2024/25 Basics of Ecology Lecture 3 PDF

Network of Life Lecture 3 Basics of Ecology – Conditions and Origin of Life  Review Lecture 2 Organelles are basic units of structure and specific function. Cells are units of combined and synchronized organelles. Two...

Network of Life Lecture 3 Basics of Ecology – Conditions and Origin of Life  Review Lecture 2 Organelles are basic units of structure and specific function. Cells are units of combined and synchronized organelles. Two main types of cells exists: prokaryotic and eukaryotic cells. Main difference is the compartmentalization in eukaryotic cells by different membranes. An organism’s metabolism transforms matter and energy. Energy is the ability to rearrange a collection of matter and energy exists in various forms. Kinetic energy: the relative motion of objects Thermal energy: random movements of atoms Potential energy: energy that matter possesses because of its location or structure Life: A self controlled system that is able to independently rearrange matter and energy approaching a highly ordered state with the ability of reproduction. Reproduction: preserving information by passing it through a code to the offspring. DNA: Matter that stores biological information as nucleotides (code). Cell division: Creating new life by transfer of whole genomic information to offspring (inheritance) Variation: Creating new biological information 2 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology What determines the variation of life we know? 3 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Life structure is based on interaction between several units. between atoms -> elements -> molecules -> polymers -> organelles -> cell -> multi cellular organism t en nm ro vi En internal internal external 4 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology What is Ecology? The subject of ecology is the scientific study of the interactions between organisms and the environment. 5 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Different hierarchical levels of ecology Organismal Ecology: includes the subdisciplines of physiological, evolutionary, and behavioural ecology, is concerned with how an organism’s structure, physiology, and behaviour meet the challenges posed by its environment. Population Ecology: analyses factors that affect population size and how and why it changes through time. Community Ecology: examines how interactions between species, such as predation and competition, affect community structure and organization. Ecosystem Ecology: emphasizes energy flow and chemical cycling between organisms and the environment. Landscape Ecology: focuses on the factors controlling exchanges of energy, materials, and organisms across multiple ecosystems. Global Ecology: examines how the regional exchange of energy and materials influences the functioning and distribution of organisms across the biosphere. 6 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology What is the environment? 7 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology The biosphere The biosphere (from Greek βίος bíos "life" and σφαῖρα sphaira "sphere"), also known as the ecosphere (from Greek οἶκος oîkos "environment" and σφαῖρα) is the sum of all the planet’s ecosystems and landscapes. The biosphere is virtually a closed system with regard to matter, with minimal inputs and outputs. With regard to energy, it is an open system, with photosynthesis capturing solar energy at a rate of around 130 Terawatts per year. However it is a self-regulating system close to energetic equilibrium. By the most general biophysiological definition, the biosphere is the global ecological system integrating all living beings and their relationships, including their interaction with the elements of the lithosphere, cryosphere, hydrosphere, and atmosphere. Bild von Gerd Altmann auf Pixabay 1. Nealson, Kenneth H.; Zeki, S.; Conrad, Pamela G. (1999). "Life: past, present and future". Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences. 354 (1392): 1923–1939. doi:10.1098/rstb.1999.0532. 2 2. "Biosphere" in The Columbia Encyclopedia, 6th ed. (2004) Columbia University Press. 8 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Global Climate Patterns Latitudinal Variation in Sunlight Intensity Earth’s curved shape causes latitudinal variation in the intensity of sunlight. Because sunlight strikes the tropics (those regions that lie between 23.5° north latitude and 23.5° south latitude) most directly, more heat and light per unit of surface area are delivered there. At higher latitudes, sunlight strikes Earth at an oblique angle, and thus the light energy is more diffuse on Earth’s surface. 9 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Technology vector created by brgfx - www.freepik.com 10 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Global Air Circulation and Precipitation Patterns Intense solar radiation near the equator initiates a global pattern of air circulation and precipitation. High temperatures in the tropics evaporate water from Earth’s surface and cause warm, wet air masses to rise (blue arrows) and flow toward the poles. As the rising air masses expand and cool, they release much of their water content, creating abundant precipitation in tropical regions. Air flowing close to Earth’s surface creates predictable global wind patterns. As Earth rotates on its axis, land near the equator moves faster than that at the poles, deflecting the winds from the vertical paths shown above and creating the more easterly and westerly flows shown at left. 11 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Weather and climate. What is the difference between weather and climate? Weather is the state of the air and atmosphere at a particular time and place : the temperature and other outside conditions (such as rain, cloudiness, etc.) at a particular time and place1. Climate: The difference between weather and climate is a measure of time. Climate is how the atmosphere "behaves" over relatively long periods of time. When we talk about climate change, we talk about changes in long- term averages of daily weather2. Four physical factors: temperature, precipitation, sunlight, and wind are key components of climate. 