1. B5 Growth and Development Route map Over the next 12 lessons you will study : Friday 21 October 2011 B5.1 Growing and Changing B5.2 Growth Patterns B5.3 Growing Plants B5.4 A look inside the nucleus End of module test B5.5 Making new Cells B5.6 Sexual Reproduction B5.7 The Mystery of Inheritance B5.8 Specialised cells – special protein B5.9 Switched on or off? B5.10 Stem Cells B5.11 Making Proteins B5.12 Phototropism

3. B5.1 Growing and Changing Decide whether the following statements are true or false: Introduction: Cells are the building block of all plant and animal life. Each cell whether plant or animal are highly specialised to perform a specific function. Many cells form a tissue which then arrange themselves into organs, for example the brain or heart. Plant and animal development can involve big changes. This means that the young and the adults look very different. Your development into an adult will be a gradual process which started when you were born. Your body is made up of more than 300 different types of cells and each cell is specialised to do a particular job. Remember a group of specialised cells form a tissue and an arranged group of tissues is an organ. Extension questions: 1: Name five cells and give their role in the human body ? 2: Name three plant cells are give their role in plants ? 3: What is the job of these three tissues: a) muscle, b) xylem and c) phloem ? 4: Explain how a) a red blood cell is specialised to transport oxygen and b) a sperm cell is specialised to fertilise an egg ? 5: Explain the difference between a cell, tissue and an organ ? Know this: a: Know the role of cells, tissue and organs. b: Know the different stages of the human life cycle. c: Know that Robert Hooke first look at cells using a light microscope. Friday 21 October 2011

4. B5.1 a Look at the photograph and information and answer all the questions: Cells are designed for the roles they play in any organism as part of the billions of cells that work together to support life. A plant root hair cell is long, thin and has a large surface area to absorb water from the soil. A red blood cell has a large surface area and no nucleus so it can transport oxygen from the lungs to the rest of the body. Explain how a human sperm cell is specialised and adapted for its function ? Explain a) which organ pumps blood around your body and b) how is a ciliated epithelia cell found in the wind pipe adapted for its roles in protecting the lung ? Other than the root hair cell pictured left, name three other specialised cells found in plants and give their function ? Key concepts

5. B5.1 b Look at the photograph and information and answer all the questions: Cells are the building blocks of life. Humans contain about 40 million million cells. There are lots of different cells, each specialised for their role, for example skin cells act as a barrier against bacteria and water loss. Robert Hook was the first scientist to observe plant and animal cells using a simple light microscope over 300 years ago. Name the three main parts found in all animal cells ? Name the three extra features found in all plant cells ? One of the cheek cells viewed left is 9mm in diameter. The microscope has magnified this cheek cell 5000 times. Work out its actual diameter in mm ? Human cheek cells 9 mm The light microscope Key concepts

6. B5.1 c Look at the photograph and information and answer all the questions: Explain why photosynthesis happens on the top side of the leaf ? Which liquid is transported up the plant that is needed for photosynthesis ? The stoma pore pictured left opens and shuts to allow two gases in and out of the leaf. Name one of those gases (name both for a commendation!) ? Light microscopes that you use in school magnify an image up to 1000 times. They use a lens, a focal gauge and a light source to allow you to see cells found in plant or animal tissues. Without microscopes you would not be able to see that in a simple green leaf there are many different cells all doing different jobs during photosynthesis. Cross section of a leaf Key concepts

7. B5.1 d Look at the photograph and information and answer all the questions: Cells performing similar jobs are organised into tissues. An organ consists of different tissues working together, for example the heart is a collection of tissues like muscle, valves and tendons. The heart pumps blood around the body. Different organs work together as part of an organ system. There are nine organ systems found in humans. Name five organs found in the human body and give a function for each organ ? Which organ system lets us sense where we are and controls all are conscious and subconscious actions ? The skin by mass is the largest organ...give three functions of the skin ? Red blood cell Plasma Platelets Red blood cells The cardiovascular system Key concepts

8. B5.1 Plenary Lesson summary: specialised building tissues organs Friday 21 October 2011 We grow form birth to the end of our puberty by produces new cells and not by our cells becoming bigger. In a single hour during puberty, about 1.2 billion cells are produced every single hour of the day. In old age this can reduce to about 400 million cells every hour. How Science Works: Research into the development stages of a foetus in the womb and how plants grow from seedling to mature plant. Preparing for the next lesson: Cells are considered the ________ blocks of life. All newly formed human cells look the same but they then develop into groups of ___________ cells. These specialised cells group to form __________ and these tissues arrange to form __________. Decide whether the following statements are true or false : False True 3: A leaf is an example of a plant tissue comprising of different specialised cells ? False True 2: Muscle cells are specialised because they are able to carry oxygen ? False True 1: Xylem tissue transports water and minerals form the root to the leaves ?

