Asexual and Sexual Reproduction PDF

2.2 Asexual and Sexual Reproduction  Reproduction Reproduction involves passing down genetic information from one generation to the next. – Essential to the survival of a species. – It is the way that organisms pass on their successful adaptations...

2.2 Asexual and Sexual Reproduction  Reproduction Reproduction involves passing down genetic information from one generation to the next. – Essential to the survival of a species. – It is the way that organisms pass on their successful adaptations to future generations – Types Asexual reproduction Sexual reproduction Reproduction can produce new individuals that are identical to (ie. asexual) or very different from one another (ie. sexual) depending on the way a species reproduces.  Asexual Reproduction Asexual reproduction involves only one parent. All of the offspring are identical to the parent. – Offspring are genetic copies (clones) of the parent. Less biodiversity is created. Note: there can still be copying errors or mutations – Doesn’t require gametes (sex cells, like eggs or sperm) or meiosis. – There are different types of asexual reproduction: binary fission budding vegetative reproduction ○ fragmentation spore production (asexual spores)  Binary Fission Only single-celled organisms (bacteria, amoeba, algae) reproduce in this way. DNA and contents are duplicated then the single cell splits into two cells and each one is identical.  Bacterial Conjugation Bacterial conjugation is a unique process that allows bacteria to exchange partial genetic material from one cell to another, without having to reproduce. The benefits are that new combinations of inherited characteristics may be produced as a result, which will then be passed down to future generations through asexual binary fission or mitosis (cell division). This implies that bacteria can change their genetic make-up while they are still alive, and share adaptations with each other, without having to wait for a second generation to express them. This increases diversity and implies that bacteria can evolve/change at a much faster rate. – They can develop resistance to antibiotics and pesticides very quickly  Budding The parent organism produces a bud (a smaller version of itself). In some organisms, such as hydra and yeast, the bud develops into a new individual while still attached to the parent. Then it detaches itself from the parent and becomes a self-sufficient independent individual - identical to the parent. In other organisms such as coral, the buds do not detach themselves. They stay attached to the parent forming a large structure composed of many identical individuals (colony). This colony can be more resilient to environmental changes and predators. The interconnectedness of these buds allows for the sharing of nutrients and genetic material, which enhances the survival of the group.  Vegetative Reproduction Is the reproduction of a plant not involving a seed. A new plant can grow from part of the parent plant thanks to meristem cells Most plants can produce cuttings/runners/suckers/tubers/bulbs which result in a new plant that’s genetically identical (clones) to the plant A specific type, known as fragmentation, is where a plant breaks into pieces (fragments) and each piece can grow into a new plant. Ex. a piece of a cactus can grow roots and become a new plant. Vegetative reproduction examples – coleus plant (cuttings) – spider plants (runners) – strawberries (runners) – tulips (bulbs) – aspen (suckers) – potatoes (tubers) Video  Spore Production Spores are similar to seeds, but are produced by the division of cells on the parent, not by the union of two cells. They are single-celled reproductive structures. Easy to distribute over large areas due to their small size. Spores are carried by wind, water, animals etc. Hardy, survive harsh conditions – They remain dormant until they land in a suitable or favourable environment. This is when they germinate. Some fungi (ex. mushrooms) reproduce asexually reproducing spores. – One parent may produce many asexual spores, each of which will grow into a new individual, identical to its parent. – Many spores are produced to ensure one survives Some fungi and algae also produce zoospores. – Zoospore: are spores that can move with a tail-like flagella, found in some algae Other organisms capable of producing spores: green algae, some moulds, and non-flowering plants (ex. ferns, mosses)  Fern Life Cycle-Alternation of Generation Alternation of generation: alternate between different forms (sporophyte & gametophyte) ○ Sporophyte: diploid and produces spores from meiosis that divide repeatedly by mitosis to become multicellular gametophytes ○ Gametophyte: haploid and produces gametes that must combine to form a zygote that divides by mitosis to become a sporophyte In plants, such as ferns and mosses, spores are single-celled, reproductive structures that are usually haploid and formed by meiosis, but then they can grow and divide by mitosis to produce a multicellular sporophyte. Moss Life Cycle-Alternation of Generation Video  Assignment -Draw diagrams (include labels) to represent the process of binary fission, budding, and vegetative reproduction. Include 3-4 sentences to explain each process.  Sexual Reproduction Sexual reproduction usually involves two individual organisms (the parents) and the offspring produced are a genetic combination of them. Produces genetically diverse offspring. – Self-fertilization only requires 1 parent BUT still produces unique gametes and diverse offspring so it is still considered sexual reproduction. The offspring that are produced from this union have a mix of characteristics, half from one parent and the other half from the other parent. Note: half=50% Sexual reproduction does not always involve male and female parents, for example – flowering plants have both male and female parts on one plant.  