• Reproduction •
DNA - Deoxyribo Nucleic Acid
• Different organisms use different methods of reproduction, depending on their body design.
Asexual reproduction [one parent]
• Fission
- 1) Parent cell splits into two daughter cells in any plane (ameoba) or in specific plame
(Leishmania) This is called binary fission. (one copy of DNA is formed)
- 2) Parent cell divides into multiple daughter cells (plasmodium). This is called
multiple fission. (multiple copy of DNA)
2. Fragmentation: In multicellular organisms with simple body design, body breaks into
pieces or fragments which may grow to form a organism. (happens in Spirogyra)
3. Regeneration: Multicellular organisms with cell differentiation, when cut in small pieces
may regrow into complete organism with the help of special cells. (Planaria & hydra)
4. Budding:
A bud is grown in the body, which can
detach and form a complete organism
(Yeast & hydra)
5. Vegetative Propagation: Many plants give rise to new plants with their vegetative parts
such as roots, stems, leaves.
~ Advantages of Vegetative Propagation:
- Used in layering & grafting of sugarcane, grapes etc
- Bear flowers & fruits earlier than plants grown from seeds.
- All plants have same characteristic to parent plant.
- Buds produced in the notches along the leaf margin of Bryophyllum fall on the soil
and develop into new plants.
6. Spore Formation: Takes place in sporangia (spore sacs). They're thick walled, so they
survive in harsh conditions & grow into complete organisms.
Seen in rhizopus which is the thread like structures on bread moulds.
7. Tissue Culture: Use of small tissues or cells from growing tip of a plant to produce a new
plant in artificial conditions.
↳ Group of cells. called callus is formed.
Sexual Reproduction
During sexual reproduction, two germ cells fuse to form zygote, giving rise to a new
individual. These are produced by a special cell division called meiosis which results in
halfing of chromosomes number. Number is restored after fusion.
• Male gamete is motile germ cell
• Female gamete is germ cell containing food.
Plant Reproduction
• Stamen is male reproductive part.
• Pistil is female reproductive part.
Pistil
● Ovary is Swollen bottom part. Itontains ovules which contain egg cells.
● Style: Middle elongated part
It joins stigma & ovary for fertilisation.
● Stigma: Terminal part
it attracts pollen and it may be sticky
• Pollen is formed in anther.
• Pollination → Fertilisation → Germination.
Self pollination is when transfer of pollen is in same flower or different flower of same plant.
● Advantage : Preserves parental characters
● Disadvantage: leads to expression of genetic defects.
Cross pollination is when pollen is transferred to answer plant (with agents).
● Advantage: more variation
● Disadvantage: Depends on external agents
Cross pollination is better as results in evolution.
After pollen lands, it travels through style to reach ovary (then fertilisation occurs)
After fertilisation:
● Zygote goes under divisions.
● As a result, embryo is formed.
● Ovule develops a thick coat.
● Ovary ripens to form fruits.
● Petals, sepall, stomen, style dry and fall off.
Conversion of embryo into seedling is called germination
Human Reproduction
• Puberty is the time of adolescence when reproductive tissues begin to mature.
Differences in boys & girls at time of adolescence:
Girls:
● Breaste enlarge
● Hips become broader
● Menstrual cycle start
● Hair in armpit and genital area
Boys
● Body becomes muscular
● Hair on face, genital, armpit
● Penis can enlarge and erect.
• Sperm formation requires a lower body temperature than normal.
Male Reproductive System
(urinogenetal as both urine and sperm comes out from this same passage)
● Testes: Release testosterone and produces sperms
● Prostate gland / seminal vesicles : Production of fluid to provide fluid medium for
sperms.
● Vas deferens: Delivers sperms from testes to urethra.
● Scrotum : Provides the right temperature for the sperms. Testes is inside scrotum.
● Urethra: Responsible for expulsion of sperms and empties urine from the bladder.
