Multicellular Organisms Key Area 2.4 Reproduction

Learning Intentions: To learn about reproduction in animals and plants Success Criteria: State that body cells contain a full chromosome complement and are therefore diploid Define the term ‘gamete’ State that all gametes contain half the number of chromosomes as body cells. This is called the haploid number Identify male and female gametes in mammals Identify the site of production of male and female gametes in mammals.

Reproduction All living organisms must reproduce to produce new individuals and continue their species. Most animals use sexual reproduction to do this. Sexual reproduction involves combining genetic information from two individuals (parents) to produce offspring.

Reproduction Reproduction is the production of new members of a species. For a species to survive, it must produce enough young to replace those lost through old age, disease and other causes of death.

Sexual versus asexual reproduction Some very small organisms tend to reproduce asexually (without sex cells) Examples include amoeba, bacteria and some plants Large organisms tend to reproduce sexually (with sex cells) Includes humans, most animals and plants.

Asexual reproduction This type of reproduction is where an organism produces an exact copy of itself. It does not involve sex cells. This type of reproduction is more common in plants than animals. Offspring are clones of the parents. Twig - Asexual reproduction Twig - Asexual reproduction in plants

Key Words Asexual reproduction – a type of reproduction that does not involve sex cells. Offspring are clones of the parent. Sexual reproduction – a type of reproduction that involves sex cells. Offspring are genetically different to their parents.

Sexual reproduction During sexual reproduction, sex cells form each parent fuse to form a zygote. Sex cells are known as gametes. Gametes are haploid which means they have only one set of chromosomes. When the male and female gametes fuse together, the zygote produced is diploid. This means it has two sets of chromosomes.

Key Words Gamete – a sex cell containing the haploid chromosome number and one set of chromosomes. Zygote – a fertilised egg cell. Twig – Gamete definition Twig – Zygote definition

Male reproductive system In animals, gametes are produced in specialised organs. Male gametes are sperm cells and are produced in the testes. Sperm cells have a tail to allow it to swim and many mitochondria for producing energy.

Female reproductive system Female gametes are called ova (singular: ovum) or eggs. The ova are produced in the ovaries. Ova are much larger than sperm and have a large food store in the cytoplasm that feed the early embryo.

Key Words Sperm cell – gamete produced in the testes of male animals. Testes – male sex organs in animals which produce sperm. Ova (Eggs) – female gametes produced by ovaries in animals (singular – ovum) Ovaries – female sex organs where ova are produced.

Fertilisation in mammals Learning Intention: Learn about the process of fertilisation in mammals. Success Criteria: Describe the process of fertilisation in mammals. State how the diploid number is restored at fertilisation.

Starter With your partner- Compare sexual and asexual reproduction.

Fertilisation in mammals During sexual intercourse, sperm that are produced in the testes travel along the sperm duct towards the penis. As the sperm move along various glands add fluid to the sperm, forming semen. The penis deposits semen (including sperm) into the female’s vagina. Sperm leaves the penis through the urethra.

Fertilisation in mammals Ova are released at regular intervals from the female ovaries during ovulation. The inner lining of each oviduct has hair-like cilia that beat the ova towards the uterus. Sperm that has been deposited in the vagina swims through the uterus and into the oviducts. Fertilisation of an ovum by a sperm cell occurs in the oviducts. The resulting zygote imbeds into the wall of the uterus and develops into a foetus. BBC – Fertilisation in humans

An ovum is released from the ovary Ovum picked up by oviduct and moved along by hair-like cilia Fertilisation occurs as sperm and egg fuse to form a zygote Zygote settles into the lining of the uterus where the cell divides many times The ball of cells develops into an embryo and receives oxygen and nutrients from the mothers blood

(A) the 4-cell stage (B) the 16-cell stage (C) a morula formed from (B) (D) a blastocyst

The process of fertilisation involves a haploid sperm reaching a haploid ovum and the sperm’s nucleus fusing with the ovum’s nucleus to form a single diploid cell called a zygote. This is how the normal diploid number of chromosomes in a human body cell is produced. In humans the haploid chromosome number of both sperm and ova is 23. The diploid chromosome number of human body cells is therefore 46. BBC – Chromosomes and fertilisation

Practical Activity Your teacher will show you some models that show how a human baby develops in the uterus. Observe each model and then watch some information clips about development of the fetus before completing the summary worksheet.