1 Merriam-Webster Online Thesaurus copyright © 2021 by Merriam-Webster, Incorporated 2 Shepherd, Dr. J. Marshall; Shindell, Drew; O'Carroll, Cynthia M. (1 February 2005). "What's the Difference Between Weather and Climate?" 12 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Climate Zones Portrait of Alexander Freiherr von Humboldt (Berlin 1769 1859) German naturalist explorer and botanist. Von Ka rl Josep h Stiel er - , Gemei nfrei, https://commo ns.wiki medi a.org/w/in dex.ph p?cu rid=922 977 13 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Leslie Holdridge's Life Zone Climate classification Classification system is essentially a climate classification scheme. By Peter Halasz - own work, based on Ecology (textboox) Peter Stiling, 4th ed. p236, and Textbook of Biodiversity K. V. Krishnamurthy 2003 p55., CC BY-SA 2.5, https://commons.wikimedia.org/w/index.php?curid=1737503 14 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology The Köppen climate classification divides climates into five main climate groups, with each group being divided based on seasonal precipitation and temperature patterns. The five main groups (first letter) are: A (tropical), B (dry), C (temperate), D (continental), and E (polar). All climates except for those in the E group are assigned a seasonal precipitation subgroup (the second letter). For example, Af indicates a tropical rainforest climate. The system assigns a temperature subgroup for all groups other than those in the A group, indicated by the third letter for climates in B, C, and D, and the second letter for climates in E. Tropical Dry Temperate Continental Polar & Alpine Beck, H.E., Zimmermann, N. E., McVicar, T. R., Vergopolan, N., Berg, A., & Wood, E. F., CC BY 4.0, via Wikimedia Common 15 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Global Climate Patterns Global climate patterns are determined largely by the input of solar energy and Earth’s movement in space. The sun warms the atmosphere, land, and water. This warming establishes the temperature variations, movements of air and water, and evaporation of water that cause dramatic latitudinal variations in climate. Regional and Local Effects on Climate Climate varies seasonally and can be modified by other factors, such as large bodies of water and mountain ranges. 16 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Seasonality In middle to high latitudes, Earth’s tilted axis of rotation and its annual passage around the sun cause strong seasonal cycles in day length, solar radiation, and temperature. The changing angle of the sun over the course of the year also affects local environments. For example, the belts of wet and dry air on either side of the equator move slightly northward and southward as the sun’s angle changes; this produces marked wet and dry seasons where many tropical deciduous forests grow. In addition, seasonal changes in wind patterns alter ocean currents, sometimes causing the upwelling of cold water from deep ocean layers. This nutrient-rich water stimulates the growth of surface-dwelling phytoplankton and the organisms that feed on them. 17 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Global circulation of surface water in the oceans Water is warmed at the equator and flows north and south toward the poles, where it cools. Because of the high specific heat of water (see water property lecture 1), oceans and large lakes tend to moderate the climate of nearby land. During a hot day, when land is warmer than the water, air over the land heats up and rises, drawing a cool breeze from the water across the land. Ocean currents influence climate along the coasts of continents by heating or cooling overlying air masses that pass across the land. Coastal regions are also generally wetter than inland areas at the same latitude. The west coast of northern Europe has a mild climate because the Gulf Stream carries warm water from the equator to the North Atlantic. As a result, north western Europe is warmer during winter than south eastern Canada, which is farther south but is cooled by the Labrador Current flowing south from the coast of Greenland. 18 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Mountains Like large bodies of water, mountains influence air flow over land. When warm, moist air approaches a mountain, the air rises and cools, releasing moisture on the windward side of the peak. Mountains also affect the amount of sunlight reaching an area and thus the local temperature and rainfall. South-facing slopes in the Northern Hemisphere receive more sunlight than north-facing slopes and are therefore warmer and drier. These physical differences influence species distributions locally. How large bodies of water and mountains affect climate. 