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PLANT PROPAGATION Plant propagation is the process of creating new plants. There are two types of propagation: sexual and asexual. Sexual reproduction is the union of the pollen and egg, drawing from the genes of two parents to create a new, third individual. Sexual propagation involves the floral parts of a plant. Asexual propagation involves taking a part of one parent plant and causing it to regenerate itself into a new plant. The resulting new plant is genetically identical to its parent. Asexual propagation involves the vegetative parts of a plant: stems, roots, or leaves. (Sorensen, 2019) ANGIOSPERMS: MONOCOTYLEDON & DICOTYLEDON The angiosperms or flowering plants are divided into two groups: monocots and dicots. Monocots have one seed leaf while dicots have two. Monocots have leaves with parallel veins while netted veins for dicots. SEED BEARING PLANTS ANGIOSPERMS & GYMNOSPERMS Seed-bearing plants could be angiosperm or flowering or gymnosperm which are non-flowering plants. The angiosperms are plants that have flowers and produce seeds enclosed within a carpel. The angiosperms are a large group and include herbaceous plants, shrubs, grasses, and most trees. Their seeds may contain one seed leaf or monocotyledon and when there are two they are dicotyledons. The gymnosperms on the other hand are seed-producing plants known as "naked seeds" like cycads, conifers, and pines. The learning materials provided below will give you comprehensive information on the difference between angiosperms and gymnosperms. SEED BEARING PLANTS The other classification of plants is what we call seed-bearing plants or vascular plants. These plants reproduce through their seeds. Most fruits and vegetables that you love to eat are seed-bearing plants. Looking at the diagram below, seed-bearing plants could be gymnosperms or non-flowering plants and angiosperms or flowering plants. The angiosperms are classified too according to the number of seed leaves: monocotyledon and dicotyledon.Figure 18-11 represents the amount of energy stored as organic material in each trophic level in an ecosystem. The pyramid shape of the diagram indicates the low percentage of energy transfer from one level to the next. On average, 10 percent of the total energy consumed in one trophic level is incor- porated into the organisms in the next. Why is the percentage of energy transfer so low? One reason is that some of the organisms in a trophic level escape being eaten. They eventually die and become food for decomposers, but the energy contained in their bodies does not pass to a higher trophic level. Even when an organism is eaten, some of the molecules in its body will be in a form that the consumer cannot break down and use. For example, a cougar cannot extract energy from the antlers, hooves, and hair of a deer. Also, the energy used by prey for cellu- lar respiration cannot be used by predators to synthesize new bio- mass. Finally, no transformation or transfer of energy is 100 percent efficient. Every time energy is transformed, such as during the reactions of metabolism, some energy is lost as heat. Limitations of Trophic Levels The low rate of energy transfer between trophic levels explains why ecosystems rarely contain more than a few trophic levels. Because only about 10 percent of the energy available at one trophic level is transferred to the next trophic level, there is not enough energy in the top trophic level to support more levels. Organisms at the lowest trophic level are usually much more abundant than organisms at the highest level. In Africa, for exam- ple, you will see about 1,000 zebras, gazelles, and other herbivores for every lion or leopard you see, and there are far more grasses and shrubs than there are herbivores. Higher trophic levels con- tain less energy, so, they can support fewer individuals.A population is a group of organisms that belong to the same species and live in a particular place at the same time. All of the bass living in a pond during a certain period of time make up a pop- ulation because they are isolated in the pond and do not interact with bass living in other ponds. The boundaries of a population may be imposed by a feature of the environment, such as a lake shore, or they can be arbitrarily chosen to simplify a study of the population. The humans shown in Figure 19-1 are part of the pop- ulation of a city. The properties of populations differ from those of individuals. An individual may be born, it may reproduce, or it may die. A population study focuses on a population as a whole—how many individuals are born, how many die, and so on. Population Size A population’s size is the number of individuals that the population contains. Size is a fundamental and important population property but can be difficult to measure directly. If a population is small and composed of immobile organisms, such as plants, its size can be determined simply by counting individuals. Often, though, individ- uals are too abundant, too widespread, or too mobile to be counted easily, and scientists must estimate the number of individuals in the population. Suppose that a scientist wants to know how many oak trees live in a 10 km2 patch of forest. Instead of searching the entire patch of forest and counting all the oak trees, the scientist could count the trees in a smaller section of the forest, such as a 1 km2 area. The scientist could then use this value to estimate the population of the larger area. SECTION 1 OBJECTIVES ● Describe the main properties that scientists measure when they study populations. ● Compare the three general patterns of population dispersion. ● Identify the measurements used to describe changing populations. ● Compare the three general types of survivorship curves. VOCABULARY population population density dispersion birth rate death rate life expectancy age structure survivorship curve FIGURE 19-1 A population can be widely distributed, as Earth’s human population is, or confined to a small area, as species of fish in a lake are. Copyright © by Holt, Rinehart and Winston. All rights reserved. 