Biology 1 Marks Question

Senescent phase:
It begins from the end of the reproductive phase. During this phase of life span, there is progressive deterioration in the body (like slowing of metabolism, etc.). Old age ultimately leads to death.

Juvenile phase:
All organisms have to reach a certain stage of growth and maturity in their life before they can reproduce sexually. That period of growth is called juvenile phase. However, this phase is known as vegetative phase in plants. This phase is of different durations in different organisms.

Reproductive phase:
The end of juvenile/ vegetative phase marks the beginning of reproductive phase. During this phase, the organisms produce offspring. In higher plants, this phase can be easily seen when they come to flower but in animals, the juvenile phase is followed by morphological and physiological changes prior to active reproductive behaviour. The reproductive phase is also of variable period in different organisms like some plants, flower throughout the year while others show seasonal flowering. In animals like birds lay eggs seasonally but when in captivity (as in poultry farms) can be made to lay eggs throughout the year. Placental female mammals, undergo cyclical changes in reproductive organs during this phase.

Agave - Bulbil.
Bryophyllum- leaf buds/adventitous buds.

Style, stigma.

A sexual reproduction in amoeba and paramoecium.

Formation of fruit without fertilisation/no formation of seeds.

Juvenile/Growth.

Morphologically (structurally) similar, genetically identical.

Amphibians–outside the body/in external medium.
Reptiles–inside the body.

Chasmogamous.

1. Eye/Eye buds.
2. Offset.

cow/ sheep/rat/ deer/ dog/ tiger.

Eicchornia crassipes/Water Hyacinth.

It flowers once in 12 years.

Wind, light weight/enormous number/non-sticky.

Resistant organic material sporopollenin, present in (hard) outer layer/exine.

Offsprings of a sexual reproduction - genetically same/clones.Offsprings of sexual reproduction - show variation.

Apomixis/Agamospermy/Parthenogenesis.

Meiosis occurs at the zygote stage in an organism exhibiting haploidic life cycle.
Thus, the product formed will be haploid spores.

The phenomenon is called parthenogenesis and the cell responsible for it is female gamete, ovum.

Asexual reproduction.

1. Amoeba/ Paramoecium.
2. Yeast.

The female flower bearing pistil is called pistillate.

Haplo-diplontic life cycle and diplontic life cycle.

Clone is a group of individuals of the same species that are genetically and morphologically identical among themselves and to the parent from which they are formed from.

Statement (iii) is true.
Multicellular organisms.like Hydra reproduce asexually by producing multlceuular bud that further develops into a new organism.

Meiosis - Haplontic life cycle.

Yeast.

Papaya/ date palm is dioecious the plants which produce only male flowers, do not bear fruits, while the plants which produce female flowers, bear fruits.

A meiocyte is diploid (2n) while a gamete is haploid (n).

Potato multiplies by buds (eyes) of the tuber (vegetative propagation).

2. Is true of Ginger.

Statement (iii) is true.
In Bryophyllum, germinating bud appears from the notch at the leaf margin which gets detached and develop into new plants.

Chlamydomonas reproduces asexually through zoospores. These reproductive structures (units) are called zoospores because they are motile.

The wall of the fruit is called pericarp.

The male and female gametes shown in the figure are morphologically different. So, they are heterogametes. The female gamete represents the egg cell and the male gamete represents the sperm.

The animal bearing both male and female sex organs are called hermaphrodites. Example, earthworms, sponge and tapeworm.

Cows/ Sheep/ Rats/ Dogs/ Deers/ Tiger.

Clone is a group of individuals of the same species that are morphologically and genetically similar.

Cladophora.

Initiation of floral buds marks the end of juvenile phase in flowering plants.

Bony fishes.

Zygote forms the vital link, which ensures continuity of species between organisms of one generation and the next.

Algae and fungi.

The two conditions that enhance the chances of syngamy in organisms exhibiting external fertilisation are:

1. Synchrony in release of gametes of two patents.
2. Both gametes should be motile.

Bacillus and Amoeba.

Off springs produced through asexual reproduction are genetically identical (clone) to each other as well as to their parents, while sexually produced off springs show genetic variations leading to evolution.

A coconut plant has both male and female flowers present on same individual thus it is known as monoecious.