Eco Chapter 8

Term: Population

Definition: A group of individuals of the same species that inhabit a given area.

What three structural features characterize a population?

Density, spacing, and age distribution.

Term: Unitary organism

Definition: An organism that exists as a genetically unique individual following a predictable life cycle after fertilization.

Most animals belong to which category of organismal construction?

Unitary organisms.

Term: Modular organism

Definition: An organism in which the zygote develops into a unit of construction that then produces more similar units.

In modular plant growth, what three components make up the fundamental unit of aboveground construction?

The leaf, its axillary bud, and the associated internode of the stem.

Term: Stolon

Definition: Specialized modified stems that grow laterally above the soil surface to produce new asexually cloned units.

Term: Rhizome

Definition: Specialized stems that grow laterally below the ground or sediment to produce vertical stems and roots.

New stems that sprout from surface roots and may appear to be individual plants are called _____.

Suckers

Term: Genet

Definition: An individual organism produced through sexual reproduction.

Term: Ramet

Definition: A module produced asexually by a genet, often functioning as a physiologically independent clone.

What is the primary ecological benefit for a genet to produce many ramets?

The genet covers a larger area and extends its total lifespan.

Besides plants, what are two examples of modular animal species?

Corals and sponges.

Term: Geographic range

Definition: The total area that encompasses all individuals of a species.

What three environmental factors typically limit the geographic range of a species?

Temperature, soil moisture, and elevation.

Term: Ubiquitous species

Definition: A species with a geographically widespread distribution.

Term: Endemic species

Definition: A species with a geographically restricted distribution, often due to specialized habitat requirements.

The shale-barren evening primrose is considered a(n) _____ species because it is only found in specific mountain environments in three states.

Endemic

What are the three categories of geographic barriers that limit species distribution?

Bodies of water, mountains, and large areas of unsuitable habitat.

How can interactions with other species serve as barriers to a population's distribution?

Through competition and predation.

Term: Metapopulation

Definition: A collection of local subpopulations that are spatially separated but connected by the movement of individuals.

What is the primary mechanism that maintains connectivity between subpopulations in a metapopulation?

The dispersal or movement of individuals between patches of suitable habitat.

Term: Abundance

Definition: The total number of individuals in a population.

Abundance is a function of which two factors?

Population density and the area over which the population is distributed.

Term: Population density

Definition: The number of individuals per unit area or per unit volume.

Term: Crude density

Definition: The number of individuals per unit of total area.

The three basic patterns of spatial distribution within a population are random, clumped, and _____.

Uniform

Under what condition does a random spatial distribution occur?

When the position of one individual is independent of the position of other individuals.

What often causes a uniform spatial distribution in animals?

Negative interactions such as individuals defending a territory.

What is the most common spatial distribution pattern found in nature?

Clumped distribution.

Give one reason why individuals in a population might exhibit a clumped distribution.

Resources or suitable habitats are found in discrete patches.

In the Southern African savanna, why are Euclea shrubs clumped under Acacia trees?

Birds perch in the trees and deposit shrub seeds in their feces underneath.

Term: Ecological density

Definition: The number of individuals per unit of available living space.

For what type of organisms is sampling using quadrats most appropriate?

Sessile organisms, such as plants or corals.

How is total population size estimated when using the quadrat sampling method?

By multiplying the mean density of the samples by the total area.

Quadrat sampling is most accurate when individuals have which type of spatial distribution?

Uniform distribution.

What is the most common technique used to measure the population size of mobile animals?

Mark-recapture.

In the Lincoln-Peterson index formula $N = \frac{nM}{R}$, what does the variable '$M$' represent?

The number of individuals initially captured, marked, and released.

In the Lincoln-Peterson index formula $N = \frac{nM}{R}$, what does the variable '$R$' represent?

The number of marked individuals found in the second capture sample.

State one assumption of the Lincoln-Peterson index for population estimation.

