Reproduction, Biology

REPRODUCTION -

  • It is not only production of new ones to increases its number but a means for the survival of a population on earth.
  • Main aim is "survival and continuation or race".
  • If there is no reproduction, species will become extinct just after one generation.
  • Reproduction is mainly of 2 types -

S .No.

Asexual

 

Se x ua l

1

W ithout reproduc tive organs

Reprodutive organs present

2

No formation of gametes

Formation of gametes

3

Uniparental

Uni or biparental

4

Meiosis absent

Meiosis present

5

Offsprings are genetically similar to parents

Different

6

No variation

Variation occur

7

Possibility of extinction is increased

Evolution occur

  • Animal may be unisexual or diocious (male & female are separate) and bisexual or monocious (male & female in same animal).
  • Unisexual are - insects, aschahelminthes & vertebrates.
  • Bisexuals are hydra, earthworm & platyhelminthes.
  • Fertilization may internal (inside body) e.g. sponges, platyhelminthes, aschahelminthes, arthropoda, reptiles, birds, mammals or external (outside body) e.g. coelenterata, earthworm, some pisces & amphibia.
  • Fertilization may be self (in same animal), e.g. tapeworm and crossed e.g. bisexual (protandrous e.g. hydra, earthworm, progynous e.g. sponges) & all unisexual animals.
  • Protandrous means testes mature first.
  • Progynous means ovary mature first.
Posted Date: 10/8/2012 5:44:11 AM | Location : United States







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