9Aa1 Fertilisation

 

The pictures and sentences below describe what happens when fertilisation happens in plants and animals.

 

1       Cut out the pictures and sentences.

2       Match each sentence with the correct picture. Put the pairs into the correct order and stick them into your book.

3       Design a table to show the similarities and differences between fertilisation in plants and in animals.

 

[ knowledge]

 

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An egg cell is contained in an ovule found in the ovary.	The fertilised egg cell grows into a seed.	The sperm cell joins with the egg cell and fertilises it.
Pollen grains are produced by the male part of the plant.	The nucleus from the pollen grain enters the egg cell and fertilises it.	A pollen tube grows from a pollen grain.
An egg cell is made in an ovary.	Pollen grains are carried by insects or the wind.	A fertilised egg cell is produced, with genetic information from the mother and father.
The egg cell is released from the ovary and travels down the oviduct.	Sperm cells are made in the testes and contain half the genetic information of a normal body cell.	Pollen grains land on the stigma of another flower.
During sex, sperm cells are released and travel through the female's uterus.	DO NOT MAKE A DOUBLE SIDED PHOTOCOPY OF THIS WORKSHEET

 

 

9Aa2 Inheritance 1

 

Name _____________________________   Class ____________

 

1       Label the diagrams using words from the box.

 

 

 

2       Look at the drawing of a sperm cell. Write down two ways in which it is adapted to its function.

A sperm cell at a magnification of x2000.

 

 i         _____________________________________________________________________

 

ii        _____________________________________________________________________

 

3       Look at the drawing of an egg cell. Write down two ways in which it is adapted to its function.  i        _____________________________              _____________________________   ii        _____________________________             _____________________________

An egg cell at a magnification of x 500.

 

[ knowledge ]

9Aa3 Inheritance 2

1
This diagram shows what happens during fertilisation.
Write down the missing words shown by the letters a-j.
Each letter may represent more  than one word.

2       Write a description of what happens during fertilisation.

3       a        Draw a labelled diagram of a sperm cell.

b        Explain how a sperm cell is adapted to its function.

4       a        Draw a labelled diagram of an egg cell.

b        Explain how an egg cell is adapted to its function.

5        a        How is the way in which the sex cells meet different in plants and animals? Explain in as much detail as you can.

b        What is the correct scientific term for a sex cell?

6       Find out how sperm and egg cells meet in:

a        cod

b        frogs.

 

[ knowledge, literacy, research ]

 

                                                                               

 

9Aa4 Double trouble!

 

Identical twins are formed when one sperm cell fertilises a single egg cell. This fertilised egg cell then divides and separates to form two cells. Each cell grows and divides and two individuals with exactly the same genetic information are born. The twins will have the same skin colour, the same sex and all their other inherited characteristics will be the same. The environment may have an effect on their personalities or their bodies which may cause them to be different but, genetically, the twins are identical.

 

Twins that are not identical (fraternal twins) are formed when two sperm cells fertilise two egg cells at the same time. Each gamete contains genes with slightly different genetic information. For example, one sperm cell may contain the gene for brown eyes while another sperm cell may contain the gene for blue eyes. Therefore, when the egg cells are fertilised the individuals will be genetically different. Many of their genes, however, will be the same.

 

Fraternal twins are very similar, genetically, to normal brothers and sisters with the same parents. They are all formed from the meeting of any sperm cell with any egg cell, whereas identical twins share the same sperm cell and egg cell and, therefore, contain the same genes.

 

Sometimes when a couple cannot have children they have gametes removed from them. The egg cells are fertilised with the sperm cells outside the body. The fertilised egg cells are then replanted back inside the mother's uterus. Lots of fertilised egg cells are placed inside the mother in case some don't grow. If many of them grow then the mother will give birth to many babies - this is known as a multiple birth.

 

1       How are identical twins formed?

2       Why are identical twins more similar than ordinary brothers and sisters?

3       Can identical twins be different sexes?

4       Why are brothers and sisters similar?

5       Will multiple births, when many egg cells are fertilised outside the body and then implanted, produce identical or similar offspring?

6        a        Draw a diagram to show how identical twins are formed. Start your diagram like this: b        Draw a diagram to show how fraternal twins are formed.

 

7       The gene that contains the genetic information for brown eyes is said to be dominant. This means that if a person's body cells contain one gene for brown eyes and one gene for blue eyes, the blue-eye gene is not allowed to work. The person will have brown eyes. Explain how two parents might have a child with blue eyes even if they both have brown eyes.

 

[ knowledge, literacy ]

 

9Aa5 Conjoined twins

 

Conjoined twins (often called Siamese twins) are like identical twins except that parts of their bodies are joined together. Normally with identical twins, one fertilised egg cell splits into two. For conjoined twins the two fertilised egg cells do not split completely. When the two cells grow and divide they form twins which are joined by some part of the body. Some conjoined twins may be joined in places like the fingers - these twins will be easy to separate by a simple operation. The twins are free to live their lives as healthy individuals. Other conjoined twins are never separated but still enjoy happy lives attached to their twin.

 

Conjoined twins may share major organs, like the heart. These twins will be very weak and if they are operated on they may die. Jodie and Mary were conjoined twins from an island called Gozo, near Malta. They were joined by a major blood vessel called the aorta. Mary's heart and lungs did not work and she relied on Jodie's heart to pump blood around both of their bodies. If they had stayed joined together then both would have died within six months, Jodie's heart could not have coped with having to pump blood for both of them and Mary would have died without Jodie. If the twins were separated Mary would definitely die as her major organs

were not functioning, but Jodie would be able to live a nearly normal life.

