?
Analyse and organise
tudy the different parts of the body in the box. What functions 1 S do they have? Copy and complete the table in your notebook. • bones • brain • eyes • neurons • skin • muscles • skeleton • taste buds • joints • spinal cord • nerves • nostrils • tongue receiving information
giving a response
ook at the photos. Do they show someone receiving 2 L information or giving a response? a
ead the text about how the brain compensates for loss of R vision, then decide if the sentences below are true or false. Stevie Wonder and Ray Charles are both examples of well-known musicians who lost their sight at an early age. It is impossible to know if this lack of sight has contributed to their excellence in music, but more and more studies are showing that those who are born blind or who lose their sight early in life are better at nonvisual tasks than those who can see. In tests, sighted and blind volunteers were asked to localise the source of different noises. It was found that the blind participants performed much better than those who could see. The unusual part, however, was that when the participants’ brains were scanned while they were performing the task, it was discovered that the blind participants were using the part of the brain associated with vision to process the information. In effect, they were seeing with their ears. So, their brains were helping them navigate a world without sight. This is just one of the ways in which scientists believe the brain adapts to overcome injuries or the loss of senses. a. All blind people are great musicians. b. Tests show blind people are better at certain tasks than sighted people. c. The participants had to say where a sound was coming from.
e. The participants’ brain activity was observed during the test. f. The blind participants had a more developed audio processing area. g. The brain can adapt itself.
d. Both groups performed the task well.
4 How else might our bodies compensate for the loss of a sense or a limb? 5
Who is Maria Lyle? Listen to the recording and complete the sentences in your notebook. a. Cerebral palsy is usually caused by ..... damage. b. Maria Lyle, who suffers from cerebral palsy, won two sprint races in August ..... c. She is only ..... years old. d. Maria holds two world ..... e. Maria was diagnosed with cerebral palsy when she was ..... f. Her mother, who is a ..... teacher, convinced Maria to take up running.
The nervous system
Living organisms are made up of cells. Cells that perform the same function come together to create tissue. Tissues group together to form organs. Organs that work together form the systems which make up the bodies of organisms. One of these systems is the nervous system. The nervous system sends messages from the brain to different parts of the body, such as the locomotor system (or musculoskeletal system) which allows us to respond to the stimuli from our senses. It also controls our internal systems such as the digestive or respiratory systems.
What are reflex actions?
Did you know? The average adult human brain weighs about 1.5 kilograms and contains about 86 billion neurons!
The central nervous system The brain and the spinal cord make up our central nervous system.
Brain The brain controls our nervous system. It is protected by the skull (or cranium). It is made up of three main parts.
• The cerebrum is the biggest part of our brain. This is where we process the information from our senses and where we do our cognitive thinking. We use the cerebrum to take decisions, to study or to play a game. • The main role of the cerebellum is controlling our movements, coordination and balance.
• The brain stem is the continuation of the spinal cord. It controls involuntary actions such as our heartbeat breathing and sleeping.
Spinal cord The spinal cord is made up of nerve tissue and runs from our brain down our spine. The spinal cord is protected by the vertebrae. It controls our reflex actions.
The peripheral nervous system
The peripheral nervous system is made up of nerves. Nerves are made up of tiny cells called neurons that transfer information through the nervous system using electrical and chemical signals. Different neurons carry out different tasks.
Sensory neurons collect information from our sense organs (eyes, ears, nose, tongue, skin).
The brain interprets the information and sends signals to the rest of the body.
hat other systems do you know? Work 1 W with a partner. Write down the names of the systems of the body and what they do. 2 What protects our brain?
hat would happen if we did not have a 3 W peripheral nervous system?
Motor neurons send messages from the brain to our locomotor system.
ow do reflex actions differ from other 4 H actions? ecide if the following movements are 5 D voluntary (V) or involuntary (I). a. breathing
b. playing the guitar
The senses An eye uses a lens to focus. What else uses a lens to focus?
Our sense organs allow us to interact with the world around us. They detect information which is then transmitted to the brain. Here, the information is deciphered and the brain then reacts to the stimulus.
Sight 1. Light reflected from an object enters our eyes through the cornea and pupil. 2. The amount of light entering our eyes is controlled by the iris. The iris gives the eye its colour. 3. The lens focuses the light on the retina at the back of the eye. 4. Nerve receptors in the retina transmit the information to the optic nerve which then sends the information to the brain.
pupil lens cornea iris
The place where the optic nerve leaves the eye is called a blind spot. This area does not respond to light.
