SECTION 2.pdf

SECTION 2 FUNDAMENTAL CONCEPTS OF ECOLOGY  Topic Learning Outcomes Familiarize with the different Ecological concepts Recognize the Biotic and Abiotic factors in the environment Distinguish different ecological relationships Identify the different terrestrial biomes Unders...

SECTION 2 FUNDAMENTAL CONCEPTS OF ECOLOGY  Topic Learning Outcomes Familiarize with the different Ecological concepts Recognize the Biotic and Abiotic factors in the environment Distinguish different ecological relationships Identify the different terrestrial biomes Understand the Biogeochemical cycle and their importance ECOLOGY Derived from the Greek oikos, meaning house, combined with logy, meaning “the study of”. Thus, literally, it is the study of the earth’s households. Ecology, can be defined as the study of the relationship between organisms and their environment. ENVIRONMENT According to Douglas and Holland, the term environment is used to describe, in the aggregate, all the external forces, influences and conditions, which affect the life, nature, behaviour and the growth, development and maturity of living organisms.  Levels of Organization Atom Organism Population a group of individuals of the Basic Unit of Matter an individual form same species in a certain area of life at a given time Community Niche Habitat Describe as the total sum of Area or environment where Population of different a species use of the biotic an organism or ecological species occupy same and abiotic resources in its community normally lives or geographic area environment orccur ECOSYSTEM Was first coined by AG Tansley in 1935. Derived from the two words, eco and system. An ecosystem is a basic functional unit of organisms and their environment. The definitions of ecosystems have been proposed by scholars. EP Odum (1971) defined an ecosystem as a basic functional unit of organisms and their environment; their interaction with each other and the various components. P. Haggeh (1975) proposed that ecosystems are ecological systems in which plants and animals are linked to their environment through a series of food chains. As theorised by CC Park (1980), an ecosystem is the sum of all natural organisms and substances within a certain area, and it can be viewed as a basic example of an open system in physical geography. Structures of an Ecosystem Any ecosystem is made up of the following two components: 1.Abiotic 2.Biotic Structures of an Ecosystem Abiotic Components They include the non-living things such as water, soil, air, temperature, climate, pressure, etc. Photo courtesy: Abiotic Components of Ecosystems — Definition & Examples - Expii Structures of an Ecosystem Biotic Components These components include the living organism such as plants, animals, bacteria, viruses, etc. They are classified into three main groups: Producers Consumers Decomposers Producers - all This is the chemical plants containing conversion of Carbon chlorophyll, these dioxide (CO2) and plants can produce water (H2O) to sugar called glucose in the their own food by presence of sunlight. the process called P___________. Consumers - are organisms that must Different types of consumers: obtain food energy ❖Primary consumer from secondary ❖Secondary sources, for consumer example, by eating ❖Tertiary consumer plants or animal ❖Detritivores matter. ❖Decomposers  Primary consumer Secondary Tertiary consumer this category consumer an organism that includes the an organism that consumes a hebivores, which consumes a secondary consume only primary consumer consumer producers Detritivores Decomposers Green cities the organisms in this group these are bacteria or fungi derive energy from consuming that absorb nutrients from nonliving organic matter such nonliving organic matter such as dead animals or fallen leaves as plant material, the wastes of living organisms. ENERGY FLOW IN AN ECOSYSTEM The transfer of energy from one trophic level to another trophic level is known as energy flow. Energy flows in one direction through ecosystems; from the sun to producers, to primary consumers, to secondary consumer, to tertiary consumer. In an ecosystem, each of these feeding levels is referred to as trophic level. ENERGY FLOW IN AN ECOSYSTEM Food chains, are usually represented as a series of steps, it is the passage of energy from one trophic level to the next as a result of one organism consuming another. Elton (1972) was the first person who introduced this concept. Food web, made of several overlapping and intersecting food chains. ENERGY FLOW IN AN ECOSYSTEM Photo Courtesy: AP Environmental Science by Princeton Review Ecological Pyramids It is the graphic representation of the various trophic levels of an ecosystem. Elton (1927) used the term “ecological pyramid “ for the first time. Three kinds of pyramids: ➔Pyramid of numbers ➔Pyramid of biomass ➔Pyramid of energy  Pyramid of Numbers It shows the number of organisms at each trophic level. In a grassland ecosystem, the producers, i.e., grasses are the largest in number. The consumer decrease in the following