Reproduction

DEFINITIONS

Reproduction: It is a fundamental evolutionary process ensuring the continuity of life.

Reproductive success: The ability of an organism to produce fertile offspring that survive to reproductive maturity and produce offspring of their own.

Biological fitness: Measure of an individual’s reproductive success.

It is the average contribution to the gene pool of a certain genotype in the population and the likelihood of those alleles being represented in the future generation.

Allele: It is a variant of a gene. Either the same form or a different form of gene.

Gametes:

Two special sex cells

carry genetic information from both parents to the offspring

Diploid: cells that contains two sets of chromosomes

Haploid: cells that contain only one set of chromosomes</li><li>Somatic cells: non-reproductive cells (two sets of chromosomes)</li><li>zygote: result of the fusion of haploid gametes when the chromosome number changes from haploid to diploid</li><li>Fertilization: The process of the fusing of gametes to give rise to a zygote and initiating its developmental stage into a new organism.</li><li>Non-motile: organisms that are not able to move on their own</li><li>Hermaphrodites: a sexually reproducing organism that produces both male and female gametes.</li><li>Reproductive strategies: behavioral, physiological and physical adaptations that facilitates access to potential mates to improve chances of fertilization and mating and increases reproductive success.</li><li>Internal fertilization: the fusion of male and female gametes occurs outside the body</li><li>External fertilization: the fusion of male and female gametes occurs inside the body.</li><li>Oviparous: producing young by means of eggs which are hatched after they have been laid by the parent (internal fertilization)</li><li>Viviparous: giving birth to living young, matured in the female’s body, from within the body rather than laying eggs obtaining nutrients from the placenta</li><li>ovo-viviparous: producing eggs that develop within the maternal body and hatch within or immediately after being released from the parent.</li><li>copulation: sexual intercourse.</li><li>embryonic diapause: an early-stage embryo refrains from implanting in the mother’s uterus, where it could be nourished to grow into a baby.</li><li>Pollination agents: external agents that carry the gametes from one parent to another.</li><li>Pollination: the male gametes inside the pollen being carried from the anther to the female part of a flower (stigma)</li><li>alternation of generations: a mechanism that involves alternating between sexual and asexual reproduction as a normal part of their life cycle.</li><li>sporangia: produces huge number of</li><li>gonadotropic hormones: main function is to help our sex glands mature and function</li><li>menarche: the first menstrual period in a female adolescent</li><li>endometrium</li></ol><h2 collapsed="true" seolevelmigrated="true">SEXUAL VS ASEXUAL REPRODUCTION</h2><ol><li>What is the difference between reproductive success and biological fitness?<ul><li>reproductive success is a feature of the organism</li><li>biological fitness is a feature of an allele in a population.</li></ul></li><li>Asexual reproduction:<ul><li>involves one parent</li><li>genetically identical offsprings (each other and the parent)</li></ul></li><li>Sexual reproduction:<ul><li>involves two parents</li><li>mix of the parents</li><li>different from each other and the parent</li></ul></li><li>Self-fertilization:<ul><li>bisexual organisms</li><li>sexual reproduction from one parent</li></ul></li></ol><table style="min-width: 398px"><colgroup><col style="width: 186px"><col style="width: 187px"><col></colgroup><tbody><tr><td colspan="1" rowspan="1" colwidth="186">Type of Reproduction</td><td colspan="1" rowspan="1" colwidth="187">Advantage</td><td colspan="1" rowspan="1">Disadvantages</td></tr><tr><td colspan="1" rowspan="1" colwidth="186">Sexual</td><td colspan="1" rowspan="1" colwidth="187"><ul><li>offspring - a mix of parental genes and not genetically identical to each other or the parents</li><li>leads to genetic variation in the population</li><li>random variation causes natural selection</li><li>genetically better suited to changing environmental conditions</li><li>Gaining a selective advantage changes the genetic makeup of the population to increase survival.</li></ul></td><td colspan="1" rowspan="1"><ul><li>greater expenditure of time and energy</li><li>finding a mate, courtship behavior, gamete production, and mating</li><li>organisms feel vulnerable to predators as it takes more investment</li></ul></td></tr><tr><td colspan="1" rowspan="1" colwidth="186">Asexual</td><td colspan="1" rowspan="1" colwidth="187"><ul><li>no mates required</li><li>reproduction is rapid</li><li>large number of organisms in very less time</li><li>positive genetic influences pass on to successive generations</li><li>occurs in various environment</li></ul></td><td colspan="1" rowspan="1"><ul><li>lack of diversity as the offsprings are identical to both the parent and each other</li><li>the diversity is limited</li><li>unable to adapt to the changing environment due to lack of variation</li><li>single change in environment may eliminate the whole species</li></ul></td></tr></tbody></table>Sexual Reproduction:<ol><li>How is a genetic variation introduced in the gene pool of the population: — advantage (continuity of life through genetic variation)<ul><li>gametes fuse in sexual reproduction</li><li>they carry different genetic data from the parents</li></ul></li><li>Natural selection and sexual reproduction</li><li>Disadvantage</li></ol>Sexual reproduction process:<img src="https://knowt-user-attachments.s3.amazonaws.com/e1424545-736e-4724-a3ef-dfaf33e25023.png" data-width="50%" data-align="center" alt="sexual reproduction process."><ol><li>every species has a characteristic number of chromosomes</li><li>humans - 46 chromosomes</li><li>each set of chromosomes has a homologous pair (each have the same genes in the same order)</li><li>Meiosis to form gametes:<ul><li>cell division taking place in the reproductive organs of plants or animals</li><li>maintains the characteristic chromosome number during sexual reproduction</li><li>prevents the doubling of chromosomes in each generation</li></ul></li><li>the chromosome number is halved - each contains only one set of chromosomes</li><li>1 set from the mother (maternal chromosomes) and 1 set from the father (paternal chromosomes).</li><li>they fertilize into a zygote</li><li>chromosome number changes from haploid to diploid</li><li>diploid cell divides by mitosis to become an embryo with identical body cells</li><li>Human cells:<ul><li>somatic cells n=46 (diploid)</li><li>germ cells n=23 (haploid)</li></ul></li><li>fertilization of an egg restores the diploid number.