Plant Kingdom: Science Study Notes for CTET 2020 Download FREE PDF

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PLANT KINGDOM

PLANT KINGDOM: Plants are living organisms belonging to the kingdom Plantae. They include familiar organisms such as trees, herbs, bushes, grasses, vines, ferns, mosses, and green algae.

Classification of Plant Kingdom:

  1. Cryptogamae:
  • Almost all are specialized for an aquatic existence.
  • Great range of size and form, including unicellular, filamentous, colonial and thalloid forms. A thallus is a body, which is not differentiated into true roots, stems and leaves and lacks a true vascular system (xylem and phloem). It is often flat photosynthetic, eukaryotic.

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  1. Thallophyta:

Fungi

  • Heterotrophic nutrition because they lack chlorophyll and are, therefore, non-photosynthetic. They can be parasites, saprotrophs or mutualists. Nutrition is absorptive digestion takes place outside the body and nutrients are absorbed directly. Digestion does not take place inside the body, unlike animals.
  • Rigid cell wall containing chitin as the fibrillar material. Chitin is a nitrogen-containing polysaccharide, very similar in structure to cellulose. Like cellulose, it has high tensile strength. It, therefore, gives shape to the hyphae and prevents osmotic bursting of cells.
  • Body is usually a mycelium, a network of fine tubular filaments called hyphae. These may be septate (have cross-walls), e.g., Penicillium or aseptate (no cross-walls), e.g., Mucor.
  • If carbohydrate is stored, it is usually as glycogen, not starch.
  • Reproduce by means of spores.
  • Non motile.
  • Some fungal species live in permanent mutually dependent relationships with blue-green algae (cyanobacteria). Such relationships are called symbiotic. These symbiotic life forms are called lichens.

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Algae

  • Algae are chlorophyll-bearing, simple, thalloid, autotrophic and largely aquatic (both fresh water and marine) organisms. They occur in a variety of other habitats: moist stones, soils and wood. Some of them also occur in association with fungi (lichen) and animals (e.g., on sloth bear).
  • The algae reproduce by vegetative, asexual and sexual methods. Vegetative reproduction is by fragmentation.
  • Asexual reproduction is by the production of different types of spores, the most common being the zoospores. They are flagellated (motile) and on germination gives rise to new plants. Sexual reproduction takes place through fusion of two gametes.
  • Algae are useful to man in a variety of ways. At least a half of the total carbon dioxide fixation on earth is carried out by algae through photosynthesis.
  • Chlorella and Spirullina are unicellular algae, rich in proteins and are used as food supplements even by space travellers.
  • Certain marine brown and red algae produce large amounts of hydrocolloids (water holding substances), e.g., algin (brown algae) and carrageen (red algae) are used commercially. Agar, one of the commercial products obtained from Gelidium and Gracilaria are used to grow microbes and in preparations of ice-creams and jellies.
  • The algae are divided into three main classes: Chlorophyceae, Phaeophyceae and Rhodophyceae.

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Bryophytes:

  • Alternation of generation is present in which the gametophyte generation is dominant.
  • No vascular tissue, that is no xylem or phloem.
  • Body is a thallus, or differentiated into simple leaves and stems.
  • No true roots, stems or leaves the gametophyte is anchored by filamentous rhizoids.
  • Sporophyte is attached to and is dependent upon, the gametophyte for its nutrition.
  • Spores are produced by the sporophyte in a spore capsule on the end of a slender stalk above the gametophyte.
  • Live mainly in damp, shady places.
  • These are called amphibians of the plant kingdom.
  • Examples are, Marchantia, Funaria.
  • Pteridophytes:

Phylum- Filicinophyta (Ferns)

  • Alternation of generation is present in which the sporophyte is dominant.
  • Gametophyte is reduced to a small, simple prothallus.
  • Vascular tissue present (xylem and phloem) in sporophyte.
  • Sporophyte, therefore has true roots, stems and leaves.
  • Leaves relatively large and called fronds.
  • Spores produced in sporangia, which are usually in clusters called sori, e.g., Dryopteris filix-mas (male fern) Pteridium (bracken fern).

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Phanerogamae

  • Sporophyte is the dominant generation gametophyte generation is severely reduced.
  • Sporophyte produces two types of spores in other words, it is heterosporous). The two types are microspores and megaspores, microspore = pollen grain, megaspore = embryo sac.
  • The embryo sac remains completely enclosed in the ovule (megasporangium), a fertilized ovule is a seed.
  • Water is not needed for sexual reproduction because male gametes do not swim (except in a few primitive members), they are conveyed to the ovum by a pollen tube to effect fertilization.
  • Complex vascular tissues in roots, stems and leaves.

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Major Difference between Dicotyledons and Monocotyledons

 

Dicotyledoneae

Monocotyledoneae

Leaf morphology

Net-like pattern of veins (reticulate venation), lamina (blade) and petiole (leaf stalk). Dorsal and ventral surfaces differ.

Veins are parallel (parallel venation). Typically long and thin (grass-like). Identical dorsal and ventral surfaces.

Steam anatomy

Ring of vascular bundles. Vascular cambium usually present, giving to rise to secondary growth.

Vascular bundles scattered. Vascular cambium usually absent so no secondary growth (exceptions occur, e.g., palms).

Root morphology

Primary root (first root from seed) persists as a tap root that develops lateral roots (secondary roots).

Adventitious roots from the base of the stem take over from the primary root, giving rise to a fibrous root system.

Root anatomy

Few groups of xylem (2-8). Vascular cambium often present, giving rise to secondary growth.

Many groups of xylem (commonly upto 30).

Vascular cambium usually absent so no secondary growth.

Seed morphology

Embryo has two cotyledons (seed leaves).

Embryo has one cotyledon.

Flowers

Parts mainly in four and five. Usually distinct petals and sepals. Often insect pollinated.

Parts usually in three.

No distinct petals and sepals. These structure are combined to form ‘perianth segments’. Often wind pollinated.

Examples

Pea, rose, buttercup, dandelion

Grass, iris, orchids, lilies.

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