Organization of Life__Classification of Living Things ... Section Two
Kingdom Plantae are non-motile, eukaryotic multicellular organisms whose cells have cellulose cell wall and chloroplast which contains chlorophyll enables plants to make their own food by photosynthesis. Chlorophyll is not only in green plants also in other color pigments, red and brown. The plant kingdom is divided into THREE PHYLA namely, Thallophyta, Bryophyta, and Tracheophyta. The thallophytes and bryophytes do not have SYSTEM for conducting food and water from any part of the plant, and this restricts their size while Tracheophytes have conducting SYSTEMS so the plants are much larger.
.., what they are, what they look like without rSL, how they reproduce. Phylum Thallophyta Thallophytes or algae are SIMPLE green plants that are all aquatic. They have thread-like(filamentous) or flat(thallus) bodies that do not have root, stems or leaves. It has three sub-phylum namely Rhodophyta(Red), Phaecophyta(Brown) and Chorophyta(Green) which are mainly SEASWEEDS although some green algae are found in freshwater. Spirogyra is a simple green alga that is found in pond and ditches and it is made up of hair-like green filaments. And these filaments functions in twos, it is made up of single chain of identical cells and drift passively in the water Volvox is a simple tiny green algae which consists of a ball of identical cells, each bearing flagella which aids its movement.
This large red and brown algae also called seaweeds) grows in marine water or on rocks below the high-water mark. Kelp is a large brown alga that has flat, branching, ribbon-like THALLUS that can grow up to a length of 30 meters. Sargassum is a large brown alga common in tropical waters. This plant body is made up of a root-like hold-fast which sticks to rocks, and stem-like stipe bearing leaf-like blades.
Algae reproduce asexually by cell division, fragmentation or spores. They reproduce sexually by fusion of male and female gametes to form zygote. Hence, the zygote forms a thick outer coat around it and becoming A RESTING ZYGOSPORE until in a favourable condition before the zygospore undergoes meiosis to form an adult plant.
The seed plants are divided into Gymnosperms and Angiosperms. The Gymnosperms are plants with naked seeds so they do not bear flowers. Their trees and shrubs are mostly evergreen with needle-like leaves, but some have scale-like leaves or broad leaves. And, the seeds are borne through special structures called cones. Examples are, cycads, ginkgoes and conifers. Of all these the conifers are the most important as they make up the world's temperate region forests, they produce soft wood which is used for timber and wood pulp(paper making), they also yield drains and turpentine. And examples of Conifers are pine, fir and spruce.
Angiosperms are plant with seeds which bears flowers, hence they are the flowering plants. They form the largest group in the plant kingdom. The angiosperms ARE MORE HIGHLY EVOLVED than the gymnosperms because they have an abundance of water-conducting vessels and bear seeds which are protected within fruits. And, these fruit develops from the ovaries of flowers—the female reproductive organ of the angiosperm.
Bryophytes show a distinct alternation of generation - a life cycle that occurs in plants that have distinct haploid sexual and diploid asexual stages. In these groups, a multicellular haploid gametophyte with n chromosomes alternates with a multicellular diploid sporophyte with 2n chromosomes, made up of n pairs. A mature sporophyte produces haploid spores by meiosis, a process which reduces the number of chromosomes to half, from 2n to n. The haploid spores germinate and grow into a haploid gametophyte. At maturity, the gametophyte produces gametes by mitosis, which does not alter the number of chromosomes. Two gametes (originating from different organisms of the same species or from the same organism) fuse to produce a diploid zygote, which develops into a diploid sporophyte. This cycle, from gametophyte to sporophyte (or equally from sporophyte to gametophyte), is the way in which all land plants and many algae undergo sexual reproduction. The sporophyte is always attached and dependent on the gametophyte.
Class of Bryophytes Class 1: Musci eg. Moss plant Class 2: Hepatica eg. Liverworts
A typical flowering plant has structures of a shoot and root. The roots, stems, and leaves are the growing or vegetative part of the plant while the flowers which give rise to fruits and seeds are the reproductive part of the plant. Plants majorly have three main tissue system that run throughout their roots, stems, leaves and flowers. And, these are, dermal tissue system or epidermis, vascular tissue system of conducting cells which are xylem and phloem to transport food, water, and minerals throughout the plant, ground tissue system which consists of all other tissues.
