BIOLOGY 3 Marks Question

Inflorescence is the manner in which the flowers are arranged on the flowering axis. During the flowering season, the vegetative apex of the stem gets converted into a floral meristem. Depending on whether the apex gets converted into a flower or continues to grow, two major types of inflorescences are defined-racemose and cymose. In racemose inflorescence, the floral axis continues to grow and produces flowers laterally while in cymose inflorescence, the main axis terminates into a flower. Hence, it is limited in growth.

2. Interacting with people of different mindsets can enrich our thought, while sticking with like-minded people can stunt our mental development.

Cross pollination of ideas is not a scientific term but is used metaphorically. Different people have different ideas on a particular topic. An idea can be very brilliant or simply dull but a single idea can never be complete in itself. When we see different perspectives on an issue then we get a clearer picture. By exchanging ideas, we learn many new things. Man has developed so much because man can exchange ideas through the use of language. Let us take the example of the aeroplane. The aeroplane was invented by Wright brothers and because of exchange of ideas, the whole world has benefited from the invention.

• It is called rachis.
• It represents the midrib.
• A leaf has a bud in its axil, while a leaflet does not have.

Tendrils of grapevine and tendrils of pumpkin have the same origin i.e., they are modification of stem, but different functions such as tendrils of grapevine help in climbing whereas tendrils of pumpkin help in creeping. So, tendrils of grapevine and tendrils of pumpkin are homologous because of same origin but different function. On the other hand, tendrils of pea are modification of leaves. Both tendrils of grapevine and tendrils of pea help in climbing. So, they are analogous because they have different origin but same function.

1. In Chrysanthemum: the lateral branches arise from the basal and underground part of the main stem, grow horizontally below the soil and emerge obliquely above the soil to give rise to leafy shoots.
2. In Eichhornia: the lateral branches of the stem have short internodes and each node bears a rosette of leaves and a tuft of roots.
3. In Jasmine: a slender lateral branch arises from the base of the main stem, grows aerially/ erect for sometime and then arches downwards to touch the ground; the part buried under the soil produces adventitious roots and new shoots at the nodes.

2. Interacting with people of different mindsets can enrich our thought, while sticking with like-minded people can stunt our mental development.

Cross pollination of ideas is not a scientific term but is used metaphorically. Different people have different ideas on a particular topic. An idea can be very brilliant or simply dull but a single idea can never be complete in itself. When we see different perspectives on an issue then we get a clearer picture. By exchanging ideas, we learn many new things. Man has developed so much because man can exchange ideas through the use of language. Let us take the example of the aeroplane. The aeroplane was invented by Wright brothers and because of exchange of ideas, the whole world has benefited from the invention.

• Root hairs are very fine, delicate, thread like extensions of the epidermal cells of the root.
• They arise from the region of maturation.
• They increase the area of absorption of water and minerals.

• In Opuntia, the leaves are modified into spines for defence against browsing animals and the stem is flattened, fleshy, contain chlorophyll and carry out photosynthesis.
• In garden pea, the terminal leaflets are modified into tendrils for climbing on the support.
• In Bougainvillea, the axillary bud is modified into thorn and protects the plant from browsing animals.

Exchange of gases.

Diagnostic features are as follows:

1. Mostly perennial herbs.
2. Flowers, actinomorphic, hypogynous and trimerous.
3. Perianth six in two whorls.
4. Stamens six in two whorls, polyandrous, epiphyllous and antiphyllous.
5. Gynoecium tricarpellary, syncarpous, ovary trilocular with axile placentation.

1. Actinomorphic: A flower is actinomorphic, if it can be cut into two equal parts along any radial plane passing through the centre.
2. Gamosepalous: The calyx of a flower is gamosepalous, if the sepals are united.
3. Syncarpous: The ovary is syncarpous, if the carpels are fused together.

2. Polyandrous.
3. Monocarpellary.
4.  

2. Actinomorphic.
3. Bicarpellary.
4. Tricarpellary.

The description of gynoecium varies in following ways:

1. Carpels- Monocarpellary/ bicarpellary/ tricarpellary tetracarpellary/ multicarpellary.
2. Cohestion- Apocarpous/ syncarpous.
3. Ovary- Superior/ semi-inferior/ inferior.
4. Placentation- Marginal axile parietal/ basal/ free-central/ superficial.
5. Style- Terminal/ lateral/ gynobasic/ stylopodium.
6. Stigma- Number, shape-simple, lobed, capitate, branched.

