Abstract
This examination paper acknowledges the spectacular diversity of reproductive adaptations for survival of various categories of land plants. It describes a typical life cycle of a land plant that reproduces via spores. It also identifies the different parts of Plant organs and their functions such as cell organelles, parts of a land plant, and epidermal cells. A microscope is an important tool for examination of biological specimens, including cell’s internal structures called organelle and is important in magnifying the focused area. Plants are classified into four main groups, namely, ferns, mosses, flowering and confers. This paper finds that meiosis occur in four main stages of prophase, prometaphase, anaphase, and telophase. From telophase, cytokinesis takes place where two identical daughter cells are formed thus the replication process is complete. Examining the nature of plant biology helps one appreciate the complex stability of plants and its parts, whether they reproduce via spores or through flowering methods.
Q1: This Diagram represents a plant life cycle
Q2: A: Zygote
B: Multicelled Sporophyte
C: Meiosis
D: Multicelled gametophyte
Q3 A: Shoot Apex B: Terminal bud
C: Leaf D: Auxiliary bud
E: Petiole F: Internode
H: Tap Root I: Lateral roots
L: Root Cap
Q4: Land plants have an alteration of generation characteristics such as gametophytes are characteristic that defines whether a plant produces gametes generation reproduction and sporophyte where plants produce spores for generations. Land plants are classified into three major grouping namely mosses, ferns, confers and flowing plants. Mosses which is also classified together with lilies, liverworts and hornworts are also called bryophytes. These are land plants that do not flower of produce seeds. They reproduce primarily through the use of spores. Typically, mosses are land plants of gametophyte generation. Ferns horsetails make up the second major group of land plants and are also known as pteridophytes. They have vascular systems that are made up of xylem and phloem which plays a significant role in water and nutrients between roots and leaves. Ferns do not flower and can be found growing under redwood shades. They reproduce by means of spores and therefore belong to predominantly to sporophyte generation. Conifers are land plants that produce seeds contained in a cone. These seeds are multicellular and contain necessary nutrition that is required for a new developing plant. The cone forms a protective cover coat for a new plant. Most confers produce via pollen cones where microsporangia takes place, and meiosis occurs producing pollen grains. The pollen grain will then be blown by the wind and into female cones to fertilize them thus producing seeds. Flowing plants are land plants that are angiosperms. These plants produce flowers that attract animals which play a significant role in the pollination process. This makes pollination more efficient as compared to one in confers. Seeds will be developed in the ovary which later becomes a fruit. This fruit will serve to help in the dispersal of the seed. Animals only eat the fruit without harming the seeds.
Q5: A: Compound light microscopes are ones in which the images formed are two dimensional. It has a high magnification and can be used in viewing specimens that are living or dead. It, however, has a relatively low resolution. Confocal light microscopes use laser light in scanning specimens using mirrors. The image is then transferred to a digital computer for analysis. Confocal light microscopes use glass lenses dichromatic mirrors while compound light microscopes use lenses made up of glasses.
B: Scanning electron microscopes are used to magnify biological specimen’s r surfaces at high resolutions in 3D mode. It cannot be used to view live organisms since samples must first be dried and metal coated before visualizing them. They are more expensive to acquire and operate. Transmission electronic microscope allows the user view thin cross-sections of a specimen with a resolution of up to 5, 000, 000x. It is best for observing internal structures of specimens at high resolutions. It is also used in viewing the relationships that exist between internal structures. This microscope is also limited in that samples must be dead before they are viewed.
C: An electron microscope makes use of electron beams to form magnified images of biological specimens. On the other hand, light microscopes use beams of light in forming magnified images of biological specimens. Both are similar in that they are used to form magnified images of biological specimens. Light microscopes are small and lighter are size as compared to electron microscopes and therefore are easier to set up and move. Electron microscopes have higher magnification as compared to light microscopes. While light microscopes require specimens to be colored thus producing color images, electronic microscopes produce gray scale images. Electron microscopes are limited in that they only observe dead specimens as preparing the cell requires the use of corrosive chemicals that destroy the cells.
Q6: A Vacuole: Site of lytic or hydrolytic activity
B Endoplasmic Reticulum: Part of the endomembrane system
C Glyoxysome: Secretory organelle
D Nucleolus: Site for RNA synthesis
E Golgi body: Cytoskeletal element
F Ribosome: Contain RNA
G Chloroplast: Site of photosynthesis, generates ATP or energy compounds
Q7: Typical epidermal cells form a surface layer of plant’s leaves, fruits, and steam. Epidermal cells form a continuous and flat sheet on the surface layer of a plant with no spaces in between the cells. Hydrophobic polymer is a cutin layer that is secreted by each epidermal cell and has the responsibility of reducing the amount of water that a plant loses through evaporation. Some specialized types of epidermal cells secrets wax on the cutin surface that further reduces transpiration and increases leaf surface wettability. This wax can be found on surfaces of such fruits like apple, and it melts immediately after friction. Epidermal cells in green leaves do not have pigmented chloroplasts thus allowing light penetration to photosynthetic tissues within the leave. Some of the specialized epidermal cells include guard cells whose work is to control the opening of stomata and other small pores on the plant leaf surface so as to allow entry of carbon dioxide which is needed during photosynthesis process. They ate crescent shaped, have the ability to change their shape rapidly in response to water status changes and have green chloroplast. When the guard cells take more water pores open and when they lose water pores close and hence. Usually, two guard cells that control the opening and closing of pores are referred to as stomata. Trichomes are also specialized epidermal cells that are hair-like and project the plant surface. Their work is preventing excessive loss of water by evaporation in a plant by trapping water vapor at the plant surface. Some plants have trichomes that secret toxic and sticky substance that repels herbivore insects. Pavement cells are unspecialized epidermal cells whose primary function is protecting layers of the epidermis of plant organs. They are irregularly shaped and are most abundant of all epidermal cells. They form a complex, puzzle-like pattern and interlocking sheet that protect the internal organs of the plant.