10. B5.2 Growth Patterns Friday 21 October 2011 Extension questions: 1: What two cell fuse to form a human zygote ? 2: During gestation, when does a human embryo become a foetus? 3: Why is it important that all living things have cells that can divide ? 4: Name the type of cell found at the tip and root in all plant that can divide forming new cell during periods of growth ? 5: Explain how plants: a) grow taller, b) grow longer roots and c) grow thicker in girth ? Know this: a: Know that life in humans starts with a single cell the zygote. b: Know that cells are specialised forming tissues and organs. c: Know that plant meristem cell divide forming new root and shoot tissue. Introduction: All the cells in your body come from just one original cell – a fertilised egg cell or zygote. So the zygote must contain the information for making all the different cells in your body. During the first week of growth, the zygote develops into a ball of about 100 cells. As it grows, some of the new cells become specialised and form different tissues and organs which by 8 weeks of gestation are fully recognisable. Plants grow by their roots and shoots getting longer. At the tips of both root sand shoots plants have meristem cells which divide rapidly to increase the length of the root or shoot.

11. Key concepts B5.2 a Look at the photograph and information and answer all the questions: The human life cycle begins at fertilization, when an egg cell and a sperm cell fuse to form a one-celled zygote. On the sixth day after fertilization, the dividing cells form three layers that fold and bend into the more complex shape of an early embryo. Gradually, the cells begin to become different from one another forming, for example, the nervous system and the circulatory system. Why do cell specialise as the embryo form inside the womb form the single celled zygote ? If you examined the amount of DNA in a sperm or egg cell how would it differ form the DNA in a normal skin cell ? When do a) males and b) female stop growing ? The human life cycle

12. Key concepts Look at the photograph and information and answer all the questions: Explain how nerves cells (neurons) are specialised to carry out their function in the nervous system? How could embryonic stem cell be used to help repair damaged organs in patients ? By growth we mean increase in size and also in the number of cells. An adult human, for example, has about 10 or even 100 trillion cells. The cell divisions are mitosis. By development we mean that as the embryo grows cells become different, a process that is called, logically enough, differentiation. Cells not only become structurally different, but they acquire correspondingly different functions, too. Cells being produce during the development from zygote to embryo B5.2 b zygote stem cell skin cell red blood cell muscle cell nerve cell cheek cell

13. Key concepts Look at the photograph and information and answer all the questions: Explain how plants a) grow taller and b) grow longer roots ? If you take a cutting from a plant stem and pace it in water soaked cotton wool, the cutting will produce roots. What has happened to the stem cells at the cut point ? A meristem at the tip of a plant shoot or root has a region of cell that are able to divide and produce new daughter cells. By continually divide the shoot and root are able to increase in length. Growth that originates in the apical meristem is called primary growth. Plants can grow by this mechanism at any part of the life cycle. t B5.2 c shoot apical meristem root apical meristem dividing cells dividing cells How plants shoots and roots grow

14. B5.2 Plenary Lesson summary: cells growing longer girth Friday 21 October 2011 A human embryo’s development is monitored using ultrasound scans. This can provide doctors with information about the developing foetus and allows them to check that it is developing correctly. You can monitor your growth pattern by measuring your height every six months. You would notice the greatest change in your height is during your early childhood and then be able to notice growth spurts as you go through puberty. How Science Works: Identify two places where stem cells can be found in your body and why people are now encouraged to donate some of these stem cells. Preparing for the next lesson: For living things to grow bigger, some of their ________ must divide to make new cells. Humans stop ________ by the time they are about 18-20 years old. Flowering plants continue to grow throughout their lives: their stems grow taller, their roots grow _______, to hold themselves upright, most increase their _______. Decide whether the following statements are true or false : False True 3: Specialised cells are adapted to carry out specific roles in plants and animals ? False True 2: A zygote is the result s of two sperm and one egg fusing ? False True 1: In plants meristem cells divide to make stems and roots longer ?

