Sexual and Asexual Reproduction

Sexual & Asexual Reproduction

• Sexual reproduction involves two parents and results in genetically different offspring through the fusion of gametes.
• Gametes are sex cells with half the number of chromosomes (haploid nucleus) compared to normal body cells.
• Human body cells contain 46 chromosomes, while each gamete contains 23 chromosomes.
• The fusion of male and female gametes forms a zygote, which contains a full set of 46 chromosomes (diploid nucleus).
• Asexual reproduction does not involve gametes or fertilization and requires only one parent, resulting in genetically identical offspring (clones).
• Many plants reproduce asexually.
• Bacteria reproduce exact genetic copies through binary fission, an asexual reproduction.

Advantages and Disadvantages: Sexual Reproduction

Advantages

• Increases genetic variation.
• Allows species to adapt to new environments.
• Reduces the likelihood of disease affecting the entire population.

Disadvantages

• Requires time and energy to find mates.
• Difficult for isolated members of the species to reproduce.

Advantages and Disadvantages: Asexual Reproduction

Advantages

• Population can increase rapidly when conditions are right.
• Allows for quick exploitation of suitable environments.
• It is more time and energy efficient.
• Reproduction completes much faster than sexual reproduction.

Disadvantages

• There is limited genetic variation in population.
• Offspring are genetically identical to their parents.
• The population is vulnerable to changes in conditions and may only be suited for one particular habitat
• An entire population is likely to be affected by disease due to lack of genetic variation

Comparing Sexual & Asexual Reproduction Features

Number of Parent Organisms:

• Asexual: One
• Sexual: Two

Type of Cell Division Required:

• Asexual: Offspring are produced by Mitosis
• Sexual: Offspring are produced from the fusion of two haploid gametes produced by Meiosis

Level of Genetic Similarity Between Offspring:

• Asexual: Offspring are genetically identical to each other and to the parent
• Sexual: Offspring are genetically unique and genetically different from both parents

Sources of Genetic Variation in Offspring:

• Asexual: Only mutation
• Sexual: Contribution of 50% of DNA from each parent, gamete production via meiosis, and random chromosome distribution during meiosis

Number of Offspring Produced:

• Asexual: Usually relatively large numbers
• Sexual: Usually relatively limited numbers

Time Taken to Produce Offspring:

• Asexual: Usually relatively fast
• Sexual: Usually relatively slow

Sexual Reproduction

• Meiosis is nuclear division that results in the production of haploid cells from diploid cells.
• Gametes in plants and animals are made via meiosis and are used in sexual reproduction.
• Meiosis occurs in two successive divisions: meiosis I and meiosis II.
• Specific mechanisms during meiosis lead to genetic variation within resulting gametes.
• Crossing over occurs when non-sister chromatids exchange alleles during meiosis I.
• Independent assortment describes the production of different combinations of alleles in daughter cells due to random alignment of homologous pairs of chromosomes during meiosis I.
• Random fertilisation means that there are millions of combinations of sperm and egg cells that result in the fusion of these sex cells.
• Within each division of meiosis, four stages exist: prophase, metaphase, anaphase, and telophase.
• Meiosis takes place in animals in the testes of male animals, and in the ovaries of female animals.
• Meiosis takes place in plants within the anthers and ovaries of flowering plants.
• Meiosis produces spermatozoa (sperm cells in male animals), ova (singular ovum in female animals).
• Male plant gametes are carried in pollen grains, and female plant gametes are held in the ovules within the plant ovary.
• The fusion of gametes during fertilisation produces new combinations of alleles.

Male & Female Differences in Sexual Reproduction

• The process of meiosis is identical, but the resulting gametes are very different.
• The differences in gametes mean that males and females strategies for reproduction also differ.