 

A decision was made to separate them and, as predicted, Mary died.

 

The decision to separate Jodie and Mary and thereby end Mary's life was criticised by Roman Catholics and pro-life groups who feel that everybody has a right to live. They felt that by separating the twins Mary was deprived of her right to live.

 

1       How are conjoined twins different from identical twins?

2       What part of the body were Jodie and Mary joined by?

3       What would have happened if the twins were not separated?

4       What happened when they were separated?

5       Why did some organisations and religions think separation was a bad decision?

6       Draw a simple diagram to show how conjoined twins are formed.

7       Find out why conjoined twins are often called Siamese twins.

 

Optional extra

8       a        Do you think Jodie and Mary should have been separated?

b        Conduct a survey to see how many people think it was right to separate Jodie and Mary.

c        What do the results of your survey show?

 

[ literacy, knowledge, research ]

 

9Ab1 Variation and varieties 1

 

What are the differences in mass between different apple varieties?

 

There are many different varieties of apple. In this experiment you will compare

two varieties.

 

Apparatus -        5 apples of one variety (variety 1)               -        Balance -        5 apples of another variety (variety 2)

Do not eat the apples.

 

Method

1       Keep the varieties in two separate piles so they don't get mixed up.

2       Measure the mass of each apple from variety 1 and record your results in a table.

3       Repeat step 2 for variety 2.

 

Recording your results

1       Record your results in a table, showing the masses of all five apples of each variety.

 

Considering your results/conclusions

2       Do all the apples in variety 1 have the same mass?

3       Do all the apples in variety 2 have the same mass?

4       Calculate the mean mass of each variety.

5       All of the apples in a variety have the same genetic information. What could have caused apples in each variety to have different masses to each other?

6       Compare the mean mass of variety 1 with the mean mass of variety 2.

a        Which has the largest mass?

b        Why do you think that is?

7       a        Do you think variety 1 and 2 have the same genetic information?

b        What has made these apples have different masses?

c        Is a difference in genetic information the only cause of variation?

 

Evaluation

8       Do you think you have enough results to be able to say that one variety of apples is always heavier than the other? Explain your reasoning.

 

[ observing, presenting, considering, evaluating ]

9Ab2 Variation and varieties 2

 

There are many different varieties of plant. Apple trees are an example. They produce fruit which differ in many characteristics, including firmness, juiciness, size, mass, taste, and colour.

 

How would you investigate how one of these characteristics varies between two varieties?

 

Apparatus -        Apples of two different varieties                           -        Skewer -        Displacement cans            -        Balance               -        Colour charts -        Pestle and mortar                                                   -        Newton meter

Do not eat the apples.

 

Planning

 1      a        Decide which characteristic or characteristics you will measure.

b        Explain your choice(s).

 2      Write down a method for your investigation. You will need to think about these things:

-        What apparatus will you use? The list in the box may give you some ideas but you may need other pieces of apparatus.

-        What will you measure?

-        How will you carry out your experiment? Will you use a computer to help you record your results?

-        What sample size will you use?

-        What will you do to make sure you stay safe?

 3      Show your method to your teacher before you begin.

 

Recording your results

 4      a        Make a table to record your results.

b        Calculate mean results for each variety of apple and add these to your table.

 5      Plot a bar chart to show your results.

 

Considering your results/conclusions

 6      Using the information shown on your chart, write a conclusion. Write down how one variety is different from the other.

 7      Why do you think there is variation between the two varieties?

 8       a        Does what you found out tell you something about what each variety of apple is used for? If so, what?

b        Does what you found out tell you something about how popular each variety of apple is? If so, what?

 

Evaluation

 9      Do you think you have enough results to support your conclusion?

10     How might you improve your experiment?

 

[ planning, observing, presenting, considering, evaluating ]

9Ab3 Variation and varieties 3

 

Some pupils measured the masses of two different varieties of apple. There were five apples of each variety. The results are recorded in the table.

 

	Variety 1 mass (g)	Variety 2 mass (g)
Apple 1	125	150
Apple 2	120	147
Apple 3	122	150
Apple 4	130	152
Apple 5	125	158

 

1       Draw a bar chart to show the differences in mass for variety 1.

2       Why do you think the variety 1 apples have different masses?

3       Plot the masses for variety 2 on the same chart.

4       Why do you think the variety 2 apples have different masses?

5       Why do you think variety 2 apples have larger masses than variety 1 apples?

 

[ knowledge, presenting, considering ]

9Ab4 Variation and varieties 4

 

Some pupils measured the masses of two different varieties of apple. There were five apples of each variety. The results are recorded in the table below.

 

	Variety 1 mass (g)	Variety 2 mass (g)
Apple 1	125	150
Apple 2	120	147
Apple 3	122	150
Apple 4	130	152
Apple 5	125	158

 

1       Enter the data in a spreadsheet.

2       Use the spreadsheet to draw a bar chart to show the range in mass for variety 1.

3       Use the spreadsheet to draw a bar chart to show the range in mass for variety 2.

4       Why do you think apples within a variety have different masses?

5       Work out the mean mass of each variety and plot this information on the chart.

6       Why do you think variety 2 is different to variety 1?

 

Optional extra

7       Calculate the following averages for these apples and explain what each average shows.

 

         a        mean                  b       median                  c        mode

 

[ knowledge, numeracy, presenting, considering ]

9Ab5 Genes and the environment

 

Name _____________________________   Class ____________

 

1       Fill in the missing words in the sentences, using words from the box.

         You may need to use some words more than once.

