Worksheet Solutions: Plant Kingdom | AP Biology - Grade 9 PDF Download

Section A. Fill in the Blanks

Q1: ________ is the process of production of male gametes in plants.
Ans: Microsporogenesis

Q2: The female gametophyte in angiosperms is also known as the ________.
Ans: Embryo sac

Q3: Gymnosperms are characterized by the presence of ________ seeds.
Ans: Naked

Q4: The cell walls of fungi are made up of ________.
Ans: Chitin

Q5: The process of fusion of male and female gametes in algae is called ________.
Ans: Fertilization

Section B. Match the Column

Ans:

Section C. Multiple Choice Questions

Q1: Which of the following is not a characteristic of algae?
(a) Multicellular
(b) Eukaryotic
(c) Photosynthetic
(d) Heterotrophic
Ans: (d) Heterotrophic

Q2: In gymnosperms, the male gametophyte is represented by:
(a) Pollen grain
(b) Antheridium
(c) Archegonium
(d) Embryo sac
Ans: (a) Pollen grain

Q3: The dominant phase in the life cycle of a fern is the:
(a) Gametophyte
(b) Sporophyte
(c) Zygote
(d) Protonema
Ans: (b) Sporophyte

Q4: Which of the following is a non-vascular plant?
(a) Fern
(b) Pine
(c) Liverwort
(d) Tulip
Ans: (c) Liverwort

Q5: What is the function of the endosperm in angiosperms?
(a) Protection of embryo
(b) Nutrient storage
(c) Pollination
(d) Gas exchange
Ans: (b) Nutrient storage

Section D. Assertion Reasoning Questions

Q1: Assertion: The gametophyte generation in angiosperms is highly reduced.
Reason: The sporophyte generation is dominant in angiosperms.
(a) Both assertion and reason are true, and the reason is the correct explanation of the assertion.
(b) Both assertion and reason are true, but the reason is not the correct explanation of the assertion.
(c) Assertion is true, but the reason is false.
(d) Assertion is false, but the reason is true.
Ans: (a) Both assertion and reason are true, and the reason is the correct explanation of the assertion.

Q2: Assertion: Fungi are heterotrophic.
Reason: They have chlorophyll for photosynthesis.
(a) Both assertion and reason are true, and the reason is the correct explanation of the assertion.
(b) Both assertion and reason are true, but the reason is not the correct explanation of the assertion.
(c) Assertion is true, but the reason is false.
(d) Assertion is false, but the reason is true.
Ans: (c) Assertion is true, but the reason is false.

Section E. Case Based Questions

Case 1: Mosses
Mosses belong to the Bryophyta division and are commonly found in moist habitats. Explain the life cycle of mosses, emphasizing their alternation of generations.
Solution: The life cycle of mosses exhibits alternation of generations. Here's how it works:

Gametophyte Generation (Haploid):

• Mosses start their life cycle as haploid spores.
• These spores germinate and give rise to the gametophyte, which is the dominant and photosynthetic phase in mosses.
• The gametophyte produces male (antheridia) and female (archegonia) reproductive structures.
• Sperm from antheridia fertilizes eggs within archegonia, forming a diploid zygote.

Sporophyte Generation (Diploid):

• The zygote develops into a sporophyte, which remains attached to the gametophyte.
• The sporophyte consists of a foot, seta, and capsule.
• The capsule contains spore mother cells, which undergo meiosis to produce haploid spores.

Spore Release and Germination:

• When the capsule matures, it bursts open, releasing haploid spores into the environment.
• These spores can be carried by wind or water to new locations.
• If conditions are suitable, the spores germinate to form new gametophytes, completing the cycle.

Case 2: Gymnosperms
Gymnosperms, like pines, are known for their "naked" seeds. Explain the unique reproductive features of gymnosperms, including the role of cones.
Solution:
Gymnosperms have several unique reproductive features:

• Naked Seeds: Gymnosperms produce seeds that are not enclosed within a fruit. Instead, they are exposed on the surface of cones.
• Heterosporous: Gymnosperms are heterosporous, meaning they produce two types of spores - microspores and megaspores.

Male Cones (Microsporangiate):

• Male cones produce microspores through the process of microsporogenesis.
• These microspores develop into pollen grains, which are the male gametophytes.
• Pollen grains are carried by the wind to female cones for fertilization.

Female Cones (Megasporangiate):

• Female cones contain megasporangia, which produce megaspores through megasporogenesis.
• Megaspores develop into the female gametophyte within the ovule.
• Fertilization occurs when pollen lands on the female cone, and the pollen tube delivers sperm to the egg cell within the ovule.

Development of Seeds:

• After fertilization, the zygote within the ovule develops into an embryo.
• The ovule matures into a seed, with the embryo enclosed.
• Eventually, the mature seed is released from the cone.

