BIO110 Chapter 35: Populations and Communities

35.1 What are the levels of ecological organization?

1) Populations 2) Species 3) Communities 4) Ecosystems 5) Biomes 6) Biosphere.

35.1 What is ecology?

The study of the relationships of organisms with one another and their environment.

35.1 What are some key elements of physical environments that determine which organisms inhabit it?

Temperature, water availability, sunlight availability, and soil composition.

35.1 How do organisms adapt to environmental changes?

Morphologically, physiologically, and behaviorally.

35.2 What 5 aspects of populations are particularly important?

1) Range 2) Distribution 3) Size 4) Density 5) Growth.

35.2 What is a population range?

The area throughout which a population occurs.

35.2 Why are ranges mobile?

They change due to environmental changes and when they are able to move from inhospitable habitats to suitable previously unoccupied areas.

35.2 What is population distribution?

The pattern of spacing individuals within that range.

35.2 What is population size?

The number of individuals a population contains.

35.2 What is population density?

How many individuals share an area.

35.2 What is population growth?

A description of whether a population is growing/shrinking & at what rate.

35.3 What are the 3 kinds of population distribution?

1) Random 2) Uniform 3) Clumped.

35.3 What is a randomly spaced population distribution?

Individuals do not interact strongly with one another; uncommon in nature.

35.3 What is a uniformly spaced population distribution?

Individuals are evenly spaced, often from behavioral interactions (more common in animals) or resource competition (more common in plants).

35.3 What is a clumped spaced population distribution?

Individuals are clumped together due to an uneven distribution of resources in the immediate environment or due to organism preference for specific habitat features or social behavior.

35.4 What is biotic potential?

The rate at which a population will increase when no limits are placed in its rate of growth.

35.4 How is biotic potential represented mathematically?

G = r_iN.

35.4 What is G?

Growth rate.

35.4 What is N?

The number of individuals in a population.

35.4 What is r_i?

The intrinsic rate of increase of a population.

35.4 What is the simplest model of population growth?

Biotic potential.

35.4 What is the actual rate of population increase?

The difference between the birthrate (b) & death rate (d) corrected for immigration (i) and emigration (e).

35.4 How is the actual rate of population increase represented mathematically?

r = (b - d) + (i - e).

35.4 What does the innate capacity for population growth look like?

Exponential, but in practice, such patterns happen for short periods of time, usually when an organism reaches a new habitat with abundant resources.

35.4 What is carrying capacity?

The size at which a population will stabilize, represented by K, the maximum number of individuals an area can support.

35.4 What is the equation for the growth curve of a population?

G = rN (K - N / K)

35.4 What is the sigmoid growth curve?

The curve you obtain when you plot N versus t (time).

35.5 What are density-independent effects that regulate population growth?

Effects that regulate growth regardless of population size.

35.5 What is an example of a density-independent effect on population growth?

Weather events, geological events.

35.5 What are density-dependent effects that regulate population growth?

Effects that regulate population growth based on its size and gets stronger as population size increases.

35.5 What is an example of a density-dependent effect on population growth?

Competition, disease.

35.6 What is a life history?

The complete life cycle of an organism.

35.6 What are r-selected adaptations?

Adaptations that favor rapid growth in habitats with unlimited resources or unpredictable environtments.

35.6 What are K-selected adaptations?

Adaptations that favor reproduction near the carrying capacity of their environment.

35.6 What happens to r-selected adaptations in unpredictable environments?

They have to take advantage of resources when they’re available.

35.6 What are some examples of r-selected organisms?

Rodents, insects, weeds.

35.6 What are some examples of K-selected organisms?

Birds, large mammals, and large plants.

35.6 Why do we have the r/K concept of life histories?

They provide a way to examine more closely-related organisms living in different types of habitats.

35.6 Do populations in rapidly changing environments tend to exhibit more r-selected or K-selected adaptations?

r-selected.

35.6 Do organisms in more stable and competitive environments tend to exhibit more r-selected or K-selected adaptations?

K-selected.

35.7 What is demography?

The statistical study of populations.

35.7 What does demography measure?

The characteristics of a population, it also helps predict how population sizes will change in the future.

35.7 What is a cohort?

A group of individuals of the same age.

