L5.2 Sexual and Asexual Methods of Reproduction (PDF)

 Lesson 5.2 SEXUAL AND ASEXUAL REPRODUCTION 1.Describe the two methods of reproduction exhibited by different kinds of organisms; 2.Describe the male and female gametes; 3.Describe the process of fertilization; 4.Discuss the different types of fertilization exhibited by living things;...

 Lesson 5.2 SEXUAL AND ASEXUAL REPRODUCTION 1.Describe the two methods of reproduction exhibited by different kinds of organisms; 2.Describe the male and female gametes; 3.Describe the process of fertilization; 4.Discuss the different types of fertilization exhibited by living things; 5.Explain the sexual reproduction is basis of heredity; 6. Identify and describe the different types of asexual reproduction; and 7. Differentiate sexual from asexual reproduction in terms of: numbers of individuals involved; and similarities of offspring to parents. Reproduction is how life continues on Earth. Without it, plants, animals, and even humans would not exist. Understanding reproduction helps us appreciate how living things survive and how we can protect life, from growing food crops to helping endangered animals.  WHAT IS Reproduction is the process by REPRODUCTIO which living things create offspring N? (babies or new individuals). There are two types: sexual reproduction (two parents) and asexual reproduction (one parent). For example: Humans = sexual, bacteria = asexual.  S E X U AL REPRODUCTI ON  WHAT IS SEXUAL REPRODUCTION? Involves two parents (male and female). Each parent contributes half of the genetic material (DNA) to make the offspring. Examples: Humans, dogs, most animals, and flowering plants.  Sexual Reproduction is a process that involves the union of sex cells or gametes the gametes come from two parents of opposite sexes—the male that produces the sperm cells and the female that produces the egg cell or ovum In humans, the sperm is comparatively smaller and equipped with a motile. On the other hand, the ovum is  G A M E T E S Humans reproduce through a process called sexual reproduction. The offspring of sexual reproduction are genetically unique, because half of their genetic material (DNA) comes from each parent. Each parent produces gametes (sex cells). The male gametes are sperm cells. The female gametes are egg cells.  S PE R M Sperm C cells LSmade in the ELare testes. Males have two testes and they are contained in a bag of skin called the scrotum. The testes also make male sex hormones such as testosterone, which regulates the male reproductive system.  THE SPERM Nucleus CELL Mitochondria Acrosome Head - The genetic material is in the nucleus, Body - The body which is haploid, contains Tail - The tail allows meaning that it contains mitochondria, which the sperm to move 23 chromosomes. The provide energy and propel along to acrosome contains essential for reach the egg. enzymes to help movement. penetrate the egg.  EG G C E L L S Egg cells exist in the ovaries and they are present from birth. Females have two ovaries, which also produce hormones responsible for regulating the menstrual cycle.  Nucleus TH E E GG CELL The egg cell contains a nucleus with the female Zona pellucida genetic material. This is haploid, meaning it contains 23 Follicle cells chromosomes. The follicle cells form a The zona pellucida protective casing around protects the egg cell and the egg cell and provide only allows one sperm to the right environment for pass through. it to develop. FERTILIZATION ➔ is the union of the male and female gametes to produce a fertilized egg called zygote ➔ considered as the defying process in sexual reproduction ➔ there are two mechanism by which fertilization can take place: external and internal fertilization  EXTERNAL FERTILIZATION ➔ a watery or moist environment is needed so that the gametes will not dry out, both the male and the female cluster into the same area to simultaneously release their gametes into the surrounding ➔ this process is called spawning ➔ the process is initiated by the release of a chemical by a mate, and this stimulates other mates to release their mates ➔ amphibians and fishes exhibits external fertilization ➔ External fertilization is advantageous since it results in the production of large number of offspring. ➔ Disadvantage is that exposure to environmental hazards greatly reduces the chance of the zygote to survive and reach adulthood.  The zygote becomes enclosed in a structure called egg. The eggs are laid, and the zygote develops outside the mother’s womb. The frog exhibits external fertilization and external development. The female lays its eggs in a suitable place; then , the male fertilizes the eggs, and the zygotes undergo development on their own.  INTERNAL FERTILIZATION ➔ the egg is fertilized within the female reproductive tract in a process called copulation (also called sexual intercourse or mating) ➔ development of fertilized egg or zygote happens in many different ways Mammals, including humans, exhibit internal fertilization and internal development. The sperm is introduced and left within the female reproductive tract. The young develops inside the mother’s womb and is born alive. Internal development is a protective mechanism that ensures and increases the chances of the zygote’s survivals since the mother supplies everything that the zygote needs for its development.  