 

         Inside every cell in our bodies there is ________________  ________________.

 

         The information is carried on ________________ that tell the cells in our body how to make

 

         us. Many________________ are controlled by genes. Eye colour, hair colour and height are

 

         just a few examples.

 

         Some characteristics are not controlled by genes but by the ________________ .

 

         For example, a ________________ is not something you are born with but some people may

 

         choose to have one. If a person has chickenpox and scratches their spots they may get

 

         ________________. You are not born with these characteristics; they are things that you get

 

         during life.

 

         Plants may have all the correct genes that allow them to grow but if the ________________ is

 

         too cold or there is not enough ________________  then they will become weak or die. The

 

         temperature and the amount of water are environmental factors.

 

         There are some characteristics that can be controlled by genes and the ________________  .

 

         An example of this is ________________ . If children have very tall parents then it is likely

 

         they will grow up to be ________________ too. Their parents will have ________________

 

         that have made them tall. These genes may be passed onto their children so they may be tall as

 

         well. However, if the child grows up in an environment where there is not enough food, so

 

         they do not get enough of the essential ________________ , then the child's growth will be

 

         stunted. This is where the environment has had an effect.

 

 

2       In the passage, circle words or phrases which are characteristics controlled by genes.

3       In the passage, underline words or phrases which are environmental factors.

 

[ knowledge, literacy ]

9Ab6 Cystic fibrosis

 

Cystic fibrosis (CF) is a genetic disorder. Sufferers have inherited 'faulty' genetic information from their parents and this makes them produce extra mucus. Mucus is a slimy substance that traps microbes. Normally, ciliated epithelial cells sweep the mucus out of your lungs and you swallow it. However, CF sufferers produce so much mucus that this does not happen. The mucus builds up in their lungs and they find breathing difficult. The mucus also encourages bacteria to grow and CF sufferers often get lung infections.

 

To get rid of this mucus, CF sufferers have physiotherapy sessions. A physiotherapist slaps them on the back to make them cough up the mucus and help them breathe better.   Most CF sufferers have problems with other organs too. Cystic fibrosis affects the pancreas. The pancreas produces enzymes which digest food. The extra mucus blocks the small tube leading from the

pancreas to the small intestine and so the enzymes cannot get to the small intestine. CF sufferers take tablets containing digestive enzymes.

 

Not many people with CF live past 30 years of age, although with modern treatments more and more sufferers are living longer and longer.

 

For a person to have cystic fibrosis they must have a CF gene from their mother and a CF gene from their father. People who have only one CF gene are called carriers. Carriers are perfectly healthy, but two parents who are both carriers may have children who have cystic fibrosis. Half of the man's sperm cells will contain the CF gene and the other half will contain the normal gene. The same is true for the mother's egg cells. Half of her egg cells will contain the CF gene. One person in 25 carries this 'faulty' gene.

 

1       How do people get cystic fibrosis?

2       What builds up in their lungs so they can't breathe?

3       What grows on the mucus that can be harmful?

4       What is done to make the cystic fibrosis sufferer feel better?

5       Give an example of an organ that may not work properly in CF sufferers.

6       a        What is a 'carrier'?

b        What percentage of people are carriers?

c        Why do only half of a carrier's gametes contain the faulty CF gene?

7        a        Draw a diagram to show how two parents who are both carriers can produce a child who has cystic fibrosis.

b        Explain why only 25% of their children get cystic fibrosis.

8       Find out what is being done to 'cure' cystic fibrosis.

 

[ literacy, research ]

9Ab7 Genetic diseases

 

Different genes which carry the genetic information for different versions of the same thing are called alleles (pronounced 'al-leels'). For example, the gene that causes brown eyes is one allele and the gene that causes blue eyes is another. Some alleles are dominant, which means that they will stop other alleles (called recessive alleles) from working. The brown-eye allele is dominant over the blue-eye allele. People with one of each allele will have brown eyes. The characteristics that alleles cause are called phenotypes. The alleles that people have are called genotypes.

 

Genotypes are written down as letters. Dominant alleles have a capital letter and recessive alleles have a small version of that capital letter. Someone with brown eyes could have these genotypes: BB (both alleles cause brown eyes) or Bb. Someone with blue eyes must have the genotype bb (both alleles cause blue eyes).

 

1       Huntington's disease is a serious genetic disease that causes sudden jerky movements. It is caused by a dominant allele and usually only develops after the age of 40. This family tree shows how it has affected a family.

 

 

a        Using H to represent the dominant allele and h to represent the normal allele, give the genotype of Richard. Explain your reasoning.

b        Give the genotype of Glenn. Explain your reasoning.

c        What chance is there that Laurie also has Huntington's disease? Give your answer as a percentage.

 

2       Cystic fibrosis is another genetic disease. It is caused by a recessive allele. Using N to represent the normal dominant allele and n to represent the cystic fibrosis allele, answer the following questions.

a        Copy and complete this diagram to show what the possible genotypes would be if two parents, both of genotype Nn, had children.

 

		Male
	Gametes	N	n
Female	N
	n

 

b        What percentage of the children would have the disease?

c        A 'carrier' is someone who does not have a genetic disease whose cells contain one allele for the disease. What percentage of the children would be carriers?

