Reproduction Biology PDF

Reproduction Biology Definition and types Reproduction is the process that makes more of the same kind of an organism. There are 2 types of reproduction: asexual and sexual. Asexual reproduction: the process resulting in the production of genetically identical offspring fr...

Reproduction Biology Definition and types Reproduction is the process that makes more of the same kind of an organism. There are 2 types of reproduction: asexual and sexual. Asexual reproduction: the process resulting in the production of genetically identical offspring from one parent. formation of a new organism, without involvement of gametes or fertilisation. Asexual reproduction……Examples Bacteria Bacteria reproduce asexually by binary fission. Inside an individual bacterium, the DNA replicates. Then the cell divides into two, with each daughter cell containing a copy of the parental DNA. Once the daughter cells have grown, they can also reproduce. Asexual reproduction ……. Example Fungi Fungi can reproduce asexually by producing spores, which may be formed inside a structure called a sporangium. When ripe, the sporangium bursts open allowing the spores to be dispersed. In suitable conditions the spores germinate and grow to form new individuals.  Asexual reproduction …… Example Potatoes Potatoes are stem tubers. The parent plant photosynthesises and stores the food produced in underground stems, which swell to form tubers. Each tuber contains stored starch, and there are buds in depressions in the surface known as eyes. In suitable conditions the buds use the stored food to form shoots, form which roots also develop. Each tuber can form a new plant. Asexual reproduction….advantages and disadvantages Sexual reproduction Sexual reproduction: the process involving the fusion of haploid nuclei to form a diploid zygote and the production of genetically dissimilar offspring. OR formation of a new organism by the fusion of gametes (fertilisation) Sexual reproduction Video: Asexual Reproduction https://www.youtube.com/watch?v=jk2RJm5RBEk Video: Sexual Reproduction https://www.youtube.com/watch?v=tFZeyFbBLXE Video: Flower Reproduction https://www.youtube.com/watch?v=YqM6rgB_l_o Video: Sexual Reproduction in Flowering Plants https://www.youtube.com/watch?v=CkBNEM2mD30  Reproduction in plant Flowers are reproductive structures; In plants, the male sex cell is they contain the reproductive organs called pollen and the female of the plant. The male organs are the stamens, which produce pollen. The sex cell is called an ovule. female organs are the carpels. After fertilisation, part of the carpel becomes the fruit of the plant and contains the seeds. In the flowers of most plants there are both stamens and carpels. These flowers are, therefore, both male and female, a condition known as bisexual or hermaphrodite. Some species of plants have unisexual flowers, i.e. any one flower will contain either stamens or carpels but not both. Structure and functions of a flower You need to be able to describe the structure and functions of a named dicotyledonous (two seed leaves) flower. Structure and functions of a flower Pollination Pollination: transfer of pollen grains from the male part of the plant (anther) to the female part (stigma). Pollination can take place with the help of agents: wind or insects.  Insect pollination Insect Pollen often pollination sticky or has spikes to attach is the Nectar and a to insects transfer of scent present to pollen (by attract insects means of Anthers are firm sticking to an Sticky and positioned stigma to inside the flower; insect) from collect ideal location to the anther to pollen rub pollen onto the stigma of insects a plant. Stigma located inside flower; ideal location for Large brightly insect to deposit coloured petals to pollen onto. attract insects  Wind pollination is the transfer of Wind pollination pollen (by means of being blown in the wind) from the anther to the Pollen grains are very small and light so they stigma of a plant. can be carried easily by the wind. Anthers are exposed to Pollen produced in very the wind so that pollen can large numbers – to easily be blown away maximise chances of landing on a stigma. Stigma hang outside the flower and are feathery to catch pollen carried on wind Petals are small and green as there No scent or nectary as is no need to attract there is no need to attract insects insects Common misconceptio Insect and wind pollinated flowers ns Students often get confused between pollination and seed dispersal. When animals such as insects carry pollen, they aid pollination. When animal carry seeds, they Self and cross pollination Self-pollination - transfer of pollen from the anther to the stigma of the same flower, or to another flower of the same plant. Cross-pollination - transfer of pollen from the anther of a flower to the stigma of a flower on a different plant of the same species. Self-pollination ∙ increase chance of successful pollination as smaller numbers of pollen ∙ Increase chance of fertilisation