way: Grass Aphids Ladybids Insectivorous birds Hawk Photo courtesy: https://www.sarthaks.com/2613106/what-is-pyramid- numbers-write-brief-note-on-the-pyramid-numbers-with-the-help-block- diagram  Pyramid of biomass Means the total weight of a living matter per unit area. In grassland forest ecosystems the biomass decreases from producers to consumers, hence forming an upright pyramid. However, in an aquatic ecosystem , the biomass gradually increases towards the apex, thus, the pyramid is inverted in shape. Pyramid of biomass Photo courtesy: https://www.insightsonindia.com/environment/basic-concepts-of-ecosystem/ecological-pyramid-meaning-types/  Pyramid of Energy Represents the amount of flow of energy at each trophic level. It is always upright in shape as the amount of energy decreases from producers, level to consumers’ level. According to Lindman (1942) only 10% energy is consumed at each trophic level. Photo Courtesy; https://www.sciencefacts.net/energy-pyramid.html  Productivity of ecosystem The productivity of an ecosystem refers to the rate of production i.e. the amount of organic matter, which is accumulated in any unit time. Productivity is of the following types: 1. Primary Productivity - It is associated with the producers which are autotrophic. It is the rate at which radiant energy is stored by photosynthetic and chemosynthetic activity of producers. it is further distinguished as: Gross primary productivity- is the rate of storage of organic matter in plant tissues in excess of the respiratory utilization by plants during the measurement period. Photo Courtesy; https://www.sciencefacts.net/energy-pyramid.html  Productivity of ecosystem 2. Secondary Productivity- These are the rates of energy storage at consumers level. Since consumers only utilize food materials (already produced) in their respiration, simply covering the food matters to different tissues by an overall process. 3. Net Productivity - refers to the rate of storage of organic matter not used by the heterotrophs (consumer) i.e. equivalent to net primary production minus consumption by the heterotrophs during the unit period. It is thus the rate of increase of biomass of the primary producers, which has been left over by the consumers. Photo Courtesy; https://www.sciencefacts.net/energy-pyramid.html  Productivity of ecosystem 4. Stability of Ecosystem - The stability of ecosystems refers to the balance between production and consumption of each element in the ecosystem. In other words, balance between input and output of energy and normal functioning of different biogeochemical cycles and stable conditions of equilibrium as under: ❏ The Equilibrium Model- states that an ecosystem, always tends towards stability. As soon as the community of an ecosystem is disturbed due to external environmental change, it quickly returns to original state. ❏ The non-equilibrium model - states that an ecosystem stability is rarely attained because disturbances caused by frequent external environmental change do not allow to develop ordered state of species assemblages in an ecosystem Relationships Between Species Some species interact quite a bit with other members of their population; for example, some animals form herds, while other species are loners-like bears. The reasons for these different levels of sociability are largely competition, predation, and a general need to exploit the resources in the environment.  Relationships Between Species COMPETITION - arises when two individuals of the same species are competing for resources in the environment. Intraspecific competition- individuals competing are of the same species Interspecific competition- individuals competing are of different species The resources that are competed for can be food, air, shelter, sunlight, and various other factors necessary for life. Gause’s Principle states that no two species can occupy the same niche at the same time, and that the species that is less fit to live in the environment will relocate, die out, or occupy a smaller niche. PREDATION- occurs when one species feed on another, and it is the force that drives changes in population size. SYMBIOTIC RELATIONSHIP - are close, prolonged associations between two or more different organisms of different species that may , but do not necessarily, benefit each member. Symbiotic Relationship MUTUALISM - in a mutualistic sybiotic relationship, both species benefit; as for example, the relationship between the sea anemone and clown fish. COMMENSALISM- in a commensalistic symbiotic relationship, one organism benefits while the other is neither helped nor hurt. One example of this type of relationship exists between trees and epiphytes (bromeliads and some orchids). PARASITISM - is a relationship in which one species is harmed and the other benefits; for example the relationship that exists between fleas and  HOW ECOSYSTEM CHANGE Often times, the biotic balance in a community is maintained by a single species, known as the KEYSTONE SPECIES. It is a species whose very presence contributes to an