Testes ➩ Vas Deferens ➩ Urethra ➩ Cervix ➩ Uterus ➩Oviduct
Female Reproductive system
● Ovary: Production of eggs (ova). Production of estrogen
● Oviduct/Fallopian Tube: Site of fertilisation and carries eggs to womb from ovaries.
● ↳ Ova are released from ovary in to the fallopian tube which leads it into uterus.
● The ovum gets fertilised in the fallopian tube, where sperms travel to fertilise the egg
from cervix to fallopian tube.
● Uterus: Embryo gets implanted in uterus and its development till child birth takes
place in uterus.
● Vagina: Site of entry of sperm.
• Placenta:
For implantation of foetus, a special tissue called placenta is developed from the maternal
uterine wall. It is disc shaped, in the uterine wall with villi on embryo's side & large blood
spaces on maternal side.
Functions :
● Provides large surface area for gluvose and O2 to pass from mothers blood to
embryo
● Removes embryonal metabolic wastes.
Reproduction Process
● Sperms enter through vagina and reach oviduct to encounter the egg.
● The zygote formed, starts dividing to form an embryo.
● Embryo is planted in the lining of uterus and it becomes foetus.
● The lining thickens and is richly supplied with blood to nourish the growing embryo.
● The development usually takes 9 months & the child is born.
Menstrual Cycle
If fertilisation doesnt take place, the lining of uterus slowly breaks and comes out through
vagina as blood and mucous. - - - This cycle happens every month and usually lasts for 2-8
days.
- The flow of blood & mucous and is called menstruation.
Methods to prevent unwanted pregnancy:
Mechanical
● Condom- A cover worn on the penis at the time of intercourse.
● Diaphragm : Covering worn by females.
● Copper-T: Intra- uterine device which prevents fertilisation. (implanted in uterus)
- Copper-T doesn't stop STDS as it doesnt provide a barrier against mixing of body
fluids from two individuals therefore acts only as contraceptive but doesnt protect
from STDS.
Chemical:
● Oral pills- OCPS or Oral Contraceptive Pills are used in females which alter hormonal
level.
Surgical [Permanent]
● Vasectomy: Portion of vas deferens is cut.
● Tubectomy: Portion of oviduct is cut.
Reasons for contraceptives :
● Help in spacing two children.
● Help in maintaining mother's & child's health.
● Less mortality among new borns.
● Better Care & healthier society.
● Prevention of STDs.
● Reducing cases of maternal mortality.
● More productivity & better economic status of society.
• STDs
Bacterial - Syphilis, gonorrhoea
Viral- AIDS, Warts
These infectious diseases are spread by sexual contact with infected person.
● Fluid discharge, burning sensation while urination are symptoms.
➩ Mustard seeds have biggerchance of self- pollination out of mustard, papaya, hibiscus
and watermelon.
Male gamete:
● Produced in large numbers.
● Smaller
● Have tails
● Are motile
● Are of Two types
● Produced a lot at a time
Female gamete:
● Larger
● Dont have tail
● Aren't motile
● Only of one type
● Produced one at a time
Chromosones are maintained:
● This has been achieved by having special lineages of cells in specialised organs
which have only half the no. of chromosomes and thus half the amount of DNA.
● When germ cells from two individualS combine, it results in re-establishment nof the
no. of chromosomes and DNA content in new generation.
Banana reproduces asexually.
Gametes ➩ Zygote ➩ Embryo ➩ Seedling
Rapid spread of bread mould is due to
• Large number of spores
• Availability of moisture and nutrients in bread.
• Length of pollen tube depends on the distance b/w upper surface of stigma and lower part
of style.
• Water does not provide required energy to yeast for reproduction, while sugar does provide
energy , hence it multiplies in sugar.
Crossing over occurs during meiosis, thus there is more variation. (Discussed in chapter 9)
Chromosomes in body remains constant as mitosis occurs in a human body and im mitosis
chromosome numbers are not halved. Meosis only occurs for gamete formation
No formation of gametes in asexual reproduction.