 

[ knowledge, considering ]

9Ac1 Inheritance - true or false?

 

For each statement, say if it is true or false. For each false statement, write out a correct version.

 

 1      The colour of your eyes is a characteristic that is inherited.

 2      You inherit characteristics from your mother only.

 3      Your brothers or sisters inherit exactly the same characteristics as you.

 4      All animals inherit some characteristics from their parents.

 5      Plants are not able to inherit characteristics.

 6      Not all characteristics are inherited.

 7      The environment has no effect on your characteristics.

 8      Genes carry genetic information and are found inside every cell.

 9      There are half as many genes in gametes as there are in normal body cells.

10     Fertilisation is when a sperm cell fuses with an egg cell.

11     A fertilised egg cell only contains half the genetic information of a normal body cell.

12     Identical twins form from a single egg cell and a single sperm cell.

 

[ knowledge ]

9Ac2 Selective breeding

 

1          Look at these sheep.

 

A The Balwen mountain sheep is able to live in cold, harsh conditions.	B The Bluefaced Leicester sheep produces good quality wool.	C The Polled Dorset sheep produces good quality meat.	D The Friesian Milk sheep produces a lot of milk.

 

a        Each of these sheep has been produced by selective breeding. For each sheep write down one characteristic that has been selected.

         Farmers often want to breed two different breeds of sheep together. This is called cross-breeding. The offspring produced by this method should have characteristics from both parent sheep.

b        Which of the sheep above might a farmer use to breed sheep with good meat and good wool?

c        Which of the sheep might a farmer use to produce sheep with good wool that can survive in the Welsh mountains?

2       A sheep farmer has a flock of Wensleydale sheep.          To win a prize at the local farming show, he wants to have sheep with very long wool. Some time ago, he took the ewes (female sheep) and rams with the longest wool and allowed them to breed. He allowed the new lambs to grow and then kept the ones with the longest wool and allowed them to breed. The others were sold at market. It took him eight years to produce sheep with wool long enough for him to win a prize.

a        What is a male sheep called?

b        Why is this farmer's method an example of selective breeding?

c        Suggest why it took him so long to win a prize.

3        a        Think about the weather conditions where you live. Write down a list of characteristics that a sheep should have if it were to be farmed in your area.

b        What other characteristics would you like your sheep to have and why?

 

[ knowledge, literacy ]

 

 

9Ac3 New breeds

 

Farmers select animals with useful features and breed from them. If they continue selecting the same characteristics over and over again, they may eventually end up with a new breed.

Breeds of hen have now been created that lay eggs earlier in their lives so that farmers get a greater yield of eggs during the hen's life.

 

Today people are very conscious of the amount of fat they consume. New breeds of chicken, pig and cow that are leaner with not as much fat have been produced because people prefer this sort of meat.

 

When a cow gives birth she will be able to produce milk for ten months. The more milk a cow can produce in this time, the more useful she is to a farmer. A typical dairy cow produces between 5000 and 6000 litres of milk a year and some breeds produce even higher yields. Cows that produce the most milk will be selected for breeding.

 

Farms also have stud bulls. These are bulls that have useful characteristics that farmers would like the offspring to inherit. The sperm cells the bull produces are collected and used to make cows pregnant. Some stud bulls are so popular that many farms in the area use them to make their cows pregnant.

 

1       Name one useful characteristic of cows.

2       Name one characteristic you think stud bulls would have to make them popular.

3       Name two useful characteristics of chickens.

4       Name two useful characteristics of sheep.

5       The process of selecting a useful characteristic and breeding only using animals which have this characteristic is called selective breeding.

a        Explain what a farmer would do to breed cows that produce more milk than cows already on the farm.

b        Selective breeding is sometimes called artificial selection. Why do you think it is called artificial selection rather than natural selection?

c        How many litres of milk will a typical cow produce per day?

6       Cows are often made pregnant by artificial insemination. Find out what artificial
insemination is.

 

[ literacy, knowledge, numeracy, research ]

9Ac4 Rare breeds

 

The farm animals that are now popular have been created from older breeds by the process of selective breeding. These older breeds no longer have all the characteristics that farmers want, but to stop them from becoming extinct they are kept in rare breeds farms. For example, large work horses (shire horses) were used to pull ploughs and heavy carts. They are not needed now because we have tractors and other machinery to do their work.

 

The animals on rare breeds farms are involved in breeding programmes so that there will always be some of these rare breeds living. It is important that their genes are not lost in case their characteristics become popular again. Around the UK there are about 19 rare breeds farms.

Animals are said to be rare if there are only a few hundred existing. English longhorn cattle and Phoenix chickens are rare breeds.

 

An English longhorn cow.   The English longhorn was bred in the middle of the 18th century by Robert Bakewell who lived in Lancashire. He was the first person to selectively breed cattle specifically for farmers. The characteristics he selected were quick growth and large rear end (where some of the best meat is). English longhorns were the most widely used cattle in Britain and Ireland until the early 19th century. At this time the shorthorn breed became more popular.   Each breed of animal has a certain set of characteristics. A breed is only a breed if all the offspring produced have the same set of characteristics. A breed is established by existing for six generations or more over 75 years. If a breed has not existed this long then it is not a proper breed and may be allowed to die out.

A phoenix cockerel.

 

1       How are new breeds of farm animal created?

2       a        Where are old breeds kept to stop them from becoming extinct?

b        Why do we keep rare breeds and not allow them to become extinct?