During fertilization, the haploid sperm and haploid egg unite. The fertilized egg, called zygote, that is formed is a diploid organism just like its parents. Thus, the offspring produced by this union will have the characteristics of both parents but definitely is not identical of either of them.  ADVANTAGES AND DISADVANTAGES Sexual Reproduction: Advantage: Produces varied offspring, which helps species survive in changing environments. Disadvantage: Takes more time and energy (needs two parents).  THE IMPORTANCE OF SEXUAL REPRODUCTION Variety for Survival: Sexual reproduction creates differences in offspring. Better Survival Chances: Some offspring will have characteristics that help them survive better, keeping the species alive over time. Example: Siblings with sickle cell trait may have some resistance to malaria. Asexu al Reprodu ction  Asexual Reproduction ➔ does not involve union of gametes ➔ it is a method wherein an individual produces offspring without the involvement of another individual of the same species ➔ the offspring produced asexually are genetically similar or exact copies of the parent (a clone) ➔ Asexual reproduction is the primary method of reproduction exhibited by unicellular organism, such as bacteria and archaea (prokaryotes); protists and yeasts; and some invertebrates Examples of Asexual Reproduction ❏Budding 0 ❏Binary fission 1 ❏Fragmentatio n ❏Spore formation  BINARY FISSION ➔ the simplest form of asexual reproduction and the most common among single-celled organisms ➔ it is a method wherein the genetic material of the parent cell replicates followed by the division of the cell into two genetically identical daughter cells ➔ common among unicellular organisms like bacteria and, protozoans, and archaeans ➔ bud formation or BUD budding is common FORMATION not only in plants but in animals as well ➔ it is a form of asexual reproduction in which a new organism develops from a outgrowth called bud that grows in a specific site in the body of a matured or ➔ A bud is a mass of tissue that contains actively dividing cells. ➔ It is cast off to become a new individual from the existing parent. ➔ Buds form when food supply in the environment is  FRAGMENTATION ➔ is an asexual process that involves the development of new organisms from fragments of the parent organism or the development of new clones of individuals from the whole body that has ➔ The body of planarian is cut into different fragments and each is capable of developing into new organism. ➔ Some animals have self-cutting ability to escape predators. This is  REGENERATION ➔ is the ability to replace any lost or missing part of the body ➔ This process that takes place in simple organisms like starfish and lizards ➔ the more complex the organism is, the more difficult the regeneration process can happen  SPORE FORMATION ➔ spore formation or sporulation involves the formation of many spores located in a special structure called sporangium SPORES are specialized microscopic cells endorsed within a case that can easily be carried by the wind from one place to another.  When spores land on suitable places, they are capable of germinating into new individuals. Fungi like mushroom and molds are examples of organisms that  VEGETATIVE PROPAGATION ➔ is a form of asexual reproduction common in plants ➔ It is a process by which new individuals are formed not from seeds or spores but from other plant ➔ This method of reproduction occurs naturally or can be induced for commercial purposes. ➔ Horticulturist artificially propagate plants in order to keep particular desirable characteristics— flavor, flower size and ➔ The new plants that emerge by vegetative propagation are exact clones of the original plants. Examples of natural vegetative propagation are runners, corms, bulbs, tubers, and rhizomes.  RUNNERS or STOLON ◆Runners are long stems that grow above the ground from the parent plant. ◆They produce new plants at certain points (nodes) along the stem. ◆The new plants are clones of the parent. ◆Example: Strawberries grow runners that form baby plants.  BULBS ◆a short underground stem with fleshy leaves (called scales) ◆as the mature plant gets to the end of its life, the lateral bud develops into a smaller bulb that attaches to the base of the parent bulb ◆the new bulb can be separated and planted: examples include Tulips, Daffodils, Lilies, and onions  TUBERS ◆Tubers are swollen underground stems that store food for the plant. ◆Each tuber has "eyes" (buds) that sprout into new plants. ◆The new plants are also clones of the parent. ◆Example: Potatoes grow new plants from their tubers.  RHIZOMES ◆rhizomes is a long, horizontal underground stem with nodes and internodes ◆new plants grow off the roots ◆long grasses, ferns, ginger, and irises are examples of rhizomes  CORMS ◆is a short, vertical underground stem with nodes and internodes where buds grow and develop into new plants ◆examples are taro, cocoyam, and arrowhead ARTIFICIAL VEGETATIVE PROPAGATION ❏ Cutting ❏ Layering ❏ Grafting ❏ Tissue culture ADVANTAGES AND DISADVANTAGES Asexual Reproduction: Advantages: Faster and needs only one parent. Disadvantage: No variation, so species might struggle to survive environmental changes.