CHAPTER-5 A Representation Study of Mammals
Morphology
- All the large land animals are mammals
- Mammals are distinguished from other vertebrates by two fundamental characteristics.
- Epidermal Hairs
- Milk producing glands.
Habitat
- The place of living of an organism is its habitat.
Mammalian Adaptations
- In the marine whales, dolphins, etc,. the limbs are modified into flippers which are used as oars to swim in water.
- The skin of camels is doubly thick and contains water storing osmotic cells to conserve water.
- To digest the cellulose rich food, they have developed a mutual partnership with bacteria
- Mammals such as cows, buffaloes, antelopes, goats, deers, etc,. have huge four chambered stomachs, that function as storage and fermentation vats.
- Mammals have heterodont dentition with different types of teeth that are highly specialized to match particular eating habits.
- In elephant the incisors are modified into tusks as a specialized weapon.
- Bats are the only mammals capable of powered flight
- The forelimbs of bats are modified into wing like structure
- The nocturnal bats can fly without crashing into things into things and still capture insects by echo location.
- As a bat flies, it emits very rapid series of extremely high pitched clickingsounds.
- The sound waves bounce off objects or flying insects and the bat hears the echo
- The marsupials, Kangaroo have developed abdominal pouches to bear thebender young ones.
- The supreme mammal – man is highly adapted as an intellectual social animal.
Basic Physiological Functions
- Mammals are warm blooded or homeotherms.
- Red blood cells of mammals are fully packed with the respiratory redblood pigment haemoglobin, to carry the maximum amount of oxygen.
PLANT MORPHOLOGY
Tissues
Types, structure and function of plant tissues
Meristematic tissues
- The meristematic tissues made up of group of similar and immature cells, which can divide and form new cells
- Meristematic cells divide continuously and thus help in increasing the length and thickness of the plant
Apical meristems
Apical meristem is present at the growing tips of stems and inceases the length of the plant body.
Intercalary meristems
Occupy base of the leaves and the base of the intermodal regions in plantssuch as grasses (mostly in monocotyledonous plants). These help in elongation of the intermodes.
Lateral meristems
Occupying the lateral regions of the stems and roots which bring about increase in the width of the plant body.
Characteristic features of meristematic tissues
- Their cell walls are thin, elastic and made up of cellulose.
- They are closely arranged without intercellular spaces.
- They have dense cytoplasm with large nucleus.
Permanent Tissues
The permanent tissues are classified as
- Simple tissues
- Complex tissues
Simple tissues
A tissue with the cells of similar structure (one type of cells) and function is called simple tissue.
- Parenchyma
- Collenchymas
- Sclerenchyma
Parenchyma
- The cells of the parenchyma are generally thin walled with intercellularspaces. They are living cells.
- They are generally present in all organs of a plant.
- Serve to store and conduct food materials, water and minerals.
Collenchyma
- Have unevenly thickened walls. These thickenings are due to thedeposition of more cellulose, hemi-cellulose and pectin.
- The thickening is confined to the corners ofthe cells.
- They generally occur in the dicot stem in two or more layers below theepidermis.
- It is absent in the roots. It also occurs in petiole and pedicel.
- Like Parenchyma, Collenchyma is also a living tissue
- The main function of Collenchyrna is to provide strength and flexibility to the growing organs.
Sclerenchyma
- It is a dead tissue. The cells are thick with lignified walls.They give mechanical support to the organs.This has two two of cells- Sclereidsand Fibres.
Sclereids
- Sclereids are stone cells which are commonly found in shells of the nut,pulp of certain fruits such as pear and Sapota
Fibres
- The fibres are elongated strands with simple pits throughout its length.
Complex permanent tissues
Xylem
- Xylem is mainly concerned with the transport of nutrients, water andminerals upwards in the plant body. It forms a continuous tube through the roots, stems, leaves, flowers and fruits by the fusion of elongated cells.
- It is composed of different kinds of cells namely.
- Tracheids
- Xylem vessels
- Xylem fibres
- Xylem parenchyma
a.Tracheids
- Tracheids are elongated, tapering cells with blunt ends. They have lignified secondary wall
- They are the chief water conducting elements in Pteridophytes and Gymnosperms
- Xylem vessels
- Xylem vessels have perforations at the end and the placed one above the other like a long pipe
- They are seen in the xylem of angiosperms .They conduct water mineral nutrients and also provide mechanical strength to the plant body
- Xylem Fibres
- The fibres of Sclerenchyma associated with the xylem are known as xylemfibres. They give additional mechanical strength to the plant. They are also called wood fibres
- Xylem Parenchyma
- The parenchyma cells associated with xylem are known as xylemparenchyma. It is the only living tissue amongst xylem cells
- They store food reserves in the form of starch and fat. They also help inconduction of water.
Phloem
- Phloem conducts food materials from leaves to the other parts of theplant Itis made up of four types of cells.
- Sieve elements
- Companion cells
- Phloem fibres
- Phloem parenchyma
Sieve elements
- Sieve elements are the conducting elements of the phloem, Sieve elementsare of two types – sieve cells and sieve tubes.
- Sieve cells are present in Pteridophytes and Gymnosperms where as sievetubes are present in Angiosperms
Companion cells
- They are associated with sieveelements.They have a prominent nucleusand cytoplasm.
- They help the sieve tube in conduction of food materials in angiosperms.
Phloem Fibres
- They are called as bast-fibresThey give mechanical support to theplant.
- Among the four types of phloem cells, phloem fibres are the only dead tissues.
Phloem Parenchyma
The parenchyma cells associated with phloem are called phloemparenchyma. They store starch and fats