SECTION – A (very short answer questions)
1. What is flora?
Flora refers to the collective term used for the plant life of a particular region or habitat. It includes all plant species, both native and introduced, within a specific area, such as a country, ecosystem, or biome. For example, the flora of India includes a vast range of plant species like the Banyan tree, Lotus, etc.
2. What do the terms phycobiont and mycobiont signify?
Phycobiont refers to the algal component of a lichen, which is responsible for photosynthesis, providing nutrients. Mycobiont refers to the fungal component of a lichen, which provides the structural support and absorbs water and minerals. Both organisms form a mutualistic relationship in lichens.
3. Name the four classes of Pteridophyta with one example each.
The four classes of Pteridophyta (ferns) are:
- Psilopsida – Example: Psilotum
- Lycopsida – Example: Lycopodium
- Sphenopsida – Example: Equisetum
- Pteropsida – Example: Pteris
Each class represents a different group of ferns with distinct characteristics.
4. Differentiate between Racemose and Cymose inflorescences.
- Racemose inflorescence is an unbranched, indeterminate type where the main axis continues to grow, and flowers develop in acropetal succession (older flowers at the base). Example: Mustard.
- Cymose inflorescence is a determinate type where the main axis grows for a limited period, and the flower at the tip blooms first, with newer flowers growing below. Example: Brinjal.
5. Differentiate between Apocarpous and Syncarpous ovary.
- Apocarpous ovary has multiple separate carpels (pistils), with each carpel being free and not fused. Example: Buttercup.
- Syncarpous ovary has multiple fused carpels, with the ovary being a single structure. Example: Tomato.
6. What is Geocarpy? Name the plant which exhibits this phenomenon.
Geocarpy is the phenomenon where the fertilized ovule (seed) develops below the ground. It is a type of underground fruit development. An example of a plant exhibiting geocarpy is Groundnut (Arachis hypogaea).
7. What is the significance of vacuole in a plant cell?
The vacuole plays a crucial role in maintaining turgor pressure within plant cells, which helps in supporting the cell structure. It also stores nutrients, waste products, and pigments and plays a role in cell growth by absorbing water. Additionally, it is involved in the regulation of pH and detoxification.
8. Explain the zwitterionic form of an amino acid.
A zwitterion is a molecule that has both a positive and a negative charge but is overall electrically neutral. In the case of amino acids, the amino group (-NH₂) can donate a proton (H⁺) and become positively charged (-NH₃⁺), while the carboxyl group (-COOH) can lose a proton and become negatively charged (-COO⁻). This forms a zwitterion at a neutral pH.
9. An anther has 1200 pollen grains. How many pollen mother cells must have been there to produce them?
Each pollen mother cell (PMC) undergoes meiosis to produce 4 pollen grains. Therefore, to produce 1200 pollen grains, the number of PMCs required would be: 12004=300 pollen mother cells\frac{1200}{4} = 300 \text{ pollen mother cells}
Thus, 300 PMCs must have been there to produce 1200 pollen grains.
10. Define population and community.
- A population is a group of individuals of the same species living in a particular area and capable of interbreeding. Example: The population of tigers in a forest.
- A community is an assembly of different populations of various species that live and interact in the same area. Example: The forest community includes tigers, deer, trees, and plants.
SECTION – B ( Short answer questions )
11. Give salient features and importance of Chrysophytes.
Chrysophytes (golden algae) are a group of protists, mostly unicellular, found in freshwater and marine habitats. Key features include:
- Presence of chlorophyll a and c, and carotenoids (giving them a golden-brown color).
- Cell walls made of cellulose, silica, or pectin.
- Some species can form cysts to survive harsh conditions. Importance: Chrysophytes are vital in aquatic ecosystems as primary producers, contributing to the food chain. They also play a role in oxygen production and carbon fixation.
12. What is heterospory? Briefly comment on its significance. Give two examples.
Heterospory is the production of two distinct types of spores: microspores (male) and megaspores (female), which develop into male and female gametophytes, respectively.
Significance: Heterospory is an adaptation to promote cross-fertilization and ensure genetic diversity. It is also associated with the evolution of seed plants.
Examples: Selaginella and Salvinia.
13. List the changes observed in angiosperm flower subsequent to pollination and fertilization.
After pollination and fertilization in angiosperms, the following changes occur:
- The ovule develops into a seed.
- The ovary transforms into a fruit.
- The style and stigma typically wither away.