Marked individuals are randomly redistributed through the population after release.

Term: Index of abundance

Definition: A measure of population size based on relative observations like vocalizations or tracks rather than direct counts.

What distinguishes a population with overlapping generations from one with non-overlapping generations?

The presence of individuals in different age classes simultaneously.

What are the three ecologically important age classes used to divide a population?

Prereproductive, reproductive, and postreproductive.

What is considered the most accurate, yet difficult, method for determining age structure in animals?

Marking young individuals and following their survival over time.

How can the age of a fish be determined without following it from birth?

By examining annual growth rings on its scales or ear bones.

Term: Dendrochronology

Definition: The process of counting annual growth rings to determine the age of a tree.

Why is diameter at breast height (DBH) an imperfect predictor of a tree's age?

Growth conditions like light and nutrients can significantly affect diameter independent of age.

Term: Age pyramid

Definition: A graphical representation showing the percentage of a population in different age classes at a specific point in time.

An age pyramid with a very wide base indicates what type of population growth?

Positive or expanding growth rate.

What does a narrow-based age pyramid suggest about a population's future?

The population is likely to experience a negative growth rate.

Why might a forest's age distribution be skewed toward older trees?

Tall, older trees can inhibit the growth of seedlings by blocking light and water.

Term: Primary sex ratio

Definition: The ratio of males to females at the time of conception.

Term: Secondary sex ratio

Definition: The ratio of males to females at the time of birth.

In humans, the secondary sex ratio is slightly weighted toward which sex?

Males (approximately 1.07 males per 100 females).

Why does the sex ratio in many mammal populations shift toward females in older age classes?

Males generally have shorter life spans due to rivalries and physiological factors.

In many bird species, why does the adult sex ratio tend to favor males?

Nesting females are more susceptible to attack and predation.

Term: Dispersal

Definition: The movement of individuals away from their place of birth or away from high-density areas.

Differentiate between 'emigration' and 'immigration'.

Emigration is leaving a subpopulation, whereas immigration is entering a subpopulation.

What are two external agents that facilitate passive dispersal in plants?

Wind and water.

Term: Ballooning

Definition: A process where spiders move through the air by releasing silk threads to catch wind and electric currents.

Active dispersal in many rodent species is most frequently performed by which age class?

Subadults.

Term: Migration

Definition: The round-trip movement of organisms, often occurring daily or seasonally.

Term: Diel vertical migration (DVM)

Definition: The daily synchronized movement of aquatic organisms toward the surface at dusk and back to deep water at dawn.

Why do Monarch butterflies migrate to the Oyamel Fir forests in Mexico?

The adults cannot tolerate the freezing winter temperatures of the central and eastern United States.

How many butterfly generations are typically required to complete one full Monarch migration cycle?

Four generations.

How can dispersal lead to the expansion of a species' geographic range?

Immigration can establish new subpopulations in previously unoccupied but suitable habitats.

The gypsy moth is an example of a species whose range expanded following a(n) _____ introduction.

Intentional

Term: Africanized bee

Definition: A hybrid subspecies of honeybee resulting from the cross between African and European honeybees.

What was the original scientific goal of introducing African honeybees to Brazil in the 1950s?

To improve the productivity and viability of honeybees in Central and South America.

In what city and county were Africanized bees found in the Bay Area in 2015?

Lafayette, Contra Costa County.

The Lincoln-Peterson index assumes that the method of marking does not affect the _____ of the individuals.

Survival

What is the primary method for determining the age of non-woody herbaceous plants?

Marking seedlings and following them through their entire life.

A population with an approximately equal distribution across all age classes (except the oldest) is at _____ population growth.

Zero

What is the general relationship between seed weight and dispersal distance in gravity-dispersed plants?

Heavier seeds generally travel shorter distances from the parent plant.

Which specific tree serves as the overwintering site for eastern Monarch populations in Mexico?

The Oyamel Fir ($Abies$ $religiosa$).