Reproduction strategies in Vertebrates and Human reproduction Gr.12 Life Sciences Reproduction strategies in Vertebrates and Human reproduction

REPRODUCTION STRATEGIES IN VERTEBRATES NAME THE TWO TYPES OF FERTILISATION: EXTERNAL INTERNAL

REPRODUCTION STRATEGIES OVOVIVIPAROUS The eggs hatch within the mothers body and the young are born. No eggs are laid. For example sharks.

OVOVIVIPAROUS DEFINE THIS TERM AND NAME 2 ADVANTAGES Refers to animals that do not lay eggs , but keep them in their bodies until they hatch. The body temperature is necessary for them to hatch. There is no connection between the embryo and the mother. Examples : Sharks , lizards cockroaches and some snakes ADVANTAGES : The young one is protected from cold and predators to ensure survival The young one can develop to a fairly large size before birth

VIVIPAROUS DEFINE THIS TERM AND NAME 2 ADVANTAGES AND 2 DISADVANTAGES Refers to animals that give birth to live young ones. There is a connection between the developing foetus and the mother. Examples : Human beings, whales and kangaroos. Advantages : The temperature is regulated by the mother The mother provides nutrition for the young one Mortality rate is lower Disadvantages : Number of off springs produced is few. More energy is used to provide parental care.

OVIPAROUS DEFINE THIS TERM, NAME 2 ADVANTAGES AND A DISADVANTAGE: Refers to egg laying animals Eggs are protected by a hard shell while others are protected by a jelly like layer after fertilisation. Development does not occur inside the body The development of an organism is completed inside the egg after it has been aid Examples: Frogs, insects, birds and marine animals Advantages: Eggs and sperm cells are produced in large numbers to increase chances of survival to adulthood. Much energy is invested for parental care. Parental care ensures survival to adulthood.

Amniotic egg

Precocial and Altricial development

PARENTAL CARE

HUMAN REPRODUCTION

The male reproductive system Name the functions of the following labels:

The male reproductive system Testes are responsible for producing sperm and testosterone. Epididymis is where sperm are stored and mature. Vas deferens or sperm ducts transport sperm to urethra / penis. Urethra conducts sperm into female body. Penis is the organ for copulation and places the semen inside the vagina Seminal vesicles add fluid to semen, which contains fructose (sugar) that provides energy to sperm. Prostate glands add fluid to semen, which contains enzymes to make the sperm more active. Cowper’s gland adds mucus (fluid) to semen, which neutralise any acidity in the urethra

TESTES Septum separates testis into compartments. Seminiferous tubules are where the sperm is produced during spermatogenesis.

PUBERTY IN MALES Stimulated by testosterone Growth of male sex organs Start of the production of sperm cells Growth of pubic hair, facial hair and body hair Development of muscles and deepening of voice

SPERM CELL

SPERMATOGENESIS Gametogenesis is the process responsible for producing gametes. Spermatogenesis is the process responsible for producing sperm cells. Epithelial cells in the testes undergo mitosis to form diploid spermatocytes Each diploid spermatocyte in the seminiferous tubules of the testes undergoes meiosis Four (4) haploid spermatids are formed Each spermatid matures to form a haploid sperm cell/spermatozoan

QUESTION 1 ON MALE REPRODUCTIVE SYSTEM 1.Study the diagrams below and answer the questions on the right hand side : 1.1. Provide labels for A, B, E and G (4) 1.2. State ONE function each of C and F, respectively. (2) 1.3.State the LETTER and NAME of the part where sperms are produced. (2) 1.4. Explain why it is necessary for part D to 'hang outside' the body of the male. (2) 1.5. Name the following: (a) The cells that secrete a male sex hormone (1) (b) The hormone that stimulates the development of secondary sexual characteristics in males (1) 1.6. During a vasectomy, part B is surgically cut. Explain how this procedure will act as a method of contraception. (2)

ANSWERS ON QUESTION 1 MALE REPRODUCTIVE SYSTEM 1.1.A - prostate gland B - vas deferens / sperm duct E - urethra G - nucleus   1.2. C - Stores sperms temporarily/sperms mature here F - Contain enzymes to break down the cell membrane of the egg cell 1.3. D - testis /seminiferous tubules 1.4. To keep the testes at a temperature that is (about 3˚ C) lower than body temperature A lower temperature is necessary for the production of healthy sperm /so that healthy sperms can survive

ANSWERS ON QUESTION 1 MALE REPRODUCTIVE SYSTEM 1.5. (a) Interstitial cells/Cells of Leydig (b) Testosterone   1.6. Severing of the vas deferens Will not allow sperms to pass to urethra and into the female and hence no fertilisation results.