Hearing 1. Sound waves enter the auditory canal in the outer ear and cause the eardrum to vibrate.
2. In turn, these vibrations make the three small bones in the middle ear vibrate.
3. The vibrations finally reach the cochlea in the inner ear, where they become electrical signals. 4. The auditory nerve then sends the signals to the brain for processing.
Smell nerve receptors
Chemicals in the air enter our nose through our nostrils. The chemicals then come into contact with nerve receptors which send the information to the brain via the olfactory nerve.
Taste Substances enter our mouth and come into contact with our tongue. The tongue is covered in taste buds which have receptor cells. These receptor cells detect the different tastes (salty, sweet, bitter and sour) and send the information to the brain. Chemicals from substances in our mouths also enter the nose which is why if we have a blocked nose, food often tastes different or bland.
Touch The skin covers and protects our whole body. The middle layer of skin, called the dermis, contains nerves and blood vessels. These detect sensations such as heat, pressure and texture. The nerves in the skin send information to the brain through the peripheral nervous system and the spinal cord.
hy do eyes have eyelashes and eyelids? 1 W What are they used for? e use our ears to hear. What other 2 W function do our ears have? 3 What do we use contact lenses for?
nerve blood vessel
ow are our senses of smell and taste 4 H connected? What can happen if we have a cold? 5 What do sensors in our skin detect?
hat healthy habits can protect our sense 6 W organs?
How we move
Our body moves in response to signals from the brain. These signals travel through the nervous system to our muscles. These contract and relax to allow us to move, hold objects, kick balls and make other movements. The muscles are supported by the skeleton and joints. The whole system is called the locomotor or musculoskeletal system.
The skeleton is made up of bones. There are three types of bones. • Short bones, such as the vertebrae in the spine, provide support and stability. Vertebrae also protect the important nerves which run through the centre of the spine. • Flat bones, such as ribs and the pelvis, protect the internal organs. • Long bones shape limbs and are used for movement.
Look at the picture of the skeleton. Identify the flexible joints.
humerus vertebral column (spine) radius ulna pelvis
Joints Our bones are connected at the joints by strong elastic tissue called ligaments. The ends of the bones at the joints are covered in strong, flexible tissue called cartilage. There are three types of joints. • Fixed joints do not move. The parts of the skull are connected by fixed joints. • Semi-flexible joints, such as the vertebrae in the spine, only allow a small amount of movement.
• Most joints in the body are flexible joints which are important for movement.
Muscles • Smooth muscles are found in organs such as the intestines or stomach.
There are over 600 muscles in the human body. These muscles are controlled by the nervous system which makes the muscles contract and relax. There are three types of muscles.
• The cardiac muscle makes up our heart. Skeletal muscles are voluntary muscles. We can move them at will. Smooth muscles and the cardiac muscle are involuntary muscles. They work automatically and we cannot control them.
• Skeletal muscles are joined to the bones by tendons. They work in pairs. For example, when the biceps contract, the triceps relax. frontal muscle
trapezius deltoid pectoral muscle biceps abdominal muscles
1 What are the functions of the skeleton?
hich bones protect the respiratory 2 W system?
5 Which muscles do we use to:
a. eat our food
c. kick a ball
b. throw a ball
d. sit on a chair?
hat is the difference between a ligament 3 W and a tendon?
hat happens to our muscles if we do not 6 W do sufficient exercise? Why is it important to keep fit?
ive examples of different flexible joints. 4 G Which joints do you think are most flexible?
hat should we do to keep our bones 7 W healthy?
How does smell affect taste?
Aim Discover how the senses of smell and taste are linked.
Hypothesis I think that ... • I can taste food more when holding my nose, or • I can taste food less when holding my nose, or • I can taste food the same when holding my nose.
• a blindfold • different foods (for example, slices of fruit and vegetables, sweets, chocolate, flavoured yogurts) • spoon (if needed) • water (if needed) • a partner
Method 1. Blindfold your partner. 2. Ask your partner to hold their nose closed. No cheating! 3. Offer some food to your partner – one type at a time. 4. Ask your partner if they can identify the food. 5. Make a note of their answers. 6. Now ask your partner to let go of their nose, and repeat the process with the same foods. 7. Swap roles with your partner and repeat the experiment. Now compare your results. Are they the same?
Test • Did your partner identify the food correctly when holding their nose? • Were the answers different the second time?
