Ecology LS2-1,2,3,4 PDF

Ecology LS2-1,2,3,4 What is an Ecosystem? An ecosystem is defined as a community (all the organisms in a given area) and the abiotic factors (such as water, soil, or climate) that affect them. ○ What does biotic and abiotic mean? ○ What are some of those factors in the pictur...

Ecology LS2-1,2,3,4 What is an Ecosystem? An ecosystem is defined as a community (all the organisms in a given area) and the abiotic factors (such as water, soil, or climate) that affect them. ○ What does biotic and abiotic mean? ○ What are some of those factors in the picture? Individual species (one single species) help to make up a population (multiple of the same species) that create a community (multiple different species) that make an ecosystem (that make up all biotic and abiotic factors) What is an Ecosystem? Different species have different niches or roles or function they play in an ecosystem. Organisms cannot have the same niche if they are competing for the same resources. If two organisms are competing for the same resources natural selection will occur. ○ This means the successful organism will continue to gain the resource, while the competition becomes reduced and eventually the other organism may go extinct. Ecosystem Stability The number of organisms in ecosystems fluctuates over time as a result of mechanisms such as migration, birth and death. These fluctuations are essential for ecosystem stability and characterize the dynamic nature of ecosystems. ○ Why might changes or fluctuations be important? Extreme fluctuations in the size of populations offset the stability of ecosystems in terms of habitat and resource availability. ○ Why might a large fluctuation offset stability of the ecosystem? Ecosystems can be reasonably stable over hundreds or thousands of years. If a disturbance to the biotic or abiotic components of an ecosystem occurs, the affected ecosystem may return to a system similar to the original one, or it may take a new direction and become a very different type of ecosystem. ○ Let’s think of an example! Ecosystem Stability Ecosystems are not always stable over short periods of time. Changes in climate, migration of an invading species, and human activity can impact the stability of an ecosystem. Other changes that may impact the stability of an ecosystem include interactions among living organisms such as competition, predation, parasitism and disease. Competition - competing for resources Predation - predators seeking prey Disease - illness affecting a species Symbiosis - interaction between two biological species ○ Parasitism - one species is benefited and the other is harmed ○ Commensalism - one species is benefited and the other is neither harmed or helped ○ Mutualism – both species are benefitted. Ecosystem Stability A change in an abiotic or biotic factor may decrease the size of a population if the population cannot acclimate or adapt to or migrate from the change. A change may increase the size of a population if that change enhances its ability to survive, flourish or reproduce. One Example of Instability Necessary Components of a Stable Ecosystem A stable ecosystem is one in which: The population numbers of each organism fluctuate at a predictable rate. The supply of resources in the physical environment fluctuates at a predictable rate. Energy flows through the ecosystem at a fairly constant rate. What Can an Ecosystem Support? A population is a group of organisms belonging to the same species that live in a particular area. ○ Example: All of the green anacondas in Florida. Populations can be described based on their size, density, or distribution. Population density is calculated by dividing the number of individuals in a population by the unit area. The size of a population is affected by the number of births, the number of deaths, and the number of individuals that enter or leave the population. ○ What might happen if the green anaconda population in Florida exponentially increases? ○ What might happen if it decreases? Limiting Factors Any factor (abiotic or biotic) that slows population growth is called a limiting factor. Population growth is regulated by limiting factors that can be: ○ Density- dependent ○ Density-independent Density is the concentration of a species in a given area. Limiting resources are any environmental resource or condition that limits the growth, distribution or abundance of an organism in an ecosystem. Limiting Factor Help Video Limiting Factors: Density-Dependent Limiting factors that are density-dependent are those that operate more strongly as population density increases. These limiting factors are triggered by increases in population density (crowding) Density-dependent limiting factors include competition, predation, parasitism, and disease. ○ In other words… Density-dependent factors should ONLY start to take place and affect the population if the population becomes too dense. Density-Dependent Examples What will happen to the hawk population? What about What will happen to this population? the mouse? How are the bunnies distributed on the island? What if there were many food sources spread throughout the island? Limiting Factors: Density-Independent Limiting factors that are density-independent are those that occur regardless of how dense (crowded) the population may be. These factors reduce the size of all populations in the area in which they occur by the same proportion. Density-independent factors are mostly abiotic such as weather, pollution, and natural disasters (such as fires or floods). ○ In other words… Density-independent factors will take place regardless of the populations density. Density-Independent Example Red-Algae Bloom Video - What kind of limiting factor cause this? Carrying Capacity Carrying capacity is the maximum number of individuals that the environment can support over a long period of time without harming the environment Once reached, populations tend to fluctuate population size based on the available resources in the environment. ○ This is important - just because the population has reached carrying capacity, does not mean that it will level off and stay the same…it will fluctuate Carrying Capacity Help Video Population Models: Exponential Growth The exponential growth model describes a population that grows at a constantly increasing rate. A graph of exponential growth has a characteristic J-shape. In real populations, exponential growth occurs only for limited periods of time when conditions are optimal and resources are unlimited. ○ Could there be an organism that can grow exponentially in the real world? Human Growth Exponentially Over Time Population Models: Logistic Growth The logistic growth model includes the influence of limiting factors on population growth. A graph of logistic population growth has a characteristic S-shape. For example, if food or space becomes limited, a population may exhibit logistic growth following a period of exponential growth. ○ Again, why is a logistic growth model more likely than an exponential? Real Example of Logistic Model Homeostasis Homeostasis in an ecosystem is a steady state or dynamic equilibrium, in which conditions are held more or less constant despite changes in biotic or abiotic environmental factors. Ecosystems are dynamic in nature; their characteristics fluctuate over time, depending on changes in the environment and in the populations of various species. ○ What are some examples of changes in homeostasis that could affect the environment. Let's think biotic and abiotic. Homeostasis An ecosystem rich in biodiversity will likely be more stable than one in which biodiversity is low. ○ Why do you think? Changing environmental conditions can cause the decline of local biodiversity. If this happens, an ecosystem’s resistance and/or resilience may decline. The end result is the loss of stability in the ecosystem. Ecosystems that are less stable may not be able to respond to a normal environmental disturbance, which may damage ecosystem structure, ecosystem function, or both. Energy Transfer - Energy Pyramid