3       Why are shire horses no longer needed?

4       a        How long does one breed have to exist for before it is properly defined as a breed?

b        A farmer has some chickens which he thinks are a new breed. How would you find out if the chickens actually are a breed?

5       a        Name two characteristics that were selected for when English longhorn cattle were bred.

b        Why were these characteristics useful to the farmer?

c        Suggest why the shorthorn breed became more popular than the longhorn.

6       In the middle of the 19th century, farmers liked to show off by having a few members of an interesting looking breed of chicken roaming around the farm. It did not matter if these chickens were not very useful for much else.

a        Which feature has been selectively bred in the Phoenix breed?

b        Why do you think farmers no longer bother having interesting looking chickens roaming around?

 

[ literacy, knowledge ]

9Ac5 Breeding animals

 

Answer one of the questions below. You should write a full account in your answer, using paragraphs and giving as much detail as you can. However, stick to answering the question!

 

1       How have the characteristics that people have found useful in farm animals changed through the ages?

2       What were the origins of modern farm animals?

3       Are the useful characteristics of some farm animals only useful in certain areas?

4       Are old fashioned breeds of animals still bred today?

 

You can use the text below to help you. You may be given other pieces of information or you could find out more using the internet or CD-ROMs. Illustrate your answer with drawings or pictures.

 

 

Many thousands of years ago all animals were wild. Humans had to hunt animals in order to eat them; they could not buy meat from shops like we do now. Humans decided to domesticate (tame) animals so that they could be killed for food or used to do heavy work. It made life easier, instead of spending hours hunting for a source of nutrients. They caught wild animals and started the first farms, where these animals were bred. They were much simpler than the farms we have today.

 

Even though there are still millions of animal species in the world today, we only eat a very small number of them. Most of these have been domesticated, like chickens, turkeys, cows and pigs. Some animals we eat are still wild, like game birds (e.g. pheasants). The fish we eat may also be wild, like salmon or tuna, although fish farms do exist.

 

Our modern animal breeds have been produced by selective breeding. Farmers take animals with the characteristics that they want and breed them with other animals that also have these characteristics. The offspring should then have these characteristics. The offspring which have the best of these characteristics (e.g. cows that produce the most milk) are then used to breed from. This happens again and again until a new breed is produced. A breed is only a breed if all the offspring produced have the same set of characteristics. A breed is established by existing for six generations or more over 75 years. If a breed has not existed this long then it is not a proper breed and may be allowed to die out.

 

Each characteristic is controlled by a gene (which carries genetic information). Genes are found in the nuclei of all cells. Selective breeding reduces the variety of genes in a species since only certain characteristics are chosen. The lost genes are no longer available to use for future selective breeding. This might be a problem if conditions change and people need the characteristics of an old breed once more. This is why breeds that are no longer used for farming are often kept on rare breeds farms. In the UK there are about 19 rare breeds farms.

 

Large work horses (shire horses) are a popular attraction at many rare breeds farms. They were used to pull ploughs and heavy carts. They are not needed now because we have tractors and other machinery to do their work. The animals on rare breeds farms are involved in breeding programmes so that there will always be some of these rare breeds living.

 

The chicken is the most common domestic animal, with over 5 billion in the world. They have been bred for meat and eggs. The chickens we see now originated from wild jungle fowl from India. Breeds of hen have now been created that lay eggs earlier in their lives so that farmers get a greater yield of eggs during the hen's life. Many of today's chickens have been specially bred for their meat and to be able to survive in confined spaces. However, this method of farming chickens packed together in large sheds is going out of fashion and so farmers once again need breeds of chicken that can survive well outdoors.

 

Wild turkeys came from North America. People used to use their feathers to make warm blankets. Selective breeding of turkeys has created breeds that are larger and more gentle than the wild turkey. They are able to convert more food into muscle (the meat) and have more breast meat, the most popular part of the animal that is eaten. Since turkey breeds now have more muscle they are heavier and can no longer fly very well. It is important for animals to be gentle because it makes them easier to handle.

 

Wild sheep were domesticated about 9000 BC from wild mouflon sheep from western Asia. They were used to provide milk, wool, meat and leather. The breeds we see today were created by selective breeding to produce wool of good quality and more muscle, for meat. They are only rarely used for milk or leather production now. Today's breeds vary greatly in their appearance from the wild animals that existed thousands of years ago.

 

Some sheep are specific to certain areas. For example some sheep breeds have short legs and so are farmed in very steep hilly areas so that they are less likely to fall over when they are climbing over rocks. Other breeds lose their wool in summer which makes them useful for farming in hot countries (unless the wool is needed!).

 

Wild cattle were much larger than the domesticated cattle that we see now. They were found in most of Europe, Asia and northern Africa and were domesticated about 6000 BC.

 

English longhorn cattle were a breed developed in the middle of the 18th century by Robert Bakewell who lived in Lancashire. He was the first person to selectively breed cattle specifically for farmers. The characteristics he selected were quick growth and large rear end (where some of the best meat is). English longhorns were the most widely used cattle in Britain and Ireland until the early 19th century. At this time the shorthorn breed became more popular. Now the most popular breeds are the Holstein and Friesian breeds.

 

When a cow gives birth she will be able to produce milk for ten months. The more milk a cow can produce in this time, the more useful she is to a farmer. A typical dairy cow produces between 5000 and 6000 litres of milk a year, but some breeds produce even higher yields. Cows that produce the most milk will be selected for breeding.