and seed formation ∙ Decrease variation in the offspring. ∙ Decrease ability to adapt to environmental change. Self and cross pollination Cross-pollination decreases chance of successful pollination as large amounts of pollen may lost during the process decreases chance of fertilisation increases variation increases ability to adapt to environmental change. Growth of pollen tube and the process of fertilization Figure below shows a section If pollen grains are of the same species as the through a single carpel. flower they land on, they may germinate. Germination is triggered by a sugary solution on the stigma, an involves the growth of a pollen tube from the pollen grain. The pollen tube contains the male nucleus, which is needed to fertilise the ovule inside the ovary. The pollen tube grows down the style, through the ovary wall, and through the micropyle of the ovule. Fertilisation is the fusion of the male nucleus with the female nucleus. If the ovary contains a lot of ovules, each will need to be fertilised by a different pollen nucleus. Formation of seed The fertilised ovule divides by mitosis to form a seed containing the embryo plant and food stores called cotyledons. ∙ The wall of the ovule forms the seed testa (coat). ∙ The ovary wall develops into a fruit, which may be fleshy (e.g. plum) or a dry pod (e.g. lupin or pea). Structure of a non- endospermic seed  RECAP: Fertilisation After fertilisation the petals, stamen and sepals fall off. The ovary turns into a fruit, the ovule turns into a seed, the fertilised egg inside develops into an embryo plant. Fleshy wall seed of the ovary (yes, you are eating an adapted ovary when you crunch into an apple!) Seed structure Testa: tough seed coat Water enters the seed through the micropyle and activates enzymes. Plumule (embryo shoot) The water also softens the testa to allow it to split. Radicle (embryo root) Cotyledon (seed leaves): Micropyle: hole made by pollen tube starch store Germination Germination: is the process by which plants grows from a seedling in to new fruit or a flower  Germination and Whilst germinating the plant uses food stores in the cotyledon to energy provide energy for growth light The seedling can now photosynthesise and make its own food germination Plant growth and development soil Environmental condition for Germination 1.Water: ∙ absorbed through microphyle until radicle is forced out of testa ∙ activate enzymes for converting soluble food stores in the cotyledons down to soluble food ---> for growth + energy production of baby plant. Environmental condition for germination 2. Oxygen: respiration ---> release energy ---> growth 3. Warmth/temperature: enzymes present in the seed get activated and work best at optimum temperature (20-400C) which trigger growth in the baby plant. 4. Light intensity: high or very low light intensity does not allow enzymes to function normally. Seed dispersal Video: Seeds - An amazing video taken from BBC's The Private Life of Plants documentary series (MUST SEE). https://www.youtube.com/watch?v=buZV0h4vfmQ The flowers produce seeds which can be dispersed by the wind or other animals, providing a means of colonising new areas. 1. Wind-dispersed seeds ∙ Fruits contain seeds, and usually have a parachute or a wing to help them be carried away from the parent plant by the wind. ∙ Examples: dandelion, sycamore The dandelion fruit has a group of fine hairs called a pappus, which catches the wind and acts like a parachute. The fruit counterbalances the pappus. The sycamore has a wing with a large surface area. When the fruit drops off the tree it spins, slowing down in descent. If caught by the wind the seed will be carried away from the parent plant, reducing competition for nutrients, water and light. Seed dispersal 2. Animal-dispersed seeds There are 2 main modification of fruits for animal dispersal: succulent fruits and hooked fruits. Succulent fruits attract animals because they are brightly coloured, juicy and nutritious. When eaten, the seed pass through animal’s faeces, which may be a long way from the parent plant. The faeces provides nutrients when the seeds germinate. Hooked fruits catch on to an animal’s fur as it brushes past the parent plant. Eventually the seeds drops off, or the animal grooms itself to remove them. This disperses the seeds away from the parent plant.  Growth and development 1. Development Growth - - increase in complexity of an organism as it permanent grows. As the number of cells increases, they increase in size become differentiated (specialized for different tasks). and dry mass, by an increase in - change in shape to adapt for a specific function. cell number or cell Examples: size or both. - nerve cells are very elongated and can Development - transmit electrical impulses increase in - xylem cells are elongated and lose their cell complexity contents, with the cell walls becoming lignified so the cells conduct water efficiently. 