Biology Concepts and Articles
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EVOLUTIONARY PRESSURES IN BIRDS Every body system of a bird shows some adaptation for flight. These adaptations are endothermy, feathers, acute senses, long, flexible necks and lightweight hones. EXTERNAL STRUCTURE AND LOCOMOTION FEATHERS Functions of feathers The covering of feathers on a bird is
DEVELOPMENT OF ENDOSPERM The primary endosperm nucleus divides repeatedly. It forms polyploidy nutritive tissue called endosperm. There are two types of seeds for storage of food: b) Endospertnic or albuminous seed: The endosperm supply food to the 0.–weloping embryo. Such seeds are called endospermic
Multiple CHOICE QUESTIONS OF PTERIDOPHYTA 1. The vascular tissue is confined to the central region of the stem forming: (a) Bundles (b) stele (c) Cortex (d) Pcricycle 2. The leaves which bear the sporangia are called: (a) sporophyl Is (b) Bract (c) Cone (d) Strobilus
The tissues in which the cells are undifferentiated and capable of division are called meristem. The activity of meristem Causes growth in plant. Meristem adds new cells continuously. The apices of roots, shoots and their lateral branches have meristems at their tips. It increases
SHORT QUESTIONS OF PTERIDOPHYTA 1. Give occurrence of pteridophytes. Ans: Pteridophyta is a group of ancient plants. They formed the dominant part of the earths during Palaeozoic and Mesozoic periods. Majority of Pteridophytes became extinct. They are preserved in the form of fossils or
NGIOSPERM Syllabus: Introduction Occurrence Angiosperms are flowering plant. Their seeds are covered by fruits. Their fertile leaves bear ovules. The fertile leaves are folded and joined to from ovaries. The ovary is changed into a fruit after fertilization. There are 235,000 species of angiosperms
TYPE 3: EPHEDRA Occurrence Ephedra is an arid plant. It is found in Europe, Western and Central Asia and Central and South America. It is also found in arid areas of Pakistan. Ephedra is source of drug Ephedrine. It is used for the treatment
MODEL SUBJECTIVE QUESTIONS OF PTERIDOPHYTA 1. Describe general structure and life cycle of Pteridophytes. 2. Give classification of pteridophytes. 3. Describe different types of stele in Pteridophytes. 4. Describe vegetative structure of Psilotum. 5. Describe reproduction and life cycle of Psilotum. 6. Describe internal
TYPE 2: PINUS cones Occurrence The genus Pinus has about 90 species. It has world wide in distribution. They are mostly present in the temperate regions. Four species of pinus are found in Pakistan: Pinus wallichiana; Pinus halepensis; Pinus roxburghil; Pinus gerardiana General structure
TYPE I: CYCAS Occurrence Cycas has a limited distribution. It is found in south East Asia and Australia. Cycas is also cultivated as an ornamental plant in the gardens and parks. Cycas plants live upto hundred years or more. Cycas is called a living