- The petals and sepals may fall off.
- The seeds are enclosed within the fruit, aiding in seed dispersal.
14. Describe the non-essential floral parts of plants belonging to Fabaceae.
In Fabaceae (legume family), the non-essential floral parts include:
- Stamens: Usually 10, often fused into a single bundle (diadelphous condition).
- Sepals: Five, typically free, forming a small calyx.
- Petals: Five, typically in a characteristic “papilionaceous” form—one large “standard,” two lateral “wings,” and two lower “keels.”
- These parts do not directly participate in reproduction but help in attracting pollinators.
15. Give a brief account of types of chromosomes based on their position of centromere.
Chromosomes are classified based on the position of the centromere:
- Metacentric: Centromere is at the center, resulting in two equal arms.
- Submetacentric: Centromere is slightly off-center, creating arms of unequal length.
- Acrocentric: Centromere is near one end, making one arm very short.
- Telocentric: Centromere is at the very end of the chromosome, leaving only one arm.
16. Nucleic acids exhibit secondary structure. Describe through Watson-Crick model.
The secondary structure of nucleic acids (DNA) refers to the double-helix structure described by Watson and Crick. It consists of:
- Two complementary strands of nucleotides twisted into a right-handed spiral.
- The strands are held together by hydrogen bonds between the nitrogenous bases (A-T, G-C).
- The backbone is made up of sugar-phosphate groups, and the helical structure is stabilized by base stacking interactions.
17. State the location and function of different types of meristems.
Meristems are regions of active cell division in plants. There are three types:
- Apical meristem: Found at the tips of roots and shoots. It is responsible for primary growth, leading to lengthening.
- Lateral meristem: Found in the cambium and cork cambium. It is responsible for secondary growth, leading to an increase in girth.
- Intercalary meristem: Located at internodes or leaf bases in monocots. It enables growth between the nodes, particularly in grasses.
18. What are hydrophytes? Briefly discuss the different kinds of hydrophytes with examples.
Hydrophytes are plants that grow in water or in environments with high moisture content. They are adapted to living in aquatic conditions. There are three main types:
- Submerged hydrophytes: Fully submerged in water. Example: Elodea.
- Floating hydrophytes: Floating on the water surface, with roots submerged. Example: Water lily (Nymphaea).
- Emergent hydrophytes: Have roots in water but the stem and leaves above the surface. Example: Cattail (Typha).
SECTION – C ( Long answer questions )
19. Explain how stem is modified variously to perform different functions.
The stem can be modified to serve different functions depending on the plant’s needs. Some examples include:
- Storage: In potato (tuber), the stem stores food, allowing the plant to survive harsh conditions.
- Climbing: In bean plants (tendrils), modified stems help in climbing by winding around supports.
- Protection: In cactus (spines), stems are modified into spines to protect the plant from herbivores and reduce water loss.
- Photosynthesis: In opuntia (cactus), stems are modified to perform photosynthesis in place of leaves.
- Reproduction: In strawberry (runner), stems spread horizontally to produce new plantlets, aiding vegetative reproduction.
20. Draw the diagram of a microsporangium and label its wall layers. Write briefly about the wall layers.
Diagram of a Microsporangium:
Brief Description of Wall Layers:
- Epidermis: The outermost layer of the microsporangium, protecting it from external damage.
- Endothecium: This layer is fibrous and helps in the dehiscence (opening) of the microsporangium for pollen grain release.
- Middle layer: Provides structural support and nourishment to the developing pollen grains.
- Tapetum: The innermost layer that is nutrient-rich and provides nourishment to the developing pollen grains.
21. Describe the internal structure of dorsiventral leaf with the help of labelled diagram.
Diagram of Dorsiventral Leaf (Example: Dicot Leaf):
Brief Description of the Internal Structure:
- Upper Epidermis: The outermost layer of the leaf, which is transparent to allow light to pass through. It has a waxy cuticle to prevent water loss.
- Palisade Mesophyll: Located just below the upper epidermis, this layer contains tightly packed cells full of chloroplasts. It is the primary site for photosynthesis.
- Spongy Mesophyll: Located beneath the palisade layer, this consists of loosely arranged cells with air spaces, facilitating gas exchange for photosynthesis.
- Lower Epidermis: Contains stomata (pores) regulated by guard cells. It controls gas exchange and water loss.
- Stomata: Openings in the lower epidermis that allow for the exchange of gases (CO₂ and O₂) and water vapor.