 

Farms also have stud bulls. These are bulls that have useful characteristics that farmers would like the offspring to inherit. The sperm cells the bull produces are collected and used to make the cows pregnant. Some stud bulls are so popular that many farms in the area use them to make their cows pregnant.

 

Pigs originally came from wild boar. Today's pigs do not have the large teeth that wild boar have, they are less hairy and they are a lot less vicious! Different breeds of pigs have been important at different times. Until the Second World War, pigs that produced a lot of fat were popular. Pig fat (lard) was used a lot for cooking and the fatty meat did not go off very quickly. Pig breeds like the Gloucester old spot were very popular. Today, almost everyone has a fridge and people use vegetable oil for cooking because it is healthier. The most common breed of pig today is the large white since it grows very big quickly and has lean (non-fatty) meat.

 

[ literacy, research ]

9Ad1 Pea practical

 

There are different varieties of plants, some share particular characteristics and others do not. You have a fresh and a frozen variety of garden pea. You are going to design an experiment to compare these different varieties of pea.

 

Planning

 1      What characteristics do these peas have that you could measure?

 2      Choose one of these characteristics and write down a method for your investigation. You will need to think about these questions.

-        What will you measure?

-        What sample size will you use?

-        What apparatus will you use?

-        How will you make this a fair test?

-        How will you make sure that you stay safe?

 3      Show your method to your teacher before you begin.

 

Recording your results

 4      Record your results in a table.

 5      Draw a bar chart to show your results.

 

Considering your results/conclusions

 6      If you can, calculate the means and show them on your chart.

 7      Compare your results with other groups' results.

 8      What have you learned from this experiment? What conclusions can you draw? Try to explain why you got the results you did.

 

Evaluation

 9      If you could do this experiment again, what would you do differently? Why?

10     Was your experiment a fair test? Explain why or why not.

 

[ planning, observing, presenting, considering, evaluating ]

9Ad2 That tastes good

 

Cooking apples are needed to make apple pies. Some characteristics of cooking apples are more useful than others.

 

1       Cut out the boxes below and separate them into piles according to whether the characteristics are always desirable, never desirable or sometimes desirable.

2       Who do you think each of these characteristics are useful to?

 

[ knowledge ]

 

---------------------------------------------------------------------------------------------------------

 

	sweet taste		sharp taste
	lasts a long time on the shelf		rots quickly
	takes a long time to cook		ripens quickly
	colour		size
	resistance to disease		likes cold temperatures
	costs a lot to grow		cheap to grow
	texture

 

9Ad3 Breeding plants 1

 

1       Look at this list of characteristics of tomato plants.

 

         big tomatoes                                                                plants are resistant to disease       

         plants will not die in temperatures below 4 °C               tomatoes are juicy

         plants produce lots of tomatoes                                    tomatoes are very tasty

         tomatoes are bright red                                                tomatoes grow in clumps of four

         tomatoes stay fresh for six days                                    small leaves

 

a        Draw a table to show whether each of these characteristics can or cannot be seen when you look at the plants.

b        Name the three characteristics in the list that you think are the most important to shoppers in a supermarket. Explain your choices.

c        Name the three characteristics that you think are the most important to farmers. Explain your choices.

d        Imagine you are a plant breeder. Write down three characteristics from the list that you would like your new variety of tomatoes to have. Explain your choices.

2        a        To breed plants a plant breeder takes pollen grains from one flower and puts them onto the stigma of another. Is this process called pollination or fertilisation?

b        Are the pollen grains the male or the female sex cells?

c        Once on the stigma, a pollen grain grows a tube down towards an egg cell which is contained in an ovule. The nucleus from the pollen grain goes into the egg cell. Is this process called pollination or fertilisation?

3       The drawings show two flowers. Flower A is a normal flower and flower B has had pollen added to its stigma by a plant breeder.

 

Flower A.	Flower B.

a        Apart from adding pollen, what else has the plant breeder done to flower B?

b        Suggest why the plant breeder has done this.

 

[ knowledge ]

 

 

9Ad4 Characteristics review

 

1       The drawing shows a family.

 

 

a        Copy and complete the following sentences.

          Characteristics that you get from your parents are said to be i________________ .

 

          The information for these characteristics is called g________________  information.

 

          This information is found on g________________ .

b        Where are the things that you named in the last sentence of part a found? Explain in as much detail as you can.

c        Name two characteristics that the girl has got from her mother.

d        Name two characteristics that the boy has got from his father.

e        Why do the children have characteristics from both their parents? Use a diagram to help you explain, if you wish.

f        The boy has a scar on his face. Is this caused by any of the things that you named in part a? Explain your answer.

2       a        What is a species?

b        What is a variety?

c        What is a breed?

3       A plant breeder takes pollen grains from one flower and puts them onto the stigma of another flower. Each pollen grain grows a tube from the stigma down the style to the egg cells inside the ovules. Here, the nucleus from the pollen grain enters the egg cell.

a        What is the name of the process in the first sentence?

b        What is the name of the process in the second sentence?

c        Which is the male gamete and which is the female gamete?

d        Plant breeders need to make sure that only the pollen grains that they select get onto the stigma. Describe one way in which this is done and explain why it works.

e        Name two characteristics that a plant breeder might want in orange trees.

f        For one of these characteristics, explain how the plant breeder could produce a new variety of orange tree with this characteristic.

g        If a plant breeder breeds two different varieties of plant together, what is this process called?