QUESTION 2 ON MALE REPRODUCTIVE SYSTEM 2. The diagram on the left represents a cross-sectional view of a human seminiferous tubule in which spermatogenesis is occurring. Study the diagram and answer the questions that follow. 2.1.Name the hormone produced by the cells of Leydig. (1) 2.2.Name TWO functions of the hormone named in QUESTION 1. (2) 2.3. Identify part labelled A. (1) 2.4.Make a neat, labeled diagram of part A. (4)

ANSWERS ON QUESTION 2 MALE REPRODUCTIVE SYSTEM 2.1. Testosterone 2.2. Stimulates the development of primary male sex organs/ penis and testes Stimulates the development of secondary male characteristics / growth of body hair/muscle development/ deep voice 2.3 spermatozoa/ sperm cell 2.4  

FEMALE REPRODUCTION SYSTEM NAME THE FUNCTIONS OF THE FOLLOWING LABELS:

FEMALE REPRODUCTION SYSTEM Fallopian tube: connect ovaries to the uterus, site of fertilisation, transport egg cells from the ovaries Ovaries: releases egg cell, secretes oestrogen and progesterone Uterus: carries embryo and foetus during pregnancy Endometrium: inner lining of uterus, place where embryo implants and placenta forms Cervix: lower narrow part of uterus, it stretches to allow baby through during childbirth Vagina: receives the penis and semen during sexual intercourse, the passage through which baby is born

PUBERTY IN FEMALES Stimulated by oestrogen Growth of female sex organs Start of the menstrual cycle and production of ova Growth of pubic hair Growth and development of breasts and widening of hips

Start with primary oocyte OOGENESIS Ovum Secondary oocyte Primary oocyte First polar body Polar body Oogonium mitosis Meiosis 1 Meiosis 2 The creation of an ovum. Start with primary oocyte Meiosis 1 results in secondary oocyte + first polar body Meiosis 2 results in ovum and second polar body Meiosis 2 will only be complete if fertilisation takes place.

HORMONES RESPONSIBLE FOR MENSTRUAL CYCLE GLAND/ STRUCTURE FUNCTION Follicle Stimulating Hormone (FSH) Pituitary Gland In females, stimulates development of a follicle in the ovary. Luteinizing Hormone (LH) In females, causes ovulation. Stimulates empty Graafian follicle to develop into corpus luteum. Oestrogen Primary follicle/Graafian follicle inside ovaries Stimulates the endometrium to thicken in preparation for implantation of a fertilized ovum. Stimulates pituitary gland to secrete LH. Inhibits secretion of FSH so that no further follicles are produced. Progesterone Corpus Luteum Maintains endometrium. Prevents pituitary gland from producing FSH and LH.

MENSTRUAL CYCLE Follicular phase FSH starts the development of a few primary follicles. The development of the follicle is through a process of oogenesis. Usually only one follicle matures.(takes about 10 days) This follicle produces oestrogen. Oestrogen causes endometrium to thicken & to be vascular.

DESCRIBE THE PROCESS OF OVULATION: is the release of an egg (ovum) from the ovary after the breaking of a mature Graafian follicle. It is stimulated by high level of LH in the blood. Ovulation usually occurs on the 14th day following the first day of the last menstrual period.

HORMONAL CONTROL

MENSTRUAL CYCLE

CHANGING HORMONE LEVELS DURING MENSTRUAL CYCLE

QUESTIONS ON FEMALE REPRODUCTIVE SYSTEM 1. Study the diagram below showing the sequence of events of the development of an ovum in a 28-day cycle. 1.1 Identify the following: (a) Follicle labelled A (1) (b) Structure labelled C (1) (c) Process shown at B (1) (d) Hormone responsible for the formation of part A (1) (e) Hormone responsible for the formation of part C (1) 1.2 What type of cell division resulted in the formation of part D? (1) A C B D 1.3 If the events shown above took place in a 28- day cycle, state whether fertilisation took place during this period. (1) 1.4 Explain your answer to QUESTION 1.3. (3) 1.5 Explain HOW and WHY the production of FSH is inhibited when fertilisation takes place. (4)