Comparison of Male & Female Gametes

Size:

• Sperm: Very Small (45 um)
• Egg: Large (0.15 mm)

Structure:

• Sperm: Head region and flagellum, many structural adaptations
• Egg: Round cell with few structural adaptations covered in a jelly coating

Motility:

• Sperm: Capable of locomotion
• Egg: Not capable of locomotion

Numbers:

• Sperm: Produced every day in huge numbers (around 100 million per dat)

• Egg: Thousands of immature eggs in each ovary, but only one released each month

• Human females release only one egg cell (per menstrual cycle) while males release thousands of sperm cells per ejaculation.

• The amount of sperm released by males is due that they are unlikely to reach and fertilise the egg cell.

• The function of each of these structures should be recalled and easily identifiable in an annotated diagram.Female Reproductive System

Female reproductive system diagram functions

• Oviduct: Connects the ovary to the uterus and is lined with ciliated cells to push the released ovum it; fertilisation occurs here
• Ovary: Contains ova (female gametes) which will mature develop when hormones are released
• Uterus: Muscular bag with a soft lining where the fertilised egg (zygote) implants to develop into a foetus
• Cervix: Ring of muscle at the lower and of the uterus to keep the developing foetus in place in pregnancy
• Vagina: Muscular tube that leads to the inside of the women's body where the male penis will enter during sexual intercourse and sperm are deposited
• Vulva: A collection of structures (including the pubic mound, Labia, clitoris and hymen), one function of which is to protect the more internal parts of the female reproductive system.
• Male Reproductive System*

Male reproductive system diagram functions

• Prostate gland and seminal vesicle Produces fluid called semen, that provide sperm cells with nutrients
• Sperm duct: Sperm passes through the sperm duct, to be mixed with fluid produced by the glands before being passed into the urethra for ejactulation.
• Urethra: Tube running down the centre of the penis that can carry out urine of semen, a ring of muscle in the urethra prevents the urine, and semen from mixing
• Testis: Contained in a bag of skin (scrotum) produces sperm (male gamete), and testosterone (hormone
• Scrotum: Sac supporting the testicle outside the body to ensure sperm are kept of temperature slightly lower than body/skin temperature
• Penis: Passes urine out of the body from the bladder and allows semen to pass into the vagina to of a woman during sexual intercourse
• Epididymis: Coiled tubes that store sperm until ejaculation

The Menstrual Cycle

• Is a series of changes that take place in the female body leading up to and following the release of an egg from the ovaries.
• Starts in early adolescence in girls & is controlled by hormones.
• Cycle is averagely 28 days long.
• Uterus lining or endometruim thickens in preparation for receiving a fertilised egg, from days 7-28.
• day 14, halfway through the cycle, ovulation takes place, and goes down the oviduct to the uterus.
• Eggs develop inside fluid filled sac known as egg follicles inside the ovary. The follicle releases the eggs at ovulation becoming the empty follicle (corpus luteum) Failure to fertilise eggs lead too menstruation, commonly known as a period. Menstruation is the lose of blood via the bloody of the vagina. Caused by the breakdown of the endometrium. Menstruation takes places usually between dates 1-7 of the circle & The number of days menstruation occur varies. After menstruation is finished ,the endometrium starts to thicken again in preparation for the possible implantation of a fertilised egg.

How ovarian and pituitary hormones control the menstrual cycle

• Hormones that control events that occur in menstruation:
• FSH (Follicle-stimulating hormone)
• LH (Luteinising hormone)
  • Two hormones are produced by the pituitary gland in the brain: FSH, and LH.Other Two hormones produced in the ovaries:
• Oestrogen
• progesterone
• FSH is secreted and stimulate development of several immature cells in the ovary, stimulating seretion of oestrogen by follicle wall
• Increase in oestrogen production stimulates pituitary gland too release LH when oestrogen levels peak. LH causes shedding of a mature egg from the follicle (ovualtion): follicle ruptures behind an empty egg called corpus luteum. LH also stimulates production of progesterone

Roles oestrogen and progsetrones:

• Oestrogen levels rise:day 1 + Peaks and decreases as just before day 14. Endometrium starts to thicken and the cells mature
• Progesterone: Stays lower from day 1-14, and starts too rise once ovulation starts and production by corpus luteum increases it's increased levels cause the endometrium too ticken.
• Fall in progesterone deteriorates corpus luteum and causes endometrium too break down :menstruation"

