Global Indian International School Biology Past Paper 2024 PDF

Kuala Lumpur, Malaysia SEMESTER I NAME: _______________________ REF: 2024-25/ SCI /STD 10/ HO 09 CLASS: _______________ SUBJECT: Biology DATE: 16/08/2024...

Kuala Lumpur, Malaysia SEMESTER I NAME: _______________________ REF: 2024-25/ SCI /STD 10/ HO 09 CLASS: _______________ SUBJECT: Biology DATE: 16/08/2024 Topic: Sexual Reproduction in Animals Introduction: Sexual reproduction in animals: - In animals the fusion of male and female gametes occurs and the process is referred to as fertilization. In lower vertebrates like fish and amphibians etc. fertilization generally occurs outside the body of the female (external fertilization). In some animals and in humans it occurs within the body of the female (internal fertilization). Animals show different methods of production of young ones. In animals where embryonic development does not occur inside mother, they lay eggs, are called oviparous. However, in viviparous animals' embryo grows inside the mother and they give birth to young ones. Fundamentally, the process of fertilization results into the restoration of the diploid (2n) number of chromosomes. The zygote grows into an embryo and then to young organism of the next generation. Fertilization: - Fertilization is the process, which results in the fusion of the sperm with an ovum to form a single diploid (2n) cell called zygote. It can occur in the following two ways: Internal / External fertilization. BASIS FOR INTERNAL FERTILIZATION EXTERNAL FERTILIZATION COMPARISON Meaning The process of fusion of male The process of fusion of male and and female gamete (sperm and female gamete (sperm and egg) egg) taking place inside the taking place in the external body of the female, is called as environment (in water bodies) and internal fertilization. is called as external fertilization. Gametes Less number of gametes Numerous gametes (sperms I.e released (sperms) are released, which male and egg i.e female) are released into the environment. Page 1 of 9 Copyright © Global Indian International School  BASIS FOR INTERNAL FERTILIZATION EXTERNAL FERTILIZATION COMPARISON gets deposited inside the female body. Process involves Only male gametes are Both male and female release or released or discharged into the discharge their gametes into their female genital tract. external surrounding. Further process of development Further process of development (syngamy) occurs inside the (syngamy) occurs outside the body only. body. Examples Mammals (including humans), Amphibians, Algae, Fish, etc. Reptiles, Birds, Advantages 1. There are more chances of 1. The offspring produced are survival of offspring, as they get higher in number. parental care. 2. Less competition between 2. Even the rates of successful offspring and their parents. fertilization are much higher. 3. There are higher chances of success of survival of the offspring even in harsh condition. Disadvantages 1. The offspring produced are 1. Less chance of survival of the few. offspring, as there is no parental care, and they (offspring) get preyed upon. 2. Hence survival rate is low. 3. Can survive only in moistened or in the wet environment Human Reproductive System: The male reproductive system is a complex system, which develops, and functions under the influence of hormones. The reproductive organs become functional only after Page 2 of 9 Copyright © Global Indian International School attaining sexual maturity, which is reached at the age of 13 –14 years in males. The male reproductive system consists of a pair of testes, ducts, accessory gland and penis. 1. Testis: -In man and most other animals, the testes are two oval bodies suspended in a sac called scrotum, hanging from the lower wall of the abdomen. Human sperms cannot develop at a higher temperature found within the body cavity. Hence the testes are suspended outside the body. They require temperature that is 20-30 C lower than the normal body temperature. Testis also produces sperms and the male sex hormone called testosterone. Testosterone promotes development of accessory glands and controls secondary male sexual characteristics. 2. Epididymis: Epididymis is made up of a mass of small-coiled tubules that lies alongside the testes. Epididymis stores the sperms and makes them motile. Chemicals produced by the lining of the epididymis are essential for maturation of the sperm. 3.Vas deferens: It is the muscular tube that carries sperms from the epididymis and along with the secretion from the seminal vesicle joins the urethra to form the ejaculatory duct. The seminal vesicle secretes a viscous fluid, which is expelled along with the sperm. The mixture of this fluid and sperm is known as semen. 4.Prostate Gland: - This gland lies below the bladder. It discharges secretions directly into the urethra, which is alkaline in nature and contributes 15 – 30% of the total volume of the semen. The Prostate Gland also secretes mucus which is released during ejaculation and helps to neutralize the acidity of the vagina, making the sperm more active. 