4       A hill farmer wants to farm sheep that he can sell for meat. Suggest characteristics that the farmer might look for when deciding which sheep to farm. Explain your suggestions.

 

[ knowledge ]

9Ad5 Breeding plants 2

 

When farmers are planning to plant a field of vegetables they want a crop that will grow well and produce a high yield so that they get more vegetables for their money. The farmers also want a crop that can withstand very cold temperatures over the winter or very high temperatures and drought over the summer. They will want plants that are resistant to disease and pests. Most of all they will want a crop that looks and tastes good so people will want to buy it.

 

For over 10000 years farmers have saved the seeds from successful crops to produce the next year's crop. They didn't realise it then but they were selecting useful genes.

 

Today, plant breeders choose plants that they know have good characteristics. They have developed simple, yet effective techniques for cross-pollination (the transfer of pollen from the anther of one plant to the stigma of another plant).

 

First of all the breeder must decide which plant is to produce the pollen and which will receive the pollen on its stigma. These must be clearly marked, perhaps with different coloured thread or a tag.

The next step is to ensure that the plant is not fertilised by its own pollen (self-pollination). Some plant breeders remove the anthers (the male parts, which produce pollen) with tweezers. They may need a magnifying glass to do this. To prevent cross-pollination (pollination by pollen from another flower) breeders tie up the petals of the flower with a piece of string or put a polythene bag over the flower to protect the stigma.

 

 

To cross-pollinate, the anther is removed from one plant and placed in a container using tweezers. The protector, e.g. polythene bag, is removed from the flower of the other plant. The anther is then taken out of the container using tweezers and is rubbed gently over the stigma of the other plant so pollen is left on it. The protector is then replaced so the plant is not pollinated by unwanted pollen. Alternatively, a paintbrush can be used to brush pollen onto the stigma.

 

 1      Make a list of all the characteristics a plant breeder may look for in:

a        red rose bushes

b        potato plants

c        tomato plants.

2       Write a list of instructions for pollinating plants for someone who has not done this before.

3       How do breeders make sure that plants don't pollinate themselves?

4       How do breeders make sure unwanted pollen doesn't pollinate the plants?

5       Find out how some plants make sure that they don't pollinate themselves.

 

[ literacy, knowledge, research ]

9Ad6 Mendelian genetics

 

Gregor Mendel (1822-1884) was a monk who was very interested in finding out how different plants were created. He didn't know it then but he was watching the effects of genes. Mendel did most of his experiments with pea plants and he did his experiments in three steps.

 

He allowed individual pea plants to pollinate themselves (pollen from the plant's own anthers was used to pollinate the plant). This is self-pollination. From the offspring plants he took only those plants that had the characteristic he was interested in. He then allowed these plants to self-pollinate. He did the same thing with the next set of offspring plants and continued doing this until all the plants always produced offspring which all had the characteristic he was interested in. He called these plants 'pure-breeding' or P plants.

 

Mendel then took one P plant with a certain characteristic (e.g. wrinkled peas) and used this plant's pollen to pollinate another P plant that had a variation of this characteristic (e.g. smooth peas). This is cross-pollination. The offspring were called the F1 generation. In the example of wrinkled and smooth peas, all the offspring produced smooth peas. He said that the smooth peas were a dominant characteristic.

 

When two F1 plants were cross-pollinated 75% of the offspring (F2 plants) had smooth peas and 25% had wrinkled peas. Mendel said that the wrinkled peas were a recessive characteristic.

 

1       What is self-pollination?

2       What is cross-pollination?

3       How did Mendel produce pure-breeding P plants?

4       What was the dominant characteristic in the F1 plants?

5       What was the recessive characteristic in the F2 plants?

 

We now know about genes. Since there are two sets of chromosomes in each nucleus of a pea plant, there are two genes for each characteristic. However, each gene may produce a variation in that characteristic. Different genes for the same characteristic are called alleles (pronounced 'al-leels'). A dominant allele stops the recessive allele from working. A dominant allele is given a capital letter (e.g. S for smooth peas) and the recessive allele gets a small version of this letter (e.g. s for wrinkled peas). The set of alleles that a pea plant has is called its genotype. What the plant looks like is called its phenotype. We can predict the percentages of the genotypes and phenotypes of the offspring using a grid like this:

 

Parent plants' alleles in gametes	S	S
s	Ss	Ss
s	Ss	Ss

The shaded area shows the four different
genotypes possible in the offspring.

 

This grid shows an SS genotype plant being cross-bred with a ss genotype plant. Remember that each gamete will only get one allele or the other. All the offspring had a genotype of Ss and so all have a phenotype of smooth peas because S is the dominant allele.

 

 6      Which step of Mendel's experiment does this grid show?

 7      What is the phenotype of plants that have the genotype ss?

 8      What two possible genotypes could plants have if they produced smooth peas?

 9      a        Draw another grid to show what would happen when two Ss plants were bred together.     Start your grid like this:

 

	S	s
S
s

 

b        What percentages of smooth and wrinkled peas do you get?

10     Tall pea plants (T) are dominant to small pea plants (t). Draw another grid to show what would happen if you crossed Tt plants with pure breeding small pea plants.