19 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Effects of Vegetation on Climate Climate affects where terrestrial organisms can live, but organisms can also affect climate. This is especially true of forests, which can alter the climate at local and even regional scales. A forest absorbs more (and reflects less) solar energy than does a desert or grassland, thereby contributing to a warming of Earth’s surface in forested areas. This warming effect, however, is more than offset by transpiration, the evaporative loss of water from a plant that cools the plant’s surface. The evaporative loss of water is much greater in forests than in other ecosystems, causing forests to affect climate in two key ways: Forests reduce Earth’s surface temperature and they increase precipitation rates. As documented in regions around the world, the climate becomes hotter and drier in areas where humans have cut down large forests and becomes cooler and wetter where humans have restored large forests. 20 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Microclimate At an even smaller scale is the microclimate, very fine, localized patterns in climatic conditions. Many features in the environment influence microclimate by casting shade, altering evaporation from soil, or changing wind patterns. A log or large stone can shelter organisms such as salamanders, worms, and insects, buffering them from the extremes of temperature and moisture. Every environment on Earth exhibits small-scale differences in chemical and physical attributes, such as temperature, light, water, and nutrients. Similarly, all of the biotic, or living, factors the other organisms that are part of an individual’s environment also influence the distribution and abundance of life on Earth. 21 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Global Climate Change Because climatic variables affect the geographic ranges of most plants and animals, any large-scale change in Earth’s climate profoundly affects the biosphere. In fact, a large-scale climate “experiment” is under way: The burning of fossil fuels and deforestation are increasing the concentrations of carbon dioxide and other greenhouse gases in the atmosphere. This has caused climate change, a directional change to the global climate that lasts three decades or more (as opposed to short-term changes in the weather). Earth has warmed an average of 0.9°C (1.6°F) since 1900 and is projected to warm 1-6°C (2–11°F) more by the year 2100. Wind and precipitation patterns also are shifting, and extreme weather events (such as major storms and droughts) are occurring more frequently. 22 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Summary Earth Climate ▪ The subject of ecology is the scientific study of the interactions between organisms and the environment. ▪ Ecology can be hierarchical subdivided into: organismal-, population-, community-, ecosystem-, landscape- and global ecology. ▪ The biosphere is virtually a closed system with regard to matter, with minimal inputs and outputs. With regard to energy, it is an open system, with photosynthesis capturing solar energy. ▪ Earth’s curved shape causes latitudinal variation in the intensity of sunlight and the tilted axis of rotation causes the strong seasonality. ▪ Weather is the state of the air and atmosphere at a particular time and place, climate is how the atmosphere "behaves" over relatively long periods of time. ▪ Climate can be divided in five main groups: A (tropical), B (dry), C (temperate), D (continental), and E (polar). ▪ Four physical factors: temperature, precipitation, sunlight, and wind are key components of climate. ▪ Global water currents, mountains and vegetation have strong effects on climate. 23 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Terrestrial and Aquatic Biomes 24 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Climate and Terrestrial Biomes Because climate has a strong influence on the distribution of plant species, it is a major factor in determining the locations of terrestrial biomes. The distribution of major terrestrial biomes. 25 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology General Features of Terrestrial Biomes Most terrestrial biomes are named for major climatic features and for their predominant vegetation. Each biome is also characterized by microorganisms, fungi, and animals adapted to that particular environment. Vertical layering of vegetation is an important feature of terrestrial biomes. In many forests, the layers from top to bottom consist of: upper canopy, the low-tree layer, the shrub understory, the ground layer of herbaceous plants, the forest floor (litter layer), and the root layer Non forest biomes have similar, though usually less pronounced, layers. Layering of vegetation provides many different habitats for animals, which sometimes exist in well-defined feeding groups, from the insectivorous birds and bats that feed above canopies to the worms, arthropods, and small mammals that search for food in the litter and root layers below. 26 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Disturbance and Terrestrial Biomes Biomes are dynamic, and disturbance rather than stability tends to be the rule. In ecological terms, disturbance is an event such as a storm, fire, or human activity that changes a community, removing organisms from it and altering resource availability. For example, hurricanes and other storms create openings for new species in many tropical and temperate forests and can alter forest composition. As a result of disturbances, biomes are often patchy, containing several different communities in a single area. In many biomes, even the dominant plants depend on periodic disturbance. Natural wildfires are an integral component of grasslands, savannas, chaparral, and many coniferous forests. 