Page 2 - LN-Reproduction_in_organism_(2)[1]

 In case of few fungi and algae, both male and female gametes are motile.
 In most cases water is the medium for gamete transfer.
 Male gametes are produced in several thousand times the number of female gametes produced to
compensate the loss during transfer.
Fertilization:
 Fusion of male and female gamete is called fertilization or syngamy.
 The female gamete undergoes development to form new organism without fertilization. This
phenomenon is calledparthenogenesis.
 Gametic fusion takes place outside the body i.e. water is called external fertilization.
 Their must be synchrony of gamete release, large number of gametes released to enhance the
chance of fertilization.
 Enable the individual to produce large number of offsprings.
 A major disadvantage is that the offsprings are extremely vulnerable to predators.
 Fertilization takes place inside the body is called internal fertilization.
Zygote:
 Formation of zygote after fertilization is universal in all sexually reproducing organisms.
 Zygote is formed usually in water in case of external fertilization.
 Zygote is formed inside the body of the organism in internal fertilization.
 Zygote of fungi and algae develops a thick wall that is resistant to dessication and damage.
 Organism with haplontic life cycle, zygote undergoes meiosis to produce haploid spores.
Embryogenesis:
 Development of zygote into an embryo is called embryogenesis.
 Zygote undergoes cell division (mitosis) and cell differentiation.
 Oviparous animal which lays eggs and development takes place inside egg.
 Viviparous animal gives birth to the young. The development takes place inside the body of the
female.
 In plants:
o Zygote developed into embryo.
o Ovule developed into seed
o Integument of the ovule developed into seed coat.
o Ovary developed into fruit.
o Ovary wall developed into pericarp.