REPRODUCTION The ability of the living organisms to produce new living beings similar to themselves is called Reproduction. FISSION Fission means ‘to break’. Thus in this method an organism can divide into two or more organisms. So it can be of two types: 1. Binary fission 2. Multiple fission Binary Fission The term ‘binary fission’ consists of two words ‘binary’ and ‘fission’. The word ‘binary’ means ‘two’ and the term ‘fission’ means ‘to break’. It may be defined as the division of an organism into two offspring's or daughter organisms. This method of reproduction is found in algae, fungi and bacteria. In this method under favorable conditions the parent organisms grows to its full extent and then divides into two parts. Each part of the parent then separates and grows into a new organism. This process is repeated further by the new organisms to produce a large number of organisms. Binary fission ALGAE FUNGI SPORE FORMATION Spore formation is a method of asexual reproduction which is found in non flowering plants such as fungi (Rhizopus) and bacteria. In this method of reproduction, the parent plant produces hundreds of tiny spores which can grow into new plants. The spores are the microscopic, tough and resistant bodies which are round in shape and can grow into a new plant under suitable conditions. We shall now discuss the formation of new plants by spores by taking the example of fungi called as bread mould or Rhizopus. In Rhizopus numerous spores are produced within sacs called sporangia as shown in the figure. The sporangia are knob like structures which are present at the top of the thread like structures called hyphae. When these sporangia bursts, the spores are scattered by rain, wind or insects and under suitable conditions develop into a new Rhizopus plant, when they fall on a suitable substance like bread. FERNS MOSSES FUNGI LICHENS FERN FUNGUS MUSHROOM n HYDRA BUDDING YEAST VEGETATIVE REPRODUCTION Learning Outcome : 9.1 - Asexual reproduction in plants and animals. Some plants have special underground stems called rhizomes. They resemble roots but are really stems, indicated by the presence of scalelike leaves, buds & nodes. They grow by branching in different directions & forming new plants as they grow. 16 rhizome 17 MODIFIED STEM Vegetative propagation by roots In some plants vegetative propagation can take place from roots. For example, in sweet potatoes the roots bear adventitious buds from which new plants can develop when it is buried in the moist soil. Such roots are called reproductive roots. MODIFIED ROOTS Learning Outcome : 9.1 - Asexual reproduction in plants and animals. • Some plants are capable of producing young plants along their leaf margin. • These miniature plants are called plantlets. • These little structures grows a short stem & roots before they drop to the ground & grow into independent new plant. • These plants have meristematic tissue along the margins of their leaves capable of producing plantlets at each notch of the leaf. 26 Bryophyllum daigremontianum produces plantlets along the margins of its leaves. When they are mature enough, they drop off and root in any suitable soil beneath. plantlets 28 Vegetative propagation by leaves Vegetative propagation can also take place from the leaves. This method is found in plants such as Bryophyllum and Begonia. Vegetative propagation by leaves in Bryophyllum In the leaves of Bryophyllum meristamatic marginal notches are present. From these meristamatic tissues new plants can develop after coming in contact of soil. The new plants can detach from the leaves and develop into a full plant after falling on the ground. Advantages of vegetative propagation 1.The new plants produced by vegetative propagation are exactly like the parent plant i.e. the new plants possess all characteristics of the parent plant. 2.The plants produced by vegetative propagation grow rapidly. 3.Desired varieties and qualities of fruits and plants can be produced by vegetative propagation. 4.Those plants can also be produced by vegetative propagation which do not produce seeds or which cannot produce viable seeds. 5.The desirable characters of a variety can be preserved indefinitely through vegetative reproduction. Grafting to produce desirable traits TISSUE CULTURE Sexual Reproduction in Plants Female Part (GYNOECIUM) Male Part(ANDROECIUM) (Pistil) (Pollen grains) Male Part(ANDROECIUM) STAMEN Female Part (GYNOECIUM) PISTIL Dispersal by Wind: Seeds of some plants are light-weight and some hairlike or wing-like structures are present on them. Such seeds float on air and are thus dispersed by wind. Example: Dandelion, maple, drumstick, etc. Dispersal by Water: Dispersal by water takes place in some aquatic plants and in some which grow near a water body. Seeds of water lily float and thus dispersed by water. The coconut seed has a tough fibrous covering which has plenty of air inside. This helps the coconut seeds in floating on water. Dispersal by Animals: Some seeds have spine like structures on them. They get stuck to the fur of animals and thus get spread to different places. Examples; guava,apple,mango etc. Some seeds are swallowed by birds and animals along with fruits. These seeds get dispersed with bird or animal droppings. Dispersal by Bursting: Some fruits burst open when they mature. The force of bursting is enough to spread the seeds. Examples; Ladyfinger, castor, balsam, etc.