16. B5.3 Growing plants Extension questions: 1: Name two parts of your body where you can find stem cells ? 2: Explain why a newt can re-grow a leg but a human can’t ? 3: Give two reasons for growing plants from cuttings. 4: Explain how rooting powder helps a plant cutting to grow ? 5: A Gardner wants to sell a tree that will produce both apples and pears. Should the gardener grow this unique fruiting tree from seeds or cuttings ? Explain your answer. Know this: a: Know the different growth and development patterns in animals and plants b: Know that tissue culture uses plant meristem to produce new identical clone individuals c: If a newt’s leg is bitten off by a predator, it can grow a replacement. Friday 21 October 2011 Introduction: Lose a limb like a leg or arm and that’s it, except if you are a newt where unspecialised stem cells found at the base of their limbs are able to form a new limb should the newt have a limb removed. Humans sadly do not have these stem cells at the base of our limbs. Most plants grow throughout their lives. They grow when meristem cells divide to make new cells. Gardners and farmers use plant meristem to grow new cloned plant. These cuttings are used gardeners to grow plants that are genetically identical to a parent plant.

17. Key concepts Look at the photograph and information and answer all the questions: B5.3 a Cutting into new cloned plants Cutting Root powder Plants meristem cells are unspecialised and some meristem cells are kept within a plant as back up cells that can divide to make any kind of cell which is needed. Plants are able to regrow whole organs such as leaves if they are damaged. Gardeners use meristem cells when they grow new plants by taking cuttings of shoots. What does rooting powder contain and why does it help plant cuttings to grow ? What are the advantages of gardeners taking cuttings to grow new plants ?

18. Key concepts Look at the photograph and information and answer all the questions: What advantage do newts and salamander have by being able to regenerate limbs lost to predators ? Adult human stem cells are already highly specialised. Does this mean that they can replace damaged tissue only or whole limbs like arms and legs ? Newts and salamanders have the ability to re-grow a lost tail or leg. How newts do this is by locating stem cell at the base of a limb. These cell then have the ability to divide and become specialised forming an entire new and full functioning limb. Scientists in the future may find a way to recreate this ability in mice, paving the way for potentially regenerating damaged tissues in humans. B5.3 b Limb regeneration in newts and salamanders

19. B5.3 c Look at the photograph and information and answer all the questions: Salad leaves, soft fruits and other crops that are high in value are often grown indoors in climate controlled conditions. No soil is used, simply a nutrient rich chemical solution that provides all the nutrients (minerals) and water that a crop required. Under these conditions the quality of the crops can also be very closely controlled. What main minerals do fertilisers contain ? List the ideal conditions for plant growth? What conditions should you avoid when growing plants? Key concepts

20. B5.3 Plenary Lesson summary: auxins phototropism meristem organs Friday 21 October 2011 By taking cuttings, gardeners can produce lots of new plants quickly and cheaply. But this is not the only reason that they do it. All the cuttings taken from one plant have identical DNA. They are genetically identical so taking cuttings is a good way of reproducing a plant with exactly the features that you want. When flowering plants produce seeds, they are reproducing sexually. So new plants grown from seeds vary and are not identical. How Science Works: Research the role of DNA in inheritance, in synthesis cellular proteins and in controlling our characteristics. Preparing for the next lesson: Some plant cells remain unspecialised. These ________ cells can develop into any type of specialised cell. This means that plants can re-grow whole _______ if they are damaged. Plants tend to grow towards the light. This is ________, and requires hormones called ________. Decide whether the following statements are true or false : False True 3: Meristem cells are not fully unspecialised cells ? False True 2: New blood cells are made from stem cells in your bone marrow ? False True 1: Stem cells divide, grow and develop into any kind of cell the body needs ?

