Science 3 Marks Question

The missing part along with the labelled part is as follows:

1. The given figure is of Bryophyllum leaf. It is also called as sprout leaf plant.
2. It shows vegetative reproduction by leaves.
3. The leaves of Bryophyllum develops some buds in its margin or edges which grow into new plants, when buried in the soil.

Sexual reproduction is a process which involves production of seeds. It requires two parents. Most plants reproduce sexually with the help of flowers. The main function of a flower is to reproduce and therefore develop new seeds that can grow into new plants.

Following are the advantages of vegetative reproduction:

1. Vegetative production allows plants to produce new plants quickly without any reproductive organs.
2. The plants produced by this method are exact copies of the parent plant.
3. New varieties of plants having required characteristics can be developed by this method.

Sugarcane and rose are propagated by stem cutting that is a method of vegetative propagation, in which stem is capable of growing into a mature independent plants that are identical to their parents. Potato is an underground modified stem having bud called eyes, which sprout and develop into a new identical plant. Thus, the plants which cannot produce seeds, can be propagated vegetatively with the help of vegetative parts such as stem, roots, buds and leaves.

Benefits of Seed Dispersals:

• Seed dispersal avoids overcrowding of young plants around their parent plants.
• It helps in preventing competition between the plants and its own seedlings for sunlight, water and minerals.
• One of the benefits of seed dispersal is that it enables the plant to grow into new habitats for wider distribution and provides them with better chance of survival.

Plant produces large number of seeds. When these seeds fall down they starts growing. The process by which the seeds are scattered to different place (far and wide from their parents) is called seed dispersal. The seeds and fruits are dispersed away through various agencies like air, water and animals. Sometimes dispersal takes place by the explosion or bursting of fruits. If all the seeds of a plant were to fall at the same place and grow, there will be a severe competition for sunlight, water, mineral and space. As a result, the survival for the plants will be difficult and the plants who survive will not grow into a healthy plants.

1. Unisexual flowers are papaya, cucumber, com.
2. Bisexual flowers are rose, mustard, lady’s finger, Petunia, pea.
3. Unisexual flowers are also called as incomplete flower while bisexual flowers are called hermaphrodite or complete flowers.

The mode of dispersal of the seeds having following properties are as follows:

1. Seeds with wings-like seeds of drumstick and maple become light weighted and can be blown away by air. Thus, these are dispersed by wind.
2. Small and light seeds like seeds of grasses and cotton (having hairy growth) are also dispersed through wind.
3. Seeds of Xanthium, Urena have spines and hooks on them, these hooks or spines are attached to the fur of the animal body. When animals move to other places and rub their body with tree, etc., these seeds fall from their body and get dispersed.. Therefore, these are dispersed through animals.

Dispersal of seeds is the spreading of seeds across places.This dispersion of seed can take place by the following means:

• Water: it takes place in aquatic plants and plants growing near water bodies, here seeds are dispersed through water. These seeds tend to develop a fibrous or spongy coating. The seeds float away from the parent plant. Example: coconut.
• Wind: Some light-weighted seeds tend to float in the air and hence are dispersed by wind. Some seeds have long, feathery tails which help them to fly, like the tail of a kite. Example: Maple.
• Animal: Seeds that are dispersed by animals have spines which help them attach to the animal bodies, hence carried to distant places. Example: urena.

Fungus, moss and fern reproduce by the method of spore formation, which is a type of asexual reproduction. Spores are asexual reproductive bodies produced by the parent plant, in spore cases. When the spore cases burst, the spores with hard protective layer are spread into air. On return of favourable conditions, the spores germinate and produce new plants.

Pollination is of two types:

• Self-pollination: The transfer of pollen grains from the anther of a flower to the stigma of the same flower or another flower of the same plant is known as self-pollination or autogamy.
• Cross pollination: The transfer of pollen grains of a flower to the stigma of another flower of a different plant of the same species is called cross pollination or allogamy.

Flowers have nectars that attract insects. Insects suck these nectars as their food. When insects like bee, butterfly, etc., sit on the flower for sucking nectar, the sticky pollen grains get attached to their legs and wings. When these insects again sit on another flower, these pollen grains are transferred to the stigma of that flower from the body of the insects. In this way, insects help in pollination.

Self-pollination	Cross-pollination
It involves the transfer of pollen from the stamen to the pistil of the same flower.	It involves the transfer of pollen from the stamen of one flower to the pistil of another flower of the same plant or that of a different plant of the same kind.
It occurs only in bisexual flowers.	It occurs in both unisexual and bisexual flowers.

When the pollen grain reaches the stigma of a flower, it starts giving rise to a pollen tube that passes through the style and reaches the ovary of the pistil. When the pollen tube reaches an ovule, it releases the male gametes. Male cells are released into the ovule for the fertilization with the female egg cell and thus the zygote is formed. After this process of fertilization, the ovary develops into fruit and ovule into seeds.
The Seed. The seed in a plant is the part that develops from the ovules after fertilization. They are enclosed in the fruit which develops from the fertilized ovary. The seeds are formed as a result of sexual reproduction and contain the young embryo which can develop into a new plant.

The sexual reproduction in flowering plants involves:

1. Pollination: Transfer of pollen grains from the anther to the stigma is called pollination. Pollen grains are transferred mainly by wind, water and insects. They are called as pollinating agents.
2. Fertilization: The fusion of a male gamete with egg is known as fertilization. The fertilized egg is known as zygote which develops into embryo.

1. Cutting: Here the cuttings of the "parent" plant are removed and placed in a suitable environment so that they can grow into a whole new plant. For example rose cutting.
2. Layering: The stem is bent down and the target region buried in the soil. The buried part of stem develops roots and is detached from the plant and develops into new plant.
3. Grafting: In grafting a shoot or bud of a selected, desired plant (scion) is grafted onto the stock of another type of plant.

The branch can be used to grow a new rose plant, as rose reproduces through vegetative
Propagation by stem cutting method. The lower end of the stem cutting is buried in soil and the upper part having the bud is kept above the ground. The planted cutting is watered everyday.
After a few days, the cutting in soil develops roots and bud produces a shoot. In this way a branch cutting of a rose plant grows to become a new rose plant.