Biology chapter 19

Type 2 Curve (Survivorship)

Intermediate, with survivorship constant over life span. that is, individuals are no more vulnerable at one stage of life than the other.--observed in some invertebrates lizards and rodents

what distinguishes invasive species from organisms that are introduced to non-native habitats but do not become invasive?

Invasive species spread far from where they are introduced and they cause environmental or economic damage

overall growth rate peaked in

1962--fell due to effective contraceptives

Invasive species

A non-native species that has spread far beyond the original point of introduction and causes environmental or economic damage by colonizing and dominating suitable habitats. In the US alone there are hundreds of invasive species including plants mammals birds fishes arthropods and molluscs. leading cause of local extinction not every organism introduced to a new habitat is successful and not every species that lives in its new habitat becomes invasive. there is no single explanation for why any non-native species turns into a damaging pest but they typically exhibit an opportunistic life history pattern. a female lionfish is sexually mature at a year old and can produce 2 million eggs per year Female zebra mussels begin reproducing early in life and can lay a million eggs in a year. fertilized eggs develop into free-swimming larvae which eventually settle and attach themselves to any available object--they secrete a combo of molecules that hardens into sticky threads--an example of the relationship between structure and function. zebra mussels were discovered in 1988 probably carried in the ballast water of ocean going ships passing through the saint lawrence seaway. they quickly spread to rivers and lakes beyond the great lakes region and are now widely distributed. the economic damage caused by these mussels results from their astronomically large populations. adults form thick layers that clog pipes and water intakes of cities, power plants and factories. they attach to larger native bivalves, interfering with their ability to feed and reproduce and they compete with native species for food and spaces. For a non-native organism like the zebra mussel to become invasive, the biotic and abiotic factors of the new environment must be compatible with the organism's needs and tolerances.--pythons set loose found a hot climate

How does the term opportunistic capture the key characteristics of that life history pattern?

An opportunistic life history is characterized by ability to produce a large number of offspring very rapidly when the environment affords a temporary opportunity for a burst of reproduction

Biocapacity

Earth's capacity to renew resources

why was the growth rate of the world's population so high during most of the 1900's? what accounts for the decrease in growth rate of the world's population?

In the 1900's the death rate decreased dramatically due to improved nutrition sanitation and health care but the birth rate remained high. as a result the overall population growth rate was high. the recent decrease in growth rate is the result of lower birth rates in some regions

Why does the exponential model of population growth produce a curve shaped like a J?

Population growth accelerates as population size increases

Sea turtles lay their eggs in nests on sandy beaches. although a single nest may have 200 eggs only a small number make the journey from the beach to the ocean. once they have matured their death rate is low. what type of survivorship?

Type 3

population ecology

concerned with changes in population size and the factors that regulate populations over time. a pop ecologist might describe a population in terms of its size, age structure (proportion of individuals of different ages) or density (number of individuals per unit area or volume) they also study population dynamics, the interactions between biotic and aboitic factors that cause variation in population size. One important aspect of population dynamics is population growth

survivorship curve

a plot of the number of individuals alive at each age in the maximum lifespan. using a percentage scale instead of actual ages on the x axis we can compare species with widely varying life spans such as humans and squirrels on the same graph

ecological footprint

an estimate of the land and water area required to provide the resources an individual or a nation consumes---our carbon footprint is the largest component of humanity's ecological footprint

intraspecific competition

competition between individuals of the same species for the same limited resources

population momentum

continued population growth that does not slow in response to growth reduction measures the population continues to be affected by earlier expansion. this situation results from increased proportion of women of childbearing age in the population is known as population momentum. putting the brakes on a rapidly expanding pop is like stopping a freight train, the actual event takes place long after the decision to do it was made. even when fertility is reduced to replacement rate (avg 2 kids per female) the total population size will keep increasing for several decades.

equilibrial life history

develop and reach sexual maturity slowly, produce few, well-cared-for offspring, are typically larger-bodied and longer-lived, and typically exhibit a type I survivorship curve. plants with comparable life history traits include certain trees like coconut palms that produce relatively few seeds that are well stocked with nutrient rich material

endangered species

in danger of extinction throughout all or a significant portion of its range

opportunistic life history

enables the plant or animal to take immediate advantage of favorable conditions--generally they have a type 3 survivorship curve The pattern of reproducing when young and producing many offspring that receive little or no parental care; often seen in short-lived, small-bodied species.

What happens when a population reaches carrying capacity?

enough resources are available to sustain that population size but the population does not continue to increase

list some density-dependent factors that limit population growth

food and nutrient limitations, insufficient space for territories or nests and increase in disease and predation and accumulation of toxins

Monoculture

genetically similar individuals/crops

population

group of individuals of a single species that occupy the same area at the same time they rely on the same resources, are influenced by the same environmental factors, and are likely to interact and breed with one another.

type 1 survivorship

high survivorship through early and middle ages (humans) usually produce few offspring but give them good care, increasing their chances or surviving to maturity

Density independent factors

in many natural populations abiotic factors like weather may limit or reduce pop size well before other limiting factors become important. a population-limiting factor whose intensity is unrelated to population density is called a density-independent factor if we look at the growth curve of such a pop, we see something like exponential growth followed by a rapid decline instead of leveling off. aphids and other insects undergo virtually exponential growth in the spring and then rapidly die off when the weather turns hot and try in the summer. a few individuals may remain, allowing population growth to resume if favorable conditions return. in some pops of insects the adults die off entirely and leave behind eggs that will initiate population growth the following year. in addition to seasonal weather changes fires floods and storms can affect a population s size regardless of its dentisy.