</li></ol><h2 collapsed="true" seolevelmigrated="true">SEXUAL REPRODUCTION IN ANIMALS</h2><ol><li>Advantage in animals:<ul><li>It is a mechanism that has evolved to ensure continuity of life</li><li>the number of sexual reproductive strategies ensures that reproduction occurs effectively in the environment in which the organism lives For Example in:</li></ul>Hermaphrodites:<ul><li>bisexual organism</li></ul><ul><li>both male and female reproductive organs</li><li>Advantage:— Do not get affected by low population densities of the species— in non-motile animals like corals</li><li>Disadvantage:— large energy expenditure to grow and maintain two sets of reproductive organs— during self-fertilization gametes carry fewer possible combinates of genes thus less variation.</li></ul>Other Examples:<ul><li>internal external fertilization</li><li>number of gametes produced</li><li>timing of the gametes released</li><li>where the organism develops</li><li>nature of paternal care</li></ul></li></ol>Fertilization (external or internal):<ol><li>In what organisms is external fertilization better suited to organisms and why?<ul><li>in aquatic environment or in moist environment</li><li>for successful fertilization requires gametes (haploid cell surrounded by a cell membrane) meet and not dehydrate in the process</li></ul></li><li>In what organisms is internal fertilization better suited to the organisms and why?<ul><li>terrestrial organisms</li><li>organisms internally fertilize as that keeps the eggs from getting dehydrated on the land</li></ul></li><li>External fertilization features:<ul><li>the success rate of fertilization is low</li><li>a large number of gametes are produced by the male and female to ensure reproductive success</li><li>water body is required to avoid dehydration</li><li>most of the gametes die due to Un fertilization</li><li>simple reproductive strategy thus does not require the involvement of any hormones or mating rituals</li></ul></li></ol><ol><li>How are the chances of successful external fertilization increased?<ul><li>synchronization of reproductive cycles</li><li>mating behaviors</li><li>release of gametes</li></ul></li></ol><img src="https://knowt-user-attachments.s3.amazonaws.com/ca75d30b-283b-477e-b13d-5ea75e0df02e.png" data-width="100%" data-align="center" alt="comparison between internal and external fertilization "><table style="min-width: 442px"><colgroup><col style="width: 157px"><col style="width: 260px"><col></colgroup><tbody><tr><td colspan="1" rowspan="1" colwidth="157">Type of Fertilization</td><td colspan="1" rowspan="1" colwidth="260">Advantage</td><td colspan="1" rowspan="1">Disadvantages</td></tr><tr><td colspan="1" rowspan="1" colwidth="157">Internal</td><td colspan="1" rowspan="1" colwidth="260"><ul><li>chances of fusion are more</li><li>probability of fertilization is increased</li><li>mates are selective</li><li>chances of gamete dehydration decreases</li><li>more parental care</li><li>prevents them from predation</li></ul></td><td colspan="1" rowspan="1"><ul><li>less offsprings are produced in a given amount of time</li><li>difficult to find a mate and intimate contact between them</li><li>risk of sexually transmitted diseases</li></ul></td></tr><tr><td colspan="1" rowspan="1" colwidth="157">External</td><td colspan="1" rowspan="1" colwidth="260"><ul><li>wide dispersal of gametes to find mating partners</li><li>reduces competition of food and living space (aquatic animals where eggs get carried away with water)</li><li>allows rapid recovery of populations away from damaged areas</li></ul></td><td colspan="1" rowspan="1"><ul><li>little to no parental care</li><li>larger number of gametes must be produced to ensure that some survive</li><li>waste of large number of unfertilized eggs</li><li>eggs and sperms may not come in contact</li></ul></td></tr></tbody></table><table style="min-width: 309px"><colgroup><col style="width: 25px"><col style="width: 44px"><col style="width: 215px"><col></colgroup><tbody><tr><td colspan="1" rowspan="1" colwidth="25">Fertilization</td><td colspan="1" rowspan="1" colwidth="44">species name</td><td colspan="1" rowspan="1" colwidth="215">Abiotic and biotic factors</td><td colspan="1" rowspan="1">Adaptation type and description</td></tr><tr><td colspan="1" rowspan="1" colwidth="25">External</td><td colspan="1" rowspan="1" colwidth="44">Staghorn Coralinvertebrate Marine animals (polyps)</td><td colspan="1" rowspan="1" colwidth="215"><ol><li>water</li><li>temperature</li><li>tides</li><li>day length(helps in synchronizing the reproductive cycle)</li><li>Predation: large number of eggs are produced as the majority of them die and only a tiny portion reaches adulthood.</li></ol></td><td colspan="1" rowspan="1">when polyps in one coral begin to spawn, pheromones are released along with gametes to stimulate spawning individuals to spawn, resulting in coordinating spawning over a wide area.<ul><li>mass gamete production causes sea to turn milky</li><li>fertilized egg takes one day to become into a larvae</li><li>larvae in a few days descend to find a suitable site to form a new colony</li></ul></td></tr><tr><td colspan="1" rowspan="1" colwidth="25">External</td><td colspan="1" rowspan="1" colwidth="44">Bony Fish</td><td colspan="1" rowspan="1" colwidth="215"><ul><li>water</li><li>dispersion of gametes is quick:</li></ul>the release of sperm and eggs should be simultaneous as the gametes disperse quickly.in most marine fish the release of gametes is restricted to brief and determined period<ul><li>microbial infections</li><li>predation</li></ul></td><td colspan="1" rowspan="1"><ul><li>produce ova in large batches</li><li>release them in the water where they fuse with the sperm outside the body</li><li>the release of sperm and eggs should be simultaneous as the gametes disperse quickly.</li></ul>in most marine fish the release of gametes is restricted to brief and determined periods</td></tr><tr><td colspan="1" rowspan="1" colwidth="25">External</td><td colspan="1" rowspan="1" colwidth="44">Amphibians</td><td colspan="1" rowspan="1" colwidth="215"><ul><li>not fully adapted to terrestrial environment</li><li>predation: enormous number of gametes produced and production of large number of offsprings</li></ul></td><td colspan="1" rowspan="1"><ul><li>both gametes are released in freshwater bodies</li><li>male grasps and straddles the females back</li><li>releasing fluid containing sperm onto the eggs as they are released by the females</li></ul></td></tr><tr><td colspan="1" rowspan="1" colwidth="25">External</td><td colspan="1" rowspan="1" colwidth="44">frog example: Southern Gastric brooding frog</td><td colspan="1" rowspan="1" colwidth="215"><ul><li>predation</li><li>infection</li><li>dispersal</li></ul>adaptation helped increase survival through these offsprings</td><td colspan="1" rowspan="1">physiological adaptationthe eggs were fertilized in the water and then swallowed by the femalethe offsprings developed in the stomach of the female ceased by the digestive secretions and settled into the stomach walls for nutrition (6-7 weeks)the female did not eat during this time</td></tr><tr><td colspan="1" rowspan="1" colwidth="25">Internal</td><td colspan="1" rowspan="1" colwidth="44">Reptile(crocodiles)</td><td colspan="1" rowspan="1" colwidth="215"><ul><li>predation</li></ul>after