Model of a human fetus inside the womb Twig – Development of the fetus 1 st trimester 2 nd trimester 3 rd trimester Pregnancy timeline

Activity Your teacher will show you 3 video clips that describe the development of a human fetus inside the uterus. Use the summary sheet on the next slide to fill in the missing words. Stick your summary in your notebook.

Fertilisation in plants Learning Intentions: To learn about how plants reproduce. Success Criteria: Identify male and female gametes in flowering plants. Describe the process of pollination and fertilisation in plants.

Starter Answer on a white board What is fertilisation? Where does fertilisation occur? Define the terms diploid and haploid. What is formed in fertilisation?

Pollination Pollination is the transfer of pollen grains from an anther to a stigma. This should not be confused with fertilisation which is the process by which the nucleus of a male sex cell from a pollen grain fuses with the nucleus of an ovule to form a zygote. Twig – Sexual reproduction in plants

Pollination Before fertilisation can occur in plants, pollination must take place. Pollination is the transfer of pollen from the anther to the 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 transfer of pollen between different plants.

Pollination Pollination occurs in two ways: –Wind pollination – the anthers and stigmas hang outside the flower to disperse pollen which is caught by the wind and transferred. The petals of these flowers are small and dull as they do not need to attract insects. eg. grasses –Animal pollination – many plants have brightly coloured petals and produce nectar and scents to attract animals. The pollen becomes attached to the animal and when they move to feed on another flower, the pollen is transferred.

Pollinators The following clips provide examples of how different plants are pollinated BBC – How do insects pollinate flowers? (5 mins) BBC – Self versus cross pollination (1 min) BBC – Mouse lemurs pollinate flowers (2 mins) BBC – Insect pollination of plants (3 mins) BBC – Giant lily pollination by the scarab beetle (3 mins) BBC – Pollination of the Elephant Yam plant by beetles (4 mins)

Wind pollinated flowers

Insect pollinated flowers

Reproduction in flowering plants Plants can use sexual or asexual reproduction to produce new individuals. Flowers are the structures responsible for reproduction in flowering plants. Usually the male and reproductive organs are both present in the same flower.

Male reproductive organs The male parts of the flower are the stamens. These are made up of the anther on top of a stalk called the filament. The anther produces the male gamete, pollen.

Female reproductive organs The female part of the flower is made up of the stigma and the ovary. The stigma is where pollen lands during pollination. The ovary produces the female gametes, the ovules.

Flower Labelling Task Your teacher will provide you with a diagram of a flower. Label each structure and provide a key to show if the structure is male or female. Write the function of each part on your diagram.

Anther Filament Stigma Style Ovary Ovulemale female Reproductive parts of a flower

Anther Filament Stigma Style Ovary Ovule contains pollen grains (male gametes) holds up anther sticky to receive pollen during pollination tube that joins stigma to ovary contains ovules (female gametes) female gamete

Homework task - Make a model flower Your task is to make a 3D model of a flower. You should label the structures in the flower which you have learned about in Biology. You can use any materials you can find at home, for example: Coloured paper, card or tissue paper for petals. Pipe cleaners, cotton buds, straws or cocktail sticks for anthers or for the style. You could also use plasticene, lego, K’nex, buttons, drawing pins, blutac, elastic bands, cotton wool, dry pasta, dry rice or anything else you can find. Felt pens, sellotape, scissors and glue will be useful. Please do not make edible flowers or use perishable materials!

Be as inventive as you can. Build it up to be partly 3D on A4 paper or card, or make it free standing and fully 3D. Make it bright and colourful. Attach labels so that they can easily be read.

Key Words Anther – organ within a flower that produces pollen grains Pollen grain – structure produced in the anthers of a flower that contains the male gamete Ovary – female sex organ in plants Ovule – structure containing a female gamete, produced in the ovaries of plants Pollination – transfer of a pollen grain from an anther to stigma, usually by wind or animal pollinator Fertilisation which is the process by which the nucleus of a male sex cell from a pollen grain fuses with the nucleus of an ovule to form a zygote

Fertilisation in plants Before fertilisation can take place, the pollen nucleus must reach the ovule nucleus. This occurs through the formation of a pollen tube.

Fertilisation in plants When a pollen grain lands on the stigma, it begins to grow a pollen tube. The pollen tube grows down towards the ovary. The haploid pollen nucleus passes down the tube and fuses with the haploid ovule nucleus forming a diploid zygote. The zygote will form a seed and the wall of the ovary will become a fruit. ovule nucleusTwig – Fertilisation

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