Conclusions 1 Which foods could be tasted when holding your nose? 2 Which foods had no taste when holding your nose? 3 How important is our sense of smell when we taste food?
Emotions and teenagers
Where are emotions located? The mind is incredibly complex, but we cannot open up the brain and see emotions, dreams and memory at work. Psychologists study human behaviour to try to understand how our minds work. However, we do know that the parts of the brain involved with emotional responses and memory are very active. This is the limbic system which is found below the cerebrum on both sides of the brain.
Growing up Adolescence is often a difficult time for humans. Teenagers can be confrontational and rebellious; arguments between teenagers and their parents or teachers are common. However, by early adulthood, these tendencies almost completely disappear. Scientists believe that adolescence is such a difficult period because the emotional part of the brain develops much faster than the cognitive part of the brain, the cerebrum, which keeps growing into adulthood. Teenagers act impulsively and emotionally, but have not developed the ability to think things through or consider the consequences of their actions. On the other hand, teenagers are usually very sensitive and empathetic. It is a period when people often form strong bonds and friendships.
hich part of the brain is mostly responsible for emotions 1 W and feelings? Why do you think we have feelings? 2 What happens to the teenage brain? What are the results?
hat functions does the brain have? How can we study 3 W these different functions? hy do you think it is important for teenagers to rebel? 4 W Why is this a transitory phase? 5
With a partner, think of the physical and emotional changes which occur during adolescence.
Revise Study skills 1 Classify the words in the box below.
• brain • cartilage • cerebrum • tissue • joints • ligaments • neurons • cells • biceps • skull • spinal cord • tendons • brain stem
ead the text below about Abu al-Qasim al-Zahrawi (A). Then, read the text about Joseph 2 R Lister on page 98 (B). In your notebook, decide whether the sentences below refer to text A, B, or both. Abu al-Qasim al-Zahrawi was born in Al Andalus in ad 936. He spent his whole life working as a surgeon in Córdoba and is considered to be the father of modern surgery. His greatest legacy was an encyclopaedia of medicine in which he described over 300 illnesses and their treatments. He also created an illustrated guide, On Surgery and Instruments, which described surgical procedures and contained diagrams of specific surgical tools. Some of his techniques and tools are still used today. He died in ad 1013.
a. He wrote books about his work. b. He developed new techniques. c. He changed the way things were done. d. He was a pioneer in his field. e. He is still relevant today. f. He used someone else’s ideas. g. He became famous in his lifetime.
Review 1 In your notebook, label the parts of the brain using the words in the box. There are some extra words.
brain stem cerebellum cerebrum
4 Identify the odd one out.
a. cerebrum tissue
c. clavicle trapezius deltoid d. scapula fibula ligament
dermis tendon spinal cord
alk about the nervous system. Use the 5 T diagram to help you.
central the nervous system
brain spinal cord
2 How do we see? In your notebook, write the
6 Complete the summary on page 99.
sentences in the correct order. a. Information travels along the optic nerve to the brain. b. The lens bends the light. c. The light produces an image on the retina. d. Light enters the eye through the cornea and the pupil. opy the chart into your notebook and put 3 C the words into the correct columns. pelvis radius biceps gluteus deltoid trapezius rib patella humerus triceps bones
Checklist • I can identify and describe the main characteristics of the function of interaction. • I understand how different parts of the body interact. • I can identify the organs of senses, the nervous system and the locomotor system. • I can describe how the body moves. • I understand how emotions and feelings form part of the body.
1 Read and discover. Humans, like many living things, reproduce by sexual reproduction. Reproductive cells in male humans are called sperm while in females they are called ova. When they meet, they produce a zygote which eventually becomes an embryo, which turns into a foetus and then finally into a baby! However, humans, like most animals, have to reach sexual maturity before they can reproduce. This happens in adolescence – the stage between childhood and being an adult. What do we call this process?
hy do we need to reproduce? What would happen if we 2 W did not? Can you think of any examples of animals that did not reproduce enough? 3 Look at the photo above. What does it show?
ow do we pass on genetic information? Why do you think 4 H this is important? 5 In many animals, including humans, offspring stay with their parents for some time. Why does this happen?
umans reproduce by sexual reproduction. 6 H What is another type of reproduction? 7 In the past many children died during infancy. Why do you think this was? What has happened that has changed this? Is this true of everywhere in the world?
