Science [2 Mark Questions]

1. Male gametes(insides pollen).
2. Female gametes (inside ovum).

When an insect sits on the flower of a plant for sucking nectar, then the pollen grains from the anther of this flower sticks to its body. And when this insect sits on another flower of another similar plant, then the pollen grains sticking to its body are transferred to the stigma of this second flower. In this way, the insect transfers the pollen grains from the anther of flower in one plant to the stigma of flower in another plant and causes cross pollination.

Hydra reproduces by budding. In hydra, first a small outgrowth called bud is formed on the side of its body by repeated mitotic divisions of its cells. This bud then grows gradually to form a small hydra by developing a mouth and tentacles. The tiny new hydra detaches itself from the parent body and develops into a separate organism.

The flowers which contain only one sex organ, either stamens or carpels are called unisexual flowers like Papaya and watermelon plants. The flowers which contain both the sex organs i.e. both the stamen and the carpel are called bisexual flowers like Hibiscus and Mustard plant.

The prevention of pregnancy in women (by preventing fertilisation) is called contraception. There are 3 methods of contraception:

1. Barrier method.
2. Chemical method.
3. Surgical method.

The process of reproduction introduces some variations in the individual organisms of a species which enables them to survive even in adverse environmental conditions such as excessive heat or cold, etc. In this way, the introduction of variations during reproduction provides stability to the populations of various species.

The secretions of seminal vesicles and prostrate gland provide nutrition to the sperms and also make their transportation easier by secreting a thick liquid.

1. The chromosomes in the nucleus of a cell contains information for the inheritance of features from the parents to the next generation in the form of DNA molecules so the characteristics of a parent organism are transmitted to their offsprings.
2. When the DNA already present in the nucleus of a parent cell is copied by making more of DNA by certain biochemical reactions, then slight variations come in the two copies formed. Thus, variations are produced in the offspring’s during reproduction which form the basis of evolution. Example: Offspring’s produced by asexual reproduction have slight variations from their parents.

1. Sexual Method: Cats, Humans, birds.
2. Asexual method: Amoeba, Hydra.

The age at which the sex hormones begin to be produced and the boy and girl become sexually mature (able to reproduce) is called puberty. Females attain puberty at an age of 10- 12 years.

The ovary of a flower develops into a fruit after fertilisation. The ovary is a part of the carpel. Thus, in spite of the young stamens being removed artificially, the flower produces fruits.

1. Rose grows by means of cutting.
2. Jasmine grows by layering.

Water does not provide any energy to the yeast cells. So, yeast cells fail to multiply in water due to inadequate energy in its cells. Sugar provides energy to them to carry out reproduction by multiplying rapidly.

1. Corolla.
2. Calyx.

Sexual reproduction: Wheat plant and sunflower plant; Asexual reproduction: Ferns and mosses.

1. Testosterone.
2. Oestrogen and Progesterone.

1. The process of fertilisation is similar in plants and humans as both involve male and female gametes and show internal fertilisation.

2. Fertilisation in plants	Fertilisation in animals
   External agents are required for pollination.	External agents are not required.
   The seed is formed after fertilisation.	The human baby is formed after fertilisation.

The fields have dry stems of the old grass plants all over them. These dry stems have buds which are in the inactive state. By getting rainwater, the buds present on the dry grass stems get activated and grow to produce new grass plants.

The offsprings and parents of organisms reproducing sexually have same number of chromosomes due to reduction division (meiosis) during gamete formation which reduces the number of chromosomes into half in both male and female gametes. During fertilisation when male and female gametes fuse the original numbers of chromosomes as in parents is restored in the offspring.

Orchids, dahlia, carnation, chrysanthemum.

Advantages of grafting method:

1. It enables us to combine the most desirable characteristics of the two plants in its flowers and fruits.
2. It can be used to produce varieties of seedless fruits.

1. Uterus.
2. Vagina.

1. The name of the device Y is copper-T or IUCD.
2. The organ Y is the uterus.
3. This method cannot protect a woman from acquiring STDs.

The diseases which are spread by sexual contact with an infected person are called Sexually Transmitted Diseases. Example: Aids, Syphilis.

1. STD – Sexually Transmitted Diseases.
2. AIDS – Acquired Immune Deficiency Syndrome.
3. HIV – Human Immunodeficiency virus.

1. Cotyledons.
2. Radicle.
3. Plumule.

Amoeba reproduces by binary fission by dividing its body into two parts. When the amoeba cell reaches its maximum size, the nucleus of amoeba lengthens and divides into two parts. After that the cytoplasm of amoeba divides into two parts, one part around each nucleus. In this way one parent amoeba divides to form two smaller amoebae.