they hatch, they crawl from the buried nest into the water body making them vulnerable to predation<ul><li>no parental care</li><li>Temperature</li></ul>incubation temperatures determine the gender of the individualhigh temperatures females hatch regardless of the XY chromosomesfemales can reproduce normally despite being genetically male</td><td colspan="1" rowspan="1">during copulation males use tubular penis to introduce sperm into the femalefemale lays small numbers of large yolky eggs in clutches along the sandbanks of the seaeggs have a soft but tough leathery shell (exceptions: tortoise, geckos, crocodiles)eggs have sufficient food reserves to last till hatching</td></tr><tr><td colspan="1" rowspan="1" colwidth="25">Internal</td><td colspan="1" rowspan="1" colwidth="44">Birds</td><td colspan="1" rowspan="1" colwidth="215"><ul><li>predation</li></ul>the hard shell distinguishes bird eggs from soft-shelled reptilian eggs them protection<ul><li>parental care is evident</li></ul>Most birds incubate their eggs after laying them to keep warm after they are hatched</td><td colspan="1" rowspan="1">copulation takes place on groundmales and females rub the opening of their cloacas together and sperm is transferred to the female’s bodybig male birds have extended cloacas to form ‘fake‘ penisafter fertilization ovum passes along the oviduct and successive glands secrete yolk (followed by protein - albumen)A calcium carbonate shell is then secreted hardens when the egg comes in contact with the air.</td></tr><tr><td colspan="1" rowspan="1" colwidth="25">Internal</td><td colspan="1" rowspan="1" colwidth="44">Mammals</td><td colspan="1" rowspan="1" colwidth="215"></td><td colspan="1" rowspan="1"></td></tr></tbody></table>Mammals:<ul><li>three subclasses - monotremes, marsupials and eutherians</li></ul><table style="min-width: 50px"><colgroup><col><col></colgroup><tbody><tr><td colspan="1" rowspan="1">Monotremesexamples:<ul><li>platypus</li><li>echidna</li></ul></td><td colspan="1" rowspan="1"><ul><li>internal fertilization</li><li>oviparous<ol><li>Platypus: incubate their eggs in a nest</li><li>Echidna:<ul><li>place their eggs into an abdominal pouch where they stay for about seven weeks</li><li>young hatchlings (puggles) obtain milk from their mother’s mammary glands by licking her abdominal skin</li></ul></li></ol></li></ul></td></tr><tr><td colspan="1" rowspan="1">Marsupialsexample:<ul><li>kangaroo</li></ul></td><td colspan="1" rowspan="1"><ul><li>develop internally for a short time after fertilization and then continue their embryonic development in a pouch.<ol><li>Kangaroo:<ul><li>can have three offsprings at different stages of development at any one time</li><li>one out of the pouch but still drinking milk</li><li>one in the pouch attached to a nipple</li><li>a fertilized ovum at the blastocyst stage in the uterus</li><li>the development is triggered when the second youngest detaches from the nipple and leaves the pouch</li></ul></li></ol></li></ul></td></tr><tr><td colspan="1" rowspan="1"></td><td colspan="1" rowspan="1"></td></tr></tbody></table><h2 collapsed="true" seolevelmigrated="true">SEXUAL REPRODUCTION IN PLANTS</h2><ul><li>plants:<ul><li>angiosperm (flowering plants)</li><li>gymnosperms (mosses, ferns, cone-bearing plants)</li></ul></li><li>relies on the successful fusion of male and female gametes</li><li>fusion is difficult because plants due to lack of locomotion</li><li>Pollinating agents: are used as reproductive strategies to spread the seeds (wind, water, birds, insects etc.)<ul><li>they do not have the ability to move away from extreme heat or cold.</li></ul><img src="https://knowt-user-attachments.s3.amazonaws.com/093767fa-c551-497b-9c5f-c017169c1b0b.png" data-width="100%" data-align="center" alt="reproductive parts of a flower"></li></ul>Fertilization in flowers:<ul><li>Pollination: the male gametes inside the pollen must be carried from the anther to the female part of a flower (stigma)</li><li>the pollen tube germinates and grows down the style</li><li>to the ovule contained in the ovary</li><li>fertilization inside the ovary<ul><li>pollen fuses with the egg cell (ovum) inside the ovule</li><li>ovule develops protected within the ovary</li><li>ovule containing an embryo is now termed a seed</li><li>surrounding ovary grows to becomes a fruit</li></ul><img src="https://knowt-user-attachments.s3.amazonaws.com/b9844d5b-2c44-49bd-bbcc-fc5beeacdb56.png" data-width="75%" data-align="center" alt="fertilization in plants"></li></ul>Pollination, fertilization and seed production<ul><li>cross pollination - ensures greater variation in the offspring (favored more for the plant’s pollen to mature at different times than its stigma)</li><li>self-pollination</li></ul><table style="min-width: 340px"><colgroup><col><col style="width: 290px"><col></colgroup><tbody><tr><td colspan="1" rowspan="1">Type of pollination</td><td colspan="1" rowspan="1" colwidth="290">Self-Fertilization</td><td colspan="1" rowspan="1">Cross-Pollination</td></tr><tr><td colspan="1" rowspan="1">Advantage</td><td colspan="1" rowspan="1" colwidth="290"><ol><li>plants don’t have to rely on pollinators</li><li>flowers do not require to create devices to draw insect pollinators</li><li>guarantees seed production</li><li>eliminates a lot of unwanted recessive characteristics</li><li>the of micropores can be avoided</li></ol></td><td colspan="1" rowspan="1"><ol><li>seeds are generated in greater quantities and are healthier</li><li>cross-pollination between two distinct kinds of the same species, or different species, produces new varieties.</li><li>allows unisexual plants to reproduce</li></ol></td></tr><tr><td colspan="1" rowspan="1">Disadvantage</td><td colspan="1" rowspan="1" colwidth="290"><ol><li>prevents new adaptations in response to environmental change</li><li>progeny gets weaker due to ongoing self-pollination</li><li>they generate seeds of low quality</li></ol></td><td colspan="1" rowspan="1"><ol><li>plants</li><li>must grow huge, fragrant, nectar-filled flowers to draw insects, which is not unfeasible</li><li>genetic recombination can remove the parent’s beneficial characteristics</li></ol></td></tr><tr><td colspan="1" rowspan="1">Features</td><td colspan="1" rowspan="1" colwidth="290"><ol><li>happens when pollen grains are transferred between the same flowers</li><li>genetic diversity is reduced, and genetic homogeneity is increased via self-fertilization</li><li>causes inbreeding</li><li>generates limited pollen grains</li><li>stigma and anthers mature concurrently during self-pollination</li><li>no need for pollinators to transmit pollen grains</li><li>a flower’s stigma receives pollen grains directly</li><li>requires less energy</li></ol></td><td colspan="1" rowspan="1"><ol><li>happens when pollen grains are transferred between flowers of different plants</li><li>cross-pollination enhances genetic diversity and reduces genetic uniformity</li><li>causes outbreeding</li><li>generates a lot of pollen grains</li><li>cross-pollination occurs when the stigma and anthers mature at various periods</li><li>need