Sexual Reproduction Sexual reproduction in plants or animals relies on the union of two specialized sex cells known as gametes. – A gamete is a cell that has one role only, which is to join with another gamete during reproduction. – Animals: male gamete (sperm), female gamete (egg cells or ova) – Plants: pollen contains male gamete, ovules contain female gamete – Fertilization - union of 2 sex cells to produce a zygote Sexual Reproduction in Animals Sexual reproduction in animals involves gametes. The male gametes are called sperm cells. The female gametes are called egg cells (ova). The union of the sperm cell with the egg cell occurs during mating and is called fertilization. The cell created by the joining of the two gametes is known as a zygote. – Most animals that live on land undergo internal fertilization, where fertilization happens within the body of the female Advantage: high success; disadvantages: more time, energy, and care to ensure the ‘parents’ are in the same place at the same time to mate Ex. insects, reptiles, birds, mammals, and even some fish and amphibians – Other animals undergo external fertilization, where fertilization happens outside the body of the female Advantages: saves time/energy/difficulty of actually being together with a mate; disadvantages: a large number of gametes must be produced because so many are killed/wasted, and a liquid medium is needed to prevent gametes from ‘drying out’ and gives sperm fluid to swim through to reach egg Ex. animals that live in water (ex. sponges), most worms, many fish and amphibians Video Sexual Reproduction in Animals This zygote is the first cell of a new individual. The zygote then divides into two cells. The same divisions are repeated again during a process called cleavage. Continued cell division results in a new multicellular life form referred to as an embryo. This embryo develops into a multicellular organism inside the female (in most mammals) or outside (in an egg) in other animals. The new individual will have characteristics of both parents. Sexual Reproduction in Animals The parental care of offspring can greatly increase the chance of the offspring surviving. – No parental care is expected to result in many zygotes dying and thus more zygotes are produced to increase the odds of a few actually surviving External fertilization usually implies there will be no parental care – Generally, the fewer the offspring a species has, the more likely they will invest more time and energy into parental care so that the offspring has a greater chance of surviving  Sexual reproduction in animals involves specialized cells called gametes. fertilization Cleavage/mitosis sperm + egg -> zygote -> embryo (1 cell) (multicellular, many cells) Mitosis Mitosis Mitosis  Sexual reproduction in animals involves specialized cells called gametes. Video  Sexual reproduction in animals involves specialized cells called gametes. In “typical or normal” humans: Fertilization Mitosis Haploid (n)- one set of chromosomes Diploid (2n)- two sets of chromosomes, one set from Haploid (n)- one set of each parent chromosomes Ex. diploid=2(23)=46  Assignment -Define sexual reproduction, male gamete, female gamete, and fertilization. -Compare and contrast internal and external fertilization. -What is a zygote? -Draw a diagram (include labels) to show the development of an embryo from gametes.  Sexual Reproduction in Plants Angiosperms and gymnosperms reproduce sexually by forming seeds. – Angiosperms: flowering plants – Gymnosperms: plants that do not produce flowers but instead produce seeds inside cones, for example conifers Sexual reproduction in plants requires the joining of a male gamete with a female gamete to produce a zygote and an embryo. Most plants produce both male and female gametes, but some produce only one. Sexual Reproduction in Plants In flowering plants (angiosperms), there are several structures devoted to sexual reproduction. – Stamen: male part of a plant Filaments: support the anther Anthers: contains pollen which contains the male gametes –Pistil: the female part of a plant Stigma: site of pollination (ie. when pollen from the anther of the stamen is transferred to the stigma of the pistil) Style: connects the stigma to the ovules; pollen grows down this structure to reach the ovules in order for fertilization to occur – Fertilization occurs when the male and female gametes unite and a zygote forms. The zygote undergoes many cell divisions to form a multicellular embryo, containing a miniature leaf, root, and stem.The embryo is supplied with food by one or two cotyledons, and together these structures make up the developing seed. Ovules: contain the female gametes and are found in the ovary of the pistil. Sexual Reproduction in Plants Many plants can self pollinate, while others separate the male and female gametes. Cross-pollination occurs when pollen from one plant is carried to the stigma of another plant by wind, water or animals (bees or butterflies). Cross-fertilization occurs when a grain of the pollen forms a long tube, which grows down the style into the ovary. The gametes unite to produce a zygote, which then develops into an embryo. – Pollen grains & ovules are sacs that contain sex cells (gametes) Sexual Reproduction in Plants Embryo production usually happens inside a seed which protects the embryo and provides food (cotyledon) for the embryo when growing conditions are right. Plants which are produced as a result of cross-fertilization show some characteristics of both plants, but are not identical to either plant. Video  Assignment -Draw a diagram to show the flower parts involved in reproduction. Label your diagram. Include the role or function of the stamen, filament, anther, pollen, pistil, stigma, style, ovary, and ovule in your diagram under the appropriate label.  