382 CHAPTER 19 If the small patch contains 25 oaks, an area 10 times larger would likely contain 10 times as many oak trees. A similar kind of sampling technique might be used to estimate the size of the pop- ulation shown in Figure 19-2. To use this kind of estimate, the sci- entist must assume that the distribution of individuals in the entire population is the same as that in the sampled group. Estimates of population size are based on many such assumptions, so all esti- mates have the potential for error. Population Density Population density measures how crowded a population is. This measurement is always expressed as the number of individuals per unit of area or volume. For example, the population density of humans in the United States is about 30 people per square kilome- ter. Table 19-1 shows the population sizes and densities of humans in several countries in 2003. These estimates are calculated for the total land area. Some areas of a country may be sparsely popu- lated, while other areas are very densely populated. Dispersion A third population property is dispersion (di-SPUHR-zhuhn). Dispersion is the spatial distribution of individuals within the popu- lation. In a clumped distribution, individuals are clustered together. In a uniform distribution, individuals are separated by a fairly con- sistent distance. In a random distribution, each individual’s location is independent of the locations of other individuals in the popula- tion. Figure 19-3 illustrates the three possible patterns of dispersion. Clumped distributions often occur when resources such as food or living space are clumped. Clumped distributions may also occur because of a species’ social behavior, such as when animals gather into herds or flocks. Uniform distributions may result from social behavior in which individuals within the same habitat stay as far away from each other as possible. For example, a bird may locate its nest so as to maximize the distance from the nests of other birds. These migrating wildebeests in East Africa are too numerous and mobile to be counted. Scientists must use sampling methods at several locations to monitor changes in the population size of the animals. FIGURE 19-2 TABLE 19-1 Population Size and Density of Some Countries Population size Population density Country (in millions) (in individuals/km2) China 1,289 135 India 1,069 325 United States 292 30 Russia 146 8 Japan 128 337 Mexico 105 54 Kenya 32 54 Australia 20 3 dispersion from the Latin dis-, meaning “out,” and spargere, meaning “to scatter” Word Roots and Origins Copyright © by Holt, Rinehart and Winston. All rights reserved. POPULATIONS 383 The social interactions of birds called gannets, which are shown in Figure 19-3b, result in a uniform distribution. Each gannet chooses a small nesting area on the coast and defends it from other gannets. In this way, each gannet tries to maximize its distance from all of its neighbors, which causes a uniform distribution of individuals. Few populations are truly randomly dispersed. Rather, they show degrees of clumping or uniformity. The dispersion pattern of a population sometimes depends on the scale at which the popu- lation is observed. The gannets shown in Figure 19-3b are uni- formly distributed on a scale of a few meters. However, if the entire island on which the gannets live is observed, the distribution appears clumped because the birds live only near the shore. POPULATION DYNAMICS All populations are dynamic—they change in size and composition over time. To understand these changes, scientists must know more than the population’s size, density, and dispersion. One important measure is the birth rate, the number of births occur- ring in a period of time. In the United States, for example, there are about 4 million births per year. A second important measure is the death rate, or mortality rate, which is the number of deaths in aShrubs English/SpanishPrune trees and small shrubs50 questions Plant trees and shrubsPURPLE W9 T3 Mystery_in_the_Shrubs_QuizPlants , herbs , shrubs , trees , creepers and climbersOrchard / fruit trees Importance of fruit trees • Fruit trees are important for the following uses: They are a source of food, they produce fruits Some are used for making medicines Others provide shade and can also act as wind breakers. Those with beautiful flowers are very decorative. They contain vitamins which means they have nutritional value. Classification of fruit trees • Fruit trees are classified as indigenous and exotic. Indigenous fruit trees • are those that natural grow in a country. • They take longer to grow. • Examples of indigenous fruit trees are: English name Shona Name Snot apple Water berry Red ivory Fig Monkey orange Wild custard