pollinators to spread pollen grains</li><li>the wind, water, animals, insects, etc. can transport pollen grains</li></ol></td></tr></tbody></table><img src="https://knowt-user-attachments.s3.amazonaws.com/33e5d3cb-4220-4cd5-8472-1cae74c4195c.png" data-width="100%" data-align="center" alt="Features of different flowers - pollination">SEED DISPERSALGERMINATIONASEXUAL REPRODUCTION - only one parent<ul><li>one parent required</li><li>all genetic material in the offspring is passed down from this single parent</li><li>offsprings are genetically identical to the parent and to each other</li><li>no production or fusion of gametes</li><li>no mixing of genetic information to introduce variationSelective pressures that make asexual reproduction more effective than sexual reproduction include:</li><li>shortage of food or other resources (uses less energy)</li><li>small mating population</li><li>short time or constraints on finding a mate (only one parent is required)Main Disadvantage:</li><li>little to no variation in the population</li><li>the whole group is particularly vulnerable to sudden changes in the environment (drought, disease, or a new parasite or predator)</li></ul><h2 collapsed="true" seolevelmigrated="true">ASEXUAL REPRODUCTION IN PLANTS</h2>Vegetative propagation: a type of asexual reproduction where new individuals arise from portions of the roots, stems, leaves or buds of adult individuals and are genetically identical to the parent<ul><li>Vegetative reproduction in adult plants:<ul><li>Produced through organs like bulbs, tubers, rhizomes, and suckers</li><li>Results in new plants that are genetically identical to the parent</li><li>Equivalent to cloning an adult plant</li></ul></li><li>Perennating organs:<ul><li>Name derived from "perennial," meaning returning year after year</li><li>Underground organs such as roots or stems</li><li>Contain stored food to sustain the plant in a dormant state</li><li>Allow plants to survive adverse conditions (extreme cold, drought)</li><li>Above-ground parts may die, but underground organs develop buds</li><li>Buds grow when favorable conditions return</li><li>Buds on deciduous trees are also considered organs of perennation</li></ul></li><li>Dual function of perennating organs:<ul><li>Survival mechanism from one year to the next</li><li>Form of asexual reproduction when separated</li></ul></li><li>Gardening applications:<ul><li>Splitting bulbs</li><li>Cutting up rhizomes or runners</li><li>Taking cuttings of shoots from stems</li></ul></li><li>Agricultural uses of vegetative propagation:<ul><li>Growing perennial crops (e.g., seedless grapes, watermelons, mangoes)</li><li>Increases crop production when seeds are unavailable or difficult to germinate</li><li>Perpetuates specific desirable traits in future generations</li></ul></li></ul>Examples:<ul><li>Runners – modified stems:<ul><li>Definition: Long, thin, modified stems growing along the soil surface</li><li>Cultivated strawberry example: • Structure:<ul><li>Leaves, flowers, and roots produced at alternate nodes on stem runner</li><li>Just beyond every second node, tip turns up and thickens • Growth pattern:</li><li>New roots and shoots produced at thickened tips</li><li>New shoots continue the runner growth</li></ul></li><li>Spinifex grass example: • Structure:<ul><li>Long stems grow horizontally along soil surface</li><li>Leaves and roots produced at each node • Reproduction:</li><li>Runner can be subdivided into new plants • Adaptation benefits:</li><li>Ensures survival in harsh dune conditions</li><li>Effective against: • High wind erosion • High salinity • High temperatures</li></ul></li></ul></li><li>Rhizomes – modified stems:<ul><li>Definition: Underground horizontal modified stems</li><li>Characteristics: • Can produce new shoots at each node</li><li>Common in plants: • Ginger • Ferns (e.g., bracken fern) • Many grass species</li><li>Horticultural use: • Gardeners often propagate ferns by splitting rhizomes • Method exploits natural growth pattern for plant multiplication</li></ul></li><li>Suckers – modified roots:<ul><li>Definition: Modified roots that give rise to new plants</li><li>Also known as: Sprouts</li><li>Plants known for suckering: • Reeds • Wattles • Blackberries</li><li>Ecological role: • Can rapidly spread into vacant habitats after disturbance</li><li>Case study: Colony wattle (Acacia murrayana) • Growth pattern:<ul><li>Sends up shoots from outer roots</li><li>Shoots can develop into separate plants if parent shrub dies • Adaptive advantage:</li><li>Allows rapid regrowth after population decline</li><li>Effective in recovery from: • Bushfires • Droughts</li></ul></li></ul></li><li>Apomixis:<ul><li>Definition: Production of offspring from special generative tissues without fertilization or seed production</li><li>Types of generative tissue involved: • Gametes (e.g., unfertilized ovules) • non-reproductive tissue (e.g., leaf tissue)</li><li>Process: • Generative tissue gives rise to plantlets • Plantlets can produce asexual seeds</li><li>Examples of plants exhibiting apomixis: • Kangaroo grass (Themeda triandra) • Citrus trees (lemon and orange) • Dandelions</li><li>Characteristics of offspring: • Genetically identical to parent plant • Can arise on various plant parts (e.g., leaves)</li><li>Advantages: • Rapid multiplication of plants • Plantlets capable of seed production • Increased seed dispersal potential • Combines benefits of:<ul><li>Asexual reproduction (genetic consistency)</li><li>Sexual reproduction (seed dispersal capability)</li></ul></li><li>Disadvantage: • Lack of genetic variation typically seen in two-parent reproduction</li><li>Related concept in animal kingdom: • Parthenogenesis: Development of new individual from unfertilized egg</li></ul></li><li>Ecological and evolutionary implications:<ul><li>These various forms of vegetative reproduction allow plants to: • Survive in harsh environments • Rapidly colonize new areas • Maintain genetic lines in the absence of pollinators or sexual partners</li><li>Trade-off between genetic consistency and adaptability to changing environments</li></ul></li></ul><img src="https://knowt-user-attachments.s3.amazonaws.com/3dc49ba5-050f-4b76-adbc-6b06c7d29d55.png" data-width="100%" data-align="center"><h2 collapsed="true" seolevelmigrated="true">ASSEXUAL REPRODUCTION IN OTHER ORGANISMS</h2><h4 collapsed="true" seolevelmigrated="true">Budding</h4><ul><li>An adult organism gives rise to a small bud</li><li>separates from the parent and grows into an individual<img src="https://knowt-user-attachments.s3.amazonaws.com/600da752-480a-4b18-a369-4af31eee4ebc.png" data-width="100%" data-align="center"></li><li>Example:<ul><li>Yeast:<ul><li>microscopic unicellular organism</li><li>classification: fungi, macroscopic Moulds, mushrooms</li><li>Types of yeast: baker’s, brewer’s, Candida albicans</li><li>Baker’s Yeast:<ul><li>oval shaped</li><li>small outgrowths or buds develop on the parent cell in favorable conditions</li><li>As it grows the parent cell replicates its DNA, then nucleus, one copy moves into the bud/daughter cell</li><li>when the daughter cell matures, it detaches itself from the parent cell and a chain of cells forms.