Science [1 Mark Questions]

False.

Ovaries in humans produce ova, which are also known as egg cells.

Placenta.

Stamen and carpel.

Fertilisation in humans can occur only once in a month because ovulation takes place once every month i.e. an egg is released once every month by ovary.

Ova (eggs).

The process of growing many plants from one plant by man-made methods is called artificial propagation of plants.

Gametes.

Spore formation; asexual reproduction.

About 9 months.

Paramecium and Leishmania.

AIDS has no cure. Its causative organism is HIV (human Immunodeficiency Virus).

Dogs and cows.

Layering.

Placenta: Placenta is a disc like special tissue which develops between the uterus wall and the embryo after implantation. Its function is the exchange of nutrients, oxygen and waste products between the embryo and the mother.

Grafting: 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.

No.

Testes.

Internal and external fertilisation.

Fertilisation is possible if mating takes place during the middle of menstrual cycle because in a normal healthy girl the ovulation takes place on the 14th day of the beginning of menstrual cycle of 28 days.

1. Testes.
2. Anther.

Condoms.

Oviducts.

Fertilisation.

Because all these methods involves a single parent for the production of a new organism, without the involvement of gametes.

Sponge and corals.

1. Budding and regeneration.
2. Multiple fission.

Layering.

The cells involved in sexual reproduction are called gametes.

Stamen.

Once every 28 days.

In flowers.

A small part of the plant which is removed by making a cut with a sharp knife is called cutting.

While making a cutting, care should be taken to see that there are some buds on it.

Penis.

Rose and grapes.

The reproduction which takes place by the combination of special reproductive cells called ‘sex cells’ is called sexual reproduction.

Sexual reproduction.

The changes observed in boys during puberty are: Hair grows under armpits, pubic region between the thighs, chest and face. Body becomes more muscular due to the development of muscles. The voice deepens. Chest and shoulder broaden. The penis and testes become larger. Feelings and sexual drives associated with adulthood begin to develop.

Multiple fission is a process in which a parent organism splits to form many new organisms at the same time. Plasmodium reproduces by multiple fission.

1. Fragmentation.
2. Binary fission.

The cut stem of a plant having roots is called stock and the cut stem of the other plant without roots is called scion.

Asexual reproduction.

Amoeba and Hydra.

The new organisms produced by one parent through asexual reproduction (which are genetically identical to the parent) are called clones. The offspring’s formed by asexual reproduction exhibit remarkably similarity because the replication of DNA in the cells is done by certain biochemical reactions which synthesise more of genetic material. When the DNA already present in the nucleus of the parent cell is replicated by making more DNA at the time of asexual reproduction then slight variations come in the two copies formed. Due to this the two DNA molecules formed will be similar but not identical.

The two methods of reproduction in living organisms are asexual reproduction and sexual reproduction.

Bryophyllum and money plant.

Ferns and mosses.

Banana and pineapple.

Potatoes.