2. Growth due to an increase in cells, produced by mitosis. controlled by hormones (in animals) and growth substance like auxins (in plants). Dry mass Often used as a measure of growth, because wet mass varies from day to day (e.g. plant will take up more water on a wet day than on a dry day, but the water does not all become part of the biomass – living material of the plant). Obtained by drying out the organism in an oven (killing it). Many individual have to be germinated at the same time and grown in the same conditions. Samples are dried at various times during the growth period.  Example: Changes of dry mass during the growth of a plant from a seed. - ↓ slightly when the seed germinates, at day 2 (some of the stores in the cotyledon are being used in respiration). - ↑ when the plumule stars to photosynthesise, and foliage leaves form to continue the process. - ↓ at the end of the growth period (loss of seeds and fruits; leaves die).  Reproduction in humans Reproduction in humans is when the male gamete (sperm) fuses together with the female gamete (ovum/egg). At first, it is just one single cell, which duplicates over and over until after 9 months…… TA-Dahh! - A baby is born! Male reproductive system Part Function epididymis a mass of tubes in which sperm are stored penis can become firm, to insert into the vagina of the female during sexual intercourse in order to transfer sperm prostate gland adds fluid and nutrients to sperm to form semen scrotum a sac that holds the testes outside the body, keeping them cooler than body temperature seminal vesicle adds fluid and nutrients to sperm to form semen sperm duct muscular tube that links the testis to the urethra to allow the passage of semen containing sperm testis male gonad that produces sperm urethra passes semen containing sperm Structure of the male reproductive system Female reproductive system Part Function cervix a ring of muscle, separating the vagina from the uterus funnel of oviduct directs an ovum (egg) from the ovary into the oviduct ovary contains follicles in which ova (eggs) are produced oviduct carries an ovum to the uterus, with propulsion provided by tiny cilia in the wall; also the site of fertilisation urethra carries urine from the bladder uterus where the foetus develops vagina receives the male penis during sexual intercourse; sperm are deposited here  Female reproductive system Video: Human Body Systems - Reproductive System https://www.youtube.com/watch?v=GArALyhGtfQ Comparing both cells Production of gametes Sperm production - The lining of the sperm-producing tubules in the testis consists of rapidly dividing cells (Figure 16.45). After a series of cell divisions, the cells grow long tails called flagella (singular: flagellum) and become sperm (Figure 16.46). Which pass into the epididymis. During copulation, the epididymis and sperm ducts contract and force sperm out through the urethra. The prostate gland and seminal vesicle add fluid to the sperm. This fluid plus the sperm it contains is called semen, and the ejection of sperm through the penis is called ejaculation.  Ovulation The egg cells (ova) are present in the ovary from the time of birth. No more are formed during the female’s lifetime, but between the ages of 10 and 14 som the egg cells start to mature and are released, one at a time about every 4 weeks from alternate ovaries. As each ovum matures, the cells around it divide rapidly and produce a fluid-filled sac. This sac is called a follicle (Figure 16.47) and, when mature, it projects from the surface of the ovary like a small blister (Figure 16.48). Finally, the follicle bursts and releases the ovum with its coating of cells into the funnel of the oviduct. This is called ovulation. From here, the ovum is wafted down the oviduct by the action of cilia (see ‘Levels of organisation’ in Chapter 2) in the lining of the tube. If the ovum meets sperm cells in the oviduct, it may be fertilised by one of them. Menstrual cycle The menstrual cycle in women is a recurring process in which the lining of the uterus is prepared for pregnancy, and if pregnancy does not happen, the lining is shed at menstruation. The cycle lasts about 28 days.  Menstrual cycle Several hormones control this cycle: 1. Menstruation Usually, one egg is released from an ovary every month. Before the egg is released, the lining of the uterus becomes thick and spongy to prepares for a fertilised egg. It is full of tiny blood vessels, ready to supply the embryo with food and oxygen if it should arrive. If the egg is not fertilised, it is dead by the time it reaches the uterus. Is does not sink into the spongy wall, but continues onwards, down through the vagina. As the spongy lining is not needed now ---> it gradually disintegrates and is slowly lost through the vagina. This is called menstruation, or period and it last for about 5 days. 2.ovulation Formation of the foetus - fertilisation, implantation After sexual intercourse, sperms swim through the cervix and the uterus into the oviducts, where they meet an egg. One sperm may fertilise the egg to produce a zygote. After ovulation, the egg is caught in the funnel of the oviduct. Very slowly, the egg travels towards the uterus. If the egg is not fertilised by a sperm within 8-24 hours after ovulation, it will die. By this time, it has only traveled a short way along the oviduct. So a sperm must reach an egg while it is quite near the top of the oviduct if fertilization is to be successful. 