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Methods of Asexual Reproduction This is what it would look like if humans reproduced by fragmentation! bud Budding • A new organism grows on another one and then separates from the parent organism only when it is mature. • Examples of organisms that reproduce by budding include: yeasts, sponges and hydra bud bud Binary Fission • Division into two parts (daughter cells) which each daughter cell has the potential to grow to the size of the original cell (parent cell) • An example of an organism that reproduces by binary fission is a paramecium. Daughter cells Regeneration • When an animal that is capable of regeneration loses a body part, it can grow a replacement part. • If the lost body part contains enough genetic information from the parent, it can regenerate into an entirely new organism. • Echinoderms and the hydra in molds are examples of organisms that reproduce by regeneration. Fragmentation • A new organism grows from a fragment of the parent. • Each fragment develops into a mature, fully grown individual. • Examples of organisms that reproduce by fragmentation include: molds and planaria. Vegetative Reproduction • New individuals are formed without the production of seeds or spores • May produce bulbs, tubers or rhizomes (runners) • Examples of organisms that reproduce by vegetative reproduction include: tulips, dahlia, strawberries rhizome bulb Vegetative Propagation • The production of a new plant from a portion of another plant, such as a stem or branch. • Examples of organisms that reproduce by vegetative propagation include: spider plants, potatoes, aloe and various other plants. cutting New spider plant Spores • In some organisms, meiosis leads to the formation of haploid spores rather than gametes. These spores grow into multicellular individuals without being fertilized. • Examples of organisms that reproduce by forming spores include: mushrooms, molds and ferns spores Asexual Reproduction Method Asexual Number Genetics of Parents 1 parent • • Pros Identical • No mate 100% of • Identical genes to parent come from 1 parent Cons • Mutations are definite • No variety Sexual Reproduction Sexual Reproduction • Two parents • Genetically speaking, the offspring get info from both parents: ½ from mother (egg) ½ from father (sperm) There are 46 chromosomes in human cells, so 23 from mom + 23 from dad = 46 total Sexual Reproduction • Requires sex cells (gametes) – Male sex cell (gamete) – sperm – Female sex cell (gamete) – egg • Fertilization is the process in which sperm and egg unite – Chromosomes double Ex) 2 + 2 = 4 Cell division by mitosis Step 3 Chromosomes line up along the middle of the cell and each centromere attaches to a spindle fiber. Step 4 • Mitosis is cell division of body cells • Mitosis produces exact copies of the parent cell • The new daughter cells have the diploid number of chromosomes Meiosis • Cell division that results in the formation of gametes (sex cells) – Sperm and egg – Cells are haploid • Cells are NOT identical – Each cell contains half the number of chromosomes but not necessarily the same chromosomes as the others How many chromosomes? • Humans have 23 pairs of chromosomes like these • The diploid number of chromosomes is 23x2 = 46 • Sex cells (gametes) have 23 single chromosomes - the haploid (half) number So……what’s the point? • An egg cell is haploid • A sperm cell is haploid • When they join at fertilization the resulting cell is diploid • This makes a full set of instructions to make a new organism! Mitosis vs Meiosis