5.Cowper’s Gland: These paired glands are also attached to the urethra just below the prostate gland. The secretions of the gland make the sperm motile and nourishes them and neutralizes the acidic environment of the vagina Page 3 of 9 Copyright © Global Indian International School 6.Penis: - The penis is the external male genital organ. 7.Seminal Vesicles - It can be seen at the base of the urinary bladder. They secrete mucus and a watery alkaline fluid that contains nutrients, including the sugar fructose, which is an energy source for the sperm. Each seminal vesicle empties its contents into the ejaculatory duct, adding to the volume of the semen. Female Reproductive System: The female reproductive system consists of a pair of ovaries, oviduct (Fallopian tube), a uterus and the vagina. 1.Ovaries: - The human ovaries are two small almond like flattened bodies lying one on each side of the abdominal cavity. Ovaries produce female gamete ova and the female sex hormones such as oestrogen and progesterone. The ovary releases one ovum every 28 days (one menstrual cycle). 2.Oviduct (Fallopian tube): Close to each ovary is an expanded funnel shaped oviduct. Both oviducts are narrow tubes opening into the uterus. Its walls are lined with cilia, which sweeps the ovum towards the uterus. An ovum is produced and released from one of the two ovaries after every four weeks and it takes three days to travel down the oviduct to the uterus. If sperms are present, fertilization takes place in the upper end of the fallopian tubes. If the ovum is not fertilized, it is discharged during the next menstrual flow. Page 4 of 9 Copyright © Global Indian International School 3.Uterus: - It is a large, thick walled, pear-shaped muscular organ. It is connected to its either side to the fallopian tubes. The lower constricted portion of the uterus is called cervix. The body of the uterus has three coverings; the inner most is the endometrium. The endometrium is glandular, containing blood vessels and uterine glands. The cervix acts as a sphincter muscle that close the uterine cavity and prevents the foreign particles from entering into the uterus. 4.Vagina: It is large muscular tube that runs from the uterus to the outside. Vagina receives sperms from the male organ(penis). It also serves as a birth canal during the birth of the child. Menstrual Cycle: the cycle of events that take place in the female reproductive organs (ovary and uterus) under the control of sex hormones, every 28 days. It is marked by bleeding or menstrual flow and is called menstrual cycle. (1) Menstruation occurs in humans and in primates. (2) Menstruation is shedding of the inner lining of the uterus along with the disintegrated ova in the form of bleeding through the vagina of adult females. (3) Beginning of menstruation or first menstruation, usually between 11-13 years is called menarche. and stopping of menstrual flow at around 50 years of age is termed menopause. (4) The cycle of events starting from one menstruation till the next one is called Menstrual Cycle. (5) In human females, menstruation is repeated at an average interval of about 28/29 days. (6) One ovum is released (ovulation) during the middle of each menstrual cycle. LH hormone causes ovulation. (7) It is regulated by certain hormones (LH, FSH), which are secreted by the pituitary gland (8) The hormones produced by the pituitary gland influence the ovaries. The hormones secreted by the ovaries (oestrogen, progesterone) repair/cause the shedding of the walls of the uterus. EXTRA INFO Phases of Menstrual Cycle The menstrual cycle consists of following four phases: (1) Menstrual Phase: (i) In a 28 days menstrual cycle, the menses takes place on cycle days 3-5. (ii) The production of LH from the anterior lobe of the pituitary gland is reduced. Page 5 of 9 Copyright © Global Indian International School (iii) The withdrawal of this hormone causes degeneration of the corpus luteum and, therefore progesterone production is reduced. (iv) Production of oestrogen is also reduced in this phase. (v) The endometrium of uterus breaks down & menstruation begins. (vi) The cells of endometrium secretions, blood & unfertilised ovum constitutes the menstrual flow. (2) Follicular Phase: (i) This phase usually includes cycle days 6-13 or 14 in a 28 days’ cycle. (ii) The follicle stimulating hormone (FSH) secreted by the anterior lobe of the pituitary gland stimulates the ovarian follicle to secrete oestrogens. (iii) Oestrogen stimulates the proliferation of the endometrium of the uterine wall. (iv) The endometrium becomes thicker by rapid cell multiplication and this is accompanied by an increase in uterine glands & blood vessels. (3) Ovulatory Phase: (i) Both LH & FSH attain a peak level in the middle of cycle (about 14 th day). (ii) Oestrogen concentration in blood increases. Page 6 of 9 Copyright © Global Indian International School  (iii) Rapid secretion of LH induces rupturing of graffian follicle and thereby the release of ovum. (iv) In fact LH causes ovulation. (4) Luteal Phase: (i) Includes cycle days 15 to 28. (ii) It is post-ovulation phase, where the fate of the corpus luteum is decided. Corpus luteum secretes progesterone. (iii) If fertilization occurs, pregnancy starts. If fertilization doesn’t occur, it marks the