QUESTIONS ON FEMALE REPRODUCTIVE SYSTEM STUDY GRAPH ON LEFT AND ANSWER QUESTIONS: 2.1. On which day does ovulation take place? (1) 2.2 Between which days does menstruation take place? (1) 2.3 State any ONE function of luteinising hormone (LH). (1) 2.4 Describe the changes in the level of LH shown in the graph. (3) 2.5 Describe the relationship between the level of oestrogen and the endometrium from day 7 to day 14. (2) 2.6 Explain why it is necessary for the level of progesterone in the blood to increase after ovulation. (2)

ANSWERS FEMALE REPRODUCTIVE SYSTEM 1.1 (a) Graafian follicle (b) Corpus luteum (c) Ovulation (d) FSH (e) LH 1.2 Meiosis 1.3 No 1.4 If fertilisation occurred the corpus luteum would stay intact and not be destroyed. 1.5 If fertilisation occurs high levels of progesterone enters the blood. The high levels of progesterone inhibits the production of FSH Low levels of FSH stop the development of a ovum inside a Graafian follicle No ovulation occurs when the individual is pregnant

ANSWERS OF QUESTION 2 2.1. day 14 or day 15 2.2 Days 0 – 7   2.2 Days 0 – 7 2.3 - Causes the follicle to burst open/stimulates ovulation - Stimulates the formation of the corpus luteum 2.4 - LH levels remain low up to day 12/13 - Then it increases sharply up to day 14 - After which it decreases and remains low 2.5 As the oestrogen level increases the thickness of the endometrium also increases    2.6 Maintain the increase in the thickness of the endometrium for greater chance of implantation

FERTILISATION

FERTILISATION FOUR MAJOR STEPS: Sperm contacts the egg Sperm or its nucleus enters the egg Egg becomes activated and developmental changes begin Sperm and egg nuclei fuse

WHAT HAPPENS AFTER FERTILISATION Development of the zygote. The zygote undergoes a series of mitotic cell divisions called cleavage. The stages of development are: Fertilized ovum (zygote)  2-cell stage  4-cell stage  8-cell stage  Morula  Blastula

WHAT HAPPENS AFTER FERTILISATION: TWO CELL STAGE DIVIDES FOUR CELL STAGE

WHAT HAPPENS AFTER FERTILISATION: MORULA DIVIDES BLASTULA

DEVELOPMENT OF PLACENTA EXPLAIN THE IMPORTANCE OF THE PLACENTA AND HOW IT IS FORMED: The placenta is the site of nutrient, gas, and waste exchange Secretes hormones that maintain pregnancy The placenta develops from the embryonic chorion and maternal uterine tissue Chorionic villi are formed from the chorion, and project into the endometrium of the uterus

Umbilical vein carries oxygenated blood from placenta towards embryo UMBILICAL CORD DESCRIBE THE STRUCTURE OF THE UMBILICAL CORD AND THE FUNCTION OF THE ARTERIES AND VEIN The umbilical cord, containing two umbilical arteries and one umbilical vein connects the embryo and the placenta Umbilical arteries carries deoxynated blood from embryo towards placenta Umbilical vein carries oxygenated blood from placenta towards embryo

IMPLANTATION It takes five to seven days to reach the uterus after fertilisation took place Implantation is when the embryo settles on the endometrium and sinks into it

DEVELOPMENT OF PLACENTA

Human Foetus at Ten Weeks

QUESTION ON GESTATION 1.1 Provide labels for A and B. (2) C The human foetus A B 1.1 Provide labels for A and B. (2) 1.2 Explain ONE way in which the part labelled B is structurally adapted for its function. (2) 1.3 List TWO functions of the fluid found at C. (2)

ANSWERS ON QUESTION 1 GESTATION 1.1 A - Umbilical cord B - Placenta   1.2 - Has folds/villi to enlarge the surface area - Enriched with blood vessels for transport of gases/nutrients/ waste products - Selective permeable membranes to promote diffusion of gases/ substances - Contains blood sinuses to bring blood of mother in close association with that of foetus 1.3 - acts as a shock absorber/prevents mechanical damage - prevent great variation in temperature - allows for movement of the foetus - passes out before birth to lubricate the birth canal

2.1 Provide the labels for parts A, B and D. (3) QUESTION 2 ON GESTATION A B C D E 2.1 Provide the labels for parts A, B and D. (3)   2.2 Describe the function of E during the birth process. (2) 2.3 State what happens to the level of progesterone after birth. (1)

ANSWERS QUESTION 2 GESTATION 2.1 A – Placenta / Chorionic villi  B – Umbilical Cord D – Cervix  (3)   2.2 Contraction of the muscular wall of the uterus pushes the foetus out/ placenta and umbilical cord/ after birth (2) 2.3.Progesterone level drops as the pregnancy stage is completed (1)