class 11 biology chapter 3

class 11 biology, ch. – 3 (part – 2)

notes for class 11th biology

  1. Endosperm is formed after the fertilization and it is generally triploid.
  2. Vessels and companion cells are present in xylem and phloem elements respectively.
  3. Fertilized ovules ripen into seeds. The seeds are covered by fruits. A fruit is technically a ripened ovary. Fruits not only protect the seeds but also help in their dispersal.
  4. Xylem contains vessels.
  5. Phloem possesses sieve tubes and companion cells.
  6. A gametophyte can be haploid or diploid but always produces gametes.
  7. Monocots do not grow in girth though they grow in length and produce new leaves and flowers. Dicots have indefinite growth and new roots, shoots, leaves, bark and wood are formed year after year.
  8. Petals are showy and are meant for attracting animal pollinators, especially insects.
  9. In most of the plants pollination is effected by animal insects, worms, birds, bats and even human beings. Insect accomplished pollination is termed as entomophily.
  10. Angiosperms are divided into two sub-groups; i.e., Dicots and monocots.

Dicots: They are angiospermic or flowering plants which are characterized the presence of two -cotyledons in the seed, generally reticulate venation in leaves (with a few exceptions Calophyllum and Eryingium),. Concentric tissues in- the stem with open vascular bundles arranged in a ring, penta-or tetramerous flowers.

Monocots : They are angiospermic or flowering plants which are characterised by the presence ofa single cotyledon in the seed, generally parallel venation in the leaves (exception Smilax, Colocasia and relatives), scattered closed vascular bundles in the stem and trimerous flowers, e.g. Banana, cereals, palms, grasses, bamboo, lilies, orchids. Alter

Class 11th, biology, ch. – 3, part – 1

ANGIOSPERM (Flowering plants)

These are the most advanced plants, characterized by the presence of flower, covered ovules and seeds. Angiosperms are the largest group of plants on Earth. There are approximately 270,000 known species alive today. There’s probably one nearby right now. These form the largest group of the plant kingdom, containing about 300 families, 8000 genera and about 300,000 species. These are the highest evolved plants on this earth. From cretaceous period, the angiosperms eclipsed all other vegetation and now they are the most dominant plants. They are found almost everywhere in all possible habitats. Angiosperms include all varieties of plants such as hydrophytes, xerophytes, epiphytes, parasites, saprophytes, insectivorous, symbionts and mangroves etc.

Characteristic features of angiosperms

  1. Presence of flower is the most striking feature of angiosperms. It contains the sex organs of the plant.
  2. Ovules are covered and are present inside the ovary.
  3. Pollen grains are received by the stigma of the carpel, so maturation of pollen grain (male gametophyte) takes place on stigma.
  4. Double fertilization (syngamy and triple fusion) is also characteristic only to angiosperms.