</li><li>yeast replicates every 90 minutes, increases exponentially</li></ul></li><li>sexual reproduction in Yeast<ul><li>only occurs when lack of nutrition</li><li>yeast exists in the haploid or diploid form</li><li>both types can reproduce asexually by budding: useful in genetic studies</li><li>diploid form is more resistant to harsh environments and can form spores that germinate when favorable conditions return creating haploid yeast cells once again</li></ul></li></ul></li><li>Multicellular organisms: jellyfish, hydra, grooved brain coral<ul><li>parent cells divide by mitosis</li><li>grow into a multicellular outgrowth</li><li>smaller but identical individuals / buds develop</li><li>it detaches from the parent and grows into a reproductive adult</li></ul></li></ul></li></ul><table style="min-width: 75px"><colgroup><col><col><col></colgroup><tbody><tr><td colspan="1" rowspan="1">Type of asexual reproduction</td><td colspan="1" rowspan="1">advantage</td><td colspan="1" rowspan="1">disadvantage</td></tr><tr><td colspan="1" rowspan="1">budding</td><td colspan="1" rowspan="1"><ul><li>Fast and efficient reproduction</li><li>Allows for genetic diversity through occasional mutation</li><li>Enables reproduction without the need for a partner</li></ul></td><td colspan="1" rowspan="1"><ul><li>Limited genetic variation compared to sexual reproduction</li><li>Can lead to overpopulation if unchecked</li><li>Offspring are vulnerable until fully separated from parent</li></ul></td></tr><tr><td colspan="1" rowspan="1">binary fission</td><td colspan="1" rowspan="1"><ul><li>Rapid population growth in favorable conditions over a short period of time</li><li>Simple process requiring minimal energy</li><li>Produces genetically identical offspring, preserving beneficial traits</li><li>requires only one parent</li></ul></td><td colspan="1" rowspan="1"><ul><li>Lack of genetic diversity, making populations vulnerable to environmental changes</li><li>Can deplete resources quickly due to exponential growth</li><li>Difficult to adapt to new environments without genetic variation</li></ul></td></tr><tr><td colspan="1" rowspan="1">Spores</td><td colspan="1" rowspan="1"><ol><li>Can survive harsh environmental conditions</li><li>Allows for wide dispersal and colonization of new areas</li><li>Produces large numbers of potential offspring</li></ol></td><td colspan="1" rowspan="1"><ul><li>Many spores may not find suitable conditions to germinate</li><li>Limited genetic diversity if produced asexually</li><li>Vulnerable to predation or environmental hazards during dispersal</li></ul></td></tr></tbody></table><h4 collapsed="true" seolevelmigrated="true">Binary fusion</h4><ul><li>a newly divided cell grows to twice its size, replicates its DNA, then splits into two cells with identical DNA</li><li>the timing of division is crucial</li><li>each individual must retain a complete and exact copy of the genetic material<ul><li>Binary Fission in Bacteria:<ul><li>Asexual reproduction method</li><li>Rapid reproduction: can double every 20 minutes in favorable conditions</li><li>Process:<ul><li>Cell grows to full adult size</li><li>DNA replicates</li><li>DNA copies attach to opposite ends of cell membrane</li><li>Proteins accumulate at cell center • Aid in cytoplasm division • Protect DNA during process</li><li>New cell wall synthesized at cleavage area</li><li>New cells grow to full size before dividing again</li></ul></li><li>Tightly controlled cell cycle</li><li>Research interest:<ul><li>Understanding regulation of binary fission</li><li>Potential for new antibiotics or synthetic chemicals</li><li>Could combat pathogenic bacterial infections</li></ul></li><li>Variations in some bacterial species:<ul><li>Multiple divisions from one enlarged cell</li><li>Budding</li></ul></li></ul>Binary Fission in Protists:<ul><li>Occurs in unicellular eukaryotes</li><li>Involves mitosis and spindle formation</li><li>Spindle distributes chromosomes equally</li><li>Example: Amoeba<ul><li>Moves via pseudopodia (cytoplasm extensions)</li><li>Reproduces asexually by binary fission</li><li>In adverse conditions: • Forms a cyst • Undergoes multiple fissions within cyst • Releases many identical cells when conditions improve</li><li>Fission is 'irregular' due to asymmetrical cell shape</li><li>Division can occur along any plane</li></ul></li></ul></li></ul></li></ul><img src="https://knowt-user-attachments.s3.amazonaws.com/bcf7470b-5dca-4613-ae4f-eb55d276c5bc.png" data-width="100%" data-align="center"><ul><li>Key Differences:<ul><li>Bacteria (prokaryotes) vs. Protists (eukaryotes)</li><li>Bacteria use simpler division process</li><li>Protists use mitosis and spindle formation</li></ul></li></ul><h4 collapsed="true" seolevelmigrated="true">Spores</h4><img src="https://knowt-user-attachments.s3.amazonaws.com/446bcc1f-e30f-4a68-9a89-8d73d8eed985.png" data-width="100%" data-align="center" alt="asexual reproduction in a fungus such as a Rhizopus (bread Mould)"><ul><li>Spore production in organisms:<ul><li>Some organisms rely on spores for reproduction</li><li>Spores are tiny, unicellular reproductive cells</li><li>Produced in large numbers by: • Fungi (e.g., Moulds and mushrooms) • Some plants (e.g., mosses and ferns)</li></ul></li><li>Sporangia:<ul><li>Structures that produce spores</li><li>Produce very large numbers of spores</li><li>Shown in Fig. 2.29 (reference to an image)</li></ul></li><li>Characteristics of spores:<ul><li>Light and easily dispersed</li><li>Can travel long distances by wind</li><li>Expand distribution of the species</li><li>Able to colonize new environments</li></ul></li><li>Differences between spores and other reproductive structures:<ul><li>Unlike gametes, spores don't need to fuse with another cell to produce a new individual</li><li>Unlike seeds, spores are single cells and don't contain: • An embryo • A food supply</li></ul></li><li>Evolutionary perspective:<ul><li>Evidence shows seed-bearing plants arose later than spore-bearing fungi and plants</li></ul></li><li>Multicellular fungi structure:<ul><li>Made up of threads or filaments called hyphae (Fig. 2.29)</li><li>Hyphae are branched and interconnected</li><li>Form the main fungal body called the mycelium (plural: mycelia)</li><li>Hyphae may grow: • Underground • In dead and decaying matter</li></ul></li><li>Fungal characteristics:<ul><li>Lack chlorophyll</li><li>Do not photosynthesize</li><li>Can grow in the dark</li></ul></li><li>Fungal nutrition types:<ul><li>Saprophytic: obtaining organic nutrients from dead and decaying matter</li><li>Parasitic: obtaining organic nutrients from living hosts</li></ul></li><li>Fungal habitat:<ul><li>Can colonize aerobic, damp, dark environments</li><li>Less competition for nutrients and water in these environments</li></ul></li><li>Example of spore formation: Black Mould Rhizopus nigricans<ul><li>Similar to: • Pin-head Mould Mucor • Antibiotic-producing Mould Penicillium</li><li>Multinucleate: many nuclei in hyphae</li><li>No cross walls