Population Ecology: Key Concepts and Dynamics

What defines a population in ecology?

A group of individuals of a single species inhabiting a specific area.

What is population ecology?

The study of populations, focusing on their dynamics and interactions with the environment.

What are the characteristics of population size?

Total number of individuals in a population.

How is population density defined?

The number of individuals per unit area.

What does distribution refer to in population ecology?

The geographic area where a species is found, including its range and environmental adaptations.

What is the difference between a fundamental niche and a realized niche?

The fundamental niche includes physical conditions without species interactions, while the realized niche includes biotic interactions.

What factors influence a species' distribution?

Physiological, anatomical, and behavioral adaptations, as well as environmental limits.

What is clumped dispersion in populations?

Individuals are found in areas of high local abundance, separated by areas of low abundance.

What is regular or uniform dispersion?

Individuals are uniformly spaced due to antagonistic interactions or resource depletion.

What is random dispersion?

Individuals have an equal probability of occurring anywhere, with neutral interactions.

How does body size relate to population density in animals?

Smaller animals tend to have higher densities, while larger animals have lower densities.

What is the principle of allocation in ecology?

The idea that organisms allocate resources to growth, reproduction, and survival based on environmental conditions.

What factors contribute to a species' vulnerability to extinction?

Population size, geographic range, habitat tolerance, and local population size.

Give an example of a species with extreme rarity.

The Hermes Copper Butterfly, which has a restricted range and small local populations.

What is the significance of microclimates in population distribution?

Microclimates are influenced by biotic and abiotic factors that drive distributions and adaptations.

What is the relationship between geographic range and population size?

There is a positive correlation; species with larger geographic ranges often have larger population sizes.

What is a common characteristic of rare species?

They often have restricted ranges, narrow habitat tolerances, and small populations.

What role do ecologists play in population management?

They work to restore endangered species, control pest species, and manage game and food species.

What is the impact of breeding seasons on population dispersion?

Population dispersion can change with the time of year, such as during breeding seasons.

How do environmental factors influence a species' niche?

They determine the growth, survival, and reproduction conditions necessary for a species' existence.

What is the significance of the relationship between density and plant size?

Larger plants typically exist at lower densities compared to smaller plants.

What is the role of competition in population dispersion?

Competition can influence the spatial arrangement of individuals within a population.

What is the effect of social structures on clumped dispersion?

Social interactions can lead to individuals aggregating in areas with resources or protection.

Population

A group of individuals of a single species inhabiting a specific area

Population Characteristics

Size, Density, Distribution/Dispersion

Population Size

Total number of individuals

Density

Individuals per unit area

Distribution/Dispersion

Shape, size, and location of area/location of individuals

Natural Population Sizes

Natural (historic) population sizes vary

Dynamic Population Sizes

Abundances change over time and space

Density and Body Size

Higher density of smaller animals, lower density of larger animals

Invertebrates Density

Invertebrates are at higher densities than vertebrates

Density and Plant Size

Larger plants at lower densities

Ecologists Study Populations

To understand population dynamics and species interactions

Fundamental Niche

The potential mode of life of a species in the absence of competition

Realized Niche

The actual mode of life of a species due to competition and other interactions

Vulnerability to Extinction

Population characteristics that make species more vulnerable

Mammals

Relatively the same size (can move)

Niche

Environmental limits of a species; factors that influence growth, survival, and reproduction

Microclimates

Biotic and abiotic factors drive distributions; resistance to drying

Dispersion

Individuals within a population determined by physical environment structure and interactions

Random Dispersion

An individual has an equal probability of occurring anywhere; neutral interactions

Regular/Uniform Dispersion

Individuals are uniformly spaced; antagonist interactions between individuals

Clumped Dispersion

Individuals found in areas of high local abundance; separated by areas of low abundance

What is the formula for calculating population size over time?

Nt = Nt - 1 + B + I - D - E, where Nt is the population at time t, B is births, I is immigration, D is deaths, and E is emigration.

What characterizes exponential population growth?

Exponential growth occurs when resources are unlimited, leading to a rapid increase in population size.

What is logistic population growth?

Logistic growth occurs when resources are limited, resulting in a population that grows slowly at first, accelerates, and then slows as it approaches carrying capacity.

What does carrying capacity (K) refer to?

Carrying capacity (K) is the maximum number of individuals an area can support.

What factors can limit population growth?

Limits can be biotic (disease, predation, competition) or abiotic (flood, drought, extreme temperatures).

How does dispersal affect local population sizes?

Dispersal, the movement of organisms away from their birthplace, can either increase or decrease local population sizes.

What is the intrinsic rate of increase (r) in population growth?

The intrinsic rate of increase (r) is calculated as r = b - d, where b is the birth rate and d is the death rate.

What happens to population size when r > 0?

When r > 0, the population size increases.

What happens to population size when r = 0?

When r = 0, the population size remains the same.

What happens to population size when r < 0?

When r < 0, the population size declines.