1. Sexual intercourse involves inserting the erect penis into the vagina. ∙ When stimulated, spongy tissue in the penis filled with blood and becomes erect. ∙ At the climax, semen is ejaculated from the penis into the neck of the vagina. ∙ Muscles in the wall of the sperm duct help to propel the semen forward ∙ The sperms with their tails swim from the vagina, through the cervix and uterus, into an oviduct. 2. Fertilisation happens in the oviduct ∙ ovum/egg pass down in oviduct ∙ a single sperm penetrates the membrane of ovum by secreting a protease enzyme; only the head of the sperm goes in, the tail is left outside. the sperm nucleus and the egg nucleus fuse to form a diploid zygote = fertilization sperm can remain active in the oviduct for at least 2 days and the ovum may take a day to pass from the ovary to the uterus, so there is a fertile period of 3 to 4 days around ovulation 3. The zygote implants in the uterus wall ∙ the zygote moves slowly down the oviduct. As it goes, it divides by mitosis. it takes several hours for the embryo to reach the uterus, and by this time it is a ball of 16 or 32 cells (a blastocyst). the uterus has a thin, spongy lining, and the embryo sinks into it = implantation.  The development of the foetus The blastula develops into an embryo and some of the cells form a placenta, linking the embryo with the uterus lining. Organs such as the heart develops and, after 8 weeks, the embryo is called a foetus. Growth of the foetus requires a good supply of nutrients and O2. This is achieved through the link between the placenta and the mother’s blood supply in the uterus lining. The placenta is soft and dark res, and has finger like projections called villi. The villi fit closely into the uterus wall. 1. Umbilical cord ∙ joins foetus to placenta; contains: ∙ 2 arteries: blood from foetus ---> placenta ∙ 1 vein: returns blood ---> foetus 2. An amnion protects the foetus The foetus is surrounded by a strong membrane, called amnion. Inside the amnion is a liquid called amniotic fluid. Amniotic sac: membrane from embryo cells: encloses fetus, prevents entry of bacteria Amniotic fluid: supports, protects fetus from mechanical damage; absorbs urine released by fetus.  Brings blood supply of foetus close to 3. mother’s Placenta ∙ Blood from the foetus passes through the umbilical cord in the umbilical artery to the placenta. ∙ Here it comes close to the mother's blood. ∙ transport O2 + nutrients (amino acids, glucose…) from mother ---> Prevents mixing foetus This is really important because the foetus and ∙ transport CO2 + wastes (urea… ) from mother may have different blood groups - any mixing foetus --->mother could result in blood clotting, which could be fatal (through umbilical to both mother and foetus. vein). Antenatal care Antenatal (before birth) care is a routine care for the healthy pregnant woman. 1. Dietary needs Before the baby is born, it obtains all its dietary requirements from its mother through the placenta. The mother’s diet needs to be balanced so that’s the fetus receives all the materials needed for healthy growth and development. If the mother’s diet is deficient in any nutrients, the bay may not develop properly. So her diet should contain plenty of: 2. Exercise ∙ amino acids ---> healthy grow and development ∙ gentle exercise (swimming, ∙ calcium ---> development of the skeleton walking…) ∙ special exercises ∙ iron ---> red blood cell formation ∙ energy (carbohydrates/ fats) – help to move mother’s heavier body. 3. Things to avoid ∙ drugs: aspirin, heroin ∙ smoking: nicotine and CO ∙ alcohol drinking ∙ viruses: HIV, rubella (can pass across the placenta, risking the foetus health). Process of birth Birth begins when the strong muscles in the wall of the uterus start to contract. This first stage of birth (called labour) is triggered by the hormone oxytocin. Stages of Birth Stage 1 The muscular walls of the uterus start to contract, slowly stretch the opening of the cervix. The pressure breaks the amniotic sac, releasing the amniotic fluid. Contraction gradually become more frequent, pushing the baby down towards the cervix, which become dilated to allow baby to pass through. Stage 2 The vagina stretches to allow the baby to be born. Stage 3 The baby is still attached to the placenta by the umbilical cord, so this is cut and tied. The placenta breaks away form the wall of the uterus and passed out (afterbirth). Process of birth 1. Labour – triggered by hormone oxytocin 2. Muscular walls of the uterus start to contract 3. The pressure breaks the amniotic sac 4. Contractions become more frequent pushing the baby down towards the cervix 5. Cervix becomes dilated to allow the baby to pass 6. The vagina too