ecosystem’s diversity and whose extinction would consequently lead to extinction of other forms of life. As a general rule, if the keystone species is removed from an ecosystem, then the ecosystem completely changes. INDICATOR SPECIES- are species that are used as a standard to evaluate the health of an ecosystem. They are more sensitive to biological changes within their ecosystems than are other species, so they can be used as an early warning system to detect dangerous changes to community. HOW ECOSYSTEM CHANGE INDIGENOUS SPECIES - are those that originate and live or occur naturally in an area or environment. With increasing frequency, however new species are being introduced into ecosystems by chance, by accident, or with intention. While some introduced species cannot find a niche and die out, many others are quite happy in their environment in their new environment, and compete successfully with the indigenous species. INTRODUCED SPECIES/ INVASIVE SPECIES - examples of invasive species are zebra mussels, which were introduced into the Great Lakes when ships dumped ballast water into the lakes and the quickly growing vine kudzu, which was originally introduced in the southeastern United States in order to control the problem of  Ecological Succession Species of plants and animals are continually coming and going; evolving and dying out. Some of the changes that takes place in a geographic area are predictable ones that can be described as ECOLOGICAL SUCCESSION. Smith (1965) stated that ecological succession is an orderly and progressive replacement of one community by another till the development of a stable community in that area. Ecological Succession The first community the appears in an area is referred to as the ‘pioneer community’. This community takes time to get modified into an intermediate community called ‘seral community’, which finally transforms into a stable community known as ‘climax community’, typically the final stage of succession, in which there is a dynamic balance between the abiotic and biotic components of the community. Types of Succession 1. Primary Succession- in this type, a community develops in an area which is not previously occupied by any other community. 2. Secondary Succession - here the community starts to develop on a site which was previously occupied by a well- developed community. It is an ecological succession that takes place where an existing community has been cleared (by events such as fire, tornado, or human impact), but the soil has been left intact.  Development Ecological succession develops as under: 1. Pioneers The first organisms to become established in an ecosystem undergoing succession are called pioneers; the stable community that ends the succession is termed the climax community. 1. Sere The whole series of communities which are involved in the ecological succession at a given area. For example, from grass to shrub to forest, and which terminates in a final stable climax community, is called as sere. 1. Seral Stage Each of the changes that take place.  Patterns of Succession 1. Hydrarch of hydrosere - The succession when starts in the aquatic environment such as ponds, lakes, streams, swamps, bogs, etc. 2. Mesarch or Mesosere - The succession when begins in and area, where adequate moisture is present. 3. Xerach or Exerosere - The succession when starts in xeric or dry habitat having minimum amounts of moisture, such as dry deserts, rocks, etc. It may be of three types as under: (1) Iithosere-succession initiating on sand; (2)Psammosere-succession initiating on sand; (3)Halosere-succession starting on saline water or soil Biome Biome - is a large, relatively distinct terrestrial region that has similar climate, soil, plants, and animals regardless of where it occurs. It covers a large geographic area and encompasses interacting landscapes. Biomes corresponds to major climate zones with temperature and precipitation as the most important factors. Terrestrial Biomes Figure 1: Using precipitatio and Temperature to Identify biomes Sources: Solomon, E. P. et al. Biology. 7th ed. 2006 Terrestrial Biomes 1.Tundra 2.Taiga 3.Temperate deciduous forest 4.Grasslands 5. Deserts 6.Savanna 7.Tropical Rainforests Tundra also called the ‘Arctic Tundra’, it is the region that lies south of the ice caps of the arctic and extends across North America, Europe, and Siberia. Arctic tundra has long, harsh winter and extremely short summers.There is little precipitation (10 to 25 cm per year). Tundra soils tend to be geologically young. These soil are usually nutrient poor and have a little organic litter (dead leaves and stems, animal droppings, and remains of organisms) Tundra It has a layer of permanently frozen ground called PERMAFROST that varies in depth and thickness. Vegetation in the Tundra is limited to: Lichens, Mosses, Grasses, Sedges and low-growing shrubs. Animals found in the Tundra include; Reindeer, musk oxen, caribou, wolves, Arctic foxes, lemmings, snowy owls, shorebirds,waterfowl, and ptarmigans, which are a type of