onset of another cycle. Sperm ▪ A typical human sperm can be divided into three sections – head, mid-piece and tail ▪ The head region contains three structures – a haploid nucleus, an acrosome cap and paired centrioles ▪ The haploid nucleus contains the DNA ▪ The acrosome cap contains hydrolytic enzymes which help the sperm to penetrate the jelly coat of the egg ▪ The centrioles are needed by a zygote in order to divide. ▪ The mid-piece contains high numbers of mitochondria which provide the energy (ATP) needed for the sperm to move ▪ The tail (flagellum) is composed of a microtubule structure called the axonema, which bends to facilitate movement Egg ▪ A typical egg cell is surrounded by two distinct layers’ jelly coat and corona radiata ▪ The jelly coat acts as a barrier to sperm entry ▪ The corona radiata is an external layer of follicular cells which provide support and nourishment to the egg cell Page 7 of 9 Copyright © Global Indian International School BIRTH CONTROL AND CONTRACEPTION Contraception: - It is possible to limit the size of family through various means. It requires the use of methods which prevent the fertilization of ova. Fertilization of the egg and its implantation is referred to as conception or pregnancy. Prevention of conceptions is called contraception. There are several ways by which conception can be prevented. Contraception Methods: These methods involve prevention of fertilization. Contraception result in birth control and is the basis of family planning. Contraception may be natural or mechanical. a) Natural Methods of contraception: If copulation is avoided for a few days during the 3 days starting from the first day of ovulation (time period when the ovum is available in the uterus), fertilization can be avoided. This is called rhythm method of contraception. b) Mechanical methods of contraception: In this approach, various mechanical methods are used to prevent the passage of semen to the fallopian tube or to prevent implantation. Condoms: It is a thin rubber tube worn on the penis before sexual intercourse. The ejaculate gets collected in this tube and is not discharged into the vagina. This method is very effective in preventing STDs (Sexually transmitted Diseases), It is simple and has no side effects. Diaphragm or cervical cap: It is a large thin rubber hemisphere fixed on a flexible metal ring. It is fitted into the cervix in a woman’s body by a doctor to prevent the entrance of sperms into the cervical canal. Intra uterine device (IUD) or loop: It is a very effective method to avoid conception. IUD or loop is made of copper or stainless steel. For example, Copper- T is inserted in the uterus by a qualified physician. Its insertion causes certain secretion which prevents the implantation of embryo in the uterine wall. These can be placed for long periods up to 5 years. c) Chemical methods of contraception Spermicides: In this method, strong spermicidal (sperm-killing) creams, jellies are placed in the vagina before copulation, which kill the sperms and avoid fertilization. Oral contraception or pills: Oral contraception prevent ovulation in females. These pills should be taken daily. Birth control pills contain synthetic hormones resembling oestrogen and progesterone which prevent ovulation but allow monthly shedding of the uterine lining through menstrual bleeding. d) Surgical methods: It is a surgical procedure which involves removal of a small portion of the sperm duct, the cut ends are then ligated or tied by a thread. The sperms Page 8 of 9 Copyright © Global Indian International School will not be able to go past the tied point. This incision and subsequent ligation (tying by thread) of the vas deferens by a surgeon is called vasectomy. In women, ligation of the fallopian tube can be done (tubectomy) to prevent passage of ova down the fallopian tube. Sexually transmitted diseases: Diseases that spread through sexual contact are called sexually transmitted diseases (STD). Some sexually transmitted diseases are: 1. Acquired immuno deficiency syndrome (AIDS) 2. Syphilis 3. Gonorrhea Acquired immuno deficiency syndrome (AIDS) Acquired immuno deficiency syndrome commonly known as AIDS is caused by HIV virus (Human Immuno deficiency Virus) is probably the most common of sexually transmitted diseases. Transmission: It can pass from one person to another during sexual intercourse. This disease can also be transmitted through blood if blood from an infected person comes in contact with that of a healthy person through a cut, or a scratch or by means of blood transfusion. Sharing of syringes, razors, needles. It spreads fast and is an incurable disease that weakens the immune system of the infected person. Gonorrhea: Is caused by bacteria, Nisseria gonorrhea. This disease causes inflammation of the mucous membrane of the urogenital tract, rectum, throat and eye. It causes a burning sensation and pain during urination. It can be cured by antibiotics. Syphilis: Caused by bacteria, Treponema pallidum. It is a chronic illness which affects the mucous membrane in genital, rectal and oral regions. It can be cured by antibiotics. Page 9 of 9 Copyright © Global Indian International School