stretches for the placenta by the umbilical cord Sex hormones Sex hormones (testosterone in boys and oestrogen in girls) are responsible for the development of secondary sexual characteristics at puberty. Puberty - the sex organs (ovaries in girls, testes in boys) become mature and start to secret hormones, making gametes (ova and sperms) - happens at about 10-14 years. Method of birth control 1. Natural methods 2. Chemical methods Method of birth control 3. Mechanical methods  4. Surgical methods Source: Letts Revise IGCSE - Biology:Complete Study and Revision Guide Artificial insemination, hormones in fertility drugs An artificial insemination procedure uses a thin, flexible tube (catheter) to put sperm into the woman's reproductive tract (vagina, cervix, uterus) around the time of ovulation. For some couples with infertility problems, insemination can improve the chances of pregnancy. Artificial insemination If the problem causing the couple's infertility is in the man (he may not be producing healthy sperms), then sperms from a donor is collected in a clinic, and can be stored at a low temperature for many months or even years. The woman can then attend the clinic, and some of the sperms can be placed into her reproductive tract. Use of hormones in fertility drugs Fertility drugs are used when the woman is not producing enough eggs. She is given hormones, including FSH and LH, that cause multiple release of eggs. - The eggs can be allowed to be released into the oviduct in the normal way. - If the woman has a problem with blocked oviducts, the eggs are removed from her ovaries just before they are due to be released, and placed in a warm liquid in a Petri dish. Some of her partner sperms are added, and fertilization takes place in the dish. 2 or 3 of the resulting zygotes are placed into her uterus, where they develop in the usual way. This is called In vitro fertilization (IVF). Problems: - The treatment is quite expensive, and not always successful. Some argue that the it should not be freely available to anyone who wants it. Other think that the inability to have children can be so devastating to a couple that they should receive the treatment free of charge. - Sometimes 2 or 3 embryos develop, so the couple might have twins or triplets when they really only wanted one child. Breastfeeding vs formula milk? This has been a tough question for many years: Which is better - breast milk or formula milk? While breast milk is nutritious, it has its inconveniences. Formula milk is convenient but expensive. What to choose? Video: Breastfeeding vs bottle feeding - DrTummmy.com https:// www.youtube.com/ watch?v=XPi0odcvegM HIV/ AIDS - transmission and prevention methods AIDS (Acquired Immune Deficiency Syndrome) is a disease caused by the HIV. HIV can not live outside the human body. It is an especially fragile virus - much less tough than the cold virus. It is transported in body fluids. You can only become infected with HIV through direct contact of your body fluid with those of someone with the virus. How HIV affects the immune system ∙ The HIV virus attacks some types of lymphocyte (white blood cells) in the bloodstream. ∙ Lymphocytes produce antibodies ---> attack the antigens on invading microbes. ∙ Some lymphocytes are stored in lymph nodes ---> protection against future infection. ∙ HIV prevents this immunity being retained, so the AIDS sufferer has no protection against diseases such as tuberculosis (TB) and pneumonia. HIV/ AIDS - transmission and prevention methods Methods of transmission: ∙ unprotected sexual intercourse with infected person ∙ drug use involving sharing needle used by infected person ∙ transfusion of infected blood ∙ infected mother to fetus ∙ feeding a baby with milk from an infected mother ∙ unsterilised surgical instruments Prevention methods ∙ condom for sexual intercourse ∙ refuse sexual intercourse ∙ screen blood (for transfusion) ∙ use sterilized needles ∙ feed baby with bottled powdered milk (if mom has HIV) ∙ use sterilised surgical instruments. Video: How is HIV Transmitted? https://www.youtube.com/watch?v=z8BwYFlTAGY Video: How to prevent HIV transmission? https://www.youtube.com/watch?v=NXnvP_sKS9k  Gonorrhoea Gonorrhoea is caused by bacteria that can be passed from one person to another during sexual intercourse. Neisseria bacterium is a small, round cell. It can only survive in moist places, such as tissues lining the tubes in the productive systems of a man and a woman. Symptoms ∙ If gonorrhoea bacteria are living in a woman’s vagina or a man’s urethra, the infection can be passed during sexual intercourse. ∙ The first symptoms occurs 2-7 days after infection. ∙ Man: the bacteria reproduce inside the urethra ---> unpleasant discharge and pain when urinating. ∙ Woman: the bacteria reproduce mostly in the cervix, although they can also do so in the vagina ---> many woman do not notice discharge or suffer a pain as men do. ∙ Most men with gonorrhoea know that they have it, many women are unaware that they have the infection. Gonorrhoea