Analyse and organise
ur lives have different stages which we pass through from 1 O birth to death. Each stage has its own characteristics and marks our passage through life. Copy the table in your notebook. Use the words from the box to complete the life stages. • adolescent • adult • baby • child • elderly person • toddler stage
characteristics and approximate age
Stage 1: .....
cannot walk or talk (0–12 months)
Stage 2: .....
starts walking and talking (1–3 years)
Stage 3: .....
fully mobile, learning to function in society (3–13 years)
Stage 4: .....
becoming independent (13–19 years)
Stage 5: .....
fully independent (19–75 years)
Stage 6: .....
declining health, may be dependent on others (75+ years)
2 Which stage of life do you associate these photos with?
ead the text about the reduction in infant mortality rates, R then decide if the sentences below are true or false. In the past, infant mortality rates (the number of children under the age of one who died per 1 000 births) was very high. A number of major scientific developments reduced this rate to what it is now – about 4 per 1 000 births in Spain. Firstly, understanding the nature of diseases, how they spread through infected water or materials, and the importance of hygiene was highly significant. Another reason for this improvement was the development of vaccines for common childhood illnesses such as whooping cough, polio and tuberculosis. The discovery of antibiotics and their widespread use in the second half of the 20th century further helped combat the spread of disease in babies and young children. Finally, the huge improvements in hospital care and widely available health care reduced mortality rates to their present all-time low level. While these advances are true for the developed world, the infant mortality rate remains high in parts of Asia, South and Central America, and in Africa, particularly Sub-Saharan Africa.
a. In the past many babies died. b. Spain has a high infant mortality rate. c. Humans have always understood how diseases spread. d. Vaccinations are an important tool in combating childhood illnesses.
e. Antibiotics are dangerous for babies and young children. f. Medical care has improved. g. Infant mortality rates are low all over the world.
hat steps can we take to lower infant mortality rates in 4 W developing countries? 5
What is an ultrasound scan? Listen and complete the sentences in your notebook. a. An ultrasound scan creates images of organs using ..... b. It is used in ..... c. Pregnant women usually have ..... ultrasound scans during their pregnancy. d. The first scan is called the ..... scan and takes places when a woman is about ..... weeks pregnant. e. The second scan takes place between ..... weeks and ..... weeks.
The female reproductive system What physical changes do girls experience during puberty?
Sexual characteristics The physical differences between men and women are called sexual characteristics. • Primary sexual characteristics are the differences between male and female reproductive organs. • Secondary sexual characteristics are other physical differences between men and women, for example women usually have wider hips and men often have more body hair. These characteristics appear during puberty.
The female reproductive organs Most of the female reproductive organs are internal. They are located in the lower abdomen.
Ovaries The ovaries produce female reproductive cells called ova. One ovum matures each month. Women are born with all the ova they will need for the rest of their life.
Uterus The uterus is an organ with muscular walls. During pregnancy a fertilised cell develops into a baby in the uterus. The part of the uterus that leads to the vagina is called the cervix.
Fallopian tubes The fallopian tubes connect the ovaries to the uterus.
Vagina The vagina is a muscular tube which connects the uterus to the outside of the body. The vulva is on the outside of the body and covers the opening to the vagina.
Puberty in girls When girls approach sexual maturity, their bodies undergo a series of changes. These changes happen during puberty, usually when a girl is between 10 and 16 years old. The breasts begin to develop and pubic hair grows. They grow taller and their body fills out; glands in the skin and scalp produce more oil which can cause spots or acne. Armpit hair begins to grow and menstruation typically starts between 10 and 15 years of age.
The menstrual cycle Once a girl reaches puberty, the ovaries, in response to hormones released by the brain, start to release ova. An ovum is released from the ovaries into one of the fallopian tubes about every 28 days. This process is called ovulation. The walls of the uterus get thicker with extra blood and tissue in preparation for fertilisation. However, if fertilisation does not happen, the ovum dries up and leaves the body through the vagina about two weeks later. Blood, and the thickened lining of the uterus comes away too, and this is what women experience as menstruation. Menstruation typically lasts from three to five days. Women menstruate until they have no eggs left. This usually happens when a woman is about 50. This period is called the menopause.
1 What role does the brain play during puberty? 2 What secondary changes occur in girls during puberty? 3 Explain what happens to an ovum if it is not fertilised. 4 What happens when a woman has no ova left?
Link it up What organs can you name? Where are they located? What functions do they perform? Look at Units 1 and 2.
The male reproductive system What What physical physical changes changes dodo boys boys experience experience during during puberty? puberty?
