Reproduction Notes - Mrs. Meyer 2024 - PDF

 Reproduction oReproduction – biological process where new individuals are produced to ensure survival of species. o 2 types of reproduction: 1. Sexual Reproduction – two parents are involved, and their genetic material combines. Gametes are produced by meiosis and these ga...

 Reproduction oReproduction – biological process where new individuals are produced to ensure survival of species. o 2 types of reproduction: 1. Sexual Reproduction – two parents are involved, and their genetic material combines. Gametes are produced by meiosis and these gametes fuse during fertilization to form a zygote. 2. Asexual Reproduction – one parent is involved, and all the offspring have the same genetic composition as the parent. No gametes are involved, and the process occurs by mitosis. Similarities Between Asexual & Sexual Reproduction o Both methods produce new offspring. Differences Between Asexual & Sexual Reproduction Asexual Reproduction Sexual Reproduction No gametes required Gametes required 1 parent needed 2 parents needed No variation since it involves mitosis Variation since gametes are produced by meiosis Offspring identical to parent & each Offspring not identical to parent or other each other Happens quickly Happens slowly Many offspring produced Few offspring produced Less energy required More energy required to find mates and reproduce Advantages of Asexual Reproduction During favourable conditions, many offspring are produced very quickly, therefore rapid population growth. Requires less energy, since no gamete formation is needed. No not need to look for a mate. Single member of species can start a whole new population. Offspring can adapt easily to the environment since identical to the parent. No mutations, since no meiosis. Or few mutations are possible. Disadvantages of Asexual Reproduction No genetic diversity (variation), therefore cannot adapt to changing environments – may become extinct. Advantages of Sexual Reproduction o Variation – allows organisms to adapt better to changing environment. Disadvantages of Sexual Reproduction oThe process takes longer, since gametes need to be produced. oFewer offspring are produced, decreasing chances of survival. oMore energy required.  Importance of Asexual Reproduction in Agriculture Plants with desired characteristics can be cloned. Don’t have to wait for seeds to germinate, therefore saving time and money. More crops are yielded in a shorter period of time. Better quality crops continuously produced.  Asexual Reproduction in Plants o Also known as vegetative propagation - part of the parent plant becomes separated and grows independently. Vegetative Propagation o 3 methods that occur artificially: 1. Stem cuttings 2. Grafting 3. Tissue culture  Stem Cuttings o Stems of plants are cut into pieces, which are placed in furrows & covered with soil. o Pieces must include 2 nodes & an internode. o Roots & shoots grow from nodes.  Grafting o Used mostly for fruit trees, to produce many identical offspring from 1 parent plant. o Piece of plant with good features is grafted onto a strong, more resistant plant. qu-graft Grafting tree_rose A cut stem of one plant (with good flower or fruit growth) (the graft) is taken and firmly attached to the rootstock of another plant (which has a strong, established root system) (the stock). Examples- roses, fruit trees  Tissue Culture – Cloning Plants 1. Isolate cells with desirable traits from parent plant. 2. Place cells in a sterile nutrient medium. 3. Cells divide by mitosis; roots & shoots develop. 4. Plantlets are planted in soil.  Flowers as Reproductive Organs Sexual reproduction in Plants o Flower is reproductive organ in Angiosperms i.e., flowering plants. o Hermaphrodite flowers – have male & female parts on the same flower. o Unisexual flowers – separate male & female flowers.  Structure of Flower Stamen Pistil 1.Pistil: female reproductive Anther Stigma Style structure Filament Ovary a.Stigma: sticky tip; traps pollen b.Style: slender tube; transports pollen from stigma to ovary c. Ovary: contains ovules; ovary develops into fruit d.Ovule: contains egg cell which develops into a Petal seed when fertilized Ovule Sepal  Structure of Flower Stamen Pistil Stigma 2.Stamen: male Anther Style Filament reproductive structure Ovary a.Filament: thin stalk; supports anther b.Anther: knob-like structure; produces pollen c. Pollen: contains microscopic cells that become sperm cells Petal Ovule Sepal  Structure of a Flower Stamen Pistil Stigma Anther 3.Sepals: encloses & Style Filament Ovary protects flower before it blooms 4.Petals: usually colorful & scented; attracts pollinators Petal Ovule Sepal  Pollination & Fertilisation Pollination o Pollen moves from anther to stigma. o Must happen before fertilisation. o Pollen carried by wind, animals e.g., insects & birds. These are known as vectors. o Male gamete = pollen. Produced by meiosis in anthers. o Female gamete= ovule. Produced by meiosis in ovaries. o Cross pollination – transfer of pollen from anther of one flower to the stigma of another flower on another plant of the same species. o Self pollination – transfer of pollen from the anther to the stigma of the same flower or other flowers on the same plant.  Cross Pollination How does pollination happen? Pollen from an anther is caught by the stigma, travels through style to the ovules in the ovary. What is the result of pollination? A Fruit: An ovary containing seeds. Fertilisation o Pollen grain lands on sticky stigma and develops a pollen tube. o Pollen tube grows down the style until it reaches the ovary where fertilisation takes place, and a zygote is produced. o After fertilisation, ovary becomes fruit & ovules become seeds. Importance of Seeds as a Food Source o Seeds store lots of food, therefore they are an excellent source of food for people. o Edible seeds are divided into 3 categories: grains, legumes, and nuts. o Grains and legumes form the staple diets of most people since they are cheap and have a high nutritional value. The Use of Seed Banks to Maintain Biodiversity o A seed bank is used to store seeds so that they can be conserved in order to maintain biodiversity. o Conservation of seeds ensures that plant species do not become extinct. Seeds stored in a seed bank can be used to: 1. Re-establish endangered or extinct plants. 2. Rehabilitate damaged or destroyed habitats. 3. Cultivate plants that are over exploited. 4. Cultivate new hybrids that are hardier and more resistant to disease. 5. Conserve endemic species.