Negative and positive feedback mechanisms

• FSH stimulates development of a follicle (which produce oestrogen): Stimules production of oestrogen as endometrium increases to produce more fHS receptors and more production of oestrogen. - POSITIVE FEEDBACK. HIGH LEVELS OF OESTROGEN inhibit secreation of FSH -NEGITIVE FEEDBACK
• Oestrogen rises too high to create LH from the pitularly gland. Which stimulates wall of follicle to develop into a corpus luteum with seretes more oestrgoen = Positively feedback LH stimulates wall follicles to develop into corpus luteurm and progstrone. progstorne thickens and maintains endometrium inhibits seretion of FSH + LH of the pitulary gland. : NEGITIVE FEEDBACK

Hormones Involved With In Vitro Fertilisation Treatment

• Due too issues effecting developemtn of egg/ sperm, affects of reproductive system of male.
• IVF is when eggs are fertilised by sperm OUTSIDE the body sterile condition in controlled laboratory setting.
• Steps of IVF:
• Stopping normal seretion of women's harmone by inhibiting the production of FSH and LG from the pitulalry gland: causing oestrgen+progetornee production to stop.
• Temporaliy haling normal mensrul cycle allow allowing controlled timing + quantity of production of eggs in the ovaries. By infection stimulation developemtn with FSH and LH stimulation of follicles. Giving super oluation (FSH level concentration) and giving many more more follicle than norm.
• Egg collected from the woman and fertilised and develpe to the emyboro then inserted during balls of cells within about 48 hours alter fetilization, with more then Embry inserted into the mothers eteru
• EXTRA progstroen maintain endometrium 30 rate of sucess of IVF

Fertilisation

• Fertilisation is the fusion of one sperm and one ovum is a 2 haploid nuclei : a diploid zygote
• Spem attrasctred towards chemical signals during sexual reproduction after released sperm.
• When a sperm cell passes, the process to prevent more the one sperm passes takes in cell surfave membranes. (polyspermy (
• Once the sperm passes though ,receptors ,head bind will protiens of on the memrbane allowing memebranse to the the cell to few and spem nucleau too enter.
• The vesicles realised will detory flagellum tail and mitochrondon The hapoliod sets of chromosones sperm are within the cyopalsm og ovacyte
• Chromes form protonuclear within the cell and which DNA undercode replication
• 2 haidoldei porcleide come together and membrane dislve creating zygote 2 cell cell with chromones to undergo mitosis to form blastsosatist

Plants

• Male/ female gametes are produced and anther into ovule
• Male gamete :within poller grain from into anthet which pollen sacs(each pollen contains diplomatic cell with four halpoid pollen mitosis creates are male cells
• Single diplomat call wit ovule into a 2 hploid egg cells (mitosis makes a female cells Pollination fertilisation Process of pollen to anther into stigma and to other different plant: herpdomophtic (female+ males), self plant (same flower to one another flower), cross (one to another with attractors (colours/scents))
• Gametes creates fusion and is called dipliod nucleu Pollen tubes from ovaries
• Ovules will become seeds/ ovary to be fruits
• Ovules- sperm to be enbyryo food storage. Preventing pollen: lack vareyt + adpatons. genes control protein prevtes grwith of polelnntudes a. falied to get a pollen to the ovlues and degenerates.