Sperm The male reproductive system produces and transports sperm cells. A sperm cell has an oval shape and a tail. The tail allows it to move up the female’s fallopian tubes and fertilise the ovum. Men produce millions of sperm every day.
The male reproductive organs Most male reproductive organs are external and are located on the outside of the body. • The testicles produce and store sperm. The testicles are located in a bag of skin called the scrotum. The scrotum regulates the temperature of the testicles. They need to be a bit cooler than the rest of the body in order to produce sperm. • S perm travels through two tubes called the vasa deferentia to the seminal vesicles. The seminal vesicles produce a liquid that forms part of semen.
• The prostate produces a liquid that also forms part of semen. Semen carries the sperm and gives it nutrients. • The penis contains the urethra. The sperm travels through the urethra to the outside of the body. The urethra also expels urine.
Puberty in boys When boys reach puberty, the brain secretes hormones which activate the testicles to produce testosterone. This hormone brings about many physical changes. Firstly, the testicles enlarge and the scrotum becomes larger and coarser. The penis grows longer and thicker, and boys become fertile. Sperm mixes with seminal fluid to form semen which is ejaculated from the penis. Secondly, pubic hair begins to grow, and boys become taller and heavier. The voice deepens, and hair starts to grow under the arms and on the face. The skin becomes coarser and can be oily or develop acne. Boys may also ejaculate spontaneously in their sleep.
Genes Human beings pass on some characteristics to their offspring through genes. Humans have about 24 000 genes. Parents pass onto their children characteristics such as eye and hair colour.
Link it up Which part of the eye gives it its colour? Look at Unit 1.
hich part of the body secretes 1 W testosterone? What does testosterone do?
hat two functions does the penis 4 W have?
hat changes do boys experience during 2 W puberty?
rite the words in the correct order from 5 W the production of sperm to ejaculation.
ow are male and female sex cells 3 H different?
urethra seminal vesicles prostate
vasa deferentia testicles
Pregnancy and birth How long does pregnancy last?
Human reproduction involves two different sex cells: a female ovum and a male sperm. Each cell carries different genetic information which is why children are unique; they have genetic code from both parents. Male and female reproductive systems are different: the male’s is designed to produce and deliver sperm, while the female’s is designed to produce ova, as well as housing, nourishing and protecting a developing foetus.
2. Development of the embryo
Fertilisation of the ovum can occur after the egg is released into the fallopian tubes. During sexual intercourse the man’s penis is inserted into the woman’s vagina, and the sperm are deposited there. Then, using their tails they swim up the vagina to the ovum in the fallopian tube. Only one sperm can fertilise an ovum. Once the ovum is fertilised, the cells will start to divide and multiply. This ball of cells is called a zygote.
After fertilisation, the zygote travels to the uterus where its cells carry on dividing and multiplying until they become an embryo. The embryo fixes itself onto the lining of the uterus where it will continue to grow. At eight weeks, the embryo is about the size of an adult’s thumb.
3. Development of the foetus
After about nine weeks, all the organs have formed and the embryo develops into a foetus. The foetus floats in a sac of amniotic fluid which protects it from knocks and bumps. The foetus receives oxygen and nourishment from the mother’s placenta. Waste matter and carbon dioxide are transferred from the foetus to the mother via the placenta. The baby is connected to the placenta by the umbilical cord.
Pregnancy lasts about 280 days. When the foetus is ready to be born, it pushes against the cervix, which starts to open and widen. Amniotic fluid is released which is often the first sign that birth is about to start. The muscles of the uterus begin to contract and the cervix opens sufficiently to allow the foetus, now a baby, to pass. The baby is pushed through the cervix and along the birth canal. Babies are usually born head first. The umbilical cord comes out with the baby. This is cut and tied, and forms our navel or belly button. The placenta or afterbirth comes out after the baby.
hich of the following is not used in 1 W fertilisation? penis ovum placenta ovaries vagina sperm
ow many sperm are needed for 2 H fertilisation to occur? 3 Put the stages in the correct order.
baby embryo foetus zygote
hat protects the foetus during 4 W pregnancy? hat precautions should mothers take 5 W during pregnancy? ow does the foetus receive oxygen and 6 H nutrients during pregnancy? 7 In which position should a foetus be for birth? What might happen if this is not the case?
Aims • Find out about life expectancy around the world. • Draw a graph representing the differences between different countries.
Hypothesis I think life expectancy in developing countries is … • lower than in developed countries, or
• paper • a pencil • a pen • a ruler • a computer • Internet access • felt-tips
• higher than in developed countries.