Type 3 Curve (Survivorship)

indicates low survivorship for the very young, followed by a period when it is high for those few individuals who live to a certain age. species with this type usually produce large numbers of offspring but provide little or no care for them.--fish for example make millions of eggs

Density dependent factors

limiting factors whose intensity is related to population density keeps population from increasing after reaching carrying capacity can limit growth in natural populations intraspecific competition is the most obvious--as limited food supply is divided among more and more individuals, birth rates may decline as they have less energy available for reproduction. density dependent factors may also depress a population's growth by increasing the death rate plants that grow close together may experience an increased death rate as intraspecific competition for resources increases. and those that do live will produce fewer flowers fruits and seeds than uncrowded individuals. after seeds sprout gardeners often pull out some of the seedlings to allow sufficient resources for the remaining plants. intraspecific competition is also the reason that plants purchased from a nursery come with instructions to space plants a certain distance apart. limited resource can be other than food or nutrients-- hiding places from predators--proportion of perch eaten increased with increasing perch density in many animals that defend a territory the availability of space may limit reproduction. for example the number of nesting sites on rocky islands may limit the pop size of oceanic birds such as gannets which maintain breeding territories orhwe factors cause density dependent deaths in a pop the death rate may climb as a result of increased disease transmission under crowded conditions or the accumulation of toxic waste products

environmental factors that restrict population growth are called

limiting factors--ultimately control the number of individuals that can occupy a habitat

one life history pattern is typified by small-bodied short-lived species t(insects rodents dandelions) that develop and reach sexual maturity rapidly, have a large number of offpsring and offer little to no parental care. in plants parental care is measured by the amount of nutritional material stocked in each seed. many small nonwoody plants produce thousands of tiny seeds such organisms have an

opportunistic life history

Population ecology

provides critical information for conservation and restoration projects. it is used to develop sustainable fisheries and manage wildlife populations provides insight into how pests spread also study human pop growth

What is a key factor in the recovery of red-cockaded woodpecker populations?

removal of understory vegetation by controlled burns

What accounts for the differences in life history patterns?

some ecologists hypothesize that the potential survival rate of offspring and the likelihood that the adult will live to reproduce again are the critical factors. In a harsh, unpredictable environment, an adult may have just one good shot at reproduction so it may be good to invest in quantity rather than quality. conversely, in an environment where favorable conditions are more dependable, an adult is more likely to survive and reproduce again. in this case having fewer offspring and caring for them is better.

Population cycles

some populations of insects birds and mammals undergo dramatic fluctuations in density with remarkable regularity Booms--characterized by rapid exponential growth are followed by bursts--when the pop falls back to minimal level. in lemming population of tundra, boom and burst growth cycles occur every three to four years-some researchers think that natural changes in their food cause it while others think that stress from crowding during the boom triggers hormonal changes that may cause the bust by reducing birth rates pop cycles of the snowshoe hare and the lynx illustrate interconnections within biological systems. lynx one of main predators of snow hare--ever ten yrs both hare and lynx pops rapidly increase and sharply decline. --either overgrazing predator prey interactionms or combo of food limitation and predators-third looking good

Biological control

the absence of biotic factors that limit pop growth like pathogens predators or herbivores may contribute to the success of invasive species-- the efforts to eliminate or control these troublesome organisms focus on biological control, the international release of a natural enemy to attack a pest population has been effective in numerous instances, especially with invasive insects and plants--beetles for st johns wort potential pitfall of biological control is the danger that an imported control agent may be as invasive as its target. mongoose to control rats--eventually became invasive themselves

J-shaped curve

the curve of the exponential growth model when graphed

what does an age structure show?

the distribution of individuals in different age-groups

Population age structure

the distribution of the population in different age groups. can reveal info not apparent from pop density can provide insight into history of population's survival or reproductive success and how it relates to environmental factors baby booms when there is more food for example useful for predicting future changes in a population

Logistic population growth

the growth rate decreases as the population size approaches carrying capacity. when the population size is at carrying capacity the growth rate is zero. carrying capacity for a population varies, depends on the species and the resources available in the habitat. Even in one location is is not a fixed number.organisms interact with other organisms in their communities including predators pathogens and food sources and these interactions may affect carrying capacity. changes in abtiotic factors may increase or decrease capacity as well. The concept of carrying capacity expresses an essential fact of nature: resources are finite. ecologists hypothesize that selection for organisms with an equilibrial life history occur in environments where the population size is at or near carrying capacity. because competition for resources is keen under these circumstances organisms gain an advantage by allocating energy to their own survival and to the survival of their descendants.