bird. Tundra Photo courtesy: https://www.treehugger.com/life-in-the- tundra-3572160 Taiga it is just the south of tundra. Taiga or boreal forest is the largest biome in the world. Covering approximately 11% of the Earth’s land. The taiga has a cold winters during which the ground is covered by deep snow. The summer days are warmer than in tundra, and the ground thaws completely. Precipitation is greater than in the taiga, averaging between 50 and 100 cm a year. Vegetation: Pines, firs, and spruce, some deciduous trees which shed their leaves are also present Animals: moose, wolves, black bears, grizzlies, lynx, deer, beavers, muskrats, elks, wolverines, snowshoe hares, porcupines, various rodents, birds, and insects. Taiga Photo courtesy: https://www.quora.com/What-kinds-of-trees-are-characteristic-of-the-Taiga-biome Temperate Deciduous Forest Seasonality that is hot summers and cold winters are characteristic of temperate deciduous forest. The soil of temperate deciduous forest consists of both a topsoil rich in organic material and a deep clay-rich lower layer. Precipitation ranges from about 75 to 126 cm annually. Vegetation - Oak, maple, hickory, beech, chestnut, and birch. Smaller trees and shrubs are also present, as well as herbaceous plants, ferns, lichens, and mosses. Animals - wolves, gray, foxes, bobcats, deer, raccoons, opossums, squirrels, cottontail rabbits. shrews, skunks, woodchunks, ad chipmunks, as well as wide variety of birds and insects. Temperate Deciduous Forest photo courtesy: https://www.pechakucha.com/presentations/biomes-project--- deciduous-forest-323 Grasslands The grasslands or prairies, are found in the interiors of North America, Asia, South America, and Africa. They occur in both temperate and tropical climates where rainfall ranges from 25 to 75 cm a year. This quantity of rainfall cannot support a deciduous forest and grasses become the dominant form of vegetation. The soil in the grasslands is often deep and rich and these areas have become the most productive farmlands of the earth. Vegetation - many species of grasses and wild flowers. In wetter areas, near rivers, the vegetation may be dense and include various shrubs. Grasslands Animals of the North America grasslands include coyotes, rattlesnakes, mice, prairie dogs, jackrabbits, and ground squirrels. In africa , elephants, antelopes, zebras, water buffalo, rhinoceros, giraffes, gazelles and other large grazing animals populate the grasslands. Predators, such as lions, leopards, and hyenas that feed on the grazers are also present. There are fewer types of birds in the grassland than in the deciduous plants. Grasslands Photo courtesy: https://education.nationalgeographic.org/resource/grasslan d-biome/ Deserts Desert occur in regions that are hot and too dry to support grasses. The soil is sandy and poor, low in organic material but often high in mineral particularly the salts NaCl, CaCO3 and CaSO4. Rainfall is usually less than 25 cm in one year. In the world’s largest desert- the Sahara in Africa - the wind is hot, dry and rain almost never falls. Desert plant have special adaptations for the conservation of water and for the completion of their reproductive cycles. Most have widespread, shallow roots that allow them to absorb the maximum amount of water when it is available. Desert Animals have a wide variety of adaptations for survival in the harsh environment. Most are active at night and spend the hot days in burrows in the ground or hidden in any available shade. Deserts Desert animals - desert iguanas, desert tortoises, and rattlesnakes, desert amphibians such as western spadefoot toads. Mammals such as the American kangaroo rat which does not need to drink water but subsists solely on the water content of its food (seeds and insects). During the driest month of the year, many desert insects, amphibians, reptiles, and mammals tunnel underground where they remain inactive. This period of dormancy is known as aestivation. Deserts Photo courtesy: https://www.trilliummontessori.org/the-desert- biome/ Savanna Savanna is found in areas of relatively low or seasonal rainfall with prolonged dry periods. Temperature in savannas vary little throughout the year and precipitation regulates season; unlike in temperate grasslands in which temperature regulates seasons. Savanna soil is low in essential nutrient minerals because it is strongly leached. The annual precipitation is 85 to 150 cm. Wide expanses of grsses interrupted by occasional trees is a characteristic of savanna. The world’s greatest presence of hoofed mammals occurs in African savanna. Great herds of herbivores, which include wild beasts, antelopes, giraffes, zebras, and elephants are present. Large predators, such as lions and hyenas kill and scavenge the herds. In areas of varying rainfall, the herds and their predators may migrate annually. Savanna It is being converted to range land for cattle and other domesticated animals, which are replacing the big herds of wild animals. In some places severe overgrazing by domestic animals has