22. B5.4 A look inside the nucleus Extension questions: 1: You have 23 pairs of chromosomes. Where do these chromosomes come from ? 2: Who are your closet living relatives genetically and explain why family members look alike ? 3: What do genes inside the nucleus code for ? 4: Name two ways in which red blood cells are different from the other cells in your body ? 5: To work as your genetic material, what two properties does DNA have? Know this: a: Know the key roles of the nucleus and cellular DNA and that DNA can replicate itself. b: Know that chimpanzees share 98% of the same DNA with humans, mice are 85% similar to us and onions are about 50% genetically similar to humans. Friday 21 October 2011 Introduction: All cells start their existence with a nucleus. Some specialised cells lose their nuclei when they finish growing e.g. human red blood cells. Within the nuclei of your cells you have about a metre of DNA which is made up of about 30 000 genes. Different species have different numbers of chromosomes and different numbers of genes. DNA has a particular sequence and structure that allows itself to be copied when new cell are formed during cell division. It is also a set of instructions which the cell uses to make new proteins. These proteins are either structural or enzymes which then go onto to make new molecules.

23. B5.4 a Look at the photograph and information and answer all the questions: All cells start their lives with a nucleus. A few specialised cells lose their nuclei when they finish growing e.g. red blood cells. A chromosome is a long molecule of DNA wound around a protein framework. You have about a metre of DNA in each of your nuclei. This is made up of about 30 000 genes. Each gene codes for a protein. Which organisms, in the table, have the highest and lowest number of estimated genes ? Is this reflected by the number of chromosomes they have present in their nucleus ? You have 23 pairs of chromosomes within your nuclei. How did you end up with 23 pairs ? Key concepts Organism Number of genes Chromosomes Human ~30 000 46 Fruit Fly 13 600 8 Mouse ~30 000 40 Round worm 19 100 6 Yeast 6 300 16

24. B5.4 b Look at the photograph and information and answer all the questions: Explain the difference between a) a gene and DNA and b) a chromosome and gene ? Explain why your chromosome stay in the cell nucleus ? We humans have 23 pairs of chromosomes making 46 in total (23 from mother 23 from father) that carry the many thousands of genes, in sequence, that determine the our characteristics. Each chromosome normally consists of one very long double strand (or molecule) of DNA, coiled and folded to produce a compact structure. The exception is just before cell division when each chromosome contains two double strands of DNA, a result of the copying of each molecule of DNA. The point on a chromosome where a particular gene occurs is known as its locus. Inside the cell Key concepts

25. B5.4 c Look at the photograph and information and answer all the questions: Write down whether you inherited your hair and eye colour form your mum or dad ? Can you always predict the traits that the children will inherit, by looking at the mother and father ? Traits Eye colour Skin colour Hair colour Height Blood group Hand span Tongue roller Freckles Proteins/enzymes Zygote 2 sets of DNA Newborn Genes hold the instructions for making protein products (like the enzymes to digest food or the pigment that gives your eyes their colour). As your cells duplicate, they pass this genetic information to the new cells. Genes can be dominant or recessive. Dominant genes show their effect even if there is only one copy of that gene in the pair. For a person to have a recessive disease or characteristic, the person must have the gene on both chromosomes of the pair. Key concepts

26. B5.4 Plenary Lesson summary: thousands chromosomes proteins 23 Friday 21 October 2011 Red blood cells develop from stem cells in your bone marrow. As they develop, they make more and more haemoglobin. By the time they leave the bone marrow, they are full of haemoglobin and their nuclei has broken down. How Science Works: Research the process of mitosis and asexual reproduction. Preparing for the next lesson: The nucleus of the cell contain ________ of genes. Your nucleus contains _______ pairs of chromosomes. You get one set of _______ from the nucleus in your mother’s egg and the other set from the nucleus of your dad’s sperm cell. DNA is able to make exact copies of itself and provides information about what ______ the cell must make. Decide whether the following statements are true or false : False True 3: Different species have different numbers of chromosomes and genes ? False True 2: Red blood cells do not lose their nuclei once they have finished developing ? False True 1: A metre of DNA codes for approximately 30,000 genes ?

28. B5.5 Making new cells Extension questions: 1: Define the following a) DNA b) gene c) chromosome and d) genome ? 2: Where are genes found inside the cell ? 3: During mitotic cell division, the chromosome are copied and double explain why ? 4: How many cells are made by mitosis ? 5: What are these new cells like compared to their parent cell ? Know this: a: Know that cells lost are replaced through mitotic cell division which produce clones of the original. b: Know that some organisms reproduce asexually using mitosis. Friday 21 October 2011 Introduction: When new body cells are made, they contain the same number of chromosomes as each other and the parent cell. They also contain the same cell parts called organelles. So, before they can divide they must make copies of its nucleus and other organelles and grow. Some plants and animals reproduce asexually and use mitosis to produce cells for a new individual. Individuals produced in this way are therefore genetically identical to their parent, so it is a clone.

