Population Structure, growth and dynamics

What is a population in ecology?

A population is made up of the individuals of a species within a particular area.

What are the three primary characteristics of population structure?

Density and spacing of individuals, proportions of individuals in age classes, and genetic structure.

What causes changes in population behavior?

Changes in population behavior occur due to births, deaths, and movements of individuals.

What is the geographic range of a population?

The geographic range is the distribution of a population within suitable and unsuitable habitats.

What defines patchy distributions in populations?

Patchy distributions occur when many populations are broken into isolated subpopulations living in suitable habitat patches.

What are the three patterns of dispersion observed in populations?

Clumped, random, and evenly spaced.

What is clumped dispersion?

Clumped dispersion occurs when individuals are found in discrete groups.

What causes evenly spaced dispersion in animals?

Evenly spaced dispersion is often caused by antagonistic behavior such as competition for resources.

What are potential causes of clumped dispersion?

Clumped dispersion may arise from clumped resource distribution, social tendencies to group, or progeny remaining near parents.

How is random dispersion characterized?

Random dispersion occurs when individuals are distributed independently of one another within a homogeneous area.

What is the metapopulation model?

The metapopulation model views a population as a set of subpopulations occupying patches of habitat.

What is a source patch?

A source patch has abundant resources and a higher birth rate than death rate, allowing surplus offspring to disperse.

What is a sink patch?

A sink patch has scarce resources, a higher death rate than birth rate, and is maintained by immigrant individuals from source patches.

What does the landscape model include that the other models do not?

The landscape model considers the effects of differences in quality of the habitat matrix surrounding patches.

How may population density be measured?

Density may be measured by total counts, plots, or the mark-recapture method.

What does the mark-recapture method involve?

The method involves marking a sample of individuals, releasing them, and then collecting a second sample to assess the proportion marked.

What influences population growth rates?

Population growth rates are influenced by density-dependent factors such as reproduction and death rates related to crowding.

Dispersal

movement of one or more individuals from one population to another

Migration

dispersal but refers to the particular direction of the movement

Geometric Growth

Geometric growth occurs with synchronous reproduction, leading to a population size that increases in discrete intervals.

What is exponential growth in populations?

Exponential growth occurs when a population increases continuously without restrictions, often illustrated as a J-shaped curve.

What are some examples of negative density-dependent factors?

Food supply shortages, competition, predation, and spread of disease.

What do trophic interactions illustrate?

Trophic interactions organize communities into food chains with producers, consumers, and higher trophic levels.

What ecological factors control the length of food chains?

Food chain lengths are affected by disturbance, primary production, and ecosystem size.

What is Lindeman’s Biomass Pyramid?

It illustrates that only about 10% of energy consumed becomes biomass, with the remaining 90% lost to waste or metabolism.

What are trophic cascades?

Changes in the structure of food chains can lead to trophic cascades, affecting population densities through predation and resource availability.

What are cursorial predators?

Cursorial predators actively move and forage for prey throughout their habitat.

What defines sit-and-wait predators?

Sit-and-wait predators remain stationary, attacking prey that come within striking distance.

What adaptations exist to help predators capture prey?

Adaptations include size, speed, sensory abilities, and physical features like teeth and camouflage.

What adaptations help species avoid becoming prey?

Adaptations include speed, camouflage, physical defenses (like spines or shells), and chemical defenses (such as toxins).

What is pack (cooperative) hunting?

Pack hunting involves predators working together to subdue prey that may be too large for a single predator.

What are some antipredator strategies?

Antipredator strategies include speed, camouflage, physical defenses, and chemical defenses.

What is Batesian mimicry?

Batesian mimicry occurs when a palatable species mimics an unpalatable species to avoid predation.

What is Müllerian mimicry?

Müllerian mimicry occurs among unpalatable species that resemble one another through convergent evolution.

What are structural defenses in plants?

Structural defenses can include spines, hairs, tough coatings, and other physical adaptations.

What impact can predators have on prey populations?

Predators can drive prey populations to extinction.

How can herbivores affect plant communities?

Herbivores can dramatically influence the species composition of plant communities through their consumption.

What is the impact of environmental resources on population growth?

Populations experience growth when environmental resources are unlimiting, but growth eventually declines as resources become limiting.

What happens to population growth rates as density increases?

As density increases, reproduction rates fall and death rates rise, regulating population size.

What are the two types of population growth patterns?

Exponential growth occurs under continuous reproduction, while geometric growth occurs with synchronous reproduction.

How do environmental conditions affect food chain lengths?

Food chain lengths are affected by disturbance, primary production, and ecosystem size.