Organismal Biology - Reproduction and Development - PDF

# Organismal Biology ## 9.1 Reproduction and Development ### PART 1: Asexual and Sexual Reproduction **Organismal Biology** Lesson 9.1 Asexual and Sexual Reproduction | **PERFORMANCE STANDARD** | discuss the advantages and disadvantages of sexual and asexual reproduction | |---------------...

# Organismal Biology ## 9.1 Reproduction and Development ### PART 1: Asexual and Sexual Reproduction **Organismal Biology** Lesson 9.1 Asexual and Sexual Reproduction | **PERFORMANCE STANDARD** | discuss the advantages and disadvantages of sexual and asexual reproduction | |-------------------------------------|-----------------------------------------------------------------------------------| | **LEARNING COMPENTENCY** | compare various modes of asexual and sexual reproduction(STEM_BIO11/12-IVa-l | | **SPECIFIC LEARNING OUTCOMES** | - differentiate asexual from sexual reproduction | | | - describe different modes of sexual and asexual reproduction | **Essentials to Life on Earth** In the past lessons, we talked about history, evolution, diversity, and heredity that sustained life as we know it today. **Biological processes** are vital for survival and interactions of organisms and the environment. - Metabolism - Responsiveness - Growth and development - Heredity - Homeostasis - Reproduction **The Cycle of Creating New Life** The continuity of life depends on many biological processes like **reproduction**, by which new “offspring” are produced from their "parents". It is also called procreation or breeding. ## Types of Asexual Reproduction ### Fission **Fission** involves the division of a body into two or more equal parts. Binary fission usually occurs in prokaryotic bacteria, while some algae can undergo multiple fission. - e.g. Paramecium caudatum ### Fragmentation **In fragmentation**, the body breaks into two or more parts, and each fragment can develop into a complete individual. It is usually followed by regeneration to produce the missing parts. - e.g. Spirogyra sp. ### Budding **In budding**, an outgrowth or bud from its parent arises and develops organs like those from the parent, then detaches itself and becomes a new individual. - e.g. Hydra sp. ### Sporulation During unfavorable conditions, a bacteria can form an **endospore**, a dormant cell with preserved DNA, in a process called **sporulation**. It can stay dormant for a long time before germinating. - e.g. Rhizopus microsporus (fungus) ## Forms of Sexual Reproduction ### Isogamy Some gametes have similar morphology, and are unusually both motile. Fertilization occur due to slight variation in alleles, with mating types either (+) or (-). This is called **isogamy**. - e.g. some fungi, algae, or protozoa **A form of isogamy is conjugation**, where two filamentous gametes line side-by-side, and one side will grow projections to form a bridge and allow fusion of protoplasts. - This forms a **zygospore** that can germinate under good conditions. - e.g. Spirogyra sp. (algae) ### Heterogamy/ Anisogamy The fusion of two gametes with different sizes or forms is called **heterogamy** or **anisogamy**. In humans, **oogamy** involves the union of a large immotile egg and a small motile sperm. ### Hermaphroditism A **hermaphrodite** is an individual having both a male and a female reproductive organs. Hence, **self-fertilization** often occurs. Some fishes are hermaphrodites, but hermaphroditic worms have means to avoid self-fertilization. ## Major differences between sexual and asexual reproduction **Comparison of gametes and genes** | | Asexual Reproduction | Sexual Reproduction | |----------------|----------------------|----------------------| | # of parents | one | two | | gametes | No need for gametic union | Present, sperm and egg | | genetic composition of offspring | CLONE of parent, genetically identical | Generally a “hybrid” of parents | ## Developmental Biology ### Growth and Development After **fertilization**, the fusion of the egg and sperm produces a **zygote**, which matures through a series of stages. The study of the growth and development of plants and animals is called **Developmental Biology**. # Organismal Biology ## 9.2 Reproduction and Development ### PART 2: Animal Reproduction and Development **Organismal Biology** Lesson 9.2 Animal Reproduction and Development | **PERFORMANCE STANDARD** | illustrate the life cycle of the Drosophila; Debate on when human life begins | |-------------------------------------|---------------------------------------------------------------------------------| | **LEARNING COMPENTENCY** | describe the life cycle of animals and human development (STEM_BIO11/12-IVa-h-1) | | **SPECIFIC LEARNING OUTCOMES** | - describe the stages of animal development; | | | - describe human reproductive systems; | | | - illustrate the human female menstrual cycle; | | | - explain processes in human development; | | | - differentiate various contraception in humans | ## Development and Reproduction ### The Stages in a Span of Life