29. Key concepts B5.5 a Look at the photograph and information and answer all the questions: Human have 46 chromosomes containing about 30,000 genes. Each gene codes for a characteristic for example eye or hair colour. One gene is made from a short length of DeoxyriboNucleic Acid. DNA is like a list of instructions made from 4 different bases located on a sugar-phosphate chain. Every 3 bases codes for a particular amino acid which are the building blocks of proteins which help build cells and enzymes. Explain why the human race has some of the best genes in the animal kingdom...give some examples ? Do you think all newborns should have their DNA profile taken and shared with the a) NHS b) the police and c) businesses ? DNA the chemical of inheritance DNA Genes Proteins Deoxyribose-Nucleic acid inherited from your mother and father Every 3 bases codes for a particular amino acid the building blocks of proteins Proteins are use in cell receptors, to make hair, and enzymes that control metabolism

30. Key concepts B5.5 b Look at the photograph and information and answer all the questions: New cells are needed for you to grow and repair. These are made by cell divisions called mitosis. During mitosis, a cell divides and forms two identical clone cells. The human body produces up to one billion cells like this every hour replacing old worn out cells. New skin, muscle, blood, and nerve cells are all produced this way. Some species like bacteria reproduce asexually using mitosis. A skin wound will heal through mitotic cell division. Explain why producing new skin cell that are identical is useful in wound healing ? Before a cell divides (stage three) what two step must happen ? Look at the picture below left, how many cells are beginning to divide ? Mitosis Parent cell 2 Daughter cells DNA replicates Chromosomes separate Stage one Stage four Stage two Stage three 2n 2n 4n 2n

31. Key concepts Look at the photograph and information and answer all the questions: Give two advantages and disadvantages to asexual reproduction ? Do bacteria reproduce themselves in the same way as we produce new skin cell after a cut or graze ? B5.5 c Mitosis and asexual reproduction Asexual reproduction differs from sexual reproduction in that it does not require two parents, and that special cells are not required. This also means that the special mechanisms necessary to bring together sex cells, and permit fertilisation, then to support development of the fairly helpless stages, from zygote to independent organism, are not required. Although we often think of plants when we consider asexual reproduction, it must be remembered that there are many animals which reproduce asexually . The simplest organisms ( Amoeba , bacteria, etc) may rely on asexual reproduction alone; but many organisms are able to use both methods.

32. B5.5 Plenary Lesson summary: asexually genetically clone individual Friday 21 October 2011 In yeast, new daughter cells grow as buds from the parent. Yeast reproduce themselves asexually by mitotic cell division. Although there is no variation between the million of yeast cell found in a colony, asexually reproduction means that the yeast organism can colinsie a food source or habitat very quickly. How Science Works: Research the process of meiosis where reductive cell division in humans lead to the formation of sperm and egg gametes and in plants pollen and ovule gametes. Preparing for the next lesson: Some plants and animals reproduce . They use mitosis to produce cells for a new _________. This means that each of the individuals produced in asexual reproduction are identical to the parent, so it is a of its parent. Decide whether the following statements are true or false : False True 3: Humans share about 99.9% of their genes share one another ? False True 2: A single gene (3 base pairs) codes for a a whole protein ? False True 1: Mitosis cell division produces 2 new cells which are identical to each other ?

34. B5.6 Sexual Reproduction Extension questions: 1: Where does meiosis take place in the body if you are a) female and b) male ? 2: How many chromosomes does a) a skin cell have b) a sperm cell c) an egg cell and d) a zygote ? 3: Why is genetic variation amongst individual of the same species important ? 4: Why is it important that gametes only have one set of chromosomes and why are male gametes made in such large numbers? Know this: a: Know how gametes are produced during reductive cell division or meiosis. b: Know that each gamete is different to any other gamete leading to genetic variation in species. Friday 21 October 2011 Introduction: Most plants and animals reproduce sexually. Males and females make sex cells or gametes, which join up at fertilisation. The fertilised egg or zygote develops into a new life. Gametes like sperm and egg cell are produced during reductive cell division or meiosis. During meiosis, random mixing of genes ensure that no two gametes have exactly the same genetic code. This means that offspring from sexual reproduction are different form each their and their parents. They show genetic variation

