how do organisms reproduce

Importance of Variation

Importance of Variation

• helps organisms adapt to changing environment

• provides stability to a species and supports evolution

• DNA variations leads to different forms of species

Importance of Reproduction

• maintenance of the existence

• preservation of species

• role in evolution

Asexual Reproduction

• a single individual gives rise to new individual

• gametes are not formed

• new individual is identical to parents

• extremely useful as a means of rapid mutation

• ex- microorganisms

Sexual Reproduction

• two individuals are needed, one mail and one female

• gametes are formed

• new individual is genetically similar but not identical to parents

• useful to generate more variations in species

• ex- animals and humans

Modes of asexual reproduction

• fission

• budding

• fragmentation

• regeneration

• spore formation

• vegetative propagation

Fission

When a parent cell divides into 2 or more daughter cells

Types of Fission

Binary Fission- Only 2 daughter cells

Multiple Fission- Multiple daughter cells

Binary fission types

Amoeba - Irregular binary fission

Euglena - Longitudinal binary fission

Paramecium- Transverse binary fission

Leishmania - Definite orientation

Multiple Fission type

Plasmodium- malarial parasite- multiple daughter cells

Fragmentation

the multicellular organism breaks up into small pieces upon maturation, each piece develops into a new individual

Example of fragmentation

Spirogyra

Regeneration

if an organism is somehow cut or broken into many pieces each piece grows into a complete organism, it is not possible in complex multicellular organisms as this process can be used to reproduce organisms which have a simple body

Regeneration examples

Planaria and Hydra

Budding

A bud is formed which develops into tiny individual, it detaches from the parent body upon maturation and develops into a new individual

Budding example

Hydra and Yeast

Spore Formation

Spores are small bulb like structures which are covered by thick walls, under favorable conditions, they germinate an produce new organism

Spore formation example

Rhizopus on bread (needs moist surface to germinate)

• the spores remain intact inside the sporangium(thick wall) which burst when there are favorable conditions

• the spores are then spread in the environment

• the spores are thousands in number to ensure reproduction as many are destroyed due to different reason

• each spore on germination give rise to a new organism, this happens when they get favorable environmental conditions

Vegetative Propagation (natural)

• by underground stem - potato

• by leaves- bryophyllum

• by roots- dahlias, sweet potato

Vegetative Propagation (artificial)

• cutting vegetative propagation

• layering

• grafting

Bryophyllum

• certain buds are produced in the notches of their leaves

• these buds are called epiphyllous buds or adventitious buds

• when these buds fall on the soil they develop into new plants

Cutting (vegetative propagation)

• small part of the plant is cut

• the small part is buried partly in the moist soil

• this cutting develops roots and grows into a new plant

• eg- rose, sugarcane, potato, cactus, bougain villea

Grafting (vegetative propagation)

• two plants of closely related varieties are joined together so they lives as one plant

• the part of the plant which roots remain in the soil is called as stock

• the cut part of the plant that is grafted on the other rooted plant is called scion

• eg- Mango, Apple, Lemon

Layering (vegetative propagation)

• a branch of the parent plant is buried in the soil

• the portion of branch which is contact with the soil produces roots and this rooted branch is called layer

• layer is then detached from the parent plant and act as a new plant

• eg - Jasmine, Hibiscus

Advantages of Vegetative Propagation

SQUID DOG (remove the vowels) - SQDDG

• S- Survival rate is almost 100%

• Q- Quick and cheap production of large number of plants

• D- Disease-free plants can be produced

• D- Desirable characteristics can be introduced

• G- Genetically identical plants can be produced

Sexual Reproduction

when reproduction takes place as a result of the fusion of male and female gametes

Parts of Plant

Types of flowers

Bisexual flower- has both male and female reproductive parts, eg- hibiscus, mustard

Unisexual- has only either male or female reproductive parts, eg- Papaya and watermelon

Pollination

the transfer of pollen grain from stamens to stigma

Self- Pollination

• if the transfer of pollen grains takes place between the stamen of a flower to the stigma of the same flower or another flow on the same plant

• only in bisexual flowers

Cross- Pollination

if the transfer of pollen grains takes place between the stamen of a flower to the stigma of another flower on a different plant

Agents of pollination

• wind

• water

• insects or animals

Fertilization of flowers

• one the pollen lands on the sticky stigma, the pollen starts germination and produces a long tube called as pollen tube