Q8: Brachysclereid: Lignified secondary wall
Bundle sheath Cell: Scalariform pitting
Collenchyma cell: Contains Chloroplasts
Guard Cell: Secretes cutin and waxes
Metaxylem vessel member: Numerous plasmodesmata
Sieve tube member: Protoplast is dead at maturity, Thickened primary wall
Q9: A cell wall is usually constructed on the outside of a cell so as to give the plant a strong, protective outer layer. A typical cell wall is divided into three major layers which are specialized to give the plant some levels of strength and protection. The three plant cell layers include primary cell wall, secondary wall, and middle lamella. Between the layers are passageways that allow nutrients to enter and wastes to leave the plant. Every growing plant cell is surrounded with a primary is rich in polysaccharide. This primary wall forms part of apoplast that is self-contiguous and is located between plasma membrane and cuticle. It accounts for apoplast for growing plant tissues. The primary cell wall provides mechanical and structural support to the cells, determine and maintain the shape of cell, control direction and rate of cell growth and is important in resisting internal turgor pressure of the cell. Structurally, primary cell walls are predominantly composed of polysaccharides with fewer amounts of glycoproteins, phenolic esters, enzymes and ionic covalently bound minerals such as boron and calcium. The primary wall also has proteins such as expansins, and this protein plays a significant role in regulating expansion of the wall. Primary cell walls have cellulose as a major polysaccharide such as hemicellulose and pectin. Primary wall typically surrounds dividing as well as growing cells. A secondary cell walls contain lines which is a macromolecule that is a primary cross-linked phenolic molecules and provide secondary strength to the cell. They secondary cell walls are made up of xylem fibers, sclereid and tracheid and are reinforced by lignin. Middle lamella is first formed during cytokinesis from cell plate. Primary cell wall follows later where it is deposited in middle lamella but in this stage, the actual structure of primary cell wall is not explicitly defined but covalently linked cross model are available. The secondary cell wall is formed when cellulose micro fibrils produced by plasma membrane held together by hydrogen bonds so as to provide high tensile strength connect with the adjacent plasma membrane of other cells.
Q10: Mitosis are processes that describe nuclear division in eukaryotic cells. In this process, the nucleus divide and two chromatids which make chromosome separate, thus moving in opposite poles of the cell forming two identical daughter cells. Mitosis are divided into five main stages, namely, prophase, prometaphase, anaphase, and telophase. In particular, mitosis happen with the intention of conserving the number of chromosomes by allocating chromosomes that have been replicated equally to daughter nuclei. On prophase stage, the chromatic condenses to discrete chromosomes that are visible using a light microscope. Mitotic spindle will begin to form at this stage and nucleolus will disappear, but nucleus remains intact. In the first stage, centrosomes will begin to move in opposite poles and microtubule fibers lengthen. Sister chromatids will big to coil tightly with the help of condensin proteins. During prometaphase, the nuclear envelope will fragment, and the process spindle microtubules attach to kinetochores of chromosomes. At metaphase stage, the spindle is completely formed while chromosomes that are attached to microtubule via kinetochores are already aligned. On anaphase stage, the chromatids for each chromatic separates and daughter chromosomes begin to move to the cell’s poles. Telophase is the last stage of mitosis where daughter nuclei form paving way for cytokinesis to begin. Chromosomes at this stage reach opposite poles and therefore begin to unravel by relaxing in de-condensed chromatin configuration. Mitotic spindles at this stage are depolymerized to tubulin monomers that play a critical role in assembling cytoskeletal components of daughter cells that will be formed. Cytokinesis is a stage in mitotic phase where the complete division of the cell occurs via physical parting of cytoplasmic constituents to form two daughter cells. Cell division is incomplete until cell constituents will be allocated and totally separated to two daughter cells. Cytokinesis for animal cells occurs when the contractile ring that has actin filaments has fully formed inside the plasma membrane pulling the equator of cell inward and finally forming a fissure. In plant cells, cytokinesis begins during interphase where Golgi apparatus will accumulate structural proteins, carbohydrates, and structural proteins before it breaks into vesicles and disperses in the dividing cells.
