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National 5 Biology – Multicellular Organisms – Reproduction Reproduction in Animals All living things need to reproduce and produce offspring similar to themselves. If living things did not reproduce then their numbers would decrease and they would become extinct. Reproduction, asexual, gamete, zygote, haploid, diploid, sperm, ovum, fertilisation Learning Outcomes You will be able to: Describe the chromosome complement of gametes. Describe the structure of the male and female gametes and where they are produced. Give details of the male and female reproductive structures and functions. Reproduction Plants and animals produce offspring in the process called reproduction. There are two types of reproduction, sexual and asexual. Asexual reproduction involves only one organism producing offspring e.g. when a bacterium divides to make an exact copy of itself. These offspring are identical to the parent and to each other, so this type of reproduction does not affect variety within a species. Sexual reproduction involves the fusion of two gametes during fertilisation and is the key to variety and therefore, to biodiversity. 1|Page National 5 Biology – Multicellular Organisms – Reproduction Gametes Organisms need to produce gametes (sex cells) for reproduction to take place. Gametes are haploid which means that they only have one set of chromosomes. During fertilisation, the nucleus of the male gamete and the nucleus of the female gamete fuse together to form a Zygote. Since the zygote has two sets of chromosomes it is said to be diploid. In animals the male gametes are called sperm and produced in the testes. A sperm has a head section and a tail section that allows it to swim. A Sperm cell also has many mitochondria. The female gamete is the ovum (egg) produced in the ovaries. This is much larger than the sperm cell as it has a large store of food in its cytoplasm. A male mammal will produce a very large number of sperm whereas a female mammal will produce a much smaller number of eggs. Learning Activity 1 1. Collect the worksheet ‘Haploid or Diploid’ and label the main parts. 2. Describe the number of sets of chromosomes found in normal body cells 3. Describe the number of sets of chromosomes found in gametes. 4. Describe what happens at fertilisation to the number of sets of chromosomes. 5. Describe the number of sets of chromosomes found in a zygote and where these sets of chromosomes originated. 6. Name and make labelled diagrams of the gametes produced in a: male animal female animal 2|Page National 5 Biology – Multicellular Organisms – Reproduction 7. Copy and complete the table to compare eggs and sperm in your jotter. Gamete Egg Sperm Site of production Comparative size Numbers produced Number of sets of chromosomes (haploid or diploid) Can swim? Contains food store? Reproductive Structures in Humans Following production in the testes, the sperm travel from the testes along the sperm ducts, past the bladder, along the urethra, which is the tube leading from the bladder out of the penis. The ovary produces the female gametes, eggs (ova). Eggs are released from the ovaries and travel along the oviducts to the uterus. The vagina is the tube in which the penis is placed during sexual intercourse. 3|Page National 5 Biology – Multicellular Organisms – Reproduction Fertilisation in Animals For fertilisation to take place the nuclei of the male and female gametes need to fuse together. The release of an egg (ovum) takes place once a month in humans and is called ovulation. The ovum is released from the ovary into the oviduct and is moved along the oviduct by tiny hair-like cilia which beat and move the ovum towards the uterus. Following sexual intercourse, ejaculated sperm swim up through the uterus and into the oviducts. Fertilisation takes place in the oviducts. Although many sperm may meet an egg, only one sperm fertilises the egg. The nucleus of the sperm fuses with the nucleus of the egg forming a diploid cell called a zygote which contains genetic material from both parents. Learning Activity 2 1. Insert and complete the ‘Human Sex Organs’ diagram from your pack into your notes. 2. Describe the process of fertilisation in humans, with reference to: the pathway taken by the sperm the exact location of fertilisation the number of sperm fertilising an egg the name of the cell formed as a result the genetic information contained within this cell the fate of this cell. 4|Page National 5 Biology – Multicellular Organisms – Reproduction Challenge task Pick one of the following stages of human embryo/foetal development: weeks 1 to 10 weeks 11 to 20 weeks 21 to 30 weeks 31 to 40 Make an A4 information sheet including the following: A TITLE showing the stage you are investigating. Pictures/diagrams Information about what is happening at this stage of development. 