notes for class 11th biology
- Endosperm is formed after the fertilization and it is generally triploid.
- Vessels and companion cells are present in xylem and phloem elements respectively.
- 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.
- Xylem contains vessels.
- Phloem possesses sieve tubes and companion cells.
- A gametophyte can be haploid or diploid but always produces gametes.
- 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.
- Petals are showy and are meant for attracting animal pollinators, especially insects.
- 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.
- 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