What is the equation for logistic population growth?

The logistic growth equation is dN/dt = rmax N (1 - N/K), where N is population size and K is carrying capacity.

How does population growth change as it approaches carrying capacity?

Population growth slows as it approaches carrying capacity, reflecting limited resources.

What is the significance of the unused portion of K?

The unused portion of K indicates potential for population growth; at half of K, the most individuals are being added.

What is the relationship between population size (N) and carrying capacity (K) when N = K?

When N = K, the growth rate is zero, indicating the population has reached its maximum sustainable size.

What is the effect of high variability in resources on population dynamics?

High variability in resources, such as rainfall affecting plant growth, can lead to fluctuations in population sizes, as seen in Darwin's finches.

What are density-dependent factors?

Density-dependent factors are influences on population growth that change with population density, such as competition and disease.

What are density-independent factors?

Density-independent factors are influences on population growth that are not affected by population density, such as natural disasters.

What is the impact of immigration (I) on population size?

Immigration increases population size by adding individuals from outside the population.

What is the impact of emigration (E) on population size?

Emigration decreases population size by removing individuals from the population.

How do mathematical models contribute to understanding population growth?

Mathematical models help predict rates and patterns of population growth based on various factors.

What is the significance of studying both laboratory and natural populations?

Studying both types of populations provides insights into population dynamics under controlled and real-world conditions.

What is the current estimated human population?

8.2 billion and growing

What type of growth pattern is characterized by unlimited resources?

Exponential population growth

What is the logistic growth equation based on?

Limited resources leading to slow growth, then acceleration, and finally slowing down

What is an ecological footprint?

The amount of land/sea used to support human demands and absorb waste

What is a sustainable ecological footprint range?

3.1 to 10.2 Earths

Who proposed the theory of population growth in 'Essay on the Principle of Population'?

Thomas Robert Malthus

What is the predicted carrying capacity (K) of the Earth according to Malthus?

9 billion by 2037

What are the three age structure groups in population dynamics?

Pre-reproductive, Reproductive, Post-reproductive

What shape represents a growing population in age structure diagrams?

Pyramidal shape

What shape represents a stable population in age structure diagrams?

Bell-shaped

What shape represents a declining population in age structure diagrams?

Urn-shaped

What historical advancements contributed to human population growth?

Stone tools, agriculture, metallurgy, and medicine

What are some causes of mortality that have changed over time?

Cholera and smallpox

What is the impact of an aging population on social systems?

Challenges for Social Security and the number of workers

What is the difference in income between developed and developing nations?

Developed nations have higher income (~$12,000/year) compared to developing nations

What are the two types of population growth patterns discussed?

Exponential growth and logistic growth

What factors limit the ecological footprint of an individual?

Diet choices, transportation options, and waste management

How does the average ecological footprint of an American compare to the Earth's capacity?

The average is 5 Earths, indicating unsustainable consumption

What are the implications of clumped distribution in human populations?

Higher population densities in coastal areas and river valleys

What is the significance of immigration in population dynamics?

It can contribute to population growth in stable or declining regions

What does the equation Nt = Nt - 1 + B + I - D - E represent?

It calculates the population size at time t (Nt) based on previous population size, births (B), immigrants (I), deaths (D), and emigrants (E).

What is dispersal in the context of population dynamics?

Dispersal is the movement of organisms away from their birthplace, which can increase or decrease local population sizes.

What is vagility?

Vagility refers to the ability of organisms to move.

What are the modes of dispersal for plants?

Plants can disperse through wind, adherent (sticky) mechanisms, fleshy fruits, water, and dehiscent fruits.

What is explosive dehiscence?

Explosive dehiscence is a ballistic form of dispersal that flings seeds or spores far from the parent plant.

What are the modes of dispersal for animals?

Animals can disperse by walking, flying, swimming, or through passive modes like larvae of sessile marine organisms.

What are some barriers to dispersal?

Barriers include distance, water (for terrestrial species), land (for aquatic species), mountains, roads, and different vegetation communities.

What are the reasons for dispersal?

Reasons include maintenance of populations, gene flow for genetic diversity, recolonization after disturbances, and responses to environmental changes.

What is long-distance dispersal?

Long-distance dispersal involves organisms expanding their populations over significant distances, often in response to environmental changes.

How do predators affect long-distance dispersal?

Predators may follow prey during long-distance dispersal, leading to changes in their distribution based on prey availability.

What is the difference between dispersal and migration?

Dispersal is the movement away from the birthplace, while migration is a seasonal movement between two areas, often with a return.

What defines a metapopulation?

A metapopulation is a group of spatially separated subpopulations connected by the movement of individuals among them.

What is a subpopulation?

A subpopulation consists of individuals of a species that live in a specific habitat patch.

What is a turnover event in metapopulations?

A turnover event is the loss of a subpopulation followed by the recolonization of that same habitat patch.

What is the rescue effect?

The rescue effect is dispersal that prevents the loss of a local population (extirpation).