carrying capacity

the maximum population size that a particular environment can sustain

how does an individual's large ecological footprint affect earth's carrying capacity?

the more resources required to sustain an individual, the lower the earth's carrying capacity will be. earth can sustain fewer people if each of those people consumes a large share of resources

Population density

the number of individuals of a species per unit area or unit volume of a habitat number of largemouth bass per cubic kilometer of a lake for example or number of oak trees per square mile in rare cases, an ecologist can actually count all the individuals within the boundaries of a population-we could count the total number of oak trees (say 200) in a forest covering 50 sq km. the pop density would be the total number of trees divided by the area, or 4 trees per sq km. in most cases it is impractical or impossible to count all the individuals in a population. instead, ecologists use a variety of sampling techniques to estimate population density. they might estimate the density of alligators in a few sample plots of 1km sq each. generally, the larger number and size of sample plots, the more accurate the estimates. population densities may also be estimated by indicators such as number of bird nests or rodent burrows rather than by actual count of organisms. pop density is not a constant number--changes w/ birth death and when new individuals enter a population (immigration) or leave it (emigration)

fertility

the number of live births in a woman's lifetime

Exponential population growth

the principal (population size) grows faster with the individuals added to the population describes the expansion of a population in an ideal unlimited environment. in this model, the pop size of each new generation is calculated by multiplying the current population size by a constant factor that represents birth minus death rate. in the example each increase is larger than the next one so the larger the population the faster it grows. the increasing speed produces a j shaped curve that is typical of exponential growth common in certain situations--disturbances like flood fire hurricane drought or cold snap may suddenly reduce the size of a pop. organisms that have opportunistic life history patterns can rapidly take advantage of the lack of competition and quickly recolonize the habitat by exponential population growth. human activity can also be a cause of disturbance and opportunistic plants and animals can occupy roads freshly cleared lots and poorly maintained lawns, however no natural environment can sustain exponential growth indefinitely

Life history

the set of traits that affect an organism's schedule of reproduction and survival some key life history traits are the age at first reproduction, the frequency of reproduction and the amount of parental care given--life history traits vary across organisms reproductive success is key to evolutionary success--reproduction is expensive in terns of time energy nd nutrients--more offspring means less care for them--the combo of life history traits represents trade offs that balance the demands of reproduction and survival--life history traits like anatomical features are shaped by evolution

global hectare

the unit of measurement of the ecological footprint, representing the biological productivity of an average hectare of land

why is the percentage of individuals under the age of 15 a good indication of future population growth?

these individuals have not yet entered their reproductive years. if they make up a large percent of the pop (bottom heavy age structure) future population growth will be high

threatened species

those that are likely to become endangered in the foreseeable future

Why do managers try to maintain populations of fish and game species at about half their carrying capacity?

to prevent overharvesting yet maintain lower population levels so that growth rate is high

Life tables

track survivorship, the chance of an individual in a given population surviving to various ages. life insurance industry uses life tables to predict how long on average a person of a given age will live.

Why is integrated pest management considered a more sustainable method of pest control than the use of chemicals alone?

use of pesticides may result in resistant pest populations which makes the pesticides less effective. also pesticide use is unsustainable in the long run because of problems with pollution

Integrated Pest Management (IPM)

uses a combination of biological, chemical, and cultural methods for sustainable control of agricultural pests. researchers are investigating IPM approaches to invasive species. IPM relies on knowledge of the population ecology of the pest and its associated predators and parasites, as well as plant growth dynamics. in contrast to traditional methods of pest control IPM advocates tolerating a low level of pests rather than attempting total eradication. thus many are aimed at lowering the habitat's carrying capacity for the pest pop by using pest resistant varieties of crops mixed species plantings and crop rotation to deprive the pest of a dependable food source. biological control is also used when possible--gardeners release ladybird beetles to control aphid infestation but adherence to the principles of IPM prevents the overuse of chemicals

Sustainable resource management

wildlife managers fishery biologists and foresters use sustainable resource management: practices that allow use of a natural resource without damaging it. means maintaining a high population growth rate to replenish the population. according to the logistic growth model, the fastest growth rate occurs when the pop size is at roughly half the carrying capacity of the habitat. theoretically a resource manager should achieve the best results by harvesting the population down to this level. however the logistic model assumes that growth rate and carrying capacity are stable over time, assumptions that are not realistic for some populations. human economic and political pressures often outweigh ecological concerns which leads to unsustainably high harvest levels that ultimately deplete the resource. fish, the only wild animals still hunted on a large scale are particularly vulnerable to over harvesting. in the northern Atlantic cod fishery, estimates of cod stocks were too high and the practice of discarding young cod (not of legal size) at sea caused higher death rate than was predicted. the fishery collapsed in 92 and has not recovered. deeper waters are colder and food is relatively scarce--fishes adapted to this environment typically grow more slowly and have a lower reproductive rate than continental shelf species sustainable catch rates cannot be estimated without knowing these essential life history traits for the target species. in addition, knowledge of population ecology alone is not sufficient; sustainable fisheries also need knowledge of community and ecosystem characteristics