Gynoecium is the female reproductive whorl of the flower. It is composed of one or more carpels. Each carpel is differentiated into three parts, i.e., the ovary, style and stigma. Placenta is the tissue on which ovule(s) develops in the ovary.The placentation in the ovary may be:

1. Marginal.
2. axile.
3. Parietali.
4. Basal.
5. Free-central.

1. Cucumber: Stem tendril.
2. Peas: Leaf tendril.
3. Pumpkins: Stem tendril.
4. Grapevine: Stem tendril.
5. Watermelon: Stem tends.

1. A flower is perigynous when the gynoecium is situated in the centre and other parts of the flower are located on the rim of the thalamus almost at the same level; the ovary is half-inferior, e.g. rose, plum, peach.
2. A flower is epigynous when the ovary is completely enclosed and fused with the thalamus and all the other parts of the flower arise above the ovary; the ovary is inferior, e.g. cucumber and guava.
3. A flower is hypogynous when the gynoecium occupies the highest position and all the other parts of the flower arise below the ovary; the ovary is superior, e.g. mustard, brinjal, etc.

S. No.	Parenchyma	Collenchyma	Sclerenchyma
i.	Living cells.	Living cells.	Dead cells.
ii.	Forms major component of organs.	Found below epidermis.	Usually found in epidermis.
iii.	Chloroplast present.	Chloroplast present sometimes.	Chloroplast absent.
iv.	Performs many vital functions.	Provides mechanical support to growing parts.	Provides mechanical support to organs.

Differences between spike and spadix are:

S.No.	Spike	Spadix
i.	The whole peduncle possess sessile flowers.	The upper part of peduncle called appendix remains flowerless.
ii.	The inflorescence does not bear spathe.	One of more spathes occur over the inflorescence.
iii.	The flowers are exposed.	The flowers are covered by spathes.
iv.	Flowers are generally bisexual.	Flowers are generally unisexual.

1.  

2. Maize grain is a single- seeded fruit, where the seed coat and the pericarp are fused to form a husk; so it cannot be called a seed.

It belongs to mustard (Brassica). Ebracteate, actinomorphic, bisexual, bimerous; calyx-4, polysepalous, in two whorls of two each; corolla 4, polypetalous, cruciform; androecium-6, polyandrous, tetradynamous in two whorls, one with two, the second with four, gynoecium-bicarpellary, syncarpous and superior.

Functions of roots in aquatic plants are:

1. Buoyancy in floating plants.
2. Anchorage in submerged fixed plants.

Differences in roots of aquatic and terrestrial plants are:

S.No.	Roots of Aquatic Plants	Roots of Terrestrial Plants
i.	Poorly developed.	Profusely developed.
ii.	Root hair absent.	Root hair present.
iii.	Xylem atrophied (poorly developed).	Xylem well-developed.
iv.	Aerenchyma occurs.	Aerenchyma is absent.

Features of sweet pea are:

1. Flower- Complete.
2. Calyx- Gamosepalous.
3. Corolla- Polypetalous.
4. Androecium- Diadelphous.
5. Gynoecium- Monocarpellary.
6. Fruit- The Legume.

Important pulses of family-Fabaceae are as follows:

Реа	Pisum sativum
Gram	Cicer arietinum
Urad	Phaseolus munga
Masur	Lens culinaris
Arhar	Cajanus cajan
Soyabean	Glycine max

S. No	Stem	Root
(i)	It is the above-ground part of the plant.	It is the underground part of the plant.
(ii)	It shows nodes and internodes.	It does not show nodes and internodes.
(iii)	It bears axillary and terminal buds.	It does not bear any bud.
(iv)	It is generally green, when young.	It is generally non green.
(v)	It is positively photo tropic and negatively geotropic.	It is negatively phototropic and positively geotropic.

Mango and coconut are drupe fruits. They develop from monocarpellary superior ovaries and are one seeded. It is differentiated into outer thin epicarp, middle fleshy mesocarp and inner stony endocarp. The edible part of coconut (Cocosnucifera) is endosperm. The milk of tender coconut represents the oily endosperm in liquid form. Later it gets deposited along the walls of endocarp and forms edible flesh.

1. The description of morphological features helps in identifying and assigning a plant its appropriate position.
2. While describing a plant, one should keep in mind that the description should be brief, in a simple and scientific language and presented in definite sequence.
3. The taxonomic characters to be described are habitat. habit, root, stem, leaves, flowers, inflorescence, calyx, corolla, androecium, gynoecium, fruits and seeds.

Stomata are found on both surfaces in monocot leaves, while they are found on ventral surface only, in dicot leaves. In monocot leaves venation is parallel, which is evident by similar size of vascular bundles. In dicot leaves venation is reticulate, so vascular bundles are of various sizes. Spongy mesophyll is present in dicot leaves, and absent in monocot leaves.

1. Opposite– e.g. Calotropis.
2. Whorled– e.g. Alstonia.
3. Alternate– e.g. Mustard/ Sunflower.