Chapter 8 Diversity among plants class 11 Biology

Q.1 How life cycle of plants show alternation of generation

ans: Alternation of generations means that plants alternate between two different life stages, or generations, in their life cycle; a haploid stage called gametophyte and a diploid stage called sporophyte. The terms haploid and diploid refer to the number of chromosomes contained in the cells.

When a male gamete (n) joins a female gamete (n) through fertilization, they form a diploid organism (2n) and forms the sporophyte

And spores are produced by meiosis which form the gametophyte which is haploid structure

Q:2 Why bryophytes are called non vascular plants?

Ans They are called non-vascular plants because of the absence of vascular tissues (xylem and phloem) that functions for the conduction of food, water, and minerals.

Q.3 how plants cope when invaded from land to sea

Plants developed following adaptations to cope from difficulties of land life 

A) Waxy cuticles developed to help reduce water loss/desiccation. 

B) Roots allowed plants greater access to water, as well as provided anchoring to the ground; this allowed plants to grow taller.

C) Vascular tissue facilitated transport of water and nutrients to all parts of the plant. 

D) Stomata in leaves and stem helped with gas exchange.

E) protection of reproductive structures and alternation of generation with heterogamy

Q.4 Why heterogamy is important for plants

Hetero means different and gamy means gametes and the production of different gametes is called heterogamy.

In heterogamy the male gametes is smaller produced in large quantity and travel to the female gamete which is produced inside the female reproductive structure and is a large gamete highly protected

This helps in protection of female gamtes and development of zygote with less chance of environmental hazards

Q.5 why flower is called reproductive structure

Ans: flower is called the reproductive structure because it contain the both male and female reproductive structures 

The male reproductive part is called the stamen or androcium and the female reproductive structure is called the carpel or pistil or gyamocium 

Sometimes both stamen and carpel are in same flower that flower is called monocious 

And sometimes stamens are in one flower and carpel are in other flower that flower is called dicious 

Q.6 why fertilization in angiosperms is called double fertilization?

Ans : the fertilization means fusion of gamtes.

In angiosperms (flowering plants) this fertilization occurs twice, at first one sperm (n) from pollen grain fuses with ovum/egg (n) to form zygote and other sperm (n) from pollen grain fuses with secondary nuclei (2n) to form the endosperm (3n)

Q.7 how seeds are evolved? 

Ans seeded are evolved in following ways

A) origin of heterospory, two types of different spores are produced one is microspore and other is megaspore

B) development of integument of ovule that later form the seed coat

C) zygote retain in the seed

Q.8: Why gymnosperms have naked seeds but not angiosperms

Ans: In gymnosperms (plants with “naked seeds” such as conifers, cycads, and ginkgo), the ovules are not enclosed in an ovary but lie exposed on leaflike structures, the megasporophylls. While the angiosperms contain overy which is letar formed into the fruits