Population Growth & Resource Limitations PDF

Population Growth & Resource Limitations Unit 1 - An Overview of Environmental Science Ms. Bartlett Population Dynamics in the Natural World. What Is Ecology? The study of interactions between organisms and their living and no...

Population Growth & Resource Limitations Unit 1 - An Overview of Environmental Science Ms. Bartlett Population Dynamics in the Natural World. What Is Ecology? The study of interactions between organisms and their living and non-living environment. Abiotic Factors - all non-living factors that influence an organism. Biotic Factors - all living factors that influence an organism. Population Dynamics. Population - a group of organisms of the same species living in a particular area. Example: a population of harbour seals living in Back Bay. In some areas, you can see several different populations. Example: in a farmers field, there can be a population of field mice, earthworms and corn! Populations in the Natural World Ecologists are interested in what is happening to populations and how and why these changes are happening. Populations of plants and animals that make up ecosystems respond in various ways to changes in environmental conditions, such as an excess or shortage of food or other critical nutrients. Keywords! Biome - large geographical area with similar species and climate. Ecosystem - all living and nonliving factors interacting. Community - many populations. Population - same species, same place, at same time. Individual - one organism. Biotic Potential With unlimited resources and ideal environmental conditions, a species can produce offspring at its maximum rate, referred to as that species' biotic potential. All living organisms have great biotic potential. Favorable Conditions If conditions are favourable, and if there are abundant food and living space, birth rates remain high and death rates low. If such ideal conditions could be maintained, populations would soon crowd out all available living space. This never happens; food eventually becomes scarce, predators become numerous, diseases take their toll and shelter becomes hard to find. These are called limiting factors because they limit the size of a population in an ecosystem. Limiting Factors. All of the biotic and abiotic components that impact the size of a population. Example: Biotic - food, access to mates, etc. Abiotic - floods, drought, extreme temp, soil type, etc. Density Dependant vs. Independent. Density Dependant Factor: any forced that affects the size of a population of living things in response to the density (size) of the population size. Example: predation, access to food, competition, disease. Density Independent Factor: any force that affects the size of the population regardless of that population's density. Examples: natural disasters, sunlight, temperature, human activities. Environmental Resistance. All limiting factors that reduce the growth rate of a population are called the population's environmental resistance. Example: The English Sparrow In 1899, after the English sparrow was introduced to North America, it was predicted that within 10 years a single pair of sparrows would be responsible for 2.8 × 1011 descendants and that by the year 1920, there would be 575 birds per 40 hectares of land; however, by 1920, the count was only 25. The Carrying Capacity. What Is Carrying Capacity? Carrying capacity refers to the number of individuals (and species) that can be supported in a given area within natural resource limits. That is, each environment has a maximum and a minimum number of a given species that it can support—if the population remains within the limits set by the carrying capacity, then the ecosystem is said to be stable. Not A Fixed Value. The carrying capacity for any given area is not fixed. It can be altered by improved technology (e.g., improved soil conditions through fertilization increases crop yields), but mostly it is changed for the worse by pressures that accompany a population increase. Environmental Impacts. As the environment is degraded, carrying capacity actually shrinks, leaving the environment no longer able to support even the number of species that could formerly have lived in the area on a sustainable basis. Many populations can surpass their carrying capacity; however, no population can live beyond the environment's carrying capacity for very long. Limiting Factors In An Environment. Review of Limiting Factors. All of the biotic and abiotic components that impact the size of a population. Example: Biotic - food, access to mates, etc. Abiotic - floods, drought, extreme temp, soil type, etc. Abiotic Limiting Factors. It is rare for a single factor to be solely responsible for the regulation of a given population; rather, stability results from many factors acting together. Examples of abiotic limiting factors are: chemical or mineral availability climate energy supply Biotic Limiting Factor - Competition. Species fights for access to resources that it needs to survive. Intraspecies Competition: Competing within the same species. Interspecies Competition: Different species competing. Biotic Limiting Factors - Invasive Species. An organism that does not normally occur in the area. This causes problems for the native species. For example, there would be more competition and less food. Predator vs. Prey Interactions. One animal is actually eaten by the second one. The “eater” is the predator. The “victim” is the prey. Biotic Limiting Factors - Symbiosis. Mutualism: Both species benefit. Ex: pollinators. Commensalism: One species benefits, the other is unaffected. Ex: cattle egret and tree frogs. Parasitism: One species benefits, the other is harmed. (The one that is harmed is called the host). Ex: ticks & mosquitos. Parasites. Parasitism is an interaction in which one organisms (the parasite) derives its nourishment from another organism (the hose) which is harmed in some way. Increase in the density of the hos population makes it possible for the parasite to increase in number. Tracking Populations. Field ecologists track wildlife populations to support wildlife management, such as setting fishing and hunting quotas. Wildlife population density affects environmental resistance, influencing death rates and the ability of populations to recover. Populations that fall below a critical threshold risk endangerment or extinction, with stability depending on the balance between biotic potential and environmental resistance. The Seven Risk Categories. Extinct - species no longer exists. Extirpated - no longer exists in the wild in Canada, but occurs elsewhere. Endangered - species facing imminent extinction or extirpation. Threatened - species likely to become endangered if limiting factors are not reversed Special Concern - species particularly sensitive to human activities or natural events. Last Two Categories… Not at Risk – species evaluated and found to be not at risk. Data Deficient – species for which there is insufficient scientific information to support a scientific designation. Atlantic Walrus. Exterpatied. Extirpated from Northwest Atlantic due to over-hunting. Once occurred in all four Atlantic provinces. The walrus is still found in Canada in the Arctic Ocean! Piping Plover. Endangered. Sparrow-sized shorebird found nesting on suitable beaches in all Atlantic provinces. Hunted at the turn of the century, it is now protected but continues to be threatened by habitat loss, human disturbance and high rates of predation on nesting grounds. Human Population Dynamics Human Population Dynamics. The human population grew slowly over millions of years, reaching 0.5 billion by 1650, but it has since accelerated rapidly, doubling multiple times in just a few centuries. Exponential population growth is unpredictable, with Earth reaching 7 billion people only a decade into the new millennium. Human Populations Much of our understanding of wildlife populations can be applied to human population dynamics. The United Nations (2009) notes that while human population has steadily increased throughout history, the modern era has seen unprecedented population growth.  Population Density Population density is the number of individuals living within a given area, with Canada's current density at 3.5 people per square kilometer. Canada's population of 35 million is concentrated mostly in the southern regions, particularly in cities like Montreal, Toronto, and Vancouver. Populations, including both human and wildlife, tend to cluster in specific areas rather than being evenly distributed. https://en.wikipedia.org/wiki/List_of_countries_and_dependencies_by_population_density Consumption Crisis. Since the mid-1800s, most global population growth has occurred in developing nations, while developed nations consume the majority of global resources. It is said that more than 80% of the people living on Earth do not have adequate food, shelter or water. The two root causes of global environmental problems are the population crisis and the consumption crisis, leading to resource depletion, deforestation, water contamination, and threats to human health and wildlife. Effects of Overpopulation. The growing human population is straining world resources, leading to negative impacts on wildlife populations. As the human population expands, environmental damage increases through land use, rising energy consumption, and pollution. Overpopulation occurs when a species exceeds the carrying capacity of its environment, but humans complicate this concept by using a wide range of resources and finding ways to substitute or import them when needed. Consequences of Overpopulation. Simply put, our planet cannot sustain this continuous increase in the human population. Human overpopulation must be brought under control and resource management strategies must be improved in order to restore our planet's degraded renewable resource base.