separating individual cells</li></ul></li><li>Asexual reproduction in fungi (Fig. 2.30):<ul><li>Occurs when environmental conditions are favorable</li><li>Develop large numbers of spore-producing units (sporangia)</li><li>Sporangia grow upwards</li><li>Visible as grey-green part of Mould on bread, fruit, and sometimes leather</li></ul></li><li>Sporangia development:<ul><li>Develop as specialized tips of hyphal threads</li><li>Contain numerous haploid nuclei</li><li>Nuclei develop into microscopic spores</li><li>Spores are initially white, then turn black as they ripen</li></ul></li><li>Spore structure:<ul><li>Each spore has several nuclei</li><li>Contains some cytoplasm</li><li>Surrounded by a wall</li></ul></li><li>Spore characteristics and dispersal:<ul><li>Produced in enormous numbers</li><li>Extremely light</li><li>Enable widespread air dispersal</li><li>Carry genetic material identical to the parent</li></ul></li><li>Spore germination process:<ul><li>Occurs under favorable environmental conditions</li><li>Absorb water through the wall</li><li>Water activates cytoplasm to grow</li><li>Nuclear divisions occur</li><li>More cytoplasm is produced</li><li>Spore grows into a new mycelium</li></ul></li><li>Benefits of fungal spore reproduction:<ul><li>Enables rapid reproduction</li><li>Allows colonization of wide areas</li><li>Ensures continuity of the species</li></ul></li></ul>Extension to asexual reproduction<ul><li>Asexual reproduction in animals:<ul><li>Not limited to Protista, fungi, and plants</li><li>Some animals can reproduce by: • Budding • Other forms of asexual reproduction</li></ul></li><li>Parthenogenesis:<ul><li>A form of asexual reproduction in animals</li><li>Falls under the category of apomixis (reference to page 50)</li><li>Etymology: • Derived from Greek words • 'Parthenos' meaning virgin • 'Genesis' meaning creation</li></ul></li><li>Definition of parthenogenesis:<ul><li>Production of offspring from an unfertilized gamete</li><li>Usually involves an egg (ovum)</li></ul></li><li>Classification of parthenogenesis:<ul><li>Considered asexual reproduction</li><li>Can also be thought of as 'incomplete' sexual reproduction</li></ul></li><li>Occurrence of parthenogenesis:<ul><li>Common in some insects: • Aphids • Ants • Bees • Wasps</li><li>Fairly common in reptiles</li></ul></li><li>Characteristics of offspring:<ul><li>Genetic clones of their mother</li></ul></li><li>Parthenogenesis in Australia:<ul><li>Many Australian lineages demonstrate parthenogenesis</li></ul></li></ul><h2 collapsed="false" seolevelmigrated="true">SEXUAL REPRODUCTION IN MAMMALS</h2><ul><li>involves: fertilization (fusion of male and female gametes to form a zygote)</li><li>zygote contains a new combination of genetic materials from both parents</li><li>the genetic variation increases the chances of survival of the population in the case of environmental change</li></ul><ol><li>How do mammals maximize their reproductive success:<ul><li>internal fertilization (likelihood of gametes meeting) (all three subclasses)</li><li>implantation of the embryo into the uterine wall with internal development of the embryo (all three subclasses)</li><li>pregnancy<ul><li>to allow the developing young to be protected from the external environment</li><li>constant nutrient supply</li><li>complete a gestation period (short in marsupials, prolonged in eutherians)</li></ul></li></ul></li></ol><ul><li>all stages are carefully timed and synchronized by a combination of hormones that coordinate the reproductive cycle to ensure greater reproductive success</li></ul><img src="https://knowt-user-attachments.s3.amazonaws.com/4f3c1387-18ee-45a7-8a32-16a5e040dc9d.png" data-width="100%" data-align="center"><h3 collapsed="true" seolevelmigrated="true">Sexual reproduction in mammals introduction</h3><h5 collapsed="true" seolevelmigrated="true">I. Overview of Sexual Reproduction in Mammals</h5><ul><li>Carefully timed and synchronized process</li><li>Regulated by hormones</li><li>Ensures greater reproductive success</li><li>Self-perpetuating cycle for species continuity</li></ul><h5 collapsed="true" seolevelmigrated="true">II. Hormonal Regulation</h5>A. Gametogenesis<ul><li>Production of sperm (spermatogenesis)</li><li>Production of eggs (oogenesis)</li><li>Regulated by gonadotropins (FSH, LH)</li></ul>B. Courtship Behavior<ul><li>Influenced by sex hormones (e.g., testosterone, estrogen)</li><li>Timing often linked to female reproductive cycle</li></ul>C. Pregnancy<ul><li>Maintained by progesterone and other hormones</li><li>Hormonal changes trigger labor and birth</li></ul>D. Birth and Lactation<ul><li>Oxytocin stimulates uterine contractions</li><li>Prolactin promotes milk production</li></ul><h5 collapsed="true" seolevelmigrated="true">III. Evolutionary Strategies for Reproductive Success</h5>A. Timing of Reproductive Cycles<ul><li>Seasonal breeding in some species</li><li>Synchronization with environmental factors (e.g., food availability)</li></ul>B. Embryonic Development in Utero<ul><li>Protected environment for fetal growth</li><li>Efficient nutrient transfer from mother to fetus</li></ul>C. Reduced Number of Young<ul><li>Focus on quality over quantity</li><li>Increased parental investment per offspring</li></ul>D. Quality of Parental Care<ul><li>Extended period of dependency</li><li>Teaching and protection of young</li></ul><h5 collapsed="true" seolevelmigrated="true">IV. Stages of Mammalian Sexual Reproduction</h5><ol><li>Gametogenesis</li><li>Courtship and Mating</li><li>Fertilization</li><li>Pregnancy</li><li>Birth</li><li>Postnatal Care</li></ol><h5 collapsed="true" seolevelmigrated="true">V. Importance of Hormonal Coordination</h5><ul><li>Ensures proper timing of reproductive events</li><li>Coordinates physiological changes in both males and females</li><li>Regulates behavioral changes associated with reproduction</li></ul><h5 collapsed="true" seolevelmigrated="true">VI. Survival to Adulthood</h5><ul><li>Successful offspring survive to become reproductive adults</li><li>Adults compete for mates</li><li>Continuation of the reproductive cycle</li></ul><h5 collapsed="true" seolevelmigrated="true">VII. Species Continuity</h5><ul><li>Self-perpetuating cycle of reproduction</li><li>Adaptation to environmental challenges</li><li>Genetic diversity through sexual reproduction</li></ul><h5 collapsed="true" seolevelmigrated="true">VIII. Key Hormones in Mammalian Reproduction</h5><ol><li>Follicle Stimulating Hormone (FSH)</li><li>Luteinizing Hormone (LH)</li><li>Testosterone</li><li>Estrogen</li><li>Progesterone</li><li>Oxytocin</li><li>Prolactin</li></ol><h3 collapsed="false" seolevelmigrated="true">Hormones</h3><ul><li>hormones are chemical substances that act as messengers in the body, coordinating many aspects of functioning, including metabolism and reproduction, so that actions within the body are synchronized</li><li>Pituitary gland:<ul><li>Structure:<ol><li>is an endocrine gland</li><li>size of a pea</li><li>attached to the base of the brain just above the roof of the mouth</li></ol></li><li>Function:<ol><li>secretes hormones that