Method 1. Use the Internet to search for information on life expectancy at birth. Collect data for life expectancy from ten countries from different continents. Collect data for both men and women. 2. In groups, prepare your data and draw a graph representing life expectancy in the countries you have chosen. Use different colours to represent life expectancy for men and for women. 3. Compare your results with other groups.
Test • Which countries have the highest life expectancy? • Which countries have the lowest life expectancy?
Conclusions o developing or developed countries have 1 D a higher life expectancy? Why do you think this is? ho tend to live longer: men or women? 2 W Why do you think this is? ind out about life expectancy in Spain. 3 F What is the life expectancy for men and women in Spain? ow has life expectancy in Spain changed 4 H over the last few decades?
A basic right Gender equality is an important part of the United Nations Universal Declaration of Human Rights. According to this, men and women should be treated equally; and no one should be discriminated against on the basis of their gender. Several laws have been passed to guarantee this, particularly in developed countries. This has led to many changes over the past 50 years. For example, these days, women can vote, they can inherit property, they have the right to be paid as much as men for doing the same work, and they can participate in government. Women can also expect to have paid time off when they have a baby (maternity leave). Changes have affected men too. These days, they are expected to play a part in housekeeping, and take more responsibility for parenting. Many men now take paternity leave so they can help look after their children. Also, more and more men are doing jobs that were traditionally carried out by women, such as nursing and cleaning.
A long way to go In spite of all the laws, there is still a lot of discrimination based on gender. This is particularly the case in developing countries. So, why is this the case? Several issues can lead to women being treated as second-class citizens. These include poverty, religion and a lack of education. Violence against women is also a problem, even in developed countries. In general, women are much more likely to suffer violence than men.
1 Why is it important to legislate for equality? 2 Why do developing countries have less gender equality?
hink of some examples of jobs which women do today 3 T which they didn’t do in the past. 4 Why do mothers need to take maternity leave? 5
What can be done about domestic violence? Think of some ideas with a partner.
Revise Study skills 1 In your notebook, copy the table and classify the words.
• prostate • semen • vagina • uterus • fallopian • vasa • prostate gland • sperm • vagina • uterus • fallopian • vasa seminal
• urethra • urethra
• ovaries • • ovaries • seminal
reproduction female reproductive system .....
male reproductive system .....
ead the text below about identical twins (A). Then, read the text about fraternal twins on 2 R page 98 (B). In your notebook, decide whether the sentences below refer to text A, B, or both. Identical twins, siblings who look the same, occur when an ovum is fertilised, and subsequently the zygote splits into two. It then goes on to form two embryos. These embryos share identical genetic material, so the babies look the same. The chance of conceiving identical twins naturally is the same all around the world: about 3 per 1 000 births. However, zygotes are often split as part of in-vitro fertilisation treatment to ensure success in pregnancy. Splitting a zygote can also result in conjoined twins. This is when the embryos are not completely separate, but may share limbs or organs.
a. They develop from one zygote. b. They have the same genes. c. They can be of different genders. d. Any woman can conceive this type of twin. e. They are more common in some parts of the world. f. Older mothers are more likely to have this type of twin. g. They can be created artificially. h. Sometimes the twins can be connected physically.
Review 1 In your notebook, complete the diagram with the sexual characteristics.
a. The breasts develop.
hat happens during pregnancy? In your 6 W notebook, put the stages in order. a
b. The voice deepens.
c. Facial hair grows.
d. The skin can develop acne. e. Menstruation begins. f. The skin gets oily. g. Hair grows under the arms.
alk about human reproduction. Use the 7 T diagram and the pictures from Activity 6 to help you. fertilisation (ovum and sperm) zygote reproduction
hat happens during the menstrual cycle? 2 W Put the sentences in the correct order.
embryo foetus birth
a. The lining of the uterus thickens. b. Blood and the lining of the uterus leave the body. c. The ovum leaves the body.
8 Complete the summary on page 99.
d. An ovum is released by the ovaries. hat is the difference between identical 3 W and fraternal twins? Explain the difference to a partner. 4 In your notebook, put the stages of life in order.
c. elderly person hat measures can we take to ensure 5 W gender equality? What changes could we make in our own lives?
Checklist • I can identify and describe the characteristics of human reproduction. • I can identify and describe the different characteristics of male and female reproductive organs. • I can describe the process of fertilisation, pregnancy and birth. • I can identify different factors which have improved health and life expectancy.