27 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Aquatic biomes are diverse and dynamic systems that cover most of Earth Unlike terrestrial biomes, aquatic biomes are characterized primarily by their physical and chemical environment. They also show far less latitudinal variation, with all types found across the globe. The oceans make up the largest marine biome, covering about 75% of Earth’s surface. Because of their vast size, they greatly impact the biosphere. Water evaporated from the oceans provides most of the planet’s rainfall. Marine algae and photosynthetic bacteria supply much of the world’s oxygen and consume large amounts of atmospheric carbon dioxide. Ocean temperatures have a major effect on global climate and wind patterns and along with large lakes, oceans tend to moderate the climate of nearby land. 28 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Zonation in Aquatic Biomes Many aquatic biomes are physically and chemically stratified (layered), vertically and horizontally. Light is absorbed by water and by photosynthetic organisms, so its intensity decreases rapidly with depth. The upper photic zone is the region where there is sufficient light for photosynthesis, while the lower aphotic zone is the region where little light penetrates. The photic and aphotic zones together make up the pelagic zone. 29 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Zonation in Aquatic Biomes Deep in the aphotic zone lies the abyssal zone, the part of the ocean 2,000– 6,000 m below the surface. At the bottom of all of these aquatic zones, deep or shallow, is the benthic zone. Made up of sand and organic and inorganic sediments, the benthic zone is occupied by communities of organisms collectively called the benthos. A major source of food for many benthic species is dead organic matter called detritus, which “rains” down from the productive surface waters of the photic zone. Thermal energy from sunlight warms surface waters to whatever depth the sunlight penetrates, but the deeper waters remain quite cold. 30 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Seasonal Turnover in Aquatic Biomes In the ocean and in most lakes, a narrow layer of abrupt temperature change called a thermocline separates the more uniformly warm upper layer from more uniformly cold deeper waters. Lakes tend to be particularly layered with respect to temperature, especially during summer and winter, but many temperate lakes undergo a semi annual mixing of their waters as a result of changing temperature profiles. This turnover, as it is called, sends oxygenated water from a lake’s surface to the bottom and brings nutrient-rich water from the bottom to the surface in both spring and autumn. In both freshwater and marine environments, communities are distributed according to water depth, degree of light penetration, distance from shore, and whether they are found in open water or near the bottom. 31 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Interactions between organisms and the environment limit the distribution of species 32 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Interactions between organisms and the environment limit the distribution of species Species distributions are a consequence of both ecological factors and evolutionary history. Ecologists ask not only where species occur, but also why species occur where they do: What ecological Factors biotic and abiotic determine their distribution? In many cases, both biotic and abiotic factors affect the distribution of a species, as is true of the saguaro cactus (Carnegiea gigantea). Saguaros are found almost exclusively in the Sonoran Desert of the southwestern United States and northwestern Mexico. To the north, their range is limited by an abiotic factor: temperature. Saguaros tolerate freezing temperatures only briefly, typically for less than a day, and generally cannot survive at temperatures below –4°C (25°F). However, temperature alone does not fully explain the distribution of saguaros, including why they are missing from the western portion of the Sonoran Desert. Biotic factors almost certainly influence their distribution as well. Mice and grazers such as goats eat the seedlings, and bats pollinate the large, white flowers that open at night. Saguaros are also vulnerable to a deadly bacterial disease. Thus, for the saguaro, as for most other species, ecologists need to consider multiple factors and alternative hypotheses when attempting to explain the distribution of a species. 33 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Dispersal and Distribution One factor that contributes greatly to the global distribution of organisms is dispersal, the movement of individuals or gametes away from their area of origin or from centers of high population density. Natural Range Expansions and Adaptive Radiation The importance of dispersal is most evident when organisms reach an area where they did not exist previously, called a range expansion. Long-distance dispersal can lead to adaptive radiation, the rapid evolution of an ancestral species into new species that fill many ecological niches. Flowchart of factors limiting geographic distribution. An ecologist studying factors limiting a species’ distribution might consider questions like these. As suggested by the arrows leading from the “Yes” responses, the ecologist would answer all of these questions because more than one factor can limit a species’ distribution. 