S4 Biology UNIT 2: Multicellular organisms Reproduction

Sexual vs. asexual reproduction

Sexual vs. asexual reproduction Learning intention: Describe the features of asexual reproduction and give examples. Why? Many species have evolved to use this type of reproduction.

Reproduction What is reproduction? Why do organisms need to reproduce?

Sexual vs. asexual reproduction Reproduction in plants and animals can fall into two different categories: Sexual reproduction – involves two parents Asexual reproduction – involves only one parent

Sexual reproduction During sexual reproduction a new organism is created using two parents. The genetic material of the parents is mixed and the offspring produced are different from both parents.

Sexual reproduction We will study sexual reproduction in plants and animals in more detail in the next few lessons.

Asexual reproduction During asexual reproduction a new organism is created using one parent. The offspring produced are identical to the parent plants – they are clones. We have looked at examples of asexual reproduction already, can you think of any examples?

Asexual reproduction

Asexual reproduction Offspring produced by asexual reproduction are identical to their parent. This means there is no increase in variation. The offspring produced have the same genetic material (genes) as their parent.

Sexual vs. asexual reproduction Collect a copy of the booklet. Complete the sexual vs. asexual section.

Asexual reproduction in animals Asexual reproduction is quite rare in animals. Sponges are an example of an animal which reproduces by asexual reproduction.

Asexual reproduction in animals The parent sponge releases a special ball of cells called a gemmule which can turn into a new sponge.

Asexual reproduction in animals A type of worm called planaria is also capable of asexual reproduction.

Asexual reproduction in animals If a planarian is cut, each part will develop into a new organism, identical to the original parent planarian.

Asexual reproduction in animals Collect a laptop and carry out some research using the internet. Make notes on asexual reproduction including: Examples in animals Examples in plants Advantages Disadvantages

Asexual reproduction in animals Suggested websites: http://biology.about.com/od/genetics/ss/Asexual-Reproduction.htm http://saburchill.com/ans02/chapters/chap051.html www.diffen.com/difference/Asexual_Reproduction_vs_Sexual_Reproduction#Advantages_and_Disadvantages

Sex cells and reproductive structures in plants

Sex cells and reproductive structures in plants Learning intention: Name the the sex cells and reproductive structures in plants. Why? This will give you an increased understanding of how plants reproduce.

Reproduction in plants Plants can reproduce in two ways: Sexual reproduction – using sex cells Asexual reproduction – without sex cells We are going to look at sexual reproduction in plants today. The flowers of a plant are responsible for sexual reproduction.

Reproduction in plants Flowers can carry out sexual reproduction. Inside a flower, there are both male and female parts. The male and female parts of the flower produce gametes. Gametes are sex cells. 21

Reproduction in plants The male part of the flower is the stamen. This is made up of two parts, the anther and the filament. The anther produces pollen – the male gamete. 22

Pollen grains 23

Reproduction in plants The female part of the flower is called the carpel. This is made up of the stigma, style, ovary and ovule. The ovary produces ovules – the female gamete. 24

Ovules 25

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Reproduction in plants The gametes (sex cells) in plants are haploid, this means they only contain one set of chromosomes. The male gamete – pollen is haploid. The female gamete – ovule is haploid.

Sex cells and reproductive structures in plants Collect a copy of the booklet. Follow the instructions under the sex cells and reproductive structures in plants section to carry out a flower dissection.

Sex cells and reproductive structures in plants After you have carried out your flower dissection complete the notes under the sex cells and reproductive structures in plants continued title.

Fertilisation in plants

Fertilisation in plants Learning intention: Describe the process of fertilisation in plants. Why? Fertilisation in plants allows a seed to form which can become a new plant.

Pollination Fertilisation is the process where the male sex cell nucleus fuses with the female sex cell nucleus. In plants before fertilisation can happen, the flower must be pollinated. Pollination is the transfer of pollen from the anther of one flower to the stigma of another.

Pollination Cross pollination is the transfer of pollen from anther to stigma of a different flower. Self pollination is the transfer of pollen from anther to stigma of the same flower.

Pollination Cross pollination can be carried out by two different methods.

Wind pollination Wind pollination involves the wind blowing pollen from one plant to another. http://www.bbc.co.uk/learningzone/clips/pollination-in-plants/118.html

Insect pollination Insect pollination involves an insect transferring pollen from one plant to another. http://www.bbc.co.uk/learningzone/clips/insect-pollination/119.html

Pollination Collect a copy of the booklet. Complete the pollination section.

Fertilisation in plants After pollination a pollen tube grows from the grain which has landed on the stigma. This allows the nucleus of the male gamete to travel down to the nucleus of the ovules so fertilisation can take place.

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Fertilisation in plants The male nucleus travels down the tip of this pollen tube to the ovules in the ovary The male nucleus and female nucleus fuse This is called fertilisation.

Fertilisation in plants For fertilisation to take place, the male and female gametes need to join together (fuse). This process is called fertilisation. Fertilisation is the fusion of the nucleus of a male gamete with the nucleus of a female gamete. 42

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Fertilisation in plants Remember the gametes (pollen and ovules) are haploid. This means they only have one set of chromosomes. After fertilisation the zygote has two sets of chromosomes and is therefore diploid.

Fertilisation in plants Eventually the zygote(s) will form a seed(s) and the wall of the ovary will develop into a fruit.

Fertilisation in plants Complete the fertilisation in plants section of the booklet.