Section F. Short Answer Type

Q1: Explain the significance of the vascular tissue in plants.
Ans:
Vascular tissue in plants, consisting of xylem and phloem, plays a crucial role in their survival and growth. Xylem transports water and minerals from the roots to the rest of the plant, providing structural support and facilitating photosynthesis. Phloem transports organic nutrients (sugars) produced during photosynthesis from the leaves to other plant parts. This enables the distribution of energy and resources throughout the plant, allowing for growth, repair, and reproduction.

Q2: Differentiate between monocot and dicot plants.
Ans: Monocot and dicot plants are two major groups of angiosperms (flowering plants) with several differences:

• Seed Leaves (Cotyledons): Monocots have one cotyledon, while dicots have two cotyledons.
• Roots: Monocots typically have fibrous roots, whereas dicots have a taproot system.
• Vascular Bundles: Monocots have scattered vascular bundles, and dicots have a ring-like arrangement.
• Leaf Veins: Monocots have parallel leaf veins, while dicots have a branching pattern.
• Flower Parts: Monocots often have flower parts in multiples of three, while dicots have multiples of four or five.

Q3: What is the role of mycorrhizae in plant nutrition?
Ans: Mycorrhizae are mutualistic associations between fungi and plant roots. Their role in plant nutrition is significant:

• Mycorrhizal fungi extend the root surface area, increasing the plant's ability to absorb water and nutrients, especially phosphorus and nitrogen.
• In return, the plant provides the fungi with carbohydrates produced through photosynthesis.
• Mycorrhizal associations enhance the plant's resistance to diseases and environmental stress.
• They improve soil structure and nutrient availability, benefiting both the plant and the ecosystem.

Q4: Describe the process of double fertilization in angiosperms.
Ans:
Double fertilization is a unique feature of angiosperms:

• After pollen lands on the stigma, a pollen tube grows down the style and enters the ovule through the micropyle.
• One sperm cell fertilizes the egg cell, forming a diploid zygote, which develops into the embryo.
• Another sperm cell fuses with two polar nuclei, forming a triploid cell that becomes the endosperm.
• The endosperm serves as a nutrient-rich tissue for the developing embryo.
• This process ensures that the embryo has sufficient nutrients for growth.

Q5: Explain how the sporophyte generation is dominant in the life cycle of ferns.
Ans:
In ferns, the sporophyte generation is dominant for several reasons:

• The sporophyte is the larger and more conspicuous phase in the fern's life cycle.
• It is long-lived and self-sustaining, capable of independent growth and reproduction.
• Sporophytes produce spore-containing structures called sporangia on the underside of fronds.
• Spore mother cells within sporangia undergo meiosis to produce haploid spores.
• These spores germinate to form a small, short-lived gametophyte, which depends on the sporophyte for nutrition.
• The gametophyte produces male and female gametes, leading to the formation of a new sporophyte when fertilization occurs.

Q6: Which pigment is responsible for red colour of red algae?
Ans: Phycobilin, phycoerythrin & phycocyanin.

Q7: Define a cone?
Ans: Cones are the organs of Reproduction in Gymnosperms. They are also called the fruiting body which consists of micro & megasporophyll. Microsporohylls are the structures of Male sex organ while megasporophylls are the structures of female sex organ.

Q8: Comment on the features that led to the dominance of vascular plants?
Ans: Three important features have to dominance of Angiosperm:-i) Development of well established deep roots capable of penetrating the soil to absorb water ii) Development of water- proofing material eg. cutin on aerial surfaces, to reduce water loss through evaporation. iii) Development of strong woody material as anchor & support above ground structures.

Section G. Long Answer Type

Q1: Discuss the evolutionary significance of seed formation in plants.
Ans: The evolution of seed formation in plants has several significant advantages, including:

• Protection: Seeds provide protection to the developing embryo, shielding it from desiccation, physical damage, and predation. This allows plants to colonize a wider range of habitats.
• Dispersal: Seeds are often adapted for dispersal by wind, water, animals, or other means. This helps plants establish themselves in new locations, reducing competition with parent plants.
• Dormancy: Seeds can remain dormant for extended periods until conditions are favorable for germination. This adaptive trait enables plants to survive unfavorable seasons or environmental conditions.
• Nutrient Reserve: Seeds contain a nutrient-rich endosperm or cotyledon, ensuring a food supply for the developing embryo. This is crucial for the initial growth of the seedling.
• Reduced Dependency on Water: Unlike spores, seeds do not require a water medium for fertilization and dispersal. This adaptation allowed plants to transition from aquatic to terrestrial environments.