34 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Ecological change and evolution affect one another over long and short periods of time. Biologists have long recognized that ecological interactions can cause evolutionary change, and vice versa. The history of life includes many examples of these reciprocal effects occurring over long periods of time (details in Lecture 4). Considering the origin and diversification of plants. The evolutionary origin of plants altered the chemical cycling of carbon, leading to the removal of large quantities of carbon dioxide from the atmosphere. As the adaptive radiation of plants continued over time, the appearance of new plant species provided new habitats and new sources of food for insects and other animals. In turn, the availability of new habitats and new food sources stimulated bursts of speciation in animals, leading to further ecological changes. 35 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Biomes Summary ▪ The distribution of terrestrial biomes is controlled by climate and disturbance. ▪ As a result of disturbances, biomes are often patchy, containing several different communities in a single area. ▪ Vertical layering of vegetation is an important feature of terrestrial biomes by providing different habitats. ▪ Aquatic biomes are diverse and dynamic systems that cover most of Earth, about 75% of Earth’s surface. ▪ Ocean temperatures have a major effect on global climate and wind patterns and along with large lakes, oceans tend to moderate the climate of nearby land. ▪ Many aquatic biomes are physically and chemically stratified (layered), vertically and horizontally. ▪ Seasonal turnover in aquatic biomes is resulting from temperature difference with strong effect on the distribution of biotic and abiotic factors. ▪ Interactions between organisms and the environment limit the distribution of species. ▪ Ecological change and evolution affect one another over long and short periods of time. 36 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Population Ecology 37 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Population Definition: A population is a group of individuals of a single species living in the same general area. Members of a population rely on the same resources, are influenced by similar environmental factors, and are likely to interact and breed with one another. 38 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology What affects the size of a population and how it changes over time? 39 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology What affects the size of a population and how it changes over time? Adding individuals to or removing individuals from a population changes the population size: 40 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Density and Dispersion The density of a population is the number of individuals per unit area or volume: the number of oak trees per square kilometre in the Minnesota county or the number of Escherichia coli bacteria per millilitre in a test tube. Density is not a static property but can increase or decrease over time as individuals are added to or removed from a population. Additions occur through reproduction and immigration, the influx of new individuals from other areas. The factors that remove individuals from a population are death (mortality) and emigration, the movement of individuals out of a population and into other locations. 41 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Dispersion is the pattern of spacing among individuals within the boundaries of the population. Within the boundaries of a population, the spacing among individuals may differ substantially, creating contrasting patterns of dispersion. clumped (a) most common pattern, clumping of animals may also be associated with mating behaviour uniform (b) result from direct interactions between individuals in the population, in animals a result of antagonistic social behaviour like territoriality random (c) the position of each individual in a population is independent of other individuals Such differences in spacing can provide insight into the biotic and abiotic factors that affect individuals in the population. 42 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Population growth Ecologists study population growth in ideal, unlimited environments to reveal how fast populations are capable of growing and the conditions under which rapid growth might actually occur. The change in population size during a fixed time interval can be described as: change in population size = (births + immigrants) – (deaths – emigrants) In mathematical terms: R=B-D Δ𝑁 Δ𝑁 Δ𝑇 = B-D = Δ𝑇 =R 43 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Population growth Population size are expressed on a per individual (per capita) basis. The per capita change in population size r𝚫t represents the contribution that an average member of the population makes to the number of individuals added to or subtracted from the population during the time interval Δt. Since the number of individuals added to (or subtracted from) the population (R) can be expressed on a per capita basis as R = rΔtN, we can revise our population growth equation to take this into account: Δ𝑁 Δ𝑇 = rΔtN Exponential population growth – exponential growth 44 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Logistic growth The logistic model describes how a population grows more slowly as it nears its carrying capacity. The exponential growth model assumes that resources remain abundant, which is rarely the case in the real world. Instead, as the size of a population increases, each individual has access to fewer resources. Ultimately, there is a limit to the number of individuals that can occupy a habitat. Ecologists define the carrying capacity, symbolized by K, as the maximum population size that a particular environment can sustain. 