Chapter: 11th 12th standard bio zoology Human Body higher secondary school

Algea Reproduction : 1. Vegetative 2. Asexual 3. Sexual

Reproduction Three common methods of reproduction found in Algae are 1. Vegetative 2. Asexual and 3. Sexual

Reproduction

Three common methods of reproduction found in Algae are 1. Vegetative 2. Asexual and 3. Sexual

Vegetative reproduction

It lakes place by fragmentation or by the formation of adventitious branches.

Asexual reproduction:

It takes place by means of different kinds of spores like Zoospores, Aplanospores and Akinetes. Zoospores are naked, flagellated and motile. eg.(Chlamydomonas) Aplanospores are thin walled and non motile (eg Chlorella) Akineties are thick walled and non motile spores (eg Pithophora)

Sexual Reproduction

Sexual reproduction involves fusion of two gametes. If fusing gametes belong to the same thallus it is called homothallic and if they belong to different thalli it is heterothallic. Fusing gametes may be isogametes or heterogametes.

Isogamy

It is the fusion of two morphologically and physiologically similar gametes.eg. Spirogyra and some species of Chlamydomonas .

Heterogamy

This refers to the fusion of dissimilar gametes. It is of two types

1. Anisogamy

2. Oogamy

Anisogamy is the fusion of two gametes which are morphologically dissimilar but physiologically similar (both motile or both non-motile)

Oogamy refers to the fusion of gametes which are both morphologically and physiologically dissimilar. In this type of fusion the male gamete is usually referred to as antherozoid which is usually motile and smaller in size and the female gamete which is usually non- motile and bigger in size is referred to as egg. The sex organ which produces the antherozoids is calledantheridium and the egg is produced in oogonium. The fusion product of antherozoid and egg is called Zygote. The zygote may germinate directly after meiosis or may produce meiospores which in turn will germinate.

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11th 12th standard bio zoology Human Body higher secondary school : Algea Reproduction : 1. Vegetative 2. Asexual 3. Sexual |