How to attract insects during cross pollination

• Reproductive organ of plant (have male and female parts).
• pollen (makes sperm/ is not not Capable of locomotion)
• pollen too the stigma/
• insects or birds (which are slightly for different/Adapted by insects/ Wind features nectar + polllen stick too budt (stigma + other plants

Insect-Pollinated

Petals

• Large and brightly coloured to attract insects.
• Moderate - insects transfer pollen grains is efficiently with a high chance.
• Larger, sticky is attached to insects the stigma to stick

Wind-Pollinated features

• Anthers open then pollen blowns into winds/ current
• Pollen lands on a plant + species features wind =small to dull/ small amount /outside stimgnas/ feather to catch pollen. ( =outisde / swinging loss long filament. "cross pollen one plant to other same plant".
• improves variation + dependent of pollen
• times, some not compatible as genes ensure to work : no variation: genes prevent pollen is not germinated , not into style
• degenerates

Germination

• distrbite seed competition between offsprings
• WIND/ WATER > light seends travel ; ANIMAL > fruits in the animal/ hooks on fu; EXPOSOLOS
• transfer polllem is to stigma
• seed form within oary; dormancy + may germnatete
• Germinaiton is a start that there is required
• water, water test to burst the seend: embryo exit
• oxygen> energy is to be released
• warmth- up, to a certain point that is to cause eznume to work and rise / controll by enzymes and not work effectivlty
• embryo> foof reservers contain cotredons. Needs replnshments and imbibion actives biochmtery in embyrs >repisnation/ protein created too through seed coat
• the structure is radicie- first formed to the resposnds hypo: shoot below cotyledons and go upwords shotos> leave so process for begin
• roo t establihed so plant will grow Hormone Puberty
• reproductive hromes cuase sedary sexial characctitcsitoc.

Homrones and Purity

• GMR: Gondotropin hormone + steroid hormones
• secrects gornadin : pitually secretre then 2 hormones.
• FSh LH , enhance effects horomes. and seocdnary characteristics MALE CHARACTERES:Lryny,muscle + body.facial hair testes/ scrotum + gland Spem producion to sex drive

FEAMALES:

• DEvlepoment of breastes
• widenling of pelvis
• hair
• enlamgent of vaing and uterus
• matruaiton
• fat under skin
• sexxx drive

Gremtogeneis= Gamestes

• sepcificalzed into zygote/ gonad;
• spepm male+ova male
• male male testes/ female ovaries Mytosis +melsodis Sermgatoenris + oogenris
• cells devoding into many to the gametes
• by yets too hpadloid Spermatogensis :take place in testes into pubtery onwards tubules > sernious +intersticails cells( leyding), hormone (testoneSertoili) , epihteilim
• sernferious divide > spemtaognia
• one becimes cells /one remai
• spermogina > serolili (innlining).
• spermogina > primaies. mature, and thein messiois froms secondayr
• spermtics remains as seroisli. beciming cell
• dectaches seroiil.

Oogenisis

• beforve birth / ovareis and epulithium
• mitososo into doiod cells > oogniona. >to the tissues or ovaries
• 7 motnsh .

Fetilization

• oognial . gwor into mesois as filicile cerws > prime

• prime : the proces pause (

• pulbtery . FSH stirmaultey 2 cells after memssi i> seocndea/ bod and smal polarbody : citalsm

mesosis i and seocnderu / comes with layber of to overation

• remanes into lutem
• donnot finsh uti spenm cnters where meiosis end

+ovvm inbreffley

• splar body
• poltspemy ; one spem aod ovoium but realsey many chemicisl and p[reven ts of

1: digets proutern > fuses by exo

Hormone in pregnauncy

chorotic : the embrotoimplants, secretes> stirnalte cuprus to maintin sectt > to the growth, intbit membstruation : after the > palcenta. to the urien

• to mobole/ sample
• antibody/urine / antobdt The palca>blood vessls arranged. number of villis blood can miox only very sort disntnce of mothet blood vessks / spaces
• seledtive to molther > water etc... To mother > C12/ water Growint foetisu. >placnemtra. Membranse / blod

HOrmrone Replacremtn Therapy

• too relive symptoms : stopping periods after month

• 55 and 65 for overaits gtoo releasing oppps> fhs ls levels

• hfs+lh levels increase - hot /breast hedah ces +replave hormp es > osortgen (sntheytrc) elpe to redice symphtms.

• blood boners

• the had drecisd 1990s increase heart diciese """"time start at early then hear reduse hear ditsease

• decrwasd whe n analysis statudds.""