contributed to the conversion of marginal savanna into desert, a process known as desertification. Photo courtesy: https://letstalkscience.ca/educational- resources/backgrounders/savanna-biome Tropical Rainforest Tropical Rainforests are found in areas around the equator. In this regions, the climate is uniform throughout the year. A tropical rainforest will typically be warm and moist. There is a constant supply of rainfall with an annual precipitation of 200 to 450 cm. Tropical rainforests contain an enormous variety of plants and animals. Vegetation- the trees of the rainforests have shallow root systems that allow them to absorb nutrients from the thin layer of wet soil. Among the 100 or more different species of trees found in a rainforests, there are many with large, broad leaves. There are thick vines, called lianas that are attached to the tree trunks and grow up through the treetops. There are also many epiphytes such as orchids, cacti, and ferns. Tropical Rainforest Animals - a wide variety of animal species inhabit tropical rainforest. Includes insects, reptile, amphibians fauna of the Earth. Birds in this biome are diverse with some specialized to consume fruits such as parrots and other that consume nectar, such as sunbirds. Most rainforest mammals, such as sloths and monkeys live only in trees. Elephants and some large ground-dwelling animals are also found in tropical rainforests. Photo courtesy: https://biologydictionary.net/biotic-factors- tropical-rainforest/ AQUATIC ECOSYSTEM are classified primarily on abiotic factors, such as salinity that help determine an aquatic life zone’s boundaries. Salinity, the concentration of dissolved salts, such as sodium chloride in a body of water affects the kinds of organisms present in aquatic ecosystems, as does the amount of dissolved oxygen. Three main ecological categories of organisms: ❏Free- floating Plankton ❏Strongly swimming Nekton ❏bottom-dwelling benthos.  Aquatic Ecosystem 1. Plankton - usually small or microscopic organisms that are relatively feeble swimmers. a. Phytoplankton - photosynthetic cyanobacteria and free- floating algae, are producers that form the base of most aquatic food webs. b.Zooplankton – non-photosynthetic organisms that include protozoa, tiny crustaceans, and the larval stages of many animals. 1. Nekton - are larger, strong swimming organisms such as fishes, turtles and whales 2. Benthos - are bottom-dwelling organisms that fix themselves to one spot (sponges, oysters, and barnacles), those that borrow into the sand (many worms, and echinoderms), or simple walk or swim about on the bottom (crayfish, and brittle stars)  Freshwater Ecosystem it include streams and rivers or free flowing ecosystem, ponds and lakes or standing-water ecosystems, and marshes, swamps or freshwater wetlands. STREAMS AND RIVERS Figure 2: Features of Typical River Photo courtesy: https://www.geographypods.com/21 -river-features.html Freshwater Ecosystem LAKES AND PONDS Figure 3: Zonation in Lakes and Ponds Photo courtesy: https://www.shutterstock.co m/search/littoral-zone  Aquatic Ecosystem Large lakes has three basic zones: the littoral, limnetic, and profundal zones. Littoral zone- is a shallow water area along the shore of a lake or pond. It includes rooted vegetation and several deep-dwelling aquatic plants and algae. This zone is the most productive zone of the lake. Limnetic zone- is the open water beyond the littoral zone, away from the shore. It extends down as far as sunlight penetrates to permit photosynthesis. The main organisms of the limnetic zone are microscopic phytoplankton and zooplankton. Larger fishes also spend some of their time in this zone. Profundal zone - it is beneath the limnetic zone of a large lake. Light does not penetrate effectively to this depth so that plants and algae do not exist in this zone.  Freshwater Ecosystem FRESHWATER WETLANDS are transitional between aquatic and terrestrial ecosystems. Shallow water usually covers for at least part of the year, have characteristics soils wetter-tolerant vegetation. They include marshes in which grasslike plants dominate, and swamps in which woody trees and shrubs dominate. Wetlands plants which are highly productive provide enough food to support a wide variety of organisms. Wetlands are wildlife habitat for migratory waterfowl and other bird species, such as beaver, muskrat, and game fishes. It also serves as the holding areas for excess water when river floods their banks  Freshwater Ecosystem ESTUARIES An estuary is a coastal body of water partly surrounded by land with access to open ocean and large supply of freshwater from rivers. It occurs where freshwater and saltwater meet. Salinity varies from unsalty freshwater at the river entrance to salty ocean water at the mouth of the estuary. With the daily, seasonal, and annual variations in temperature, salinity, and other physical properties, organisms have wide tolerance to such changes. Temperate estuaries usually contain salt marshes, shallow wetlands in which salt-tolerant grasses dominates. The tropical equivalent of salt marshes is the mangrove forests. It covers about 70% of tropical and subtropical coastal mud flats where tidal waves fluctuate.  