35. Key concepts Look at the photograph and information and answer all the questions: What are the gamete cell produced by meiosis called in planets? At what stage during meiosis does the random mixing of genes occur ? Stage 1: Chromosomes double and randomly mix inside the nucleus. Stage 2: The chromosomes line up before separation. Stage 3: The cell divides, producing two new cells each containing 23 pairs of chromosomes. Stage 4: The two daughter cells divide again halving the number of chromosomes. Each gamete now contains only 23 single chromosomes. B5.6 a egg sperm Meiosis Stage one Stage four Stage two Stage three Parent cell & replicates 2 daughter cells 4 daughter cells DNA mixes 2n n 4n 2n

36. B5.6 b Look at the photograph and information and answer all the questions: Every plant or animal is the result of reproduction, and all organisms reproduce. Sexual reproduction needs two individuals of the opposite sex. During sexual reproduction, an embryo is formed when an egg carried by the female is fertilized by the male sperm. The embryo has a unique set of genes inherited from the mother and father. Pick three traits from the list in the diagram below left…decide which of these traits you have inherited from your mother or your father ? Which trait for a) hair colour and b) eye colour is most common in the UK ? Looking at the traits of a mother and father, can you always predict the traits that the children will inherit ? Traits Eye colour Skin colour Hair colour Height Blood group Hand span Tongue roller Freckles Attached lobes Fertilisation Egg Sperm 1 set of DNA 1 set of DNA Zygote 2 sets of DNA Newborn Key concepts

37. B5.6 c Look at the photograph and information and answer all the questions: Sometimes people in the same family look a lot alike but in other families the brothers and sisters look very different. They may also look very different from their parents. The key to the mystery lies in our genes. Parents pass on genes in their sex cells. In animals these are sperm and egg cells (ova). Fertilisation Egg Sperm 1 set of DNA 1 set of DNA Write down whether you inherited your hair and eye colour from your mum or dad ? Looking around the class, which is the dominant allele for a) hair colour brown or blonde and b) eye colour blue or brown ? Explain using your knowledge of inheritance why children look more like their parent that their sisters or brothers ? Key concepts

38. B5.6 d Look at the photograph and information and answer all the questions: Gametes cells, in males the sperm and in females the egg carry only half the parent’s chromosomes. This makes sure that the fertilised egg (called a zygote) has the right number (23 pairs) of chromosomes. This code is unique to you (unless you are an identical twin) and determine your characteristics from your skin colour to your blood type. Explain why your parents are your closest biological relatives ? Which a) organs store the eggs cells until they mature and b) how often are egg cells released by the female ? Once the zygote has formed form the fusion of the sperm and egg, how does the zygote then continually divide forming the embryo and then foetus ? Key concepts

39. B5.6 e Look at the photograph and information and answer all the questions: The role of the male reproductive system is to produce, store and release sperm cells. During sexual intercourse up to 400 million sperm cells in a fluid called semen are ejaculated into the vagina. Sperm then swim through the cervix and uterus and into one of the egg tubes where they will fuse with an egg cell forming a zygote. Explain a) where sperm cells are made and b) why new sperm cells are made all the time ? Describe a sperm’s journey from the testis where they are made to the fallopian or egg tubes where they will meet and fertilise a human egg cell ? Up to 400 million sperm are released during a single ejaculation...how many of these sperm are required to fertilize an egg cell ? Key concepts

40. B5.6 Plenary Lesson summary: gametes 23 daughter meiosis Friday 21 October 2011 Meiosis starts with normal body cells. It only happens in the sex organs. Meiosis halves the number of chromosomes in gametes and fertilisation restores the number of chromosomes in a zygote. This is essential, if this didn’t happen the zygote would not develop into a healthy foetus How Science Works: Identify the four bases which make up DNA. Research how DNA replicates itself and what is its structure like. Preparing for the next lesson: _________ starts with normal body cells and only takes place in sex organs. The parent cell divides twice to produce 4 _______ cells (gametes), which have half the number of chromosomes in the parent cell. Human body cells have _______ pairs of chromosomes....46 in total. ________ have only 23 single chromosomes. Decide whether the following statements are true or false : False True 3: Male gametes or sperm cells are always produced in high numbers? False True 2: Human females produce egg cells in the testes ? False True 1: A snail has both male and female sex organs ?