Advantages and Disadvantages of Asexual and Sexual Reproduction Variation usually helps a species survive when the environment changes. The way an organism reproduces affects the variation in the offspring. Asexual reproduction produces no variation. – How could this be an advantage? Advantages and Disadvantages of Asexual Reproduction Asexual reproduction does not require any specialized cells to produce a new organism. It can therefore produce many organisms very quickly. There is no partner required so reproduction can happen in isolation. – This is an advantage in places where the environment doesn't change very much (bacteria). By building a large population of organisms very quickly the species is able to thrive (efficient). If the parent was successful the offspring should be as well because they are identical. – The great disadvantage is that when the environment changes, all of the organisms will die if they do not have the ability to adapt to the change as there is limited diversity (variation) since the parent and offspring are identical. Therefore, reduces the population’s ability to adapt to environmental changes and resist disease. Advantages and Disadvantages of Sexual Reproduction Sexual reproduction provides lots of variability within a species. – This provides an advantage when it helps an organism survive in a changing environment. Also, winning adaptations have increased chances of reproducing and losing adaptations have a lower chance so populations weed out the weak members. – The main disadvantage is that this process takes a lot of energy and time (less efficient). It also requires both male and female gametes so it is difficult to reproduce in isolation. This means that they can only produce small populations. Reproduce Both Sexually & Asexually Some organisms can reproduce both sexually and asexually. – Hermaphrodite: appear to be a combination of sexual and asexual, because they can usually reproduce by themselves or with a mate, but they are actually considered a variant of sexual reproduction Not considered the best of both worlds because they don’t have as much diversity or weed out the weak as well as ‘purely sexually reproducing’ species, and they are not as efficient as asexual ones Ex. slugs, worms, sponges Female hermaphroditic worms can produce eggs and sperm via meiosis when no males are present and self-fertilize; however, if males are present they will mate with the male and the male’s sperm will be used instead – Some moulds, such as Rhizopus, can produce asexual spores or sexual spores called zygospores (from 2 different genetic sources) Zygospore: a type of spore which is generated sexually by 2 parents; it is a specific type of sexual spore formed from the fusion of two compatible algal cells or two fungal cells for example. – Most plants that produce seeds can also reproduce asexually (cuttings, runners). – Depending on the environmental conditions, the amount of energy the organism devotes to each type of reproduction varies. Poor conditions – asexual reproduction Favourable conditions – sexual reproduction. Sexual Vs. Asexual Reproduction Sexual Asexual Requires 2 parents Requires 1 parent Sperm fertilizes egg Single organism makes an exact copy of itself Use by animals, flowering Bacteria, some plants and plants, some fungi fungi, few animals (sponges) Provides genetic variation, Fast and easy, but no but time-consuming genetic variation  Video- Internal Fertilization Internal fertilization has the advantage of protecting the fertilized egg from dehydration on land.  Video- External Fertilization External fertilization in an aquatic environment protects the eggs from drying out.  Assignment -Read textbook pages -FOCUS: pages 26-36 -Science in Action: pages 30-36 -2.2 Worksheet -Flower handout and worksheet -Flower lab?  1. What is a zygote and how is it formed? Assignment 2. Define asexual reproduction. List three examples of asexual reproduction. 3. Make a table to compare the male and female gametes in plants. Indicate where they are found. 4. List three ways in which pollination can occur. Give an example of each. 5. What is similar about sperm cells and egg cells? What is different? 6. List the steps of fertilization and embryo development in animal sexual reproduction. Be sure to include the words “gametes” and “zygote” in your description. 7. Explain what happens to male and female gametes during sexual reproduction in plants and animals. 8. Using a Venn diagram, compare and contrast sexual and asexual reproduction. 9. An individual produced by asexual reproduction may be identical to one of its parents. Do you agree or disagree with this statement? Support your answer. 10. Give three examples of a heritable characteristic. 11. Make a table to compare the advantages and disadvantages of sexual and asexual reproduction. 12. An amoeba reproduces by binary fission. Briefly describe the process of binary fission. Explain whether it is an example of sexual or asexual reproduction. 13. A person with a hitchhiker’s thumb plays guitar with a local rock band. Explain how she displays both heritable and non-heritable characteristics. 14. Compare the process of fertilization in plants and animals. 15. Using a diagram, explain how a zygote forms in a flowering plant. 16. Compare discrete and continuous variation using a Venn diagram. 17. Describe the steps of vegetative reproduction that occur when a plant is grown from a cutting. Why is this process considered to be an example of asexual reproduction? 18. Imagine an organism that lives where there are often big changes in environmental conditions. What type of reproduction would be more advantageous for this organism? Explain your answer.