Freshwater Ecosystem Mangrove forests Photo courtesy: https://www.discovery.com/nature/the- world-is-waking-up-to-the-importance-of-mangroves  Marine Ecosystem The large and complex marine environment is subdivided into several zones: the intertidal zone, the benthic (ocean floor) environment, and the pelagic (ocean water) environment.  Marine Ecosystem INTERTIDAL ZONE is the shoreline area between low and high tide. It is the transitional zone between land and ocean. It has a high levels of light and nutrients with an abundance of oxygen. It is biologically productive environment. BENTHIC ENVIRONMENT it is the ocean floor and is divided into zones based on distance from land, light availability, and depth. This type of environment consists of sediment (mostly sand and mud) in which worms and clams burrows. The abyssal zone is part of the benthic environment that extends to a depth of 4000 to 6000 m. The hadal zone extends to a depth more than 6000 m. The benthic communities in shallow ocean waters consists of the seagrass beds, the kelp forest, and the coral reefs.  Marine Ecosystem Seagrass beds Seagrass are flowering plants that have adapted to complete submersion in ocean water. Kelps reaches a length of 60 m are the largest brown algae. They are photosynthetic and are primary food producer for the kelp ecosystem. Kelps forest provide habitats for many marine animals. Coral reefs are built from accumulated layers of calcium carbonate, found in warm (usually higher than 21 degree celcius, shallow seawater. Many coral reefs are composed primarily of red coralline algae that require light for photosynthesis. Coral reefs ecosystem is the most diverse of all marine environments and contains hundreds or thousands of species of fishes and invertebrates, such as giant clams, sea urchins, sea stars, sponges, sea fans, and shrimps KELPS CORAL REEFS Photo courtesy: https://news.virginia.edu/content/study- finds-kelp-key-californias-coastal-ecosystems Photo courtesy: https://www.outsideonline.com/outdoor- adventure/environment/why-your-next-outdoor-adventure-should-be-to- a-coral-reef/ Ecotones The transition zone, where two communities or biomes meet and integrate. It vary in size from small, such as the area when an agricultural land or field meets a woodland or where a stream flows through a forest which cover several countries. Photo courtesy: https://www.ecotoneinc.com/wp- content/uploads/2020/12/Ecotone- Conference-display.jpg Biogeochemical Cycle Matter moves in numerous cycles form one part of an ecosystem to another that is, from one organism to another and from living organisms to the abiotic environment and back again. These cycle of matter is called the biogeochemical cycle, as they involved biological, geologic, and chemical interactions. With respect to matter, the Earth is essentially a closed system. FOUR CYCLES OF MATTER: ❏Carbon ❏Nitrogen ❏Phosphorus ❏Water Carbon Cycle ❏Carbon is the pivotal molecule in the carbon cycle. Carbon is present in the atmosphere as the gas carbon dioxide, which makes up approximately 0.04% of the atmosphere. It is also present in the ocean and fresh water as dissolved carbon dioxide. It is also present in rocks such as limestone (CaCO3). The global movement of carbon between the abiotic environment, including the atmosphere and ocean, and organisms is known as the Carbon cycle. Carbon Cycle Photo courtesy: https://byjus.com/biology/carbon- cycle/ Nitrogen Cycle ❏Nitrogen is important for all organisms because it is an essential part of proteins, nucleic acids, and chlorophyll. ❏The Nitrogen cycle, in which it cycles between the abiotic environment and organisms has five steps: 1)Nirogen Fixation, 2) Nitrification, 3) Assimilation, 4) Ammonification; and 5) Denitrification. Bacteria are involved in all the steps except assimilation. Nitrogen Cycle Photo courtesy: https://sciencenotes.org/nitrogen-cycle/ NITROGEN CYCLE Phosphorus Cycle ❏Phosphorus does not exist in a gaseous state and thus, it does not enter the atmosphere, cycles from the land to sediments in the ocean and back to tha land. Photo courtesy: https://www.geeksforgeeks.org/phosphorus- cycle/ Phosphorus Cycle Hydrologic Cycle ❏Water has many properties that help shape the continents, moderate climate and allow organisms to survive. Water continuously circulates from the ocean to the atmosphere to the land and back to the ocean. It provides a renewable supply of purified water for use by terrestrial organisms. This complex cycle is called Hydrologic Cycle which results in a balance between water in the ocean, on land and in the atmosphere. Hydrologic Cycle Photo courtesy: https://gpm.nasa.gov/education/water- cycle/hydrologic-cycle HYDROLOGIC CYCLE  Thank you very much! References: Introduction to Environmental Science (Revised Edition) by: Joel E. Unday, et. al. , 2012 Environmental Science 2012 Edition by; Arnaldo P. Mosteiro