Important features of gymnosperms:
1. The term gymnosperm refers to plants with naked seeds (gymnos – naked, sperma – seeds), i.e., the seeds of these plants are not enclosed in fruits.
2. The plant-body ranges from medium to tall trees and shrubs. The giant redwood tree Sequoia is one of the tallest trees in the world.
3. The root system consists of tap roots. The coralloid roots present in Cycas are associated with nitrogen-fixing cyanobacteria.
4. The stem can be branched (as in Pinus and Cedrus) or un-branched (as in Cycas). 5. The leaves can be simple (as in Pinus)or compound (pinnate in Cycas). The leaves are needle-like, with a thick cuticle and sunken stomata. These help in preventing water loss.
6. Gymnosperms are heterosporous. They bear two kinds of spores – microspores and megaspores.
7. Flowers are absent. The microsporophylls and megasporophylls are arranged to form compact male and female cones.
8. Pollination occurs mostly through wind and pollen grains reach the pollen chamber of the ovule through the micropyle.
9. The male and female gametophytes are dependent on the sporophyte.
10. The seeds contain haploid endosperms and remain uncovered.
Mention the ploidy of the following:
protonemal cell of a moss;
primary endosperm nucleus in dicot,
leaf cell of a moss;
prothallus cell of a fern;
gemma cell in Marchantia;
meristem cell of monocot,
ovum of a liverwort, and
zygote of a fern.
Which of the following is not correct?
(a) Robert Brown discovered the cell.
(b) Schleiden and Schwann formulated the cell theory.
(c) Virchow explained that cells are formed from pre-existing cells.
(d) A unicellular organism carries out its life activities within a single cell.
What is a centromere? How does the position of centromere form the basis of classification of chromosomes. Support your answer with a diagram showing the position of centromere on different types of chromosomes.
Describe the role of liver, lungs and skin in excretion.
Define oxygen dissociation curve. Can you suggest any reason for its sigmoidal pattern?
Describe the important steps in muscle contraction.
Are all points from never?
Give shotrt answer
Too good
Very nice and in very easy way
Good
Thank you thank you so much for notes
To good
Answer are good
nice answers