stimulate or inhibit other endocrine glands, regulating the release of their hormones for growth, metabolism and reproduction</li></ol></li></ul></li><li>Sex hormones:<ul><li>hormones that affect the growth and functioning of the reproductive organs or development of secondary sex characteristics is called Sex Hormones</li><li>produced in:<ul><li>tissues of ovaries and testes</li><li>pituitary gland</li><li>adrenal cortex</li></ul></li></ul></li><li>The function of hormones:<ul><li>role in all aspects of the development and functioning of male and female reproductive systems</li><li>secreted hormones stimulate the reproductive functions of the reproductive organs during puberty</li></ul></li><li>Puberty:<ul><li>between ages: 10-14 (girls) 12-16(boys)</li><li>Gonads: (reproductive organs) become functional at puberty and the reproductive cycle commences</li></ul></li><li>Gametogenesis: the process of production of gametes in the male and female gonads</li></ul><h4 collapsed="false" seolevelmigrated="true">Hormonal control of breeding seasons</h4><ul><li>regulate the sexual behavior of mammals by limiting the ability of some mammals to reproduce to certain times of the year</li><li>Breeding Seasons: time of the year when the organisms are reproducing</li><li>Breeding cycle: periods of female fertility being limited to once or twice a year<ol><li>Seasonal breeders:<ul><li>ex. sheep and cattle</li><li>mating only occurs during periods of female fertility</li><li>commonly referred to as “heat” or “in season”</li><li>biological term: “in OESTRUS “</li></ul></li><li>Continuous breeders:<ul><li>ex. humans and other mammals (pigs, rates, mice, rabbits)</li><li>female fertility occurs in a cycle that repeats throughout the year</li><li>organisms are sexually active all year round</li></ul></li></ol></li></ul><table style="min-width: 75px"><colgroup><col><col><col></colgroup><tbody><tr><td colspan="1" rowspan="1">Type of breeding cycle</td><td colspan="1" rowspan="1">Advantage</td><td colspan="1" rowspan="1">Disadvantage</td></tr><tr><td colspan="1" rowspan="1">Seasonal breeding</td><td colspan="1" rowspan="1"><ul><li>Synchronized with environmental conditions (food availability, weather)</li><li>Conserves energy by concentrating reproductive efforts</li><li>Allows for focused parental care during optimal conditions</li></ul></td><td colspan="1" rowspan="1"><ul><li>Limited reproductive opportunities throughout the year</li><li>Vulnerable to environmental disruptions during breeding season</li><li>May lead to intense competition for mates in a short period</li></ul></td></tr><tr><td colspan="1" rowspan="1">Continuous breeding</td><td colspan="1" rowspan="1"><ul><li>Maximizes reproductive output throughout the year</li><li>Allows for rapid population growth in favorable conditions</li><li>Provides flexibility in response to unpredictable environments</li></ul></td><td colspan="1" rowspan="1"><ul><li>Requires constant energy investment in reproduction</li><li>May lead to parental exhaustion or reduced offspring care</li><li>Can result in overpopulation if resources are consistently abundant</li></ul></td></tr></tbody></table><table style="min-width: 50px"><colgroup><col><col></colgroup><tbody><tr><td colspan="1" rowspan="1">Seasonal breeding</td><td colspan="1" rowspan="1">Continuous breeding</td></tr><tr><td colspan="1" rowspan="1"><ul><li>Occurs at specific times of the year</li><li>Typically triggered by environmental cues (e.g., day length, temperature)</li><li>Common in temperate regions and among migratory species</li><li>Often results in synchronized births within a population</li><li>Clear distinction between breeding and non-breeding periods</li><li>Intense energy investment during breeding season, conservation during off-season</li><li>Often timed to coincide with optimal conditions for offspring survival</li><li>Often accompanied by physiological changes (e.g., antler growth, colorful plumage)</li><li>Can lead to population boom-bust cycles</li><li>Examples: deer, birds, many fish species</li></ul></td><td colspan="1" rowspan="1"><ul><li>Occurs throughout the year</li><li>Not dependent on specific seasonal cues</li><li>More common in tropical regions or stable environments</li><li>Results in births spread out over time</li><li>No clear cyclic pattern</li><li>More consistent energy expenditure throughout the year</li><li>Relies on parents' ability to provide resources year-round</li><li>May have less dramatic physical changes related to breeding</li><li>May result in more stable population growth</li><li>Examples: humans, some rodents, many domesticated animals</li></ul></td></tr><tr><td colspan="1" rowspan="1"></td><td colspan="1" rowspan="1"></td></tr></tbody></table><h4 collapsed="false" seolevelmigrated="true">Hormones involved in mammals</h4><table style="min-width: 224px"><colgroup><col style="width: 174px"><col><col></colgroup><tbody><tr><td colspan="1" rowspan="1" colwidth="174">Name of hormone</td><td colspan="1" rowspan="1">Function</td><td colspan="1" rowspan="1">Found in</td></tr><tr><td colspan="1" rowspan="1" colwidth="174">Androgens - commonly referred to male hormones</td><td colspan="1" rowspan="1"><ul><li>control the development</li><li>functioning of male sex organs</li><li>secondary sex characteristics<ul><li>deep voice,</li><li>increase in the growth</li><li>thickness of hair and size of muscles and bones</li></ul></li><li>Type of androgen: Testosterone<ul><li>cells in testes</li><li>primary role in spermatogenesis (production of sperms)</li></ul></li></ul></td><td colspan="1" rowspan="1"><ul><li>in both male and females</li><li>production increases during puberty in both sexes</li><li>higher level in males</li><li>androgens are<ul><li>precursors (margin note) of estrogen (a group of female hormones)</li></ul></li></ul></td></tr><tr><td colspan="1" rowspan="1" colwidth="174">estrogen<ul><li>main group of female hormones</li></ul></td><td colspan="1" rowspan="1"><ul><li>control the development and functioning of the female reproductive system</li><li>secondary sex characteristics<ul><li>enlarged breasts</li><li>pubic hair</li><li>widening of hips</li></ul></li><li>Males: together with testosterone<ul><li>maturation of sperm</li></ul></li><li>responsible for the onset of estrus just before ovulation in female mammals that are seasonal breeders</li><li>Main Function:<ul><li>ovarian functioning and fertility of females</li></ul></li></ul></td><td colspan="1" rowspan="1"><ul><li>in both male and female</li><li>higher level in females</li></ul></td></tr><tr><td colspan="1" rowspan="1" colwidth="174">Progestogens<ul><li>second group of female hormones</li></ul></td><td colspan="1" rowspan="1"><ul><li>primary role in pregnancy</li><li>stimulates secretion of milk in mammary glands (lactation)</li><li>drop in its level plays a role in initiating menstruation</li></ul></td><td colspan="1" rowspan="1"><ul><li>females</li></ul></td></tr></tbody></table>Extra information:<ul><li>can be artificially manufactured and used either<ul><li>as a form of contraception to prevent pregnancy</li><li>to