In vegetative propagation, new plants are obtained from the parts of old plants (stems, roots and leaves), without the help of reproductive organs. Example? Bryophyllum plant reproduces from its leaves and money plant grows from its stem. Advantages of vegetative propagation:

1. Plants grow faster by the process of vegetative propagation.
2. They need less care.

1. 24.
2. 48.

Fission:

1. It is a process in which an organism splits to form two or more new organisms.
2. Fission occurs in unicellular organisms.

Example : Amoeba.
Fragmentation:

1. It is a process in which the body breaks up into two or more pieces on maturing, each of which subsequently grows to form a complete new organism.
2. It takes place in multicellular organisms.

Example : Spirogyra.

The fertilised egg divides several times to form an embryo within the ovule which develops a tough coat around it and is gradually converted into a seed. The ovary of the flower develops and becomes a fruit with seeds inside it.

Asexual Reproduction:

1. The offspring arises from a single parent.
2. The production of new organism does not involve gametes

Example: Amoeba, Yeast.
Sexual Reproduction:

1. The offspring arises from two parents of different sexes.
2. The production of new organisms involves the use of gametes.

Example: Fish, Frogs, etc.

The transfer of pollen grains from the anther of a stamen to the stigma of a carpel is called pollination. It takes place when pollen grains are carried from the anther to the stigma of the flower.

Moisture is necessary for the growth of bread mould. The moist slice of bread provides both moisture and nutrients due to which bread mould grows profusely. On the other hand, the dry slice of bread provides nutrients but no moisture. So, in the absence of moisture, bread mould does not grow on the dry slice of bread.

When a pollen grain falls on the stigma of the carpel, it bursts open and grows into a pollen tube downwards through the style towards the female gamete in the ovary. A male gamete moves down the pollen tube and enters the ovule in the ovary. The tip of the pollen tube bursts open and male gamete comes out of the pollen tube which combines with the nucleus of the female gamete present in the ovule to form a fertilised egg called zygote.

The methods used for artificial propagation of plants are:

1. Cutting.
2. Layering
3. Grafting

Yeast is tiny, unicellular non green plant which reproduces by budding. In yeast, first a bud appears on the outside of the cell wall. The nucleus of the parent yeast cell divides into two parts and one part of the nucleus moves into the bud. Ultimately, the bud separates off from the parent yeast cell and forms a new yeast cell.

The testes are situated in the scrotal sac outside the main body cavity because the formation of sperms requires a lower temperature than the normal body temperature. Its disadvantage of being outside the main body cavity is that it is more prone to injury.

Cutting:

1. A small part of the plant which is removed by making a cut with a sharp knife is called cutting.
2. The new plant formed is exactly similar to the parent plant.

Grafting:

1. It is a method in which the cut stems of two different plants (one with roots and other without roots) are joined together in such a way that the stems join and grow as a single plant.
2. The new plant produced has the characteristics of both the parent plants

In this method, a cutting of the parent plant having some buds on it is taken and its lower part is buried in the moist soil. After few days, the cutting develops roots and shoot, and grows into a new plant which is exactly similar to the parent plant.

Pollination	Fertilisation
In polination, the pollens are transferred from anther to the stigma of carpel	In fertilisation, the male gamate fuses with the female gamate present in ovule inside the ovary of flower to from a fertilisation egg or zygote.

Gamete Gamete represents the sex cell or germ cell in sexual reproduction and it is of two types: Male gametes (Sperm) and Female gamete (Eee). Zygote It is the product of fertilization in which a male and a female gamete fuse with each other.

A tuber is the thickened, underground stem (or root) of a plant which is swollen with stored food.
Stem tuber: Potato.
Root tuber: Sweet potato.

Rose and Bougainvillea.

1. Self pollination? When the pollen grains from the anther of a flower are transferred to the stigma of the same flower (or another flower on the same plant), it is called self pollination.
2. When the pollen grains from the anther of a flower on one plant are transferred to the stigma of a flower on another similar plant, it is called cross pollination.

1. The function of testes is to make sex cells called sperms and to make sex hormone called testosterone.
2. The function of the ovaries is to make mature female sex cell called ova or egg and also to make female sex hormones called oestrogen and progesterone.

1. Vasectomy.
2. Tubectomy.

1. Ovaries in female; Both make gametes.
2. Oviducts in females; Both transport gametes.
3. Vagina in female; Both are copulatory organs.