PURE AND APPLIED BIOLOGY PROGRAMME · 2021. 6. 22. · Angiospermae. Sub-division: Gymnospermae...
Transcript of PURE AND APPLIED BIOLOGY PROGRAMME · 2021. 6. 22. · Angiospermae. Sub-division: Gymnospermae...
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BOWEN UNIVERSITY, IWO
PURE AND APPLIED BIOLOGY PROGRAMME
COURSE CODE: BLY 102
COURSE TITLE: GENERAL BIOLOGY II
SEMESTER: SECOND
TITLE: GENERAL CHARACTERISTICS AND STRUCTURE OF PLANT DIVISION
1. Division: Thallophyta
These are plants that do not have well-differentiated body form (i.e. thalloid). They are found both
in terrestrial and aquatic habitats, but are predominantly aquatic; freshwater or marine. It has only
one subdivision Algae. Examples are Spirogyra, Ulothrix, Cladophora and Chara. Various types
of fungi like yeasts and moulds which do not have chlorophyll are also included in this group.
Sub-division: Algae
• They are autotrophs
• The body is simple and not well differentiated (i.e. they possess thalloid body form)
• The form and size of algae are variable. Chlamydomonas is microscopic unicellular algae.
Volvox is in colonial form. Ulothrix and Spirogyra are filamentous.
• They are further classified as green algae, red algae and brown algae. Red and brown algae are due
to the presence of accessory photosynthetic pigments.
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Clamydomonas
Volvox Spirogyra
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2. Division: Bryophyta
The plant body in this group is commonly differentiated to form stem and leaf-like structures.
Roots are not presents, but a small root-like structure called rhizoid is present. They are called the
amphibians of the plant kingdom because they grow in moist areas. It has embryo stage in its
developmental process. The sex organs are multicellular. Male sex organ is called antheridium and
produces antherozoids. Female sex organ is called archegonium and produces a single egg.
Examples are Moss (Funaria) and Marchantia (Liverwort), Anthoceros, Riccia
Diagram of a Moss Showing the sporophyte and gametophyte
A Moss Plant
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Liverwort Riccia
3. Division: Pteridophyta
In this group, the plant body is sporophyte and can be differentiated into roots, stem and leaves. It
is the highest group of cryptogams. They have a specialized tissue for the conduction of water and
other substances form one part of the plant body to another. Hence they are also called vascular
cryptogams. Seeds are absent and they produce naked embryo called spores.
Sporophytes bear sporangia which produce spores. On germination, this spore gives rise to
gametophyte called prothallus. Prothallus bear male sex organ antheridia and female sex organ
archegonia. Some examples are Marsilea, Ferns, Selaginella, Equisetum, Pteris, Adiatum,
Lycopodium and Horsetails.
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Selaginella kraussiana
Selaginella kraussiana Fern (Maiden hair)
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4. Division: Spermatophyta
This is a division of seed producing plants. The seed contain embryo that contains reserve food
(i.e. cotyledon) for future growth. Its main plant body is sporophyte and can be differentiated into
stem, leaves and roots. Male and female gametophytes are distinct. They have a well-developed
vascular system throughout the body. Spermatophyta has two sub-divisions – Gymnospermae and
Angiospermae.
Sub-division: Gymnospermae (Greek; gymno – naked, spermae – seed)
• The plants of this group bear naked seeds and are usually perennial, evergreen and woody.
• It includes medium sized trees and shrubs.
• Sporangia are formed over modified leaf-like structure called sporophylls.
There are two types of sporophylls. Megasporophyll which bears megasporangium (ovules). It
produces female gamete. Microsporophyll which bears microsporangium (pollen sac). It produces
male gamete.
• Examples are Pinus (pines), Cedrus (deodar), Cycas, Picea (Christmas Tree), Thuja (Morpankhi).
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Picea abies Picea abies tree
Sub-division: Angiospermae (Greek – angio – covered, sperma – seed)
These are flowering plants.
• The seeds develop inside an organ which is modified to become a fruit.
• These are the highly evolved group of plants
• The reproductive organs are aggregated into flower. The male sex organs are called stamens and
female sex organs are called pistil.
• Plant embryos in seeds have structures called cotyledons are also called ‘seed leaves’ because in
many instances they emerge and become green when the seed germinates. Cotyledons store food
for developing embryo.
• The angiosperms are divided into two groups on the basis of the number of cotyledons present in
the seed. Plants with seeds having a single cotyledon are called monocotyledonous or monocots
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(e.g. Maize, rice, wheat). Plants with seeds having two cotyledons are called dicots (e.g. garden
pea).
Talinum traingulare an herb Citrus spp. a tree