35.7 What is fecundity?

The birthrate within a cohort; the number of offspring produced in a standard time which is usually related to the number of females in the cohort.

35.7 What is mortality?

The death rate within a cohort; the number of individuals that die in the same standard of time that fecundity is measured.

35.7 How is a population’s age structure defined?

By the relative number of individuals in each cohort.

35.7 What is a sex ratio?

The proportion of males & females in a population.

35.7 What is age distribution?

The proportion of individuals in different age categories.

35.7 What is the survivorship curve?

A way to express the age distribution characteristics of a population; the percentage of an original population that survives to a given age, of which there are three types.

35.7 What are the 3 types of survivorship curves?

1) Type I 2) Type II 3) Type III.

35.7 What are characteristics of a type I survivorship curve?

They have the highest mortality rate for the oldest individuals.

35.7 What are characteristics of a type II survivorship curve?

They have relatively the same mortality risk for all individuals regardless of age.

35.7 What are characteristics of a type III survivorship curve?

They have the highest mortality rate for the youngest individuals.

35.8 How are communities charatcerized?

By their constituent species (a list of all species present) or by their properties, such as primary productivity.

35.9 What is a niche?

The sum total of all the ways an organism utilizes the resources of its environment.

35.9 What is competition?

The interaction when two organisms attempt to use the same resource when there isn’t enough of the resource to satisfy both.

35.9 What is interspecific competition?

Competition that occurs between individuals of different species.

35.9 What is intraspecific competition?

Competition that occurs between individuals of the same species.

35.9 What is a fundamental niche?

The entire niche an organism may theoretically occupy.

35.9 What is a realized niche?

The actual niche an organism is able to occupy because of competition.

35.9 What is the principle of competitive exclusion?

If two species are competing for a resource, the species that uses the resource more efficiently will eventually eliminate the other locally, in other words, no two species with the same niche can coexist.

35.9 What two outcomes are possible when niches overlap?

Competitive exclusion & resource partitioning.

35.9 What is resource partitioning?

The division of resources to create two niches.

35.9 What are sympatric species?

Closely related species that avoid competition by evolving different adaptations to use different portions of the habitat, food, or other resources.

35.9 What are allopatric species?

Closely related species that don’t live in the same geographical area.

35.9 What is character displacement?

The evident differences between sympatric species that are thought to have been favored by natural selection as a way to facilitate resource partitioning and reduce competition.

35.10 What is coevolution?

The adaptation of two or more species to each other.

35.10 What are the three kinds of symbiotic relationships?

1) Mutualism 2) Parasitism 3) Commensalism.

35.10 What is mutualism?

A relationship in which both species benefit.

35.10 What is parasitism?

A relationship in which one species benefits while the other is harmed; a predator-prey relationship.

35.10 What are external parasites?

Ectoparasites; they feed on the exterior surface of the host.

35.10 What are parasitoids?

Insects that lay eggs on living hosts.

35.10 What are internal parasites?

Endoparasites; they feed internally on their hosts.

35.10 What is brood parasitism?

The parasite doesn’t consume the body of its host.

35.10 What is commensalism?

A relationship that benefits one species and has a neutral effect on the other.

35.11 What is predation?

The consuming of one organism by another.

35.12 What is Batesian mimicry?

When a palatable species resembles a poisonous one.

35.12 What is Müllerian mimicry?

When several unrelated, but protected, species come to resemble on another.

35.13 What is succession?

The orderly replacement of one community by another.

35.13 What is primary succesion?

Succession that occurs on previously inhabited substrates, like those left behind when a glacier retreats or when a volcanic island emerges.

35.13 What is a pioneering community?

The first community to be established during primary succession.

35.13 What is secondary succession?

Succession that occurs after an already established community has been disturbed.

35.13 Why does succession happen?

Species alter the habitat and resources available in it, often in ways that favor other species.

35.13 What is tolerance?

Early successional stages are characterized by weedy, r-selected species hat tolerate harsh conditions but don’t compete well.

35.13 What is facilitation?

The weedy, r-selected species introduce local changes in the habitat that favor nonweedy speecies.

35.13 What is inhibition?

Sometimes, changes in the habitat caused by one species may inhibit the growth of the species that caused them,