increase fertility and help women get pregnant</li></ul></li><li>Example: Progestin<ul><li>synthetically produced version of the hormone progesterone</li></ul></li></ul><ol><li>estrogens and progestogens may be used<ul><li>hormone replacement therapy for women during menopause</li><li>treatment of prostate cancer and some forms of breasts and endometrial cancers</li></ul></li></ol><h3 collapsed="true" seolevelmigrated="true">Hormone control of the female reproductive cycle</h3><ul><li>Endocrine glands regulate and control the ovarian and menstrual cycles in a coordinated manner, synchronizing these cycles to ensure fertility</li><li>increase in the probability of successful production, biological fitness, the continuity of the species<img src="https://knowt-user-attachments.s3.amazonaws.com/cf80284a-b2c5-4b67-a4e9-7f996ff505df.png" data-width="100%" data-align="center" alt="hormone production and action in the female reproductive system"></li><li>FHS: follicle-stimulating hormone<ul><li>main function: regulation of the menstrual cycle</li><li>stimulates follicles on the ovary to grow and prepare the eggs for ovulation (release of oestrogen)</li></ul></li><li>LH: luteinizing hormone<ul><li>helps in regulating the menstrual cycle</li></ul></li><li>GnRH: gonadotrophic releasing hormone<ul><li>a key regulator of the reproductive axis</li><li>causes the pituitary gland in the brain to make and secrete hormones LH and FSH</li></ul></li></ul><h3 collapsed="true" seolevelmigrated="true">Hormone production process</h3><ol><li>In the hypothalamus: GnRH stimulates the anterior lobe cells to secrete FSH and LH.</li><li>In the ovary: FHS and LH are released<ul><li>promoting follicle growth and oocyte maturation</li><li>estrogen production</li><li>priming the endometrium and initiating other reproductive events</li></ul></li><li>Blood level of estrogens rises, stimulating a surge in LH secretion</li><li>In the ovary: mid-cycle surge of LH triggers ovulation, then formation of corpus luteum</li><li>Progesterone secreted by corpus luteum maintain the endometrium of pregnancy occurs</li></ol><h3 collapsed="true" seolevelmigrated="true">Pituitary gland</h3><ol><li>secretes a number of hormones that regulate other endocrine glands, including the ovaries of females<ul><li>key players in the regulation of the reproductive cycles in mammals</li></ul></li></ol><h5 collapsed="true" seolevelmigrated="true">Estrogen and progesterone</h5><ol><li>produced by the ovaries and controlled by the pituitary gland</li></ol>Helps in regulating<ol><li>Ovarian cycle: by controlling the production and maturation of ova in the ovaries</li><li>maintenance of pregnancy</li><li>preparation for and maintenance of lactation</li><li>menstrual cycle<ul><li>by preparing the uterus for implantation of the fertilized egg each cycle</li><li>if not pregnant the levels decrease results in the uterus lining tearing away accompanied by bleeding (menstruation)</li></ul></li><li>Secretion of two GONADOTROPIC HORMONES:<ul><li>LH (luteinizing hormones): promotes<ul><li>promotes final maturation of the ovarian follicle</li><li>ovulation and the development of the corpus luteum in females</li><li>stimulates the secretion of testosterone</li></ul></li><li>FHS (follicle stimulating hormone)<ul><li>stimulates the maturation of follicles in the ovaries of females</li></ul></li></ul></li><li>Secretion of lactogenic hormone<ul><li>Prolactin:<ul><li>acts on breast tissue to prepare for and maintain milk production to suckle the young one</li></ul></li></ul></li></ol><h3 collapsed="true" seolevelmigrated="true">Ovarian cycle</h3><ul><li>cycle of changes in the ovaries</li></ul><ol><li>Overview<ul><li>Female babies are born with all the ova that will be produced in the whole lifestyle</li><li>they are immature and partially developed</li><li>During puberty the ovarian and menstrual cycle begins<ul><li>the ova become surrounded by a single layer of cells that envelop them and begin to divide</li><li>resulting in the formation of primary follicles in the ovary</li><li>hormones (till 36-40 years) that are secreted during puberty trigger the development and maturation of the ova each month (except during pregnancy)</li></ul></li><li>Menopause reached after 36-40 years of hormone production</li></ul></li></ol><img src="https://knowt-user-attachments.s3.amazonaws.com/03abb58d-a39a-46df-82e3-b12fe41cfc35.png" data-width="100%" data-align="center" alt="ovarian cycle"><h5 collapsed="true" seolevelmigrated="true">follicular phase</h5><ol><li>follicle cells secrete fluid which pushes the egg to one side of the follicle</li><li>the enlarged dominant follicle moves to the surface of the ovary and creates a bulge</li><li>it is now mature and is termed Graafian follicle<ul><li>the development from primary follicle to Graafian follicle takes 10-14 days</li></ul></li><li>the cells lining the follicle secrete estradiol (an estrogen hormone)<ul><li>causes a surge in the production of LH > leads to ovulation</li><li>stimulates the next phase of the ovarian cycle</li><li>meanwhile the corpus luteum forms</li><li>progesterone is synthesized</li></ul></li><li>ovulation: the graafian follicle bursts > releasing the egg<ul><li>the funnel-shaped open ends of the uterine tubes contain cilia that beat > drawing the egg into the tube</li></ul></li><li>the egg (has some follicles attached) moves down the tube towards the uterus<ul><li>if sperm is present: fertilization occurs</li><li>if not, it moves through the uterus and disintegrates in </li></ul></li><li>Ovulation occurs mid-cycle </li><li>female ovum is only viable (successfully working) for 12-24 hours</li></ol><img src="https://upload.wikimedia.org/wikipedia/commons/thumb/9/92/Menstrual_cycle.svg/1200px-Menstrual_cycle.svg.png" data-width="100%" data-align="center" alt="Follicular phase "><h5 collapsed="true" seolevelmigrated="true">luteinizing phase</h5><ol><li>The luteinizing phase is usually 14 days</li><li>begins after ovulation > Graafian follicle bursts in the ovary > releases eggs > the ovary enlarges > changes color > building up a yellow protein called lutein</li><li>The large mass of vacuolated cells is now called the CORPUS LUTEUM (Latin for ‘yellow body ‘) <ul><li>the corpus luteum secretes the hormone == progesterone</li><li>progesterone == acts in uterus > prepares for pregnancy<img src="https://naturalwomanhood.org/wp-content/uploads/image-3.png" data-width="100%" data-align="center" alt=""> <img src="https://img.brainkart.com/imagebk21/w039q6Y.jpg" data-width="100%" data-align="center" alt="Ovarian Follicle Growth- “Follicular” Phase of the Ovarian Cycle"></li></ul></li></ol><h3 collapsed="false" seolevelmigrated="true">Menstrual cycle</h3><ol><li>menstrual cycle: cycle of changes in the uterus</li><li>repeats every 28 days (depends)<img src="https://knowt-user-attachments.s3.amazonaws.com/82a5a9de-2be4-4cfe-85c2-a379be12412a.png" data-width="100%" data-align="center" alt="1. ovarian phases 2. uterine phase 3. ovarian cycle 4. uterine cycle"></li></ol>

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