Q2: Explain the ecological importance of lichens in terrestrial ecosystems.
Ans: Lichens, mutualistic associations between fungi and photosynthetic organisms (usually algae or cyanobacteria), have significant ecological importance in terrestrial ecosystems:

• Pioneer Species: Lichens are often the first organisms to colonize bare or disturbed surfaces, such as rocks, soil, or tree bark. They play a crucial role in primary succession by stabilizing substrates and creating conditions suitable for other plants to grow.
• Nutrient Cycling: Lichens contribute to nutrient cycling by absorbing nutrients from the atmosphere, rain, and dust. They can grow in nutrient-poor environments and release nutrients when they die or shed fragments.
• Air Quality Indicators: Lichens are sensitive to air pollution and can serve as bioindicators of air quality. Changes in lichen populations or health can signal environmental pollution, helping monitor ecosystem health.
• Habitat and Food: Lichens provide habitat and food for various organisms, including insects, birds, and herbivores. Reindeer and caribou, for example, rely on lichens as a winter food source.
• Medicinal and Traditional Uses: Some lichens have medicinal properties and are used in traditional medicine. They have also been employed for dyeing fabrics.

In summary, lichens are ecologically versatile and essential components of many terrestrial ecosystems, contributing to habitat creation, nutrient cycling, air quality assessment, and even human uses.

Q3: Describe the process of water transport in plants, including the role of transpiration and cohesion-tension theory.
Ans: Water transport in plants occurs primarily through the xylem tissue and relies on several mechanisms, including transpiration and the cohesion-tension theory:

• Transpiration: Transpiration is the loss of water vapor from the aerial parts of the plant, primarily through small openings called stomata on leaves. It serves multiple purposes:
  • It creates a negative pressure gradient within the leaf, pulling water up from the roots.
  • It facilitates the transport of minerals and nutrients from the roots to the leaves.
  • It helps maintain cell turgidity, necessary for support and growth.
• Cohesion-Tension Theory: This theory explains how water is pulled up from the roots to the leaves:
  • Water molecules exhibit cohesion, sticking together due to hydrogen bonding.
  • As water evaporates from the stomata during transpiration, it creates tension (negative pressure) in the xylem.
  • This tension is transmitted down the xylem to the roots, creating a continuous column of water in the plant.
  • Adhesion, the attraction between water molecules and the xylem cell walls, helps prevent the water column from breaking.
• Root Pressure: Root pressure, driven by osmotic uptake of water into the root cells, can contribute to the upward movement of water in some plants. However, it is generally insufficient to explain the entire process of long-distance water transport.
  
• Capillary Action: Capillary action, the ability of water to rise in narrow tubes against gravity, can aid in water movement within smaller vessels like the tracheids and vessel elements of the xylem.

Overall, the cohesion-tension theory, driven by transpiration and the cohesive and adhesive properties of water, is the primary mechanism responsible for the long-distance transport of water in plants.

Q4: Discuss the ecological significance of mycorrhizal associations in forest ecosystems.
Ans:
Mycorrhizal associations have immense ecological significance in forest ecosystems for various reasons:

• Enhanced Nutrient Uptake: Mycorrhizal fungi form a network of hyphae that extend far beyond the root zone, increasing the absorption of essential nutrients, such as phosphorus and nitrogen, from the soil. This enhances the nutrient status of forest plants.
• Improved Water Absorption: Mycorrhizal hyphae also improve water uptake by increasing the effective root surface area. In water-limited ecosystems, this can be critical for plant survival and growth.
• Host Plant Tolerance: Mycorrhizal associations can enhance the tolerance of host plants to various environmental stressors, including drought, pathogens, and heavy metals. This contributes to the overall health and resilience of forest ecosystems.
• Carbon Sequestration: Mycorrhizal fungi allocate a portion of the photosynthetic carbon produced by host plants to their own growth. This carbon allocation contributes to the sequestration of carbon in forest soils, helping mitigate climate change.
• Soil Structure and Stability: Mycorrhizal hyphae bind soil particles together, improving soil structure and stability. This reduces erosion and soil loss in forested areas.
• Facilitation of Succession: Mycorrhizal associations often play a crucial role in the early stages of primary succession by aiding plant colonization of bare or disturbed substrates. This facilitates the development of more complex forest communities.
• Biodiversity Promotion: Mycorrhizal associations can enhance plant diversity in forests by promoting the coexistence of different plant species through niche differentiation and improved resource utilization.

Q5: Point out differences between the mode of sexual reproduction of moss & fern?
Ans: MOSS (Bryophyte)

• Sex organs are borne on the Primary gametophytic plant body.
• Antheridia are well developed & often possess a stalk caled Antheridiophore
• Antheridial jacket made up of a layer of several cells.
• Sperms biflagellate
• Archegonia often have stalk caled

Fern (pteridophytes)

• Sex organs are borne on an inconspicuous gametophyte or prothallus which represents an alternate and secondary phase to sporophytic phase which is the primary plant body.
• Antheridia are less developed & mostly devoid of a stalk.
• Antheridial jacket is mostly made up of only 3 - cells.
• Multiflagella te sperms
  Archegonia do not have stalk