Sex cells and reproductive structures in animals

Sex cells and reproductive structures in animals Learning intention: Describe the structure of the sex cells and reproductive structures in animals. Why? Animals use a similar method of reproduction across the animal groups.

Animal sex cells In animals the male sex cell is sperm. In animals the female sex cell is the egg. 49

Animal sex cells Remember gametes (sex cells) are haploid. This means they only contain one set of chromosomes. Why is this important?

Egg cell Cell membrane Cytoplasm Nucleus 51

Sperm cell Cytoplasm Cell membrane Nucleus Tail 52

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Animal sex cells? In your groups discuss the following: Why do sperm have tails? Why are eggs much larger than sperm? Sperm have tails so they can swim to the egg. Eggs are much larger because they have a large food store. 55

The male reproductive system The male reproductive system contains these parts: Penis Testes Sperm ducts

Penis The penis has two functions: to pass urine out of the man's body to pass semen into the vagina of a woman during sexual intercourse.

Testes The two testes (one of them is called a testis) are contained in a bag of skin called the scrotum. They produce millions of male sex cells called sperm.

Sperm ducts The sperm ducts allow sperm to pass from the testes to the penis so it can leave the body.

The female reproductive system The female reproductive system contains these parts: Ovaries Oviducts Uterus Vagina

Ovaries The ovaries produce the female sex cell, the egg.

Oviducts The oviducts allow the egg to pass through to the uterus. Fertilisation takes place here if sperm are present.

Uterus The uterus is where the baby develops until birth.

Vagina Sperm is deposited in the vagina, which leads to the uterus.

Sex cells and reproductive structures in animals Collect and copy of the booklet. Complete the sex cells and reproductive structures in animals section.

Sex cells and reproductive structures in animals Your teacher will give you 30 seconds to study the pictures of the male and female reproductive systems. After 30 seconds you need to close your notes and draw them from memory, including labels!

Sex cells and reproductive structures in animals Your teacher will give you the definitions of the structures found in the male and female reproductive systems. You will stand up and work as a group to memorise the definitions, when everyone has them memorised, sit down and your teacher will come over and test you!

Fertilisation in animals

Fertilisation in animals Learning intention: Describe the process of fertilisation in animals. Why? This is the point where a cell (zygote) is formed which has the ability to form a new individual.

Fertilisation We have looked at fertilisation in S2. What is fertilisation? Where does it take place?

Fertilisation Fertilisation is the process where a sperm cell nucleus fuses (joins) with an egg cell nucleus. This happens in the oviduct of the female reproductive system. After an egg is fertilised it becomes known as a zygote.

Sperm swim up through the uterus and along the oviducts Sperm are deposited in the vagina

The zygote begins to divide and travels towards the uterus. A sperm cell nucleus fuses with an egg cell nucleus to form a zygote.

Fertilisation Remember gametes (sex cells) are haploid. This means they only have one set of chromosomes. What do you think happens to the chromosome number after fertilisation?

Fertilisation When the two haploid gametes fuse together, they produce a diploid zygote.

Fertilisation in land animals Collect a copy of the booklet. Complete the fertilisation in land animals section.

Fertilisation in aquatic animals Animals which live in water (aquatic animals) carry out fertilisation differently from land animals. Where does fertilisation take place in land animals?

Fertilisation in aquatic animals In fish, fertilisation takes place outside the body. This is an example of external fertilisation.

Fertilisation in aquatic animals During the breeding season, the male stickle back builds a nest of waterweeds and develops a red belly which attracts the female. The two fish then perform courting movements.

Fertilisation in aquatic animals A female fish lays her eggs in the nest. A male fish then passes over the eggs and releases sperm. The sperm swim through the water to the eggs and fertilisation takes place in the water.

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Fertilisation in aquatic animals Most species of fish do not protect their fertilised eggs. This means many of the embryos formed are eaten by predators. The fertilised eggs do have a protective covering which helps them to survive if predators try to eat them.

Fertilisation in aquatic animals Fish embryos obtain food from a yolk sac enclosed inside their own egg. Yolk Developing fish

Internal Fertilisation External Fertilisation Birds, reptiles, mammals Fish, frogs, toads Fewer gametes needed, efficient Many more gametes needed, wasteful Sperm swim in body fluids Sperm swim to eggs in the water Fertilised eggs protected inside mother’s body or by hard shell Very little protection for fertilised eggs Gametes meet in a small space, increased chance of fertilisation Gametes in larger space, decreased chance of fertilisation 84

Fertilisation in aquatic animals Complete the fertilisation in aquatic (water) animals section of the booklet.

Internal vs. external fertilisation On the next slide there is a table showing some facts about survival of offspring in different animals. Your teacher will talk you through a problem solving activity to analyse this information.

Animal No. eggs produced No. eggs fertilised No. eggs diseased No eggs eaten No. young eaten Rabbit 8 4 Trout 3000 2000 200 800 850 Pheasant 15 12 2 3 Human 1 Frog 1000 750 50 400 Copy and complete the table below using the information above, the first one has been completed for you. Animal Total young surviving Total no. eggs produced % survival Rabbit 4 8 50

Internal vs. external fertilisation Which animal has the greatest % survival? Which animal has the lowest % survival? Can you think of a reason for the difference?

Reproduction review

Reproduction review Learning intention: Revise your knowledge of reproduction. Why? This will allow you to display all that you have learned about reproduction.

Reproduction review You are going to make a poster, you can either make a poster showing: All the information you have learned about reproduction OR Comparing reproduction in plants and animals.