Lec 7 Population Dynamics I Flashcards
Population:
A group of organisms of the same species occupying a particular space at a particular time, or a potentially interbreeding group of individuals of the same species living within a restricted geographic area.
Fecundity:
An animal’s ability to produce sperm or eggs.
Natality:
The production of new individuals by birth or hatching.
Natality Rate:
The number of births (or hatches) divided by the number of adult females.
Potential Natality:
The theoretical genetically imposed upper limit on natality, observed only in an ideal environment.
Realized Natality:
The actual natality observed in the real world, almost always less than potential natality due to environmental factors interfering with reproduction.
Recruitment:
The production of individuals that are sexually mature (usually) or self-sufficient (sometimes).
Recruitment Rate:
The number of individuals recruited divided by the number of females (or sometimes adults).
Biotic Potential (Intrinsic Growth Rate):
The theoretical genetically imposed upper limit on the rate of increase for a given population, observed with potential natality in an ideal and infinite environment, resulting in an exponential rate of increase.
Describe the difficulty of delimiting populations and explain how drawing the borders around populations is often done in practice. answer this question using the document above
Delimiting populations can be challenging using traditional methods due to the dynamic and often complex nature of wildlife populations. In practice, the difficulty is addressed in the following ways:
Wildlife Management Units: Many provincial and state jurisdictions divide their territories into wildlife management units. These units are designed more for ease of management than for biological significance. They have different regulations, such as permitted species to hunt, open season dates, and permitted hunting methods.
Migratory Species: For migratory species like ducks and geese, local management can lead to problems, such as overharvesting in some areas. To address this, limits are often set by popular migration routes, known as “flyways.” These flyways are used as a basis for managing and delimiting populations rather than relying solely on local or regional boundaries.
These approaches reflect a balance between practical management needs and the biological realities of animal populations. They are designed to ensure that populations are managed sustainably, taking into account their ability to reproduce and replace themselves, as well as their movement patterns and ecological requirements.
Identify the major flyways of migrating birds.
The document doesn’t specifically list the major flyways of migrating birds. However, it mentions that for migratory species like ducks and geese, management strategies are often based on popular migration routes known as “flyways.” These flyways are used to set limits and manage bird populations, particularly to prevent issues such as overharvesting in certain areas. The concept of flyways is crucial in wildlife management as it acknowledges the long-distance movements of migratory birds and the need for international cooperation in their conservation.
In general, major bird flyways around the world include the Pacific Flyway, Central Flyway, Mississippi Flyway, and Atlantic Flyway in North America; the East Atlantic Flyway in Europe and Africa; and the East Asian-Australasian Flyway. These routes are used by birds to travel between breeding and wintering grounds and are vital for the survival of many migratory bird species.
- Explain how birds and mammals differ with respect to how various factors influence the reproductive variables we discussed in class.
The document outlines how birds and mammals differ with respect to the influence of various factors on reproductive variables:
Birds: In birds, many eggs are abandoned without being incubated. This indicates that factors influencing bird reproduction can lead to a significant number of eggs not developing into mature individuals. The factors affecting bird reproduction are not explicitly detailed in the document, but they could include environmental conditions, predation, and the availability of resources.
Mammals: In mammals, fecundity (the ability to produce sperm or eggs) is modulated by environmental variables and resource availability. This means that the reproductive success of mammals is more directly influenced by the environment and the availability of resources needed for raising offspring. Factors like nutrition, habitat conditions, and population density can play a significant role in affecting the fecundity and overall reproductive success of mammalian species.
In both groups, natality (the production of new individuals by birth or hatching), potential natality (the theoretical upper limit on natality), and realized natality (the actual natality observed, which is almost always less than the potential due to environmental factors) are important concepts. Recruitment, or the production of sexually mature or self-sufficient individuals, also plays a key role in population dynamics, with the recruitment rate being a critical measure of a population’s ability to sustain itself.
- Explain the relationship between fecundity, natality, and recruitment.
The document explains the relationship between fecundity, natality, and recruitment as follows:
Fecundity: This refers to an organism’s ability to produce sperm or eggs. It is a measure of potential reproductive capacity and sets the upper limit for how many offspring an organism can theoretically produce.
Natality: Natality is the production of new individuals by birth or hatching. The natality rate is calculated as the number of births (or hatches) divided by the number of adult females. There are two types of natality:
Potential Natality: This is the theoretical upper limit on natality, imposed genetically and observed only in an ideal environment.
Realized Natality: This is the actual natality observed in the real world. It is almost always less than the potential natality due to environmental factors that interfere with reproduction.
Recruitment: Recruitment refers to the production of individuals that are sexually mature or, in some cases, self-sufficient. The recruitment rate is the number of individuals recruited divided by the number of females (or sometimes the number of adults).
In practice, the relationship between these three variables can be summarized as follows: Fecundity Rate > Natality Rate > Recruitment Rate. This means that the number of eggs or sperm produced (fecundity) is greater than the number of offspring born or hatched (natality), which in turn is greater than the number of individuals that reach sexual maturity or self-sufficiency (recruitment). For stable populations, the recruitment averages around 1, but for growing populations, it will be greater than 1.
- Describe how recruitment and biotic potential varies across populations, time, and space. A graph may help.
The relationship between recruitment and biotic potential across populations, time, and space varies significantly, and it’s influenced by several factors as explained in the document:
Variation in Reproductive Strategies Across Species: Different species have varying reproductive strategies. For example, some species, like mallards, have a high rate of reproduction and can breed multiple times per year, indicating a high potential natality. Others, like deer, have a medium rate of reproduction, possibly breeding only once per year, which indicates a lower potential natality. There are also species that do not breed every year, showing even lower potential natality.
Influence of Environmental Conditions: The environmental conditions also play a significant role. In ideal environments, species might reach their potential natality, but in less than ideal environments, the realized natality is often lower. This can occur when either mortality rates increase or birth rates decrease with increasing population size.
Variation Over Time and Space: The size of broods or clutches can vary not only between different species but also within the same species across different populations. These variations are often a result of natural selection aiming to maximize lifetime fitness.
Biotic Potential: Biotic potential, or the intrinsic growth rate, represents the theoretical genetically imposed upper limit on the rate of increase for a given population, observed with potential natality in an ideal and infinite environment. This results in an exponential rate of increase, but in reality, the growth is often less due to environmental constraints.
The document suggests that these factors, including reproductive strategies and environmental conditions, contribute to the variability in recruitment and biotic potential across different populations and over time and space.
- Explain what affects reproductive strategies by a species. Identify which factors are affected by a variety of environmental changes, and explain why certain environmental variables affect those factors.
ChatGPT
The document discusses how reproductive strategies in species are influenced by various factors. It highlights the importance of fecundity, natality, recruitment, and biotic potential in determining population dynamics. Environmental variables like nutrition, weather, crowding, predation, and disease significantly affect these reproductive factors. For instance, nutrition impacts fecundity and survival of young, weather and predation influence pre-natal survival rates and survival of young, and crowding and disease can affect overall population health and reproductive success. These interactions underline the complex relationship between environmental conditions and reproductive strategies, demonstrating how changes in the environment can lead to adaptations in reproductive behaviors to maximize lifetime fitness.