11     Find out what these grids are called.

 

[ literacy, research ]

9A Summary Sheets

 

Inheritance and selection

 

Inherited variation

The features of organisms are called their characteristics (e.g. blue eyes). Offspring normally share some characteristics with their parents and brothers and/or sisters. Offspring can inherit characteristics from their parents. Characteristics can be different and this is known as variation (e.g. brown eyes and blue eyes). Variation occurs in both plants and animals.

 

 

An organism's characteristics are controlled by genetic information which is found inside the nucleus of almost all of its cells. Genetic information is passed from parents to offspring during reproduction. In sexual reproduction, a male sex cell or gamete (e.g. a sperm cell) and a female gamete (e.g. an egg cell) fuse. This fusing (joining together) produces a fertilised egg cell which grows into the new organism. Each gamete contains half the amount of genetic information that a normal body cell has. So the fertilised egg cell gets half its genetic information from the male and half from the female.

 

In many animals, when two egg cells are each fertilised by a sperm cell, non-identical twins are born. Sometimes a fertilised egg cell splits into two and identical twins form.

 

Species, breeds and varieties

A species is a group of organisms that are able to produce offspring that are also able to reproduce. Members of the same species have very similar characteristics but there is some variation in these characteristics.   A group of animals may have special differences in their inherited characteristics from the rest of their species. A group like this is called breed (e.g. different breeds of dog). There are also breeds of plants and these are called varieties.

All tigers have stripes but there is variation in the stripes between each tiger.

 

Selective breeding

Farmers and plant breeders may choose or 'select' an animal or plant with certain characteristics (e.g. good milk production in cows). This animal or plant is then used to breed from. The offspring that have the best of these characteristics are then bred from again. This is called selective breeding and is how many new breeds and varieties are created. Sometimes two different breeds or varieties are bred together to produce offspring with characteristics from both breeds or varieties. This is called cross-breeding.

 

Plant breeding

In nature, pollen grains (the male gametes) are carried by the wind or insects to the stigma of another flower. This is called pollination. Plant breeders transfer the pollen that they want to the stigma that they choose, sometimes using a paintbrush.

 

A pollen grain grows a tube down through the style until it meets an ovule. It grows into the ovule and meets an egg cell. The nucleus from the pollen grain goes into the egg cell and fuses with the egg cell nucleus. This is fertilisation.

 

 

Many of the characteristics that plant breeders choose are visible (e.g. fruit size, yield) but some are not visible (e.g. disease resistance).

 

Variation caused by the environment

Some characteristics vary due to an organism's surroundings (environment). For example, plants growing in different areas of a field may be different heights depending on the amount of light, water and mineral salts that they get. These things are all physical environmental factors.

 

9A Target Sheet

 

Name _____________________________   Class ____________

 

Topic		Targets	Before the unit	I have learned this	I have revised this
9Aa	1	Know what variation is.
	2	Know some examples of inherited characteristics.
	3	Know what happens during fertilisation.
	4	Know how characteristics are inherited.
9Ab	1	Know some examples of characteristics that cannot be seen.
	2	Know what an environmental factor is.
	3	Know what a species is.
	4	Know what a variety is.
9Ac	1	Know what a breed is.
	2	Know some examples of useful characteristics in animals.
	3	Know what selective breeding is.
	4	Know what cross-breeding is.
9Ad	1	Know the names of the gametes in plants.
	2	Know some examples of useful characteristics in plants.
	3	Know what happens in pollination.
	4	Know how plant breeders breed plants.

 

9A Word Sheet

 

Word sheets that include new words from the 'Focus on:' pages are available on the Exploring Science website.

 

9Aa - Inherited characteristics/How variation occurs

 

Word	Pronunciation	Meaning
characteristics		The features of an organism.
DNA		A large molecule that contains genes.
gamete	gam-meet	Scientific word for sex cell.
gene	jeen	A length of DNA that controls one inherited characteristic of an organism.
genetic information		The instructions that control your characteristics. These instructions are found on genes.
inherited		Passed on to an organism from its parents.
variation		The differences between things or organisms.

 

 

9Ab - Different varieties/Environmental effect

 

Word	Pronunciation	Meaning
environment		The surroundings of an organism.
environmental factors		Things in an environment that can change something about an organism.
resistant		Something that is not affected by disease is said to be resistant to it.
species	spee-shees	A group of organisms that can reproduce with each other to produce offspring that will also be able to reproduce.
variety		A set of plants that are in some way different from other members of the same species.

 

 

9Ac - Animal breeding

 

Word	Pronunciation	Meaning
breed		A set of animals that are in some way different from other members of the same species.
breeding		To mate two organisms of the same species to produce offspring.
cross-breeding		When different varieties or breeds are mated with one another.
selective breeding		When humans choose certain animals and plants that have useful characteristics and breed more of these organisms.
yield		How much of something useful to humans that an organism produces.

 

 

9Ad - Plant breeding

 

Word	Pronunciation	Meaning
fertilisation	fert-ill-eyes-ay-shun	Fusing of a male sex cell with a female sex cell.
ovary	o-very	Part of the female reproductive organs in a plant. It contains ovules, each of which contains an egg cell.
ovule	ov-you'll	Contains egg cells in plants. Found in the ovary.
pollen		The male sex cell (gamete) in plants.
pollen tube		Tube that grows from a pollen grain down through the stigma and style and into the ovary.
pollination	poll-in-ay-shun	Transfer of pollen from an anther to a stigma.
seed		Grows into a new plant. Made by conifers and flowering plants.
stigma		Part of the female reproductive organs in a plant. It is where pollen lands.