5|Page National 5 Biology – Multicellular Organisms – Reproduction Reproduction in Flowering Plants Pollen, anther, stamen, ovules, ovary, stigma, pollination, pollen tube Learning Outcomes You will be able to: Name the sex cells found in plants and where they are produced. Describe the reproductive structures found in plants and give their functions. Describe the process of fertilisation in plants. Explain the chromosome complement of a gamete and a zygote in plants. Gamete Production in Plants In flowering plants, the flowers are the part of the plant responsible for reproduction. All flowers have the same basic structure. Usually both male and female parts are present in the same flower. Male parts of the flower are the stamens. The stamens are made up of an anther and a filament. The anther produces the male gamete pollen. The female part of the flower is made up of the stigma and the ovary. The stigma is where pollen lands during pollination and the ovary is the site of ovule production (female gamete). Formatted: Indent: Left: 1.27 cm, Line spacing: Multiple 1.15 li 6|Page National 5 Biology – Multicellular Organisms – Reproduction Learning Activity 1 1. Collect the diagram ‘Sexual Reproduction in a Flower’. 2. Label the following parts of the flower: 3. SEPAL, PETAL, NECTARY, STIGMA, STAMEN, OVARY, ANTHER 4. Copy and Complete the table below by matching the flower part with the correct function. Part Function Stigma Produces the female sex cells (ovules) Stamens Produce sugary nectar which attracts insects Anther Collects the pollen grains and starts them growing Ovary Produces the male sex cells (pollen) Petals Protects the unopened flower bud Nectaries May be brightly coloured to attract insects Sepals Male parts of the flower consisting of the anther and filament 7|Page National 5 Biology – Multicellular Organisms – Reproduction Collect the experiment cards ‘Dissecting a Flower’ and ‘Examining Pollen and Ovules’. Carefully follow the instructions on the work cards to complete the experiment. Copy and complete the table to compare ovules and pollen in your jotter. Gamete Site of production Comparative size Comparative Numbers numbers produced Number of sets of chromosomes (haploid or diploid) Do they move from site of production? Contains food store? 8|Page Ovules Pollen National 5 Biology – Multicellular Organisms – Reproduction Pollination Pollination is the transfer of pollen from an anther to a stigma. There are two types of pollination. Self-pollination involves pollen moving from the anther to the stigma of the same plant. Cross-pollination involves the tranfer of pollen between different plants. Cross-pollination can be brought about by different methods. Some plants use the wind to transfer their pollen while other plants may rely on insects. Wind pollinated flowers are very different in structure to insect pollinated flowers. Fertilisation When a pollen grain lands on the stigma, it responds to the presence of sugar on the stigma, the pollen uses the sugar as a source of energy to grow a pollen tube. The pollen tube grows down towards the ovary. The haploid pollen nucleus makes it way down the pollen tube into the pvary and fuses with the haploid ovule nucleus, forming a diploid zygote. Eventually this zygote will form a seed, and the wall of the ovary will develop into a fruit. 9|Page National 5 Biology – Multicellular Organisms – Reproduction Learning Activity 2 1. Before fertilisation can occur in a flowering plant pollination must take place. Describe this process with reference to: where the pollen grains have to be transferred from and to the role of the pollen tube. 2. Describe the process of fertilisation in a flowering plant, with reference to the: name of the gametes involved exact location of fertilisation name of the cell formed as a result genetic information contained within this cell fate of this cell. Challenge task The shape, size and surface marking of a grain of pollen are unique to each species of plant. Pollen grains have a tough outer coat, which enables them to survive harsh conditions. Fossilised pollen has been found which was made millions of years ago. Carry out some research to try and answer the following questions: 1. What information does fossilised pollen provide us with? 2. The pollen found in honey can be analysed, what will this tell us about the bees that made the honey? 3. How can pollen be used to solve crimes? 10 | P a g e