Development overlaps with reproduction. It involves the formation of sex cells, the growth of the zygote, and other **stages** during one’s life span until it terminates in death. ## Gametogenesis ### The egg and sperm A diploid (2n) individual has two sets of chromosomes. Meiosis yields four **haploid (n) cells**, with half the genes of a parent. In **gametogenesis**, these cells develop into gametes, one egg in females, and four sperms in males. ## Fertilization and development of the zygote ### Totipotent Zygote **Fertilization** is a stage when a sperm and an egg fuse into a single-celled, diploid **zygote**. A human zygote is a potent stem cells that can differentiate into any kind of cell, called a **totipotent cell**. ## Cleavage Stage and Gastrulation ### The Blastula and the Gastrula **In the cleavage stage**, a series of mitosis forms a multicellular **blastula**. Then, cells migrate during the **gastrulation stage** to create the **gastrula**, which in vertebrates has three distinct germ layers, the ectoderm, the endoderm, and the mesoderm. ## Organogenesis ### Differentiation of germ layers During **organogenesis**, the germ layers differentiate into specific organ systems, followed by continuous growth and cell division. ## Monozygotic and Dizygotic Twins ### How is it possible? Sometimes, the zygote splits up during the first cleavage stage, resulting in **identical** or **monozygotic twins**. If two or more fertilization events result in two zygotes rising at the same time, it is said to be **fraternal** or **dizygotic twins**. ## Reproductive Organ Systems ### Sperm Production Sperm cells are produced in the **testis**, temporarily stored in the **epididymis** supported by the **scrotum**, and pass through the **vas deferens** before reaching the **urethra**, a passage for both urine and semen, that terminates in the opening at the tip of the penis. ### Important Glands of the Male Reproductive System The **seminal vesicle** creates a part of the semen that counteracts the acidity of the vagina to protect the sperm, while the **prostate** adds enzymes, lipids, etc. to the semen. **Bulbourethral glands** secrete the **pre-ejaculate** to lubricate and clear urine before semen passes. ### Parts of the Female Reproductive System The homologue of the penis is the **clitoris**, near the external opening which is the **labia**. The **vagina** is the main entrance to the female reproductive tract and ends in the **cervix**, a small passage to the **uterus**. ### Ovum Production to Morula to Blastula **Ovaries** make eggs which are released in ovulation and must be caught by the **fallopian tube**, the site of fertilization. A zygote grows to a solid blastula, called **morula**, then moved as a hollow blastula, or **blastocyst**, for implantation in the **endometrial lining**. ## Implantation and Gestation ### Embryo to Fetus to Infant **Implantation** signals the start of pregnancy, as the blastocyst grows into an embryo. After two months, the embryo becomes a fetus. **Gestation** is the stage of carrying the embryo/fetus inside the uterus. In humans, it takes nine months. ## The Menstrual Cycle ### The Ovarian Cycle The **menstrual cycle** lasts for about 28 days in the ovary and uterus. In the ovary, it consists of the **follicular phase**, where follicles in the ovary mature, and the **luteal phase**, as the matured oocytes (with egg) are released from follicles. ### The Uterine Cycle In the uterus, the **menstrual phase** is the “period” phase as the endometrium degenerates and sheds off; the **proliferative phase** is when endometrium heals; and, the **secretory phase** corresponds to the luteal phase to prepare for implantation. ## Contraception ### Blocking the stages of reproduction **Contraception** is a process blocking any of these stages of reproduction: - Release and transport of gametes - Fertilization - Implantation - Actual completion of development of the embryo/fetus ### Ovulation-suppressing methods Some contraceptives prevent the oocyte, or egg, to mature. **Oral contraceptives** like birth control pills prevent them from ovulating. ### Barrier and surgical methods prevent fertilization To prevent fertilization, a **condom** (penis), a **diaphragm** (cervix), or a **cervical cap** (cervix) are forms of barriers. There are also chemical means such as **spermicidal cream** (vaginal canal), killing sperm on contact, or surgical, **vasectomy** for men or **tubal ligation** for women. ### Implantation-suppressing methods Some contraceptives block the implantation of the blastocyst in the uterine wall, like the **intra-uterine device (IUD)**, or prevent implantatior by preventing the action of hormone that prepare the uterus to receive the embryo, like the **morning-after pill**. ### Behavioral methods **Abortion** is the deliberate removal of the embryo or fetus before it completes gestation. **Coitus interruptus**, known as withdrawal method, is ending intercourse before ejaculation. **Abstinence** is the practice of not engaging in sexual intercourse.