Presentation on theme: "The two modes of Reproduction"— Presentation transcript:
1 The two modes of Reproduction ASEXUAL REPRODUCTION ANDSEXUAL REPRODUCTIONIn asexual reproduction, a new individual develops or grows from a single parent.There is no fusion of cells from two different parents.
2 SEXUAL REPRODUCTIONIn sexual reproduction, new individuals are formed by the fusion of a male reproductive cell (male gamete) and a female reproductive cell (female gamete).This fusion is known as fertilization.
3 How about asexual reproduction? Since there is only one parent, the new individual would be identical in characteristics to the one parent which produced it.Can you think of advantages of sexual reproduction and advantages of asexual reproduction?
4 Detached portion of Parent Asexual ReproductionSexual ReproductionAdult parentAdult parentAdult parentDetached portion of ParentMale gameteFemale gametefertilizationNew AdultzygoteNew Adult
5 Reproductive vs Vegetative Structures Plant parts : roots, stem, leaves, flowers and fruits.Reproductive Structures :flowers and fruitsVegetative Structures:roots, stem and leavesSome plants can reproduce both ways – reproductively as well as vegetatively.
6 Vegetative Reproduction Two types : Natural Vegetative Propagation and Artificial Vegetative PropagationNatural Vegetative Propagation:They are also flowering plantsBut they can reproduce through underground storage organs e.g. rhizomes, bulbs, corms, tubers, rootsOr shoots e.g. runners, offsets, suckersEssentially, same principle :These organs have a store of food. Shoots grow from these organs bearing leaves and flowers. In the process, food is withdrawn from the underground storage organ which shrivels. As the leaves manufacture food, food is transported to the buds which gradually swell to become new underground stems.
7 Natural Vegetative Reproduction Rhizomes (e.g. canna, lallang, ginger)Stem that grows horizontally above or below surface of soil
11 Natural Vegetative Reproduction Bulbs (e.g. onion)Flattened, disc-like stem with closely set nodes bearing fleshy scale leaves surrounded by some dry scale leaves.Buds are in the axils of the fleshy scale leaves.
12 Natural Vegetative Reproduction Tubers (e.g. potato)Swollen underground stem bearing a number of scale leaves.
16 Natural Vegetative Reproduction Offsets (e.g. water hyacinth and water lettuce)Like runners but shorter and thicker
17 Natural Vegetative Reproduction Suckers (e.g. pineapple, banana, chrysanthemum)A shoot arising either from the underground portion of the stem or from an adventitious bud on the root.
18 Advantages and Disadvantages of Natural Vegetative Propagation No need external agencies e.g. insects, wind etcFood is usually present in the vegetative structures, a rapid development of buds into daughter plants can take place.New plants resemble parent plant in every way.Involves only one parentDisadvantagesLack of dispersal mechanism may lead to overcrowding.New plants are less variedNew plants may be less adaptable to changes in environmental condition.