𝑑𝑁 (𝐾 − 𝑁) = rN 𝑑𝑡 𝐾 45 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology How well do populations fit the logistic growth model? A Paramecium population in the lab. A Daphnia population in the lab. The growth of Paramecium aurelia in a small The growth of a population of water fleas (Daphnia) in a small laboratory culture closely approximates logistic growth if culture does not correspond well to the logistic model. This population the researcher maintains a constant overshoots the carrying capacity of its artificial environment before it settles environment. down to an approximately stable population size. 46 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Density-dependent factors regulate population growth. What environmental factors keep populations from growing indefinitely? Why are some populations fairly stable in size, while others are not? Population Change and Population Density If immigration and emigration offset each other, then a population grows when the birth rate exceeds the death rate and declines when the death rate exceeds the birth rate. Variation in density-independent factors such as temperature and precipitation can cause dramatic changes in population size. 47 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Mechanisms of Density-Dependent Regulation Competition for Resources Increasing population density leads to competition among members of a population for nutrients and other resources, reducing reproductive rates. Territoriality Territoriality can limit population density when space becomes the resource for which individuals compete. Disease If the transmission rate of a disease increases as a population becomes more crowded, then the disease’s impact is density de pendent. Toxic Wastes Yeasts, such as the brewer’s yeast Saccharomyces cerevisiae, are used to convert carbohydrates to ethanol in winemaking. The ethanol that accumulates in the wine is toxic to yeasts and contributes to density-dependent regulation of yeast population size. Intrinsic factors Physiological factors operating within an individual organism. For examples hormones produced by an organisms due to stress in highly dense populations can affect reproduction rates. 48 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Summary Population Ecology ▪ A population is a group of individuals of a single species living in the same general area. ▪ Adding individuals (birth, immigration) to or removing individuals (death, emigration) from a population changes the population size. ▪ The density of a population is the number of individuals per unit area or volume, can increase or decrease over time as individuals are added to or removed from a population. ▪ Dispersion is the pattern of spacing among individuals within the boundaries of the population. ▪ Three main dispersion pattern are: clumped, uniform and random. ▪ Change in population size can be describe by e.g.: exponential grow logistic function (considering carrying capacity as limit) ▪ Density-dependent factors regulate population growth: Competition for Resources Territoriality Disease Toxic Wastes Intrinsic factors 49 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Community Ecology 50 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology What is a community from ecological perspective? Definition: A community is a group of populations of different species living in close enough proximity to interact. 51 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology What are some factors that influence the structure of a community? Some key relationships in the life of an organism are its interactions with individuals of other species in the community. These interspecific interactions include Competition Interaction that occurs when individuals of different species each use a resource that limits the survival and reproduction o f both individuals. Predation Interaction in which an individual of one species, the predator, kills and eats an individual of the other species, the prey. Herbivory Exploitative interaction in which an organism -an herbivore- eats parts of a plant or alga, thereby harming it but usually not killing it. Parasitism Exploitative interaction in which one organism, the parasite, derives its nourishment from another organism, its host, which is harmed in the process. Mutualism Interaction that benefits individuals of both of the interacting species. Commensalism An interaction that benefits the individuals of one of the interacting species but neither harms nor helps the individuals of the other species. 52 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Diversity and trophic structure characterize biological communities Ecological communities can be characterized by certain general attributes, including how diverse they are and the feeding relationships of their species. The species diversity of a community -the variety of different kinds of organisms that make up the community- has two components. One is species richness, the number of different species in the community. The other is the relative abundance of the different species, the proportion each species represents of all individuals in the community. Ecologists use many tools to compare the diversity of communities. They often calculate indexes of diversity based on species richness and relative abundance. One widely used index is the Shannon diversity index. 