• this tube travels through he style and reaches the ovule present inside the ovary

• the male cells from the pollen grain enters the ovule through this tube

• the male cells fuses with the egg cell present inside the ovule and forms a zygote

After fertilization in plants

• after fertilization the zygote divides several times and forms an embryo

• the ovule develops a tough covering around it and it turns into a seed

• the ovary grows in size and gets ripen to become a fruit

• after fertilization the ovule of the flower becomes seed and the ovary becomes fruit

• the remaining parts of the plant get dried up, shrivel and fall off

Puberty

female - 10-12

male - 13-14

Puberty in both male and female

• growth of thick hairs under chest, armpits and around pubic area

• increased activity of sweat and sebaceous gland

• oily skin and appearance of pimples

• darkening in skin color of the genital area

Puberty in girls

• initiation of menstrual cycle

• breast size begin to increase

• darkening in skin color of nipples

• maturation of sex organs like fallopian tubes, uterus

• widening of pelvis and hips

Puberty in boys

• appearance of beard and moustaches

• cracking and deepening of voice

• penis occasionally begins to become enlarged and erect

• growth of sex organs like testes and penis

Male reproductive system

• sperms produced at the testes travel through a duct called vas deference

• the decertations from the seminal vesicles and the prostate gland are added to the sperms

• these secretions make the movement of sperms smooth and easier

• they provide nourishment to the sperms

• together they are called semen

• this semen passes out through this duct called urethra present inside the penis

Testes

• testes are present outside the body cavity

• the are located in an elastic sac like structure called as scrotum

• testes produces male sex harmone called testosterone

• testosterone helps in puberty of males

• testes cannot produce sperms at body temperature

• they need a low temperature to produce sperms

Female Reproductive System

• by birth each girl has two ovaries, each ovary contains thousands of immature eggs

• on reaching puberty these eggs starts maturing and get released

• each ovary alternately releases one eggs approximately every month

• the released egg is collected into the fallopian tube

• if the egg is not fertilized in the fallopian tube, every month the walls of the uterus gets lined by blood vessels and tissues in the anticipation of embryo

• the unfertilized egg lives for one day after that the egg gets dissolved

• the tissues formed along with the blood slowly breaks and expels out through the vagina

• this is called menstrual cycle

Reproductive in Humans

• during mating the sperms are deposited into the vagina of the female reproductive system by the penis of the male reproductive system

• the sperms travels through the cervix and uterus and reaches the egg present in the fallopian tube

• if the sperms fertilize the egg, it becomes zygote

• the zygote dives repeatedly and forms an embryo

• this embryo moves towards the uterus and gets implanted on the wall there

• the lining of the uterus grow tissues and blood vessels to accommodate the embryo

• after implantation the embryo grows into a foetus

Foetus

• the embryo gets nutrition from the mothers blood from the help of the special tissue called placenta

• it is a disk-like structure embedded in the walls of the uterus

• the placenta has blood spaces on the mother side

• and villi on the foetus side

• this arrangement provides large surface area for the exchange of materials between the blood of the mother and blood of the baby

• the nutrients and oxygen are absorbed and wastes are released into the mother blood

foetus development

• the development of this baby inside the mothers womb takes approximately 9 months

• this period is called gestation period

• the delivery of the baby takes place by the rhythmic contractions of the uterus

Health complications of sexual acts

sexual acts involves the intimate contact of body parts which may lead to the transmission of certain bacterial and viral diseases

sexual infections

bacterial infections

• gonnorhea

• syphyliis

viral infections

• warts

• HIV-AIDS

Risks and effects of teenage pregnancy

• interrupted education

• health risks

• maternal morality

• premature birth of baby

• still birth of baby

Contraceptive devices - condom

Condom- rubbery covering that is worn on the penis during intercourse, to prevent the entry of sperms in to the female reproductive system, also prevents the transfer of germs between the partners

Contraceptive devices - copper- t

it is placed in the uterus of the females to present the fusion of sperm and egg cell

Contraceptive devices - pills

birth control pills

• these are the drugs which change the hormonal balance in female body and stop the release of eggs

• the prolonged use of these pills causes side effects

Contraceptive Methods

Vasectomy - the vas deference of males is cut and ligated to prevent the release of sperms

Tubectomy- the fallopian tube of females is cut and ligated to prevent release the eggs

These are permanent methods, but if the surgery is not done properly it may lead to infections