apple Mobola fruit Exotic fruit trees • These are trees that were brought from other countries. • They are commercially grown in orchards. • Common exotic fruit trees include: • Exotic fruit trees grow faster than indigenous. Ornamental horticulture • It deals with the growing of decorative plants. • Decorative plants are collectively called ornamental plants. • They include trees, shrubs, flowers and lawn grasses. Importance of ornamental plants They beautify the environment. Flowers often produce a pleasing fragrance. Flowers attract insects like bees that are responsible for pollination. Plants produce oxygen that we need for breathing. • Some are used for making medicines. • Lawn grasses prevent soil erosion. • Plants provide shelter for birds and insects. Classification of ornamental plants • There are four classes of ornamental plants. Trees Shrubs Flowers Lawn Trees: • Ornamental trees are very useful as decorative plants. • This is because most of these trees produce beautiful flowers and some are ever green. • Examples of decorative trees include flamboyant, jacaranda, pines, Cyprus. Shrubs: • A shrub is a woody plant with many branches but smaller than a tree. • Some of them are ornamentals because they produce beautiful flowers. • Others can be cut into decorative shapes. • The golden duranta is good example because it can be cut into nice shapes. • The bougainvillea is another example of a decorative plant because: It can act as a climbing plant. It produces decorative flowers. It can also be cut into any shape using a hedge shear. Flowers: • Flowers have the following functions: They are used for decorations at weddings, hotels and parties. They are used as an expression of love and appreciation such as valentine’s day and get well soon messages. They are useful in bee farming called apiculture as they are a source of nectar used for making honey. Flowers produce a pleasant fragrance used in the production of soaps and scents for perfumes, deodorant and lotions. Lawn: • A lawn is an area of grass that is kept cut short and is usually part of someone's garden or backyard, or part of a park. • Some lawn grasses grown in Zimbabwe are Durban, kikuyu, couch and buffalo lawn. • They prevent soil erosion. • They also provide a comfortable outdoor resting place. Forestry Importance of trees • Trees are important to us and animals. • The Forestry Commission is responsible for taking care of trees in Zimbabwe. • Trees are also important to the environment because: They are a source of fuel in the form of firewood. They are used for making most of the furniture we use. Most medicines come from both exotic and indigenous trees, for example pine trees and gum trees are used for making cough medicines. Trees provide browsing animals like the kudu and giraffe with food. Fruits from both exotic and indigenous fruit trees are a rich source of vitamins Trees give out oxygen which we need for breathing. Trees provide timber that can be used for roofing. • Trees are grouped according to where they come from. • The groups are indigenous and exotic. 1 . Indigenous trees : • These are local trees that have always been grown in their country. Shona name English name Mutohwe Snot apple Mususu Yellow wood Mubvamaropa Blood wood Muuyu Baobab Muonde Fig tree Musasa msasa Characteristics of indigenous trees take longer to mature Do not produce straight poles Grow on their own Hard wood 2 .Exotic trees : • These are trees that have been brought from another country to be grown in Zimbabwe. Characteristics of exotic trees They are brought in a country from another country. Grow very fast. Have soft woods Usually grow straight Usually grown in orchards and plantations Common exotic trees in Zimbabwe are: Gum trees Pine trees Wattle Cyprus Date palm Mango Apple pawpaw Causes of plant damage • plant damage is when cultivated crops are kept from normal growth that leads to reduced yields. • plant damage is caused by both living and non living things. • Some of the common causes of crop damage are: (a)Pests • These are living organisms that cause physical damage to crops. • Examples of pests are weevils, army worm, aphids, cutworms and locusts. (b) Diseases • Plant diseases are caused by living organisms called pathogens. • These pathogens infest the plant and take away nutrients. • Fruit rot and bacteria spot are some of the examples of plant diseases. (c) Weeds • these are plant which grow where they are not wanted. • For example if black jack grows in a groundnut field, it is a weed. • Weeds compete for nutrients with cultivated plants. (d) Very high temperatures • High temperatures may cause crops to wither. • High temperatures may also lead to lightning and fires. • This can burn up crops. ( e) Frost • Frost damages crops in winter. • Tomatoes, potatoes, and beans are easily damaged by frost. (f) Drought • drought is when there is no rainfall in a season where it supposed to be raining. • It is one of the most serious forms of crop damage. • Plants wither and die if there is no rainfall. ( g) Animals • Wild animals like baboons often eat maize crops before they mature. • Birds also are a problem to crops like sorghum. Signs of plant damage • There are various signs that show plant damage. • Some can be corrected but some lead to total loss. • Some signs of plant damage include: Lodged plants Flowers and small fruits blown to the ground Dull leaf color Wilted plants Stunted growth