Functions of the VARIOUS PART of the flowering plant. ROOT- Holds the plant firmly in the soil, absorbs water and mineral salts from the soil, and stores food in some plants. STEM- act as support to the plant, holds the leaves in the best position for receiving sunlight, it conducts water and mineral salts from the root to the leaves, and conducts manufactured food from the leaves to the different parts of the plants, holds the flowers and fruits in the best position so that they are easily pollinated and dispersed respectively LEAVES- to produce food for the plant by photosynthesis — Main photosynthetic organs FLOWERS- the reproductive organs
Also, in the red and brown algae, the gamete producing plant(gametophyte) is the dominant plant while in green alga, ulva, two independent dominant plants are present which show an alternation of generation.
Phylum Bryophyta include the liverworts and mosses which grows in damp places on land. A liverwort has a simpler structure than a moss. It has a ribbon-like body that lies flat on the ground and is attached to the soil by many rhizoids. A moss has an erect slender stem with 'many small leaves' arising from it and these leaves are only one cell thick. Rhizoids grow into the soil from the base of the stem.
Phylum Tracheophyta Tracheophytes are known as vascular plants since they have vessels or vascular tissues to conducting water and food. And it the largest group of plants which includes seed plants like the familiar flowering plants like , as well as some spore-bearing non-flowering plants like ferns. It's divided into two sub-phylum; Sub-Phylum Pteridophyte It's a land plant that has roots, stems and 'leaves' similar to those of flowering plants. Its leaves or fronds are coiled when young and unroll as they grow, the frond is several cells thick like the leaf of a flowering plant and similar in internal structure and they bear spores on the underside as they mature. And, it exhibits dichotomous branching, the branches form as a result of an equal division of a terminal bud (i.e., a bud formed at the apex of a stem) into two equal branches that are not derived from axillary buds, although axillary buds are present elsewhere on the plant body. It stems usually grow horizontally below the ground which is called a rhizome while its many small roots grow from the rhizome into the soil. BUT their fronds SPROUT AT INTERVAL ALONG THE RHIZOME and grows upwards above the ground. The gametophyte of ferns is a small heart-shaped structure which bears the sex organs which produces their eggs and sperms. Because both Sporophyte and Gametophyte of a Fern leads different existences—and these are, a well adaptation to dry conditions and needing of moist conditions as the sperms need water to swim to the eggs
Sub-Phylum Spermatophyte It is a vascular plant that produces seeds. Their roots, stems and leaves are well-developed which makes them a true land plants. They reproduce via seed which contains embryo that develops from a fertilized egg of a very small gametophyte which is the plant body or organ that produces gametes which is completely dependent on the sporophytes producing the haploid spores from which haploid gametophytes develop. Many seed plants have additional structures which helps them disperse by traveling in the wind or stick to animals. Example are; Dandelion seeds have tiny "parachutes." Maple seeds have "wings" that act like little gliders. Burdock seeds are covered with tiny hooks that cling to animal fur. Because dispersal of seeds away from parent plants helps reduce competition with the parents and increases the chance of offspring surviving. The fertilization of the egg by the sperm is brought about by pollination-a transfer of the pollen from the sperm into the egg which happens after the pollen tube grows. Though water is not needed in this process as it was in ferns
The angiosperm are grouped into dicotyledons and monocotyledons The Dicotyledons are the more primitive angiosperms. They may become trees, shrubs, or herbs. Their trees are large with spreading branches. And, they have this different features; They bear seeds which have two seed leaves, the vascular bundles of their stems and roots are arranged in a regular pattern, their floral parts — sepals, petals, pistils, and stamens exist in group of four or five, their leaves have veins arranged in a BRANCHED NETWORK, they have a tap root system(one main root which consist of lateral branches), they usually under secondary growth. Examples of Dicotyledons are Hibiscus, Ipomea batatas(sweet potato), Carica papaya(pawpaw), Dioscorea sp. (yam), and Vigna unguiculata(cowpea).
The Monocotyledons are the most advanced plants. They tend to be more efficient and specialized because they have fewer parts. Due to this, they show a very high degree of adaptation to their environment. They are generally herbs. And, these are its different features; They bear seed which has one seed, the vascular bundles of the stem are scattered, their floral parts exist in groups of three, their leaves have veins running parallel to one another, they have a fibrous root system(many roots which are from base of stem), and they do not undergo secondary growth. Examples of Monocotyledons are Zea mays(maize), Elaeis guineensis(oil-palm), Axonopus compressus(carpet grass), Panicum maximum(Guinea grass), and Oryza sp. (rice). All Cereal plants are Monocotyledons
