Ecology

• Exponential growth occurs when a population grows at a constant rate with no limiting factors, leading to rapid growth under ideal conditions
• Doubling time represents the duration it takes for a population to double in size, reflecting the rate at which individuals reproduce and contribute to population growth
• Logistic growth occurs when a population grows at a decreasing rate as it approaches its carrying capacity, which is the maximum population size that can be supported by the environment over time
• Carrying capacity is determined by the resources available in the environment, such as food, water, and habitat, and is a form of density dependence that limits population growth
• Density-independent factors can also limit population growth, impacting populations regardless of size or density, often due to abiotic factors or random events like extreme weather or natural disasters
• Populations can vary due to environmental variability, with factors like food scarcity, new habitat availability, and natural disasters affecting population dynamics
• Evolution and Ecology can explain how species are distributed:

  • Possible explanations include endemism, range expansion, range shift, dispersal, and vicariance
• Reasons for species not being in certain areas:

  • Hasn't arrived yet
  • Can't/doesn't survive there
• Reasons for the existence of a tree line:

  • It marks the edge of the habitat where trees can grow
• Extremophiles are organisms that are able to live in extreme conditions
• Organisms are adapted to their environments, but not to every environment
• Abiotic factors can limit the distribution of a species, such as the physical and chemical features of an environment
• Biotic factors can also limit the distribution of a species, including the living things that shape an ecosystem
• A species' ecological niche includes both abiotic and biotic factors, describing the range of resources and conditions allowing the species to maintain a viable population
• The range of tolerance refers to the range of environmental conditions within which an organism can survive, grow, and reproduce
• The range of tolerance defines the fundamental niche, which is the spaces where a species could survive based on a set of conditions regarding that species' range of physiological tolerances
• The realized niche is where a species actually survives after the effects of biotic interactions
• Populations can exhibit exponential growth under ideal conditions, where the population grows at a constant rate with no limiting factors
• Doubling time represents the duration it takes for a population to double in size, reflecting the rate at which individuals reproduce and contribute to population growth
• Logistic growth occurs when a population grows at a decreasing rate as it approaches its carrying capacity, which is the maximum population size that can be supported by the environment over time
• Carrying capacity is determined by the resources available in the environment and can limit population growth
• Carrying capacity is determined by the resources available in that environment, such as food, water, and habitat
• Carrying capacity is a form of density dependence, where the growth, mortality, or other vital rates of a population are influenced by that population’s density or size
• Every population has a carrying capacity, which is the maximum population size that can be supported by the environment over time
• Populations are dynamic and change over time due to density-independent factors that can limit population growth regardless of the population’s size or density
• Density-independent factors are often abiotic, random events like extreme weather events, natural disasters, or predictable events like season changes in climate
• Decline happens when deaths and emigration outweigh births and immigration
• The carrying capacity of a population is the maximum number of individuals the environment can support
• If a population is isolated, the number of individuals born in a specific period can be limited
• Resources may limit population growth, even if the population is currently growing
• The range of tolerance refers to the environmental conditions within which an organism can survive, grow, and reproduce
• The range of tolerance defines the fundamental niche, which is the space where a species could survive based on a set of conditions regarding its physiological tolerances
• A species' ecological niche includes both abiotic and biotic factors
• Possible explanations (hypotheses) for how a species arrived in a specific area include:

  • Endemism: evolved in the region and is only found there
  • Range expansion: evolved elsewhere and expanded its range to include the area
  • Range shift: evolved elsewhere, used to be found elsewhere, but its range shifted to include only the current distribution
  • Dispersal: arrived from somewhere else not nearby
  • Vicariance: evolved under certain environmental conditions, but then the physical landscape moved, exposing the species to different conditions
• Competition between species can lead to outcomes affecting population growth and ecological interactions
• Fundamental niche refers to spaces where a species could survive based on a set of conditions regarding its physiological tolerances, while realized niche includes spaces within the fundamental niche where biotic factors are also sufficient for survival
• Competitive exclusion principle states that if two species with identical niches compete, one will inevitably drive the other to extinction
• Exploitative competition refers to indirect competition for limited resources, while interference competition involves direct interactions impeding access to essential resources
• Competitors can coexist through temporary co-existence at reduced carrying capacity, competitive exclusion where one species disappears from the area, or niche partitioning
• In an ecological network, species are connected by interactions, and food webs show who eats whom and how much, with real food webs being very complex