53 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Trophic Structure In addition to species diversity, the structure and dynamics of a community also depend on the feeding relationships between organisms the trophic structure of the community. The transfer of “chemical” energy from its source in plants and other autotrophs (primary producers) through herbivores (primary consumers) to carnivores (secondary, tertiary, and quaternary consumers) and eventually to decomposers is referred to as a food chain. terrestrial food chains marine food chains 54 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Disturbance influences species diversity and composition A disturbance is an event, such as a storm, fire, flood, drought, or human activity, that changes a community by removing organisms from it or altering resource availability. Disturbance is characterise as: low, high or intermediate disturbance. The intermediate disturbance hypothesis states that moderate levels of disturbance foster greater species diversity than do high or low levels of disturbance. High levels of disturbance reduce diversity by creating environmental stresses. Low levels of disturbance can reduce species diversity by allowing competitively dominant species to exclude less competitive ones. 55 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Biogeographic factors affect community diversity. Large-scale biogeographic factors also contribute to the tremendous range of diversity observed in biological communities. Two biogeographic factors have been investigated for more than a century, in particular: the latitude of a community and the area it occupies. Two key factors that can affect latitudinal gradients of species richness are evolutionary history and climate. In 1807, naturalist and explorer Alexander von Humboldt described one of the first patterns of species richness to be recognized, the species-area curve: All other factors being equal, the larger the geographic area of a community, the more species it has. One explanation for this relationship is that larger areas offer a greater diversity of habitats and microhabitats. 56 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Review Community Ecology ▪ A community is a group of populations of different species living in close enough proximity to interact. ▪ Some key relationships in the life of an organism are its interactions with individuals of other species in the community. These interspecific interactions include: Competition, Predation, Herbivory, Parasitism, Mutualism, Commensalism. ▪ Diversity and trophic structure characterize biological communities. ▪ Disturbance influences species diversity and composition. ▪ Biogeographic factors affect community diversity. 57 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Ecosystems Ecology 58 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology What are the dynamics of energy and chemical nutrients in an ecosystem? An ecosystem, regardless of its size, has two key emergent properties: energy flow and chemical cycling. Energy enters most ecosystems as sunlight. As for chemical cycling, elements such as carbon and nitrogen are passed between the biotic and abiotic components of the ecosystem. Both energy and chemicals are transformed in ecosystems through photosynthesis and feeding relationships. Conservation of Mass Matter, like energy, cannot be created or destroyed. This law of conservation of mass is as important for ecosystems as are the laws of thermodynamics. Because mass is conserved, we can determine how much of a chemical element cycles within an ecosystem or is gained or lost by that ecosystem over time. In addition to cycling within ecosystems, elements can also be gained or lost by an ecosystem. Most gains and losses to ecosystems are small compared to the amounts that cycle within them. 59 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Energy, Mass, and Trophic Levels The trophic level that ultimately supports all others An overview of energy consists of the primary producers of the ecosystem. and nutrient dynamics in an ecosystem. These are photosynthetic organisms that use light energy to synthesize sugars and other organic compounds, which they use as fuel for cellular respiration and as building material for growth. Herbivores, which eat plants and other primary producers, are primary consumers. Carnivores that eat herbivores are secondary consumers, and carnivores that eat other carnivores are tertiary consumers. Another group of heterotrophs is the decomposers, consumers that get their energy from detritus. Detritus is non living organic material, such as the remains of dead organisms, feces, and fallen leaves. 60 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Energy and other limiting factors control primary production in ecosystems. In most ecosystems, the amount of light energy converted to chemical energy in the form of organic compounds by autotrophs during a given time period is the ecosystem’s primary production. Total primary production in an ecosystem is known as that ecosystem’s gross primary production (GPP) – the amount of energy from light (or chemicals, in chemoautotrophic systems) converted to the chemical energy of organic molecules per unit time. Net primary production (NPP) is equal to gross primary production minus the energy used by the primary producers for their cellular respiration. 61 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Global net primary production. The map is based on satellite-collected data, such as amount of sunlight absorbed by vegetation. Note that tropical land areas have the highest rates of production (yellow to red). 62 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de  Basics of Ecology Summary